Kitting Up To Make Model IC Engines, Part 1
Click on photographs to view in more detail
- The Lathe
- Tool Holder
- Drills, Drill Chucks, and Drilling
- Knurling Tools
- Hand Tools and Measuring Equipment
- The Bench Vice
Aside from What engine is this?, the next most popular request arriving in the Model Engine News in-box would be What is the minimum machinery and tools I need to start making my own model engines? Good question, deserving of a good answer, and to hopefully prevent me having to ever respond to it again, this page gives some suggestions to absolute beginners about how they can get started in this fabulous hobby.
My good friend and mentor, the late Roger Schroeder has, to a certain extent, already covered this ground in his paper, Building A Model Airplane Engine that Runs. I don't disagree with anything Roger says, but times and circumstances change and since Roger is no longer with us to update his work, best read both pages before forming your own opinions on what is right for you.
Lastly, why the "Part 1" in the title? Well, recognizing that some would-be Model Engineers are willing to leap in with both feet while others prefer to gingerly insert a big toe, this page (Part 1) will deal with the minimum requirements; Part 2 will list extra equipment which will save you time and effort, but is not "necessary" in the strict sense of the word (opinions may vary).
You are not going to scratch-build a model engine with a hand-drill and some worn-out files, you need a lathe. The lathe has been called The King of Machine Tools due its ability to perform a wide variety of tasks. At the rock-bottom minimum, a lathe and some necessary accessories are all you need to build a simple model engine.
A great site for browsing just about every lathe ever built is Lathes (catchy title, huh?), a UK site with details, documentation, and pictures of everything from the smallest to the largest.
The best advice I've ever read—and with which I totally agree—boils down to buy the best and biggest your budget will stretch to. Note the order, "best" trumps "big". It does not have to be new, in fact there is an advantage in buying second-hand because there's a good possibility that a second-hand machine will come with a lot of extra, useful tooling. Regardless, look at what you have to spend, what space you have available for it, how you are going to get it into that space, then start shopping. I'm going to assume you've done some research and know basically what a lathe does, but a couple of things are worth going over again.
Knowing your budget and space limitations, you can start considering "throw", "between centers" distance, and "gap". The first designates either the distance between the lathe axis and the bed (English convention), or twice that dimension (USA). Obviously one is the radius, the other diameter of the largest lump that will "swing" without hitting something. A lathe with a "gap bed" allows you to swing larger things close to the headstock in the gap; a very useful feature in smaller lathes, say those with a UK throw of around 3-1/2". The distance between centers is what it sounds like and is not generally of concern to model engine builders, though if you plan on being a Model Engineer, not restricting yourself purely to IC work, bigger is better (as in most things ).
Getting down to options, at one end of the spectrum, we have "table-top" machines like the excellent little Sherline, the venerable Unimat and the like. These should not be overlooked, nor looked down on. Precision work can be done on machines like these, in fact, World Class award winning work has been delivered by exceptional, talented people. But the swing when machining the crankcase is going to limit what you can build and you'll probably be limited to IC engines with a maximum displacement of under 2cc per cylinder.
Small vs Large Lathes
Going up in size, a lathe with a 3-1/2" (89mm) UK swing and about 18" (457mm) between centers will accommodate engine making up to 20cc with no great drama. In this category, we encounter machines such as the Emco, and my choice, the Myford Super 7 Plus, as seen here . The Myford has become the Model Engineer's lathe of choice in the UK, due partly to the company's excellent reputation and the vast number of articles detailing shop-made tools and accessories for it. Most of these can be adapted to other lathes, but it's always easier just to follow the words and music. My decision to "go Myford" was the result of looking at Asian machines, looking at the Myford, then doubling my original budget, taking a deep breath, and ordering a new one. I've never regretted this decision for a second; the machine is an absolute joy to use.
A limiting factor can be the spindle bore. The Super 7 has a #2 Morse Taper (MT) spindle which limits the diameter of rod you can pass through it for any distance. While occasionally frustrating, that's life with just about any of the smaller tool-room lathes, and there are ways around it. A 4MT spindle like that found on Myford's Connoisseur series improves matters giving 25mm headstock pass-through, but for more, you need to go onwards and upwards.
Going even further up to machines like the Harrison, Hardinge, South Bend, etc, you can generally forget the gap-bed for starters; they don't have then and they don't need them. Things to consider now include, how is the chuck fixed? Threaded reduces cost, cam-lock allows you to run the spindle backwards without fear of the chuck dropping onto the bed while revolving at frightening speed. But space requirements then become a consideration and you will probably find such a second-hand machine to be fitted with a three-phase motor, although this is not such a bad thing in these days of efficient and inexpensive single to three phase power converters. If you have the space, bigger is generally better, provided you still have precision and suitable tooling at reasonable prices and availability.
While I've heard of people who have done precision work using a "three in one" machine, I've never actually met one! The machines of this type I've examined look like the compromise they are; you save space and cost at the expense of rigidity and precision. Machines designed and built for one purpose alone can be expected to be good at that task, and generally are. Combination tools involve compromises, and making a model IC engine requires more precision than just about any other kind of model engineering, even live-steam (after a few IC engines, loco cylinders, pistons and slide-valves are a walk in the park). For precision work, you need precision equipment. My opinion is to forget the 3-in-1 utterly.
Power and Back-gear
Then there's the motor to consider. On many new machines, you may be surprised to discover that this is a cost-extra option, even if a rather mandatory one. Modern thinking is to forget the old single phase, fixed speed motors, go for a three-phase inverter set-up. This will give you variable speed at high torque and time saved changing belts on pulleys. It may even save you having to worry about whether your lathe has "back gear" or not (a feature that reduces spindle speed and increases torque, very useful when tackling larger jobs, thread-cutting, and working with cast-iron).
The ability to reverse the motor is worth mentioning here. I'm calling this a must-have feature. Even though owners of screw-on chucks won't be making cuts in the reverse direction, there will be times when an inability to run the machine backwards will be a very frustrating disadvantage.
Self-act, Change Wheels, and Gear Boxes
Screw-cutting lathes depend on a lead-screw to move the saddle a precise, selectable distance per spindle revolution. This movement is sometimes referred to as the "self-act", and cunning mechanisms allow it to be applied to the cross-slide as well as the saddle. The good old Myford even allows it to be applied to both at the same time, though this is usually due to operator stupidity or inattention and expensive noises are soon heard (don't ask).
Obviously the ratio between spindle and leadscrew needs to be variable and this can be achieved in two ways: easily through a quick-change gear-box, or less quickly through the set-up of change-wheels and sector-arms. If budget and availability permit, avoid change-wheels like the plague, get a lathe with a gear box! Working out ratios may look like fun, but it's time consuming and that is one thing most of us today are rather short on these days.
The Top, or Compound Slide
I'd imagine that every lathe you look at will have a top slide. This is mounted on the cross-slide and is the bit which mounts the tooling. I mention it because for model IC work, you will need to pivot this slide from its normal alignment parallel to the lathe axis. This allows short tapers to be cut, such as those typically found on the end of crankshafts, or when shaping the profile of the cylinder cooling fins. For this reason the top slide is often called the "compound slide". The important thing is the amount by which the slide can be rotated: more is better. The original Myford ML7 restricted rotation to a rather narrow arc. The Super 7 changed the design to allow a full 360° of rotation, although several positions are unusable due to other things interfering with the handle. But being able to rotate to wherever you want is very useful, so give preference to lathes which do not restrict the compound angle.
While we are talking about the saddle, cross-slide and top-slide, it's worth mentioning that you will never be able to use the full swing of the lathe between centers; the cross-slide gets in the way. The full swing is only available for short-ish work gripped in the chuck (or on the faceplate, perhaps in the gap). So you might like to also check the dimension given for swing over the saddle.
Thread Cutting, and Tumblers
Talking about lead-screws and gear-boxes leads us to thread cutting considerations. Trust me, you may not want to cut one now, but someday you will, doubly so as you make more advanced model IC engines.
Beginners seem to view thread cutting as an operation for experts. It's not. Yes, some practice and skill development is required, but with a decent screw-cutting lathe, inside and outside threads are a breeze and a whole new world opens up for you. Obviously your lathe needs to have the ability to set a very precise distance by which the saddle moves for each revolution of the spindle, either through a quick-change gear-box, or a less then quick set of change-wheels.
The pitch of the lead-screw is going to determine whether your lathe is Imperial, or metric. This is not to say that threads of the other persuasion can't be cut, they can! For the change-wheel addict, this just requires some rather complicated trains (and gears with an odd numbers of teeth). If you have a gear-box, you just moved into the gear train world, though the trains are simpler. There are other caveats, such as once you start, the leadscrew clasp-nut must not be disengaged, so you must stop and reverse the saddle motion to reposition for the next cut (see? I said the motor needed to be reversible). But it can be done, if you need to.
I've already said go for the gear-box if you can, but there's one other important thing to consider: does your prospective lathe have some way of reversing the leadscrew rotation independent of the spindle rotation? If not, you will never be able to cut a left-hand thread, nor perform a cut towards the tailstock under self-act. The ability to reverse the leadscrew rotation is generally achieved by what is called a "tumbler", though there are other mechanisms as well. Be warned: a recent survey of low-end, budget Asian lathes showed that many lacked this feature! My opinion: a lathe without this ability is no King of Machines; it's not even a Prince, in fact, it's hardly worth considering.
This leads us to a gadget which may not be in the up-front purchase list, but will become mandatory when you start cutting threads. Depending on the pitch, the point at which the clasp-nuts are engaged on the lead-screw makes the difference between cutting the same thread path, and creating entirely new and wrong one! The exception is when the pitch is a multiple of the lead-screw pitch; for all others you absolutely need the little thread dial indicator gadget. Surprisingly, many lathes, including the Myford, sell this as an option. They don't cost a lot so it could well be an initial piece of kit—the choice is yours, but you will need it eventually.
Taps, Dies, and Die Holders
Male and female thread can also be produced with taps and dies. Almost certainly, your first model IC engine project will require several such operations. With the single and notable exception of BA (British Association) I see no value in tap and die sets. Buy individual ones as the need arise. Even if you only need a tap, buy the die at the same time. Having the tap, being able to cut the appropriate male thread follows like night and day. Regarding taps, I've found no value in "first taper" taps, however you should always buy two taps, an "intermediate" (or "second"), and the bottoming (or "third", or "plug") tap, plus the die and make sure the latter is of the adjustable type.
Another piece of start-up kit that you should equip yourself with is a sliding, tailstock die holder. At our work sizes, Button Imperial and Unified dies generally are 13/16", or 1" in diameter, so it's good to have holders for both. The die holder assures that the die is started and held in the correct relation to the shaft being threaded. My experience is that above diameters of 3/16" (say 5mm), the effort required to thread becomes uncomfortably high and the amount of metal removed makes a clean thread more difficult to obtain. The fix is to begin by screw-cutting the thread, but not to full depth. Run the die—in the holder—over it to finish the thread and form the correct profile. I've often thought thread "chasers" would be nice, but so far have managed to do without to no apparent determent.
ColletsNice, but not necessary. Collets provide a precision way of concentrically holding round stuff with a high level of even pressure that does not distort or mark the surface (unlike a 3-jaw chuck, for example). But as usual, precision comes at a price and you do not need collets of any sort for now. When you progress, think about the ER32 type. These close from two tapers on either end assuring the work is held on the collet axis (unlike the 5C split type which can only close at the tip).
The Last Word, For Now...
That about winds it up for lathe choice and you may be wondering why I've not made any great song and dance about Imperial as opposed to metric lead-screws and dial calibrations. The reason is that I no longer consider this to be of any great significance. Get a lathe you like, can afford, that will fit in your shop and can be gotten into your shop. Arm yourself with a workshop calculator and commit the number 25.4 to memory. Depending on what your plans are dimensioned in and what your dials are calibrated in, multiply by 25.4 to convert inches to millimeters, divide to go the other way. You don't even have to remember which is which because if you get it wrong, the answer will be so wrong, Blind Freddy and his dog will be able to spot the error. Machine to .001" or 0.02mm precision on important stuff, make parts to fit already made parts, and you'll produce good, running engines regardless of what the dials say.
Assuming you now have your lathe, you are going to need three important accessories which attach to the headstock spindle: a 3-jaw, "self-centering" chuck with inside and outside jaw sets, a 4-jaw "independent" chuck, and a slotted faceplate. Some old texts say you can omit the 3-jaw as better precision can be had with the 4-jaw—perfectly true, though at the expense of time, effort, and an appreciable degree of hard-earned experience. I regard all three as mandatory, especially the faceplate. This, together with a small precision angle-plate that can be bolted to it are the absolute best way to mount crankcases for boring operations. This is where a gap-bed is useful, allowing the faceplate, angle-plate, and counter-balance to swing in the gap while the work extends over the bed. I repeat: you need a faceplate and an angle plate!
A catch-plate is a nice-to-have, but with ingenuity, the faceplate or even one of your chucks can serve as a catch-plate for between centers work. Using a three-jaw and shop-made "dog" even has an advantage for between center work over the traditional catch-plate with hard and soft centers. Just chuck a piece of scrap rod, set over the compound slide 30° and turn the rod to be your "soft" center. This assures maximum accuracy and saves you an accessory.
Centers come as soft and hard, the latter being fitted with a tungsten core before grinding to 60° included angle. You really should equip your shop with at least one hard center, preferably two. One should be ground (or milled) away on one side into a "half-center". You'll need this for supporting small diameter work that needs the cutting tool to be brought down to it at the tailstock end at the start of a cut; something you just can't do with a full dead-center. You can get away with just a half-center, though it's nice to have both.
Occasionally, a soft-center can be useful, but as noted earlier under catch-plates, you can improvise easily, with total precision.
A revolving "live" center for the tailstock can be a useful thing too, but it's not really needed for most IC building, provided you have your half-center (a dead one) in the tooling drawer and an easily reachable pot of grease under the bench.
Budget expanding time again. A quick change tool-post with as many tool holders as you can hide from the wife is THE way to go. The type seen here is the Myford-Dixon, now available as a cheap but quite serviceable Asian replica. If the budget does not stretch to it yet, wait! Don't waste money on a four-way tool holder, just use whatever the lathe comes with until you can afford the quick-change holder. You'll be better off putting the cost of a four-way in a jar towards ultimately equipping yourself with the quick-change setup, and you'll save extra money on the band-aids required to stop dropping blood over bed when you accidentally stab yourself on one of the tools in the four-way. Corrosive stuff, blood; it's all the salt, I'm told.
Tooling and Grinding
Tough decision. The options are high-speed steel (HSS), carbide tipped tools, or insert based tooling. The first two look like the cheapest, but if you go that way, you absolutely must get a decent bench grinder and probably replace whatever it jokingly includes as a grinding rest with something more substantial and adjustable. If you go for carbide tipped tools, the grinder will need a "green" wheel or the tooling will grind away the wheel!
A rather nice variation on the HSS tooling approach is a tangential tool holder such as the Diamond Tool Holder, originally developed by Australian Des Burke in 1985. The Diamond makes producing a tool that will cut freely and well a snap for the beginner with just a bench grinder and the included grinding jig. If you go traditional square HSS tooling, you are in for a time learning what works in relation to relief angles, rake, chip-breakers, etc for different metals. This is very valuable knowledge to have, but it takes time and effort to acquire.
HSS and Carbide Tipped
If you choose HSS, or carbide-tipped, I really suggest starting with a set of pre-ground tools. As they come in the box, the carbide tools I've examined won't cut butter, but at least the reliefs and rakes are about right and the beginner can bring them up to scratch easily enough on the bench grinder, provided it has an adjustable rest and a green wheel. You should make some grinding jigs (look how simple the Diamond grinding jig is)! Steel or ally is nice for the various jigs required to present all the tool faces to the wheel at the right angle, but hardwood will work well too.
Disposable Insert Technology
The most expensive option is replaceable insert tooling, although prices are falling as this technology migrates from industry to the small (and home) machine shop. Some caution is called for as toolholders for inserts can be quite bulky. I have just one, and it won't fit in a Myford-Dixon Quick-change holder! To use it, I have to remove the Quick-change holder and replace it with the "elephant's foot" holder which came with the lathe. Insert technology can produce nice results with higher spindle speeds, but there is a learning curve, and they don't call inserts "throw-away" for nothing; this is not an inexpensive way to tool-up, neither is instant success guaranteed for the beginner; there is a learning curve that is greater than for HSS/carbide.
Then you need to consider the jobs for which there is no commercial tooling, or for which what is available is just too hard to get in small quantity, or not economical. We are talking cylinder fin cutting tools and the like. For this job, shop-ground HSS, either square or round, is about the only option. Yes, you can make of use things like re-ground power hacksaw blades in shop-made holders, but the lack of side rake will warp the fins unless absolutely flooded with coolant, and coolant pumps are not something the average Model Engineer equips itself with.
Unless you go totally insert, you'll need a bench grinder. This should be positioned as far away from the lathe as your shop will allow (we don't want wheel grit anywhere near the bed). A half-way decent grinder is not expensive, but the table supplied will be a source of great frustration when trying to grind tooling off-hand. The illustration here shows the typical sort of thing you should replace the supplied table with. This one appeared in the Model Engineer, #3165, March 8, 1962, although there have been literally hundreds of similar tables described over the years. It just needs to be adjustable, rigid, and a decent size. The protractor shown will be a great help and the whole thing can be done in a weekend. So do I have one? No. I took a year off to make a Quorn cutter-grinder instead!
If you go HSS or carbide, you'll also need a good, flat oil-stone to hone the final edge. I suggest squirting it the RP-7, not oil. Oil loads up the stone and is a device advocated by oil-stone salesmen to sell more oil-stones. The fastidious will get an Arkansas stone to really put the razor edge to the honed tool. Not totally necessary though.
The most effective parting-off tool is the hacksaw, preferably of the powered variety. After several years (and a completed Quorn), I think I finally became moderately competent at parting off with a parting-off tool! For a long time, this was a tense time and close examination of my lathe bed bears mute, accusatory testament to many parting off disasters involving large diameter bar, fixed steadies, and tool dig-ins. When starting out, just saw it off and face it off. Much quicker, easier, and safer.
But you are going to need a parting tool setup eventually. A Quick-change set will come with a holder for the standard 3/32" relieved blade stock that can't be beat. You can buy dedicated holders, but they become instant boat anchors after the Quick-change arrives on the scene. Up to you, but see how you go with the saw and face approach until your give in to QC holders. Saves you some money too.
Drills, Drill Chucks, and Drilling
Oh dear. More expense. Most people have some odd twist drill bits lying around that have been used for all sorts of drill-blunting purposes. Forget them. You will be doing precision work and that requires good quality new ones. The choice of metric, or Imperial plus Numbers is up to you. You MUST get something like Kenwells Engineering Data Charts and Reference Tables which, amongst many other things, lists all drill types together in ascending order, letting you easily identify a close-enough Imperial, Number, or Letter drill for a metric diameter, and vice-versa.
If you think in Imperial, get a full set of fractionals, 1/16" to 3/8" (preferably 1/2") in 1/64 steps, AND a full set of number drills, #1 through #60. Letter drills are handy to have and I've noticed Asian import box sets having all three, but be cautious about quality which I'll return to in a moment. You can skip the Letter drills initially if you wish, waiting until the stated tapping size is a Letter drill once too often.
For Metric Dudes, life is simpler. You need a set of (ahem) metric drills, 1.5mm to 6.5mm, or larger, in 0.5mm steps.
Regardless of religious persuasion, the drills need to be new and must be hidden when any household task is contemplated, or commanded by She Who Must Be Obeyed. You should not even use them for wood; they are intended for drilling precision holes in metal.
Now a word of caution. I've experienced more than my fair share of inexpensive Asian twist drills ground with no apparent relief resulting in a drill that won't even drill plastic. Relief can be added, but if it's even slightly asymmetrical, the drill is going to drill over-size. This is why I say more expense: you really should buy industrial grade to save yourself frustration and breakages.
Owners of larger machines making larger engines, or tooling, are someday going to wish that had a set of "reduced shank" drills in the range 17/32" to 1" in 1/32 steps, but you can put these off until later.
I suggest you also get drill stands for all your drills. Those metal boxes with finger-biting folding sections are just too inconvenient for words. A good drill stand will last a lifetime and make that lifetime more enjoyable.
You also must get a set of center drills, aka "Slocombe" drills. For work at beginner IC engine project sizes, the first three (#1 to #3) will do. Go to #5 if the budget allows. Get a block of wood and make a bench-top stand for them, and put a drop of red paint in the flutes at one end. Use the other end for work until it becomes blunt, or you break it, then swap over. The hard part becomes remembering which end is in use for which drill. Your bench block holder may help, if you always put them in with the in-use end up.
You most definitely are going to need a tailstock drill chuck. Depending on your lathe size, you may even need two! A standard, key operated Jacobs, either 0-3/8", or 0-1/2" is ok, but a good Asian keyless chuck is not much more expensive these days and is a big boon to productivity. These are available as 0-3/8 (or more likely 0-6.5mm), and 4-13mm. Note that the big one does not close all the way down, which is why you may need two. Naturally, you'll need an arbor for each of a taper to fit your tailstock.
You may be tempted to grip a drill in the 3-jaw for some jobs. This can be done, but take care the work does not "screw" the drill out of the chuck. If your tailstock arbor also fits the headstock, remove the adjustable chuck and fit the drill chuck. This too can be pulled out, so a draw-bar (shop made) is good insurance. I'll have more to say about this when we get to milling operations.
The Drill Press
Ok, we can drill in the lathe with precision and accuracy, at the expense of setup time and some occasional lateral thinking. Drilling in a drill press looks quicker, so do you need one? I have mixed feelings. Drill presses are ok, but unless you pay for it, they can lack precision. Try this: visit your local machinery supplier, or Home Depot, walk up to an average table model drill press, extend the quill to half travel or further, then grip the chuck and try to waggle it side to side. I bet it moves, probably alarmingly so. You can get ones that don't, but you've moved into a whole new world of cost. Even if you already have a drill press, don't even think about of using it for say drilling holes in a crankcase to be tapped for cylinder hold-down screws unless you have a good quality drill press vice, preferably one that can be easily clamped to the table.
The better option is the Mill-Drill, but that is not something we are going to fit into your initial kit-up budget. So if you have a "consumer" grade drill press, get a decent vice for it and see how you go. If not, I'd say skip it and see how the King of Machines manages with your drilling needs, especially if you've kitted up with a vertical slide.
While not utterly a requirement item in the initial purchase, the ability to put a nice fine knurl on a needle valve adds to function and satisfaction. For this, you most certainly don't want the type of knurling tool seen on the left of the picture, which I stupidly bought as part of my initial kit-out and have never used! The caliper type seen on the right however is just the ticket. You can buy a commercial one like this these days at a reasonable cost, but far better to make your own. The one seen here was made from a Hemingway kit. Building tooling is a great way to develop your skills before starting on an engine project.
Most new machines seem to include a fixed steady as standard equipment. Second hand machines may have a travelling steady as well. You probably won't need either on the average model IC engine build. There are times when a travelling steady looks like just the ticket for some task, at which point you'll find that the factory model is too large to be of any use. For the sizes at which we work, shop-made travelling steadies, or box-tools are what is required and those can be made as required. So don't worry too much about steadies until you move to non-IC projects requiring mutilation of big iron.
A mill, or even a mill/drill is not a small purchase and while the cost is nothing like it was even ten years back, it is still a big-ticket item for when you are first kitting out the workshop. Additionally, your first projects will (or at least should) be at the "beginner" level, so they probably won't require any milling at all. Even if there is some small amount required, our King of Machine Tools can do the job using shop made fly-cutters to face and size blocks of aluminum mounted on the cross-slide table with packing blocks and shop-made clamps.
Milling in the Lathe
If you need more sophisticated milling, say for the manufacture of some shop tool, add a vertical slide to your kit. The one seen here is intended for the Myford, but similar ones are available for other lathes, as are quite reasonable "generic" types, from Asian sources, naturally. The idea should be intuitively obvious: the cutter is turned by the lathe headstock, so is fixed. The saddle and top-slide provide the moral equivalent of the mill X-Y axis feeds. The Z axis (depth of cut) is put on by moving the saddle, then locking it. For this, it is very handy to be able to use the leadscrew, provided it is fitted with a calibrated handwheel. Sadly the Myford is one of the few lathes with this feature. A note of caution: after setting, disengage the half-nuts to prevent the saddle moving under self-act when power is applied, despite the saddle lock! Again, don't ask .
For precision work—and just about all work on a model IC engine project is precision work—the top-slide must be set at right angles to the lathe axis. For this, your faceplate is the ideal reference; fit the faceplate to the spindle, flatten the slide face against it and tighten up. What could be easier and aren't you glad I made you buy that faceplate?
A small machine vice for the vertical slide will come in handy too, but you can get by with just a set of clamps. These can be purchased, or shop-made, or both as needs be. They are also used in faceplate work, so should be considered essential equipment in any case.
Milling Cutters and Holders
You can purchase milling cutters of various sizes as the need arises, or get one of the many boxed sets now available. I suggest buying both four and two flute cutters. These are known respectively as "mills" and "slot drills" in my part of the world. The late, great George H Thomas describes why a two-flute cutter is a slot-drill and why a four-flute cutter isn't in his excellent Model Engineers' Workshop Manual (reprinting his Model Engineer articles with original photos and art-work). The problem when milling in the lathe is how to hold them.
Milling is a violent operation. The forces on the cutter are high and the effect of the helical flutes is to cause the cutter to act like a drill. When this happens, they pull out of a 3-jaw chuck with suppressing ease and auto-deepen the cut with fatal results to work and cutter. The BANG! of a cutter breaking is an alarmingly loud and expensive noise. The only fix is a for-real cutter holder. I should also mention NEVER to use a drill chuck to hold a milling cutter unless you are using it purely as a drill; not that is if you ever expect to drill precision holes with that chuck again.
Cutters are made as plain-shank "disposable" type, or with a screwed shank. Both are available as Imperial or metric. The disposable type require a very simple holder, generally with a Morse taper to suite the headstock. The holder for the threaded type is more complicated and expensive, and is known as a self-tightening, or "Clarkson" type. It uses precision collets, so can be used for both Imperial and metric cutters. You really, really, really should equip yourself with one or the other before doing any serious milling in the lathe. In either case, a draw-bar to prevent the Morse taper from breaking is essential, but this is an easy project, requiring just a bit of thread cutting that can be done with a die, although it's better to almost complete the thread in the lathe and only finish it with the appropriate die.
The Vertical Mill
Provided you keep the cuts light, the lathe and a vertical slide will probably do all the milling you ever need. Certainly I'd suggest putting off thoughts of a mill until you got several projects under the belt, know that Model Engineering is for you, and want to increase your productivity, capability, and skills. Therefore I'm not going to say much about mills except to say that the round column mill/drill is a really great drill! More in Part 2.
Hand Tools and Measuring Equipment
Chuck-board. If you are ever going to be tempted to apply said hacksaw to something still held in the lathe chuck, take three minutes and some scrap wood to first make a chuck-board similar to the one seen here. Eventually you'll have an accident. Without the board, you'll quickly discover hacksaw teeth are harder than lathe beds and probably not be too pleased with yourself. The board is also handy precaution to place on the bed while removing heavy chucks, which have a tendency to escape as the last thread emerges.
Hand files. You also need some hand files and a set of needle files (aka "Swiss" pattern files). The latter can be had as a set of six, or more. Six is fine provided they include round, square, triangular, and flat. For hand files, you could go with what you've got, provided that includes something like a first-cut bastard, a mill-cut "straight" file with a safe-edge, and a 6" warding file. You are eventually going to apply one of these big files to something spinning in the chuck. Don't even think about it unless the file has a handle! The damage the tang of a file can inflict on a human wrist (where some serious veins reside) does not bear thinking about. Fit all files apart from needle files with handles.
Hacksaws and Hammers. A plastic mallet is another thing you'll likely need sooner than later. You'll use it to tap work and fixtures like the angle plate during set-up operations. The shape and feel of a hammer is just ideal for this, but metal on metal is bad for the work and jigs. A brass faced hammer is a reasonable alternate, but plastic ones are cheap and better to have the right tool for the right job. You'll also need a hacksaw of the old manual variety. I'm talking the full-size variety with the adjustable frame and blade tensioner here. The "Junior" type is a nice addition, but hard to keep straight. If you don't already have one, get one, and some 24 TPI blades to go with it.
While at the hardware store, pick up some small plastic squirt bottles. In the old days, how-to articles by luminaries in the ME suggested brushing cutting lubricant onto the job. It's exciting watching that brush spin around after it finally becomes trapped between cutter and work, so don't brush; squirt, or dribble from the plastic bottle instead. Flood coolant is nice for production work where the lathe is run to maximum capacity and the chips come off blue. For us, the squirt bottle is better.
Squares. An engineers' combination square is nice to have. Good quality like those from Starrett are best, but expensive, while those of the hardware store variety are somewhere beyond atrocious. There are acceptable intermediate ones. As a general guide, if the rule is engraved, it's probably good; if the markings are stamped, forget it. You may also consider a small engineers square. You will be using it, or your combination square, to align stuff against the faceplate, machine vice etc. Sometimes a little 4" engineers square is the better choice due to space restrictions. But consider a square of one or both types essential equipment.
Scribing and Punching. You'll need some means of prick-punching centers accurately. A fine prick-punch is nice, but most get by just fine with a good old automatic center-pop. You'll also need a scriber. If you have a good combination square, it will have a scriber snapped into it. If not, get one of the pocket type. Again Starrett and Eclipse make real nice ones that will last a lifetime (with sharpening).
Calibrated Measuring Sticks. Get a little 6" flexible steel rule of your unit proclivity. Most today have dual scales which can be handy (some countries even mandate this). I've found the little ones with the gold "TIN" coating really make the marks and numbers stand out well in the workshop. The slight flexibility is handy and the having a little one saves you pulling the combination square apart. You'll eventually need to set something at an angle. For this, where reasonable but not sine-bar precision is all that is required, get a small protractor of the type seen here.
Dividers. Straight calipers and odd-leg, or "Jenny" calipers should be considered essential too. You'll figure out why before your first project is finished. In the old days, inside and outside calipers would have been mandatory too, but no more. Digital devices have rather removed the need for them, mostly.
Digital Measuring Devices. Consider a digital "Vernier" essential equipment too. I've put talky-marks around Mr Vernier's name because apart from the anvil shape, these instruments are not "Vernier" in any other sense of the word. For simple model IC engines, their 0.001" (0.02mm) precision is all you'll need. Later, you may consider adding a digital micrometer, but it will get little use.
Bore Measuring. In conjunction with the digital calipers, a set of telescopic gauges is essential equipment for the model engine builder. Taking a bore measurement with the inside jaws of the digital caliper will just not suffice for accurate measurement of something like a cylinder bore. As well as giving the true size to measure, the telescoping set can be slid back and forth to "feel" the degree of taper and allow you to gauge the bore at the point above the exhaust where we want the piston to start to pinch on a lapped bore. The caliper jaws will just measure your bell-mouthed opening.
The other gadgets seen in the photo would be nice for smaller bores if they were real Starrett or Eclipse brand. These have precision ground ball ends which are split and can be forced apart slightly by the screw end wedge. The Asian knock-off type are pressed tin with horrible raised edges that prevent accurate contact. The can be reworked to improve them, but they remain an instrument of poor quality and questionable accuracy. Good idea though; suggest you haunt eBay for the real thing.
Tap wrenches. You will almost certainly require both of the type seen here on you first model IC engine project. The small T-bar type holds the second and plug-taper taps for tapping cylinder and bearing housing and backplate mounting holes. Your first project should have a plain crankshaft bearing, either reamed in the casting or turned nose-piece, or bored to take reamed bronze bushes. To do the reaming, you MUST "float" the reamer into an undersize hole (drilling through 1/64" undersize is perfect for reamers as they must be allowed to cut—between 0.005 to 0.010 per side is correct). For this, you push the reamer in using a hard center in the recess on its end, preventing it from rotating using the larger handle type tap wrench with one leg against the cross slide.
DTI's. Although there are other ways to do it, the plunger type Dial Test Indicator (DTI) is the easiest way to accurately set a crankshaft blank when off-setting for the crankpin and all-important throw. You can use the dividers to mark a center-pop at the pin center, then use a wobbler and the DTI to center the mark, or apply the DTI against the outside of the blank and adjust to read the actual throw. For this, a plunger type, set precisely on lathe center height, having a travel of at least 1/2" (13mm) is required. Larger is better, but more expensive. The other type seen in the photo will become essential equipment as you progress, but you can avoid it as an initial purchase (mine was a gift from the Myford supplier).
Counter Sinks. A nice to have item and I wish I'd bought the full set from the closing down sale where these came from. The type seen here have a hole drilled through the head that does the actual cutting. This does an excellent job used under power, or just in the hand for hole de-burring. The hardware store type with the multiple flutes are just about useless for metal, working more as a burr-putter-onner, rather than a taker-offer. A shop-made D-bit counter sink will do a better job under power, but is not as good as the angled hole cutter used free-hand.
The Bench Vice
You may sneak your first engine in without needing a bench vice, but you'll probably wish you hadn't, so let's call it an essential bit of kit (as is the rigid, solid bench it's screwed to). When selecting your vice, I strongly suggest you get an offset vice as opposed to a straight one (this sentence is not getting any better, is it). The reason should be obvious from the photo showing my own venerable 4" offset bench vice holding a long bar vertically. This would be somewhat difficult with a standard vice where the screw is in the middle of the jaws. Yes, the clamping force is offset but unless you intend to abuse your vice as a press, you shouldn't be applying bone crushing force anyway. While you are looking, a vice with removable jaw inserts is a better deal than a cheap one-piece unit too.
Your author holds a Bachelor's Degree in Applied Science, a Higher Degree in Computer Science, and some ancient formal training in hand tools and metal bashing as applied to the making of electronics chassis, gained during an apprenticeship served way back in the days of valves (vacuum tubes). Although he did a Technical College course in fitting and turning, this ran to all of eight lessons, making a bottle-jack, so there's no way he can claim any kind of professional experience in machining and machine tools.
In compensation, he's been making model IC engines and tooling for about twenty years, has made every mistake in the book, and about seventy engines from simple single cylinder jobs to multi-cylinder in-line and radial four-strokes. The hints on kitting up your shop were written by examining his own shop contents while thinking of an engine like the ML Midge (barstock), the the Boll-Aero (barstock), and Gotham Hobby Deezil (casting), all of which make fine beginner projects (although the latter involves thread cutting).
Undoubtedly, something important has been forgotten, and something less important specified as mandatory. Hopefully though, the notes have given you an idea or two of what may be required and what sort of budget you'll need.
Leaping into an engine after the lathe is bolted down and leveled (didn't mention that, did I ), is a very bad idea. You should start with some shop made tooling projects and I can't recommend any book more highly than George H Thomas's Model Engineer's Workshop Manual. Although many of the accessories described are specifically tailored to the Myford, the book contains several non-denominational pieces of essential work-shop tooling and a wealth of information about why things act and cut the way they do.
Start with Chapter One and make GHT's lathe tooling height gauge. It's beautifully over-engineered and every skill you learn making it will be used on your first engine. Then proceed to Chapter Two and make the wobbler, and optionally, center finder as well. The wobbler is another tool that will be used making your first engine. His 3/16 and 1/4" round HSS tool holders are also good projects and tools you'll use frequently for head fins and other odd jobs. His discussion on end-mills and slot-drills is well thought out, enlightening, and may prevent you making costly blunders later. His boring bar designs will come in handy too. After you've made the tools and accessories just mentioned, you'll be in a very good shape to make your first model IC engine with every confidence of success.
Model Engineering is a very satisfying hobby. Entry is not cheap, but the rewards are great and best of all, your workshop equipment will tend to hold its value over time.
Ron Chernich, May 2011.