Sure, it's been done. You can buy the spars with sliding LCD heads about as cheaply as playing with digital calipers I think. I want a DRO on my lathe & mill but so far have always put it off in favour of buying more big tools. One day...
OK, 3" is well within the capacity of a small lathe. There are a lot of people doing gun work using those mini lathes and the machines seem capable enough.
Nope. The Grizzly mini lathe has a 6 1/2" faceplate so that's max swing
*over the bed*. They don't say what it is over the cross slide but I'd guesstimate 5" max. This is pretty limiting when you add a vertical slide unless you clamp directly to a flat front face rather than mount a vice on it. With a vice, you have to allow for the thickness of the fixed jaw. The work envelope is going to be fairly small. Big enough to use slot drills and the like for putting keyways in shafts up to 2" dia I'd say, and that's a big shaft for your purposes.
I wouldn't consider mounting a vertical slide on the compound. First, it's not going to be rigid enough. Second, you'll lose so much air space you'll never get anything reasonable done. This means that you'll need to put a handwheel on the end of the carriage leadscrew and use the leadscrew to set the depth of cut. The Grizzly machine is a 16 tpi screw so 62.5 thou per rev. Good first project would be to install a cheap DRO.
Gear cutting on a machine like this is going to be quite tricky I think. If the cutter is being driven from the lathe headstock, its cutting axis will be parallel to the cross slide and immovable. The gear blank has to have its outside surface presented to the cutter and traversed vertically to mill the tooth space. I can see some interesting fixturing here. Finding a way of mounting a milling spindle would be needed real quick, I think. Plenty of designs in Home Shop Machinist and the like.
Hmm ... it depends on the kind of gear. A worm gear can be hobbed on a lathe (with some home-made accessories) using a tap which matches the thread of the worm gear.
However, making a normal straight gear would be a *lot* more difficult with a lathe -- though having a lathe to make the blanks would be a big help in addition to having a mill and an index head to cut the teeth.
Note that the tooling which you need with either a mill or a lathe can easily cost as much as the machine before you feel semi-satisfied. So the machine is just the first part of the expenses (though a well-tooled machine can help you to get a start on it.
Do you have precision measuring instruments? (Micrometers -- or for less precision but lower cost, a caliper) are pretty necessary for precision work.
For a lathe, you will need a 3-jaw chuck, a 4-jaw chuck, a drill chuck for the tailstock, a toolpost (ideally a quick-change toolpost), lathe cutters (either HSS and a grinder to shape your own, or a set of carbide insert tooling for heavy-duty work), a faceplate, a steady rest, a follower rest, files (with handles for safety) and various other things.
For a mill, you will need a good milling vise (of appropriate size for your machine), end mill holders, collets, lots of end mills, and again the precision measuring instruments,
If it is a horizontal spindle milling machine, add some arbors in the most common sizes (7/8", 1", and 1-1/4") plus conventional milling cutters -- and for what you want to do, gear tooth mills (a set of eight for a given tooth pitch and pressure angle, to cover the various tooth counts). And -- a good index head with a full set of dividing plates can be quite expensive, unless you are lucky on ebay.
Hmm so you're basically tapping the inside of a flatbottomed woodscrew? i couldn't find the inserts you're talking about on the site you link to, but I can probably get something along the same lines at ace hardware. If worse comes to worse I can just epoxy some washers to either side of a nut and use small bolts in tension to hold the wood in place around it. Either way will also allow me to use a four-post design and set some dowels between each of the posts to make a nice smooth, reletively rigid glide all the way up and down the posts. Thanks for the idea. GCC
A digital one will have more resolution than the dial would (0.0005" vs 0.001"), but you need a *good* digital one to really deliver that resolution as precision -- *and* you need to know the proper feel for using either. A good micrometer will give you greater precision.
However -- the really major benefit of the digital tools is that they allow you to switch back and forth between inch and metric units. (And also, a digital has a trick which allows you to more easily measure the distance between the centers of two equal-sized holes. Measure the ID of one hole, and zero the caliper there (a button press), then shift it to measuring between the most distant sides of the two holes, and your reading will be the distance between centers.
Really -- if you are aiming at precision, my suggestion is to get a set of good micrometers (0.0001" reading vernier, carbide anvils, and a friction thimble or a ratchet spinner) and use those when accuracy matters. (You can learn to use feel to substitute for the friction thimble or the ratchet, but for an inexperienced user either of the above will give better readings until you learn the right way to operate one without.) And -- for certain things, such as thin-walled tubing, you want to do it by feel anyway -- because either of the above two will distort the tubing during the reading.
*And*, when you can find a good metal digital caliper for a reasonable price, pick it up, along with gauge blocks, so you can check the accuracy and adjust for errors if any. Usually, a reasonably good Chinese digital caliper will be pretty good, and will be a lot less expensive (I picked up a nice one for $18.00 at a hamfest), but it will eat batteries compared to a good Mitutoyo. (Granted -- for the price difference between the two, you can pay for a lot of batteries. :-)
Steer clear of the plastic-bodied ones.
And learn the right feel for the digital calipers, too. There, it is the jaws and the fit to the beam which flexes rather than the workpiece, so you need to know how much pressure introduces how much error when measuring near the tips of the jaw vs near the beam.
Hmm well, I daresay that I won't be needing ten-thousandth accuracy for a bit, so I guess I'll grab a set of the steel HF calipers and pick up the micrometers on an as-needed basis, and a dial indicator and base when I get a machine. It seems wrong somehow to wind up looking so hard for a good deal on a machine while simultaneously spending so much on measuring equipment, but I do recognize the wisdom. Too bad wisdom is so seldom as thrilling as folly.
And just so you know-
- you, sir, rock. I haven't laughed so hard in years. GCC
Measuring is the basis of precision. Regardless of your ability, or that of any machine, you will be able to work only as closely as your ability to measure.
Look at it this way: You need to make a snug slip fit for two components. Lets say, for discussion, a pin in a hole. You use a caliper of any description, and rely on the inside and outside jaws for all your measurements.
Calipers are rarely, if ever, in sync., inside versus outside measurements. The level of precision required to get both sets of jaws in perfect alignment and size is difficult to achieve, but worsened by the fact that they're only in sync, even if correct, when the jaws are properly adjusted. The slightest tilt in either direction has an opposite effect on the inside as compared to the outside jaws, so a tenth error suddenly becomes two tenths discrepancy, depending on the length of the jaws. It's not unusual for calipers to vary inside/outside as much as three thou. A snug slip fit is made or broken by only a couple tenths.
You use your calipers to measure one component (a pin, for example), then, using the same instrument, you measure the hole as you machine it for size. If you trusted the calipers, your chance of a proper fit would be almost zero.
Buy the best quality you can afford, and use the proper tool for measuring. You're far better off to use a telescoping gauge and poor micrometer when sizing a job of this nature, even if the micrometer isn't deadly accurate. By using the same instrument under like conditions, you have a far better chance of hitting a size, even if the size is off a thou or two. Parts will still fit within themselves. This concept applies to making your own parts for your own use. Needless to say, if you interact with industry, you must be able to measure within the confines of the standards set forth.
Ah, hmm. Well, I've already raided half.com and ebay to be honest. Thanks for the advice, though- ill probably grab some more once the xmas madness is over. GCC
On 15 Nov 2006 12:40:27 -0800, with neither quill nor qualm, "gcc" quickly quoth:
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is where I got my 1953 copy of Machinery's Handbook for $4 or so. I also picked up a jig and fixture book cheap, which I traded to another gent here for the Tabletop Machining book. Try tha first, then
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then
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then
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. Bargains abound! Also, gov't manuals are available dirt cheap on CD from Ron Thompson, another wreck.metalhead here.
------------------------------------------- Crapsman tools are their own punishment
O.K. For either kind of mill, you will need a good milling vise. Price will be a function of size, with a 6" vise (assuming Kurt brand) costing significantly less than either larger or smaller ones. This is because the 6" size is what the typical Bridgeport vertical mill uses, and you benefit from quantity production. The same applies to hold-down kits.
If you are lucky, you will get a good vise with the mill. I didn't with my Nichols, and wound up using some import clones of the kurt in the 3" size which worked well -- and eventually I stumbled across a genuine Nichols vise made for the machine. Call the range of prices from $150.00 to $800.00 depending on size and quality. (I also got a 4" import clone of a Kurt -- but that was a bit too large for the Nichols mill.
for gear cutting on a horizontal mill, you will need an arbor (1" or perhaps 7/8" size) to fit the mill. If you are lucky, one will come with the machine.
To go with that, you will need a set of gear tooth cutters, eight to a set, for *each* tooth pitch and pressure angle which you want to cut. (You can grind a lathe bit to the right shape and use it in a fly cutter instead -- less cost, but not quite as good, and a lot slower, since it makes one cut per revolution, while the gear tooth cutters will make perhaps eight cuts per revolution.
You will also need a dividing head, to move the gear blank the right angle for the next tooth -- you will be cutting one tooth per position. The dividing head will come with a chart, a set of plates full of circles of holes, and a pair of radial arms which fit over the circles of holes. The chart will tell you the angle to set the arms to, and you will crank an arm with a pin the number of turns specified, plus the number of holes (which will move from touching one arm to touching the other), after which you move the pair of arms so the first is touching again. This makes it easy to repeat the same angle for each subsequent tooth. The dividing head *may* cost more than the mill. (For that matter, the vise may cost more than the mill.) The dividing head should also have a center and a "tailstock" which bolts down to the bed a distance away from the head. The gear blank will be put on a very slightly tapered arbor, and rotated by the head with the help of a "dog" (which also should be part of the index head).
There are ways to improvise a dividing head -- and others have mentioned them -- but a real dividing head is more versatile. However, even that has limits, as one with the standard set of plates will not allow you to produce a 127 tooth gear -- which is on of the pair of gears needed for cutting metric threads on an inch lathe, or inch threads on a metric lathe. But the chart which comes with the dividing head will allow you to cut a large number of common tooth counts.
A book which I would strongly suggest is _Machinery's Handbook_, either a new one (expensive) or an older one. The older one might even be better for a lot of manual machines. I have both a 15th edition and a 25th edition. I think that they are now up to the 27th edition. I got the 25th new, and the 15th used for a much better price. Among many other useful tables, the book has the dividing charts for the common dividing head ratios (20:1, 40:1 (which is what I have), and 60:1).
For slots -- it depends on what kind of slots. If you want to make one which passes through the full length of the workpiece, or which curves up at one end or at both (such as a keyway in a shaft), you will use a conventional milling cutter on the same type of arbor which holds the gear tooth cutters. The conventional milling cutter looks sort of like a small diameter circular saw blade -- but as thick as the needed slot.
For as slot which has both ends within the workpiece, you will probably want to use an endmill (which could be as easily used in a vertical mill) in an endmill holder (or perhaps a collet, but be warned that endmills can slip in a collet, resulting in the cut getting deeper as you go. A good end mill holder will not have this problem.
*If* you get the Nichols mill (e.g. from Gunner), with or without the right-angle head, the endmill holders which you will need will be # 40 NMTB taper. Your best bet here is to get most of them by following eBay and used tool sales. New ones are expensive -- though you may wish to buy one new to get started quickly. For slots, you also will need two-flute endmills (called "slot drills" in the UK because they are better at milling slots than a 4-flute one would be. (For other mills, you will need to determine what the proper holder is.
The hold-down set, which I mentioned above, is a set of T-nuts, studs, clamping bars, step blocks, and nuts to clamp down on the bars to hold down workpieces directly to the table. This is especially good for something too large for the vise -- but also can supply the parts needed to mount the vise to the table.
Obviously, you will also need the previously mentioned measuring tools. And you will probably need a good index of drills, a drill press (though you can use the mill), and a selection of taps for making threaded holes for setscrews to hold the hubs of the gears to the shafts.
I would suggest that you also call MSC and sign up with them. They will send you a hardcover catalog with over 4000 pages of tools and supplies -- so you can use this both as a source for tools which you need quickly (I typically get an order less than 24 hours after I phone it in, but it may take longer depending on where you live related to where the MSC warehouses are), and as a reference to tell you what tools are available new and what they look like. This is an excellent addition to other books which have been suggested. (BTW -- has anyone mentioned the two-volume set _Machine Shop Practice_ by Moultrecht? Those are available (sometimes on sale) from MSC as well as other sources. That two volume set will tell you a *lot* about machine tools and hand tools -- both modern and quite old ones -- and how to use them.
Yeah, thats pretty much what I expected in terms of tooling, except for the cost of the vise, $800 seems more than a bit steep compared to the ones I've been seeing on ebay and such... maybe you get what you pay for? As for the mill though, I'm actually still trying to get in touch with gunner... haven't gotten an email back yet. I guess I'll just wait and hope. And thank all of you for the book suggestions- I wouldn't even have known where to start except for yall. Hopefully the first couple will roll in any time now! GCC
The digital calipers have a resolution of 0.0005", but (as others have indicated) this does to mean that they are *accurate* to that -- just that they will detect a difference that small. To be sure of the accuracy -- pick up a set of gauge blocks (even the cheap Chinese ones are good to 0.000,050") and use them to verify the accuracy near where you are measuring. The main problems with the Chinese ones is that they don't have a good enough finish so they will "wring" together properly. But by the time you need that, you will be interested in a serious set of Starrett Webber or B&S "Jo" blocks, and even on eBay the prices will be noticeably higher. :-)
And the instruments can be use on any future machines as well, unlike things like faceplates and toolholders which may or may not fit another machine.
Thanks! I got that from a button I picked up at a Science Fiction convention back in the 1980s (I think). I never found who originally said it, so I have not been able to attribute the quote properly.
But I actually wore that button to work for a while. :-)
There have been a lot of other good buttons from the same vendor, but this is the one which I picked all those years ago to use as a .sig quote, and have not yet found anything which tempts me to change.
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