This question will be a bit hard to answer. With a smallish lathe (600 mm centre)and a small drill mill which module cutter set would be the best to to cut the sort of general purpose gears? not tiny ones for model making. one instance would be a gearbox to turn a pig on a spit. maybe the gears on the end of a sheet metal roller or a swage & jenny machine,or replacement thread turning gears for a lathe. Module 1 or 1.5 or 2 etc?
I cut only those gears I can't buy:
Roasting speeds are generally attained by using a worm gear reduction.
And as long as you're not delivering any serious torque, they're a lot easier to make.on home-shop machine tools.
I've never made one that big, but I did make a couple of small sets for my fishing-rod rotisseries, for distributing epoxy around guide wraps. I cut the gears with ordinary thread taps in my SB 10L lathe,, and the worm is just a threaded shaft.
Don't you still have to cut a gear? and the worm on a lathe?
How would you work out the module of the set for a change gear in your hand if you do not have the cutter?
A good worm gear is somewhat concave in the middle -- exactly what you get when you cut it with a tap mounted in the spindle, with the gear blank freewheeling on some kind of fixture. I have used a lathe, with the tap in a collet (or maybe in my 4-jaw; it was a long time ago, and I forget), and the gear blank turning free on a simple spindle held in my milling attachment. There are other ways to rig it if you don't have a milling attachment.
The worm is a simple thread-cutting job in the lathe. The set will match quite well but it's not something you'd want to use for a real high-torque job.
Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:
You could buy a Whitworth or Acme tap, and do a more robust job, still without "special" tooling.
LLoyd
F Murtz fired this volley in news:yp4hr.5616$% snipped-for-privacy@viwinnwfe01.internal.bigpond.com:
yep.
"Stock" gears are pretty cheap compared to the tooling and time you have to spend.
The last set of gears I made was in the mid 1980's, because they had to be fabric/phenolic, and I couldn't find a set anywhere made of them.
It's a lot more efficient in time AND cost to adjust your design (if you can) to fit off-the-shelf gears and worms.
LLoyd
It's all in here:
Determining the pressure angle is harder. 20 degrees is a common standard for power transmission, the older 14.5 degree PA has hung on for some lathe change gears. I use the drawings in catalogs to identify it.
jsw
In fact, my last one was made with a long-shank 1/2" Acme tap, which is better and probably stronger, but I didn't want to make it sound complicated. You can do a credible job for a low-torque application, like a rotisserie (unless you're roasting whole pigs) with a regular tap.
I made one that way around 30 years ago that still drives my fishing-rod rotisserie. The one I made with the Acme tap was supposed to replace it, but the original worked fine so I gave the newer set to another rod-builder friend.
I made a spit to turn a whole lamb. I used mild steel rod and turn it using a 12V worm-geared window winder motor further geared down using ANSI 35 chain, weld-on sprockets and hubs to fit the shafts. Works great and runs for hours on a 12V utility battery.
____________________________________________________________________ Gardner Buchanan gbuchana(a)teksavvy(dot)com FreeBSD: Where you want to go. Today.
Is that "center height", or "between centers"? It makes a big difference in the size of the lathe. :-)
Well ... I'm not really familiar with the module gears, but in Imperial ones, for the first task (the pig on a spit) I would probably of with something like 32 DP (Diametrical Pitch). (I've made such gears for repairing a piece of electronic test equipment.)
For the lathe threading gears, it really depends on the size of the lathe. Presumably, since you say "replacement gears", you should duplicate what the manufacturer used originally -- so the new ones would mesh with the old ones. FWIW, My Clausing (12" swing or 6" center height) (that would be about 300 mm swing, or 150 mm center height) is not small by hobby standards, though certainly so by industrial standards, and it uses 20 DP (Diametrical Pitch).
By consulting a book like _Machinery's Handbook_, you can convert one system into an approximate size for at tooth thickness (not width) at the pitch diameter, convert that into the other system, and find what is the closest standard size in the new system.
At present, I have no real motivation to make metric (module) gears, because the gear cutter sets are much harder to find (at least here in the USA) than those for the imperial gears -- and nothing which I have needed to repair has yet needed Module gears.
FWIW -- I have a full set of the 20 DP cutters (for my lathe's gears), and only one of the 32 DP ones, as I only needed to make one size of gear.
Good Luck, DoN.
HEY NOW! That might be a relative!
the lathe is 600 mm between centres 320 mm swing (160 mm high)38 mm spindle bore. My question was not so much that I need any of the things that I mentioned, just an indication of the size that I may want in the future, I was just thinking of getting a set of cutters so that if I got a bee in my bonnet in the middle of the night I could set to making something and I was just trying to get an idea of which set of cutters would be the most useful to have on hand.If I had a special job which would require matching I would probably have to get cutters specially. If you were making the whole set of gears you are not restricted to matching
Law's book shows how to make a gear cutting bit yourself. I think you could grind an HSS bit to fit an unhardened version of his form tool. I've fitted a gear cutting bit to the tooth form by eye:
jsw
I have not got a dividing head but I do have a small rotary table.
With no indexing wheel.
More likely, 'The black sheep of the family'. ;-)
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O.K. Then for that size, (a bit over 6" swing), I would probably go somewhere closer to the 32 DP (again in Imperial than the 20 DP. Perhaps 24 or 28 DP (I should to look it up to make sure that those are standard sizes, but they could be, and would be pretty good choices for that size lathe. :-)
If my guesses about the size ratios is right, 32 DP would be about module 0.80 , and 24 DP would be around module 1.0. So I would say that your module 1.0 would probably be a good choice for most things in your size range.
O.K. Do you have an index head for dividing the gear? Three dividing plates and a 40:1 ratio are what I am familiar with. It *can* be done with a rotary table, but without dividing plates and sector arms, it is rather error prone.
Understood. When you mentioned change gears for a lathe, I was thinking in terms of replacing a few missing ones.
FWIW While I got a full set of 20 DP gear cutters to match my lathe, the first gear that I actually *cut* required ordering a separate cutter -- different DP, and different pressure angle (PA) as well. :-)
Good Luck, DoN.
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