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View Full Version : suggestions on way to cut gear teeth on the cheap?



andy_b
02-16-2005, 10:21 AM
i've read many of the posts lately dealing with cutting gears (especially for threading dials). well i need a threading dial for my lathe (an old SB 11") and i guess i need to figure out how to build one. my problem is cutting the gear for the dial. i don't have a dividing head or a rotary table of any taps of the correct size. i've read where a few of you have used a tap in the lathe to cut the teeth on a brass gear and i'm thinking this may be the easiest method. the downside is that an ACME thread tap of the correct size is about $100. anyone have any other suggestions? i'm really interested in cutting some threads on a few things, but without the dial indicator i don't see much chance of a newbie such as myself getting it right.

andy b.

JCHannum
02-16-2005, 10:28 AM
Threading without a thread dial is possible, and commonly done. You do not release the half nuts, but stop the spindle, withdrae the tool and reverse the spindle to return the carriage to the starting point.

I am sure you know that. It is cumbersome, but if you will suffer through it long enough to manufacture one Acme thread of the appropriate size in drill rod or mild steel that can be case hardened, you can make a hob to make the gear with.

G.A. Ewen
02-16-2005, 10:39 AM
Andy,
The first thing to do is make yourself a simple index. It doesn't have to be anything fancy to work well. Two pillow block bearings bolted to a piece of flat bar will work in a pinch. A 24 tooth gear or even roller chain sprocket can be used to do the indexing. Turning down the shaft that fits into the pillow blocks to the diameter of the gear blank bore is all you need to mount the gear blank with set screws.

This may help to see what I mean...........

http://img.photobucket.com/albums/0603/GAEWEN/4c313f0a.jpg

http://img.photobucket.com/albums/0603/GAEWEN/eefeeca1.jpg

Mike Burdick
02-16-2005, 11:13 AM
Andy,

Regarding the last part of your question. Like J.C. said, you don’t need a thread dial to cut threads, in fact if you’re threading something less than two inches and it’s not a very, very fine thread – leaving the halfnuts engaged and reversing the motor is probably faster. Remember the thread dial is ONLY AN AID to help speed up the thread cutting process and is not in any way “essential” for properly cut threads! I’ll bet that most of your threading is done within that range.

Regarding the thread dial. If you want, I have a set of prints that I can email you. All you would have to do is change the dimensions and perhaps the mount to fit your lathe. It could be a handy “go-by” for you.

http://img.photobucket.com/albums/v157/MikeBur****/thread_2.jpg
____________________________________

precisionworks
02-16-2005, 12:07 PM
G.A. - nicely done! It's so simple to do the way you did that I'm going to make one.

Mike - stunning work. Looks like an industrial museum piece.



------------------
Barry Milton

andy_b
02-16-2005, 01:24 PM
thanks for the excellent ideas!!!
i was thinking of leaving the halfnuts engaged and shutting off the lathe as some suggested, but i thought for cutting normal right-hand threads you thread with the carriage moving TOWARDS the headstock? my spindle does not stop instantaneously when i turn the power off and if i have a shoulder on the piece i am threading, i'm worried that the cutting tool will smash into it.

i have to build G. A.'s index. that is a GREAT idea!

andy b.

Charlie Rose
02-16-2005, 06:54 PM
Turn the tool over run the machine in reverse. If the thread is a multiple of your lead screw you don't need a thread dial just engage the half nuts when ever they will.Try it you'll see how it works.

torker
02-16-2005, 07:00 PM
Andy...when you have the half nuts engaged and the tool cutting it stops the carriage immediately...or just hit reverse! I prefer not to slam it into reverse but have done it by mistake a few times and nothing seemed to go wrong. I thread with the back gears anyway so it's going pretty slow. Just watch when reversing that you back the tool out enough in case you have slack..the tool will try to cut on the way out. I pull mine back(keep pressure on it) and pull back on the carriage when starting to cut. Seems to cut cleaner that way.
Russ

wierdscience
02-16-2005, 09:12 PM
Assuming your leadscrew has a keyway as most do,close the halfnut,roll the chuck until the keyway is in sight,mark the carrage position on the ways with chaulk or marks-a-lot,start the cut,finish and return the carrage to the mark,when you see the keyway come around to the same spot close the halfnut and make the next pass.Works on leadscrews without keys too,just mark the screw with a strip of tape.

PolskiFran
02-16-2005, 11:27 PM
A friend of mine made an improvised thread dial by using an even number tooth gear that would somewhat mesh with the lead screw and made the dial with only one mark on it. I believed it worked for him. I never heard him complain.

Frank

Thrud
02-17-2005, 02:28 AM
Mike & George
Outstanding!

George do you have drawings for that spin indexer - I are drooling man!

G.A. Ewen
02-17-2005, 08:20 AM
Thrud,
The main part of my indexer is a piece of surplus junk from Princess Auto. It had two sealed bearings aqnd a 5/8" shaft in it. I was checking out the store in Barrie Ontario just after it opened and found it there. The spindle is a piece of 660 bronze that I turned to to fit where the bearings were. It takes R8 collets.

Sorry ,no plans. When I picked it up in the store my wife asked me what it was and I said "well whats it look like, it's a spin index of coarse" http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

shaque
02-17-2005, 08:41 AM
C'mon George, give us some plans for that. That is cool and I see uses for it on my Cinci #2 T&C grinder. The one that came with the machine has seen hard use, and I mean hard use...
Thanks
Jim
PS. For any of you guys that don't know Grorge, he is one smart cookie when it comes to making things out of stuff anyone would say is crap. If I'm not mistaking that is the "engine mill" that he built out of a car engine (le car) that the indexer is sitting on,I have seen it first hand...AWESOME!!!

[This message has been edited by shaque (edited 02-17-2005).]

[This message has been edited by shaque (edited 02-17-2005).]

John Stevenson
02-17-2005, 09:30 AM
Would there be any demand for running some wheels off to suit SB's on my hobber?

John S.