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worm gear cutting success

I've read about cutting worm gears with a high spiral tap in the
lathe. I needed one so I though it was time to try it. I just used a 1
inch diameter disc for the blank and a 3/8-16 tap. The disc was
mounted to a 1/2 in square steel tool shank and rotated on a 5/16"
dia. axle. I just centered the disc by eye and fed it into the tap. It
worked perfectly. Since I didn't need an exact reduction the tooth
count didn't matter. It worked so well I tried using a 1/2-10 acme tap
with straight flutes. No dice. But the 3/8-16 high spiral tap cut
great gear teeth. Next I'll try a 1/4-20 tap. An acme tooth form would
be much better so I may try threading a hob out of drill rod.
ERS
Reply to
Eric R Snow
Loading thread data ...
Post a pic if you think about it, I'm having a hard time visualizing.
Reply to
Tom Gardner
You can use one of your ANS thread worm gears to drive the blank to cut the acme. Just match the ratio. Ain't it amazing how fast they cut?
Reply to
Ron Thompson
Me too, Tom. I don't make the connection between the tap and the gear tooth profile.
BobSwinney
Reply to
Robert Swinney
Me too,..but a Google for "worm gear cutting spiral tap" shows a few links on how it's done
Reply to
bart
Great work! I've been thinking about trying this too.
A link to photos was posted here a few months ago by someone else:
formatting link
And here's the thread:
formatting link
Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"I'm not grown up enough to be so old!"
Reply to
Keith Marshall
From what I have read about this method I think the main problem is in getting the circumference of the blank to divide correctly into the number of teeth so that once the blank goes around it will start in the same tooth spaces. It seems that the spacing is only correct at the pitch circle so the blank is a little too far around when starting. Feeding at full depth from the side of the blank is supposed to make it easier but sometimes it syncs right and sometimes it doesn't. Coarse gashing of the teeth supposedly can make it work reliably but then it isn't near as simple.
For the acme thread it might help if you can first cut a shallow V thread for the acme tap to follow.
Don Young
Reply to
Don Young
I'll try to post a picture later today. Thanks Keith for the "great work!" compiment but it was really too easy to get exited about. ERS
Reply to
Eric R Snow
Several amateur telescope makers have done the exact same process but made a special tap for it instead of using a regular tap. The process is to first make a threaded rod (large diameter with relatively fine threads) and then split the rod into two, one to be used as the tap and one as the worm. The tap piece then gets cut for the cutters on the face and is then fed into the wormwheel piece. For the older line frequency drives, the number of teeth was usually 359 theeth (an odd number that actually is pretty close to the needed rate for the differeence between the sidereal rate and the normal clock time) and when you measured everything right, you got that number of teeth on the wormwheel. Often, the wormwheel is roughed out with a hacksaw so that the number of teeth is done and the majority of the material is already removed so you don't end up with having to cut the whole tooth at one stroke. Doing a worm and wheel this way usually ends up with a fairly low tracking rate error (theroetical rate vs. what happens), usually on the 1 arcsecond or less error.
-- Why do penguins walk so far to get to their nesting grounds?
Reply to
Bob May
Tom-I've been looking all over for the cable that goes from my camera to the computer. As soo as I find it I'll post pics to the dropbox. ERS
Reply to
Eric R Snow
work!" compiment but it was really too easy to get exited about. >
Reply to
Keith Marshall
Eric, It's right *there*, to the left of the phone on the top of the desk - geeeezzzzz- I gotta find *everything* for you.... Ken.
Reply to
Ken Sterling
According to Eric R Snow :
Assuming a standard digital camera with removable media, you can generally get faster transfers from a USB interfaced card reader (most will fit several types of cards), or (in my case) I put the CF cards in a PCMCIA adaptor and shove that into the PCMCIA slot in the computer, because I don't run a computer with USB for my normal operations.
I've never actually *used* the USB cords which came with my various digital cameras. :-)
And these card readers seem to be priced between $6.00 and $18.00, depending on sales at the time you get it. At that price, get a spare, and keep it where you can find it again. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
My current camera uses compact flash..and Ive picked up 3 readers at second hand stores , all totalling less than $5 for the 3. Each are USB..so I can keep one at home, one at my work RV and one in the laptop case.
Pretty slick and most will do various other formats, one at home does PCMCIA, compact flash, smart card, mem stick and something else I dont recognize
Gunner
"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."
"Democrat. In the dictionary it's right after demobilize and right before demode` (out of fashion). -Buddy Jordan 2001
Reply to
Gunner
I emailed you a simple spreadsheet to figure the numbers. It lacks the shoulder diameter as this depends on your worm diameter. IIRC, you add about 1/3 of the diameter of your worm to the radius of your blank and then turn the trough to the number on the spreadsheet.
Reply to
Ron Thompson
Greetings Keith, Since I didn't need an exact number, just a reduction in a certain range, I started with 1 inch diameter and fed in until the teeth started to come out even. ERS
Reply to
Eric R Snow
"Ron Thompson" wrote in message
I got it and it should help a ton, thanks!!
Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"I'm not grown up enough to be so old!"
Reply to
Keith Marshall
I thought it might work like that but it seems it would end up a mangled mess where the two meet. I'll have to give it a try this weekend. I always want to try out Ron's spreadsheet which should make it come out right the first time... if I do it right. :-)
It just so happens I need to do this soon anyway. I just built a simple radius cutter for my lathe and it works OK but would give a nicer finish if I put a crank and worm gear on it so I could feed it more slowly and smoothly.
Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"I'm not grown up enough to be so old!"
Reply to
Keith Marshall
Greetings Tom, Everyone else too. I just uploaded the pics and a text file to the dropbox at
formatting link
. The files are below: Worm gear cutting.txt Worm gear blanks. Worm gear fixture 1 Worm gear fixture 2 Worm gear blank on fixture Worm gear setup Worm gear cutting 1 Worm gear cutting 2 Worm gear cutting 8mm Worm gear finished There is only one text file and all the others are jpg files. I included the gear cut with the 8mm x 1.25 tap so I wouldn't leave out the rest of the world. I chose the 8mm x 1.25 tap because I had a high spiral one in that size. Cheers, Eric
Reply to
Eric R Snow
Thanks for those, Eric. It's a helluva lot of fun, isn't it! Seeing the thread (rack?) form *automatically* on the blank is a real hoot. I'm interested that you didn't pre-turn the "hole", that is, the groove for the tap to run into. Any particular reason for that?
Cheers -- Jeff R.
Reply to
Jeff R.

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