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Author Topic: Let's get some conventional gear talk going . . .  (Read 8530 times)
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Archie
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« on: May 24, 2011, 08:57:42 PM »

Hi to the conventio nal gear-cutting folks.

While I am have an interest in the software side of gears, I have some limited experienc e in hobbing (Barber-Colman), form-cutting, and am now getting started in gear shaping (Fellows). I have a special interest in John S's electroni c hobber. I have a current need to make a pair of 25-tooth, 5 DP, 5" PD miter gears for a 99-year old Lucas horizonta l boring mill, plus a custom 30-tooth helical gear to drive the universal milling head on my Kearney-Trecker universal mill. Machine tools are my "thing".

Anyway, I am a retired teacher with a lot of time, so let's discuss gears.

Archie
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Archie
Chuck
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« Reply #1 on: May 25, 2011, 09:11:19 AM »

Archie,

What model Kearney-Trecker do you have?

I rebuilt a 1942 model 2HL with a universal attachmen t and made 2-two gear cluster gears that had been stolen from the main drive.  My machine had been used for parts to keep a second running.  I was able to make or repair everythin g that was missing.

Here is a photo of the mill making it's own gears. This is one of the 2 high speed range spindle drive gears using my one tooth hobbing process.  I had made a single low speed range gear to get it working  while I was in high school.   I posted an updated hobbing program on this forum in "3rd party software".

If you want you may contact me off list at hoelzen@wyoming.com I may be able to be of some help.

Chuck in Wyoming


* TH_compoundspur.JPG (36.08 KB, 605x480 - viewed 735 times.)
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Archie
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« Reply #2 on: May 25, 2011, 09:47:17 AM »

Chuck,

The main thing I could use is more time . . .

I have a 1954 2CH universal and a good set of its accessori es -- universal milling attachmen t, K-model dividing head, 12" powered rotary table, slotter attachmen t, and low-lead attachmen t. At this point, I have all this safe in my climate-controlled shop, but am immersed in restoring the Lucas HBM. All my K&T stuff was bought on a tight budget and had been in storage for decades, so most of it needs a lot of flushing and de-gumming, not to mention some cosmetic work. The only thing that is mint is an Astronomi cal Indexing attachmen t for the K dividing head. As soon as I get caught up, I will start at the bottom of the 2CH and clean out the coolant sump and then work upward from there.

I am missing the drive gear for the universal head. One of my options is to use "one-tooth hobbing". I looked at your posts on your software and will  try it as soon as I get my Mac set up for Windows. Did you cut all the passes for a tooth (or gap between teeth, actually) and then index? I was thinking of going round & round with each set of simulated hob positions . I also will be cutting a helical gear, but I see no real problem with using your approach.

Thanks,

Archie

P.S.: The irony of "a lot of time" in my first post and "could use more time" in this one is not lost on me. I always seem to have more time for talking than getting to work in my shop. I have the time, but not the stamina I used to. I am probably the only one with this problem . . .
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Archie
Chuck
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« Reply #3 on: May 25, 2011, 10:30:34 AM »

Archie,

If the gear you are missing is the one that goes int the #40 spindle taper to drive the universal head I have it but need it for mine.  If I can help with dimension s off the gear let me know.

The one tooth hobbing program I posted is for strait spurs only and makes slicing cuts on each tooth. This requires you index each tooth a bunch of time around the circle.  The photo shows the off center position generatin g the rolling action of the rack tooth.  You do a circle then offset the table and rotate the head by the amount the gear would rotate with the rack movement.

Chuck
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Archie
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« Reply #4 on: May 25, 2011, 05:40:10 PM »

Chuck,

I already acquired and sold off a 32-tooth gear that fits the smaller units. The gear I need has 30 teeth and I have borrowed one, checked that it fits properly, and then carefully measured it, so I am pretty clear on what I need. There is no rush as I have many things to do on the mill before I need the gear. One option is to make a spur gear pair instead of reverse engineeri ng half of a pair of helical gears. In order to use spur gears, they would have to be non-standard -- I think that this would be an interesti ng exercise on the Fellows gear shaper.

Your descripti on of how you indexed is the same as what I was describin g -- I would think it would be easier to index all the way around (a single action) than to reset angle and offset (two actions) for each indexing.

I will have to think about it, but it seems to me that if the same hob can cut spur and helical gears, your method would also work. This would require using a universal mill, dividing head, and lead gears, but I have all of these.

Thanks for your attention,

Archie
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Archie
Chuck
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« Reply #5 on: May 25, 2011, 09:38:55 PM »

Archie,

If you can swing the table over to the helix angle and  have a table driven dividing head you are correct you can use this one tooth hobbing to make helical gears on a universal mill.  My 2HL is can't do helicals. But my Mach3 retrofitt ed CNC Bridgepor t BOSS can with Art's GM program spitting out Gcode.

I agree you may be ahead making a matched pair of gears in stead of making a helical to mate with the one in the head.

Chuck
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Archie
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« Reply #6 on: May 26, 2011, 06:40:07 AM »

Chuck,

It will be a while before I actually get around to cutting the gear, but I enjoy working out the different approache s -- probably more than the actual cutting. As the saying goes: "Life is a journey, not a destinati on."

Now, from general philosoph y to gear philosoph y: An extension (done by others, not me) to your one tooth hobbing is to make a rack-shaped cutter referred to as a "pseudo-hob". The cutting teeth are rack shaped, but there is no helix. Cutting time is reduced because more than one tooth is cutting per turn of the arbor. The cutting is spread out over several teeth on the gear blank and if the gashes in the cutter are timed so that they are spaced around the arbor, the different cuts are spaced out over the rotation of the arbor. The pseudo-hob can be made up of a stack of disc-shaped cutters and these can be made on an ordinary lathe if they have only a few cutting edges. I am posting a few graphics showing how to make simple form-relieved cutters without using a relieving attachmen t.

Archie

P.S.: These are not my graphics, but I believe originate d from John Stevenson . (Now, that is a familiar name.)


* Eccentric Mandrel.jpg (18.47 KB, 429x207 - viewed 680 times.)

* Cutter after eccentric turning.jpg (21.35 KB, 329x332 - viewed 613 times.)
« Last Edit: May 26, 2011, 06:44:55 AM by Archie » Logged

Archie
John S
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« Reply #7 on: May 26, 2011, 04:36:48 PM »

Can't be mine they are readable  Tongue

However you may be intereste d in this post.

http://bbs.homeshopmachinist.net/showthread.php?t=41591

Nothing unique but just more ways to skin a cat and started pre Gearotic hence the use of the 'other' program.

John S.
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John S.
Nottingha m, England
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