Author Topic: Gear Cutting Help  (Read 8362 times)

Offline 75Plus

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Gear Cutting Help
« on: July 12, 2011, 05:48:40 PM »
I am in the process of restoring an old Rockwell/Delta drill press. I estimate that it was made in the late 50's or early 60's. The spindle shows signs of being mistreated and I would like to make a new one. Spares are unavailable.

The part is 14" long and 5/8",(.625") There are two grooves, 5 3/4" long. 180 degrees apart, that appear to have been cut with a gear cutter designed for a 14.5 degree pressure angle. Each groove is approx. .152" deep. As I know nothing about gear cutting I am asking the EXPERTS ( I know there must be some here) for help.

How do I do it at the least cost?

This is what it looks like except the Jacobs #33 taper is not shown.

Offline Bernd

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Re: Gear Cutting Help
« Reply #1 on: July 12, 2011, 06:44:30 PM »
Your in luck 75Plus because my neighbor has one like that and I'm in the process of repairing the same spindle for him.

I'm going to get a piece of cold rolled and mill two slots just using a small 4 fluted or 2 fluted end mill. I saw no reason for the shape of the slot in the original.

In the original it looks like the spindle moved in a piec of cast metal. The two teath, if that' what you want to call them, were worn to the point of almost being square.
By chance have you tried taking the top pulley's off? We couldn't figure out how that upper part is keep in. Almost looks like it could be a press fit.

Bernd
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Offline dsquire

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Re: Gear Cutting Help
« Reply #2 on: July 12, 2011, 07:01:29 PM »
Bernd

I am not sure exactly what you mean but I had one that had a left hand thread involved. Just something else to check.  :D :D

Cheers  :beer:

Don

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Offline 75Plus

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Re: Gear Cutting Help
« Reply #3 on: July 12, 2011, 07:47:29 PM »
Bernd,

The drive sleeve on my machine is still in good shape. The teeth still have the original profile so I need to try to cut the grooves that way also.

The top pulley is held on by a 3/8 24 cap screw tucked under the pulley in front. Removing the screw allows you to pull the pulley and bearing as a unit. Then there is three screws holding a plate that covers the bearing and holds the drive sleeve in. The bearing has an extended inner race that slips into the housing. That bearing is no longer available

As for the one you are working on this may answer your questions.

http://vintagemachinery.org/pubs/detail.aspx?id=903

This one may be a later model but all the parts still look the same.

Joe

Offline Lew_Merrick_PE

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Re: Gear Cutting Help
« Reply #4 on: July 13, 2011, 11:04:27 AM »
Joe,

If the slot looks like a 14.5 groove, it probably is.  If you grind a (square or rectangular) lathe bit to a well symmetrical 14.5 taper (using an Acme thread gage), the "issue" becomes making it the proper width for the "bottom" of the groove.  Add a couple of thou to the width at the (engagement end) of the mating part.  Give yourself plenty (probably 10-15) side clearance and appropriate end clearance.  Stone it up nice and sharp.  Mount up the form ground lathe bit in a 90 boring bar (or homemade equivalent) and cut the groove very carefully.  Use lots of cutting oil.  Keep the feed as light as you can and still get a good chip.  Watch everything carefully.

Does that help?

Offline 75Plus

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Re: Gear Cutting Help
« Reply #5 on: July 13, 2011, 11:12:42 AM »
Lew, The groove is actually 29 degrees. 14.5 PA. I was wondering if single point cutting would work in this situation. BTW, the bottom flat measures approx. .085" and the top is approx .163". That is about as close as I can measure.

Joe

Offline Bernd

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Re: Gear Cutting Help
« Reply #6 on: July 13, 2011, 06:56:42 PM »
Don't want to steel Joe's thunder here so thanks Joe and Don for the info.

Going to take a close look at that drill press of his.

Bernd
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Offline Lew_Merrick_PE

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Re: Gear Cutting Help
« Reply #7 on: July 14, 2011, 12:33:12 PM »
Lew, The groove is actually 29 degrees. 14.5 PA. I was wondering if single point cutting would work in this situation. BTW, the bottom flat measures approx. .085" and the top is approx .163". That is about as close as I can measure.

Joe,  Engineers such as myself often think in terms of the half-angle of a symmetrical form.  An Acme thread has a 29 included angle (14.5 half-angle).  If you have access to an Acme thread gage, one end of the gage has a 29 included angle female opening used to compare the sides of an Acme threading tool.  The "trick" is that you will need to split that angle on your toolbit such that it lines up with the centerline of your bit accurately.  (A miter gage on your grinder will help here.)  You mount this in a tool holder (boring bars are the most common ones) that will support the bit perpendicular to your spindle's axis of rotation.

This is very like unto single-point cutting of gear teeth.  There are several video examples here in this forum and others on YouTube.  Light cuts and slow feeds are the order of the day.  It is not as solid or effective as a true (expensive) form cutter, but it does work.  The mating "teeth" will want to be a (fairly) close slip fit.  That is a matter of "touch" in getting things right (assuming you do not have access to form dimensions).

Rob.Wilson

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Re: Gear Cutting Help
« Reply #8 on: July 14, 2011, 06:23:20 PM »
Hi Joe

There is a bit on grinding the cutter shape you require here , scroll down a bit ,,,, http://madmodder.net/index.php?topic=2624.100 ,,,,,,,may help


Rob

Offline 75Plus

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Re: Gear Cutting Help
« Reply #9 on: July 14, 2011, 08:13:30 PM »
Thanks everyone for the suggestions. Once it became apparent that I would have to single point this project I dug up a grinding fixture that I made a couple of years ago for grinding tools for 60 degree threads. Once I added 14.5 degree lines it worked a treat. As seen in the picture it also has provision for grinding the relief needed.

Offline Pappy Frank

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Re: Gear Cutting Help
« Reply #10 on: July 17, 2011, 01:46:51 AM »
Hi 75Plus,

Single point that if you must, but before you get to far along check out this link. It explains how to make envololute Gear cutters, which is what you really need. It is easy and inexpensive.

www.metalwebnews.com/howto/gear/gear1.html

Lots of luck

Pappy Frank

Offline Pete.

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Re: Gear Cutting Help
« Reply #11 on: August 18, 2011, 04:12:15 AM »
I followed that and mine came out spot on.