# CNC gear help.



## mrich0908 (Aug 28, 2014)

I dont post much here but read allot. 
I was wondering if some one can point me in the correct direct. 
I  purchased a used Wohlhaupter Upa2. It was in need of some tlc. 
The boring and facing head was missing its  gear rack and pinion that matched to the worm.It doesn't look like a normal pinion rack either .  was wondering if any of you knows the procedure to machine out the missing parts and how to determine the proper pitch to the existing worm attached are a break down list and picture. The part I need is #3 in the picture its in the top left.










The Last Picture is NOT MINE I came by the picture off the internet.


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## mrich0908 (Aug 28, 2014)

Well so far this what Ive come up with using what I have . Maybe this will help some one. 
The DP is 44 and the TPI is 13.94283 using these forumlas .
I have to figure out cuter tip width next.


If you know the number of teeth and the OD of the gear just use this formula: Number of teeth +2 / OD = DP 
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BlanK OD = T+2/Diamtetral Pitch
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Depth of tooth =
2.157 / D.P.
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Circular Pitch = (pi x Diametral Pitch)/number of teeth in the gear


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## mrich0908 (Aug 28, 2014)

Any one know the answer to radius x N = length? (2???)
Its gettign late here . Ive been starign at this screen allday trying to figure this out.


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## DMS (Aug 28, 2014)

The image is pretty small, but the part you are describing looks more like the section of an internal thread than a rack. If you have the mating screw, you could try cutting an internal thread to match, and than milling off the top bit.


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## mrich0908 (Aug 29, 2014)

I have all the the sections besides. .. The part in question.Its mate is a worm . The wom is in the colored photo top left second gear to the right..
 As described in the break (im in need of #3) down they say its a rack but I agree with you it does look like a thread . 
At that Ive seen (on the net) people make work gears and there mates using threaded rods and or taps . Ive seen much lager rack and worm gears also while searching...So ... I dunno
My plan was to cut an ark for the worm,  thread mill a plate of 6061 or brass or bronze unsure still


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## mrich0908 (Aug 29, 2014)

HEAD Slap , Face in palm
The boring head is German . Im starting to think its MODULE.....


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## DMS (Aug 30, 2014)

I would not recommend 6061 for a bearing surface (unless it is just a test) it's too sticky. You want brass, bronze, or cast iron. Thread milling seems a bit tricky for that part, mainly because the aspect ratio is so large. I guess since it is open, you will have more clearance.

As far as calculating the module, you don't really care, since it is straight (not curved), you just need the TPI (or thread pitch, yeah, it's probably metric) of the worm, and just cut the opposite to match. The form is going to be simple, just like a thread, though you should verify the angle of the worm (it's probably not 60 degrees included like the threads on a fastener, more like 40).


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## mrich0908 (Aug 30, 2014)

Thanks DMS, 
I do belive the \worm is a 40 degree angle.
That makes sence not using 6061 I have some cast here I could use. I think I have brass also . I think the original was made from cast. 
So far Ive ended up making a fly cutter with tooth profile to match I working on writing the program to fly cut the rack now. Very tediuos. 
I have solidcam and was going to use that but making the the cad would be worse for me that writing the gcode out. 
I undestand how to make a spur gear but I just cant wrap my mind around making a worm gear.


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## DMS (Aug 30, 2014)

When you say worm gear, what do you mean? Usually a there are two parts, the "worm" which is the screw like part, and the "worm-wheel". Which is what I think you are talking about. One technique that I have used is based on hobbing, but involves a custom cutter. If you have a CNC system, and a 4th axis, you could probably code it and cut with a small ball mill of tapered mill, though.. the I am honestly not sure where I would start


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## mrich0908 (Aug 31, 2014)

DMS said:


> When you say worm gear, what do you mean? Usually a there are two parts, the "worm" which is the screw like part, and the "worm-wheel". Which is what I think you are talking about. One technique that I have used is based on hobbing, but involves a custom cutter. If you have a CNC system, and a 4th axis, you could probably code it and cut with a small ball mill of tapered mill, though.. the I am honestly not sure where I would start



I know there are ussaully two parts but this worms mate isnt a wheel. I have the worm , the round screw part. 
  The flat threaded peice looks like a pinion rack is its mate. BUT. 
As defined  in Ivan Laws book about gear . Picture the rack as the worm wheel but laid out into a rack . The D.P. when divided into pie is infinit. The idea is to take a piece of infinity and and use it as a mate.
I know its weird and unheard of but the worms mate is a gear that flat. 
Im running code right now I wrote I ground a HSS rod ground to the tool tip .We will see how that goes
After all this I want to make a solid model since I have it apart and see if I could make one exactly 2x as big but with a TTS style shank.
Thatll be a fun project


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## DMS (Aug 31, 2014)

Keep in mind the path you will be cutting is helical. That will effect the geometry if you attempt to use a form cutter in a boring head/fly cutter, or similar setup, unless you are planning on using a rigid tap cycle to co-ordinate Z axis and spindle motion (similar to what you would do when threading on a lathe). If you are doing that, the form cutter would match the worm profile exactly, just make sure you have enough relief on the tool.


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## mrich0908 (Sep 1, 2014)

DMS said:


> Keep in mind the path you will be cutting is helical. That will effect the geometry if you attempt to use a form cutter in a boring head/fly cutter, or similar setup, unless you are planning on using a rigid tap cycle to co-ordinate Z axis and spindle motion (similar to what you would do when threading on a lathe). If you are doing that, the form cutter would match the worm profile exactly, just make sure you have enough relief on the tool.




Y a I was running code till late last night and stopped. I wrote a simple program that just grooved back and forth. After I did ruffly five teeth I stopped . 
There was no helical twist. The teeth meshed , line up properly but just didnt look right. Im not into hacking stuff together I would like to do this right no mater how long it takes.
 I need to study more. 
My machine doesn't have rigid tapping feature. 
That why I wanted to try thread milling the piece.


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