Hardinge pinion gear repair

mellejonker · Oct 23, 2016

Hello,
I am having my HLV-H apron apart to replace some bearing and solve the problem of a "slipping" handwheel. As can be seen on the picture my poinion gear has been replaced by a spare part gear that was press fitted inside and locked with a through hole pin. When I just bought the lathe the press fit was totaly worn out and I decided to make a bush to restore the press fit, I did not however replaced the pin, cos I thought the press fit would be strong enough on its own.

I was wrong

and it starts to slip there, so i took it apart to add some loctite, and also to replace the bearings that hold the pinion gear because they showe play.
Now i also had a change to take a closer look at the 'repair gear' that runs into the rack. It does not look too good anymore unfortunately.

That brings me to the question, can anybody point me to a gear cutter with the correct shape to cut this gear? I learned from old threads it is a specific (old fashioned) shape but when I can buy a matching cutter I would like to give it a try and cut my own.

My lathe is metric, the gear has 14 teeth.

Thanks for suggestion,
Melle (in Holland, even my profile says Afghanistan, i never been there, cant change it though)

Billtodd · Oct 23, 2016

The gears are a 22/19 dp stub form apparently, but what that actually means is best asked of a gear cutting specialist. I had wondered if the 14t would had an undercut but, looking at the one i have in the boot of my car, it hasn't so could be cut with a gear cutter in a mill.

However, it might be easier to contact ZMT and see if they have any of the repair gears in stock ; it'll save you making a cutter (i doubt you'll buy one anywhere).

bill

P.s. I always thought the mountainous regions of holland resembled Afghanistan ;-)

Zahnrad Kopf · Oct 23, 2016

Billtodd said:
The gears are a 22/19 dp stub form apparently, but what that actually means is best asked of a gear cutting specialist.

Errr... Not quite. They are 22/29 Fellows Stub Pitch. Last ones we made were a few months back for member rke[pler here.

Peter from Holland · Oct 23, 2016

You don`t need to keep the same profiel if you make both gears new
Only centre to centre distance and ratio is important
So probably any 22/29 DP will work
And with a hobbing machine you could perhaps even use a modul pitch

Peter

mellejonker · Oct 23, 2016

Hi,
The gear is meshing with a rack so i have to use the correct shape or also exchange the rack. I was hoping that it was as simple as finding a DP22 20PA gear cutter for the correct number of teeth. But those gear cutters are not easily available it seems. Thanks Zahnrad (sounds german) for the shape and nice pic, looks like original Hardinge gears! I think for you would be easy to copy the complete part in stead of press fitting in a replacement gear.

As Bill suggested I have contacted ZMT in the meanwhile. Within 2 weeks they can supply the 14T gear, they have some on the way. Perhaps thats the most easy solution, but it would be fun to cut my own on the mill.

Maybe some one still knows a source for a cutter. Thanks all for the reactions.
Melle

mellejonker · Nov 9, 2016

I found a 22DP PA20 gear cutting hob at a chinese shop and order it since it was cheap. If i run a change gear over it by hand it seems to mesh correctly.

I found an arbor to use it on my Aciera F3, now i just need to drive the dividing head with the correct ratio speed. Will have to think abou that one

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mellejonker · Nov 9, 2016

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mellejonker · Nov 9, 2016

Verstuurd vanaf mijn Nexus 5X met Tapatalk

mellejonker · Nov 9, 2016

mellejonker · Nov 9, 2016

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SteveBausch · Nov 9, 2016

Not to minimize the skills of those who have forgotten more about gear cutting than I will learn, but when the gear is hand-powered (and perhaps made of urethane, or acetal/nylon), the resulting gear should tolerate a modest interference, and the happy outcome could be zero backlash.

Peter from Holland · Nov 9, 2016

mellejonker said:
I found a 22DP PA20 gear cutting hob at a chinese shop and order it since it was cheap. If i run a change gear over it by hand it seems to mesh correctly.

I found an arbor to use it on my Aciera F3, now i just need to drive the dividing head with the correct ratio speed. Will have to think abou that one

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Mecanicly very difficult
Electronicly is your best shot
Or find someone with a hobbing machine

Peter

mellejonker · Nov 10, 2016

Yes I tink electronicly is the way of doing it. I will try with a servo motor. Its more for fun and to learn how hobbing works then that I realy need it Peter, finding someone with a hobbing machine would break that fun. Though would be intresting to see a hobbing machine at work in reality in stead on youtube.
I will update the thread if I have some progress.
Regards,
Melle from Holland

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gjrepesh · Nov 11, 2016

Will you post information on where you bought this hob? Thanks. Gary R.

Zahnrad Kopf · Nov 11, 2016

mellejonker said:
I found a 22DP PA20 gear cutting hob at a chinese shop and order it since it was cheap. If i run a change gear over it by hand it seems to mesh correctly.

I found an arbor to use it on my Aciera F3, now i just need to drive the dividing head with the correct ratio speed. Will have to think abou that one

Just do not expect much from that thing. They are more oft than not very poorly hardened, and the grinding leaves a bit to be desired. They are also very frequently powdered metal, and not of much quality to boot. Lastly, the chinese themselves rated it for classification, and quite frankly they treat the practice the same as rating motor horsepower - They lie about it. I have never seen one that actually met its classification when tested independently. AA hobs are more like B, A hobs are more like C, and B hobs look like D. And, they will typically have runout of the form outside even the lower classification. That said, for messing about in a home shop where inspection and adherence to a class are not needed they should be okay.

Key to remember here -

mellejonker said:
... ... it was cheap.

mellejonker · Nov 11, 2016

Yes, i dont expect profesional results from the cutter nor my setup, but its more to learn how gear hobbing works anyway. If in the end I cut a gear that can replace my pinion gear in the future, its nice. It can hardly be worse then the weared out gear in at the moment.

For Gary, just search in ebay or aliexpress on "DP22 20PA gear cutter" and you will find them. I bought mine for 34€ i believe, that was including shipping to Holland.

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mellejonker · Nov 13, 2016

DP22 HSS6542 Gear Hob Cutters, PA20, 50*40*22mm
http://s.aliexpress.com/zmI77n2m
(from AliExpress Android)

Thats an example

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Peter Colman · Nov 15, 2016

You now have the hob and from over 40 years making gears, including hobbling, I would try this
Make an arbour for the hob that fits in the vertical head
Make a blank for the gear but about 3/8" wider across the gear face and put a centre in both ends
Mount the blank in the dividing head and gash the roots of the teeth with a slitting saw, pick a saw that is just narrower than the tip of the hob tooth
Look at the hob and note down the helix angle and depth
Mount the hob on its arbour, set the vertical head over to the helix angle
Put the blank between centres so it can freely rotate
Position the hob so the arbour is in front of the blank Andy bring it into touch the od of the blank.
Wind the X axis so the hob is in line with the edge of the face of the gear
Set head to about two hundred RPM
Align a hob tooth with a gear space in the blank
Turn on and wind y axis to full depth
Hob and blank will rotate like a gear and worm
Slowly wind hob across the blank,
You will get some toothbdamage as the hob leaves the blank, hence th extra width.
This is free hobbing,lots of people talk about this but few try it, I often use it for gears to big to hob normally.

mellejonker · Nov 15, 2016

Hi Peter,
Great feedback, I will give that a try soon. I will post the results here, positive or negative, maybe others can benefit from that. Thanks for your suggestion. I was allready busy with a servo, but this is much simpler.
Melle

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Peter Colman · Nov 15, 2016

PM me if you need more guidance
Peter

Hardinge pinion gear repair

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