Bodging an enveloping worm wheel

[waddycall]

My mill has a worn (but still useable) worm wheel which acts as a bronze half nut for the x axis and is connected to four ball ended handles with a clutch for rapidly traversing the bed. It’s a very handy feature - finish a cut, squeeze the ball handles to release the clutch and throw the table back to the start to take another bite without stopping the machine or disengaging the power feed.
The worm wheel is badly worn in some places and not so bad in others. It’s an enveloping worm wheel that wraps partially around the feed screw.
Replacements aren’t available so I’m day dreaming about making one (purely hypothetical at this stage). I understand you really need a universal dividing head geared to the table feed of a universal mill to correctly cut this kind of gear (correct me if I’m wrong) and free hobbing is out of the question due to the enveloping nature - I don’t just want shallow teeth.
Could I rough this out as a spur gear with the cutter at an angle to approximate the helix angle of the screw and then use a home made hob to get it to final shape?
Or can someone else make me one

 

[waddycall]

This sucker -

 

[nickk]

Never heard of that,I just thought it’s split along its axis. Ironically soon after I bought my Victoria I had to make a new lead screw nut.
Good luck anyway.

 

[Martin-Sy]

If I understand this correctly.... for rapid table movement the worm-wheel and feedscrew behave as a rack & pinion??
@Pete. ??
What's the machine?

 

[waddycall]

If I understand this correctly.... for rapid table movement the worm-wheel and feedscrew behave as a rack & pinion??
@Pete. ??
What's the machine?

Yep,that’s it. 1951 Fritz Werner 5.160WS

 

[Agroshield]

I understand you really need a universal dividing head geared to the table feed of a universal mill to correctly cut this kind of gear

On a universal dividing head, you cut one tooth at a time, hence the need to gear the head to the table feed to produce the helix.

When cutting the wheel using a hob, it is a continuous process. Blank and hob rotate synchronously and the only feed is pushing the cutter into the blank. Hence, I think that for this, you would not need table feed. I think it could be made just by feeding the hob vertically into the blank.

What you do need is synchronised rotation between the hob and the blank. Anything that provides the correct ratio would suffice.

Do check that it is a single start item and also note the hand of the screw.

 

[waddycall]

On a universal dividing head, you cut one tooth at a time, hence the need to gear the head to the table feed to produce the helix.

When cutting the wheel using a hob, it is a continuous process. Blank and hob rotate synchronously and the only feed is pushing the cutter into the blank. Hence, I think that for this, you would not need table feed. I think it could be made just by feeding the hob vertically into the blank.

What you do need is synchronised rotation between the hob and the blank. Anything that provides the correct ratio would suffice.

Do check that it is a single start item and also note the hand of the screw.

Well I’ve got the horizontal spindle available so could gear something off that to a dividing head

 

[Pete.]

What is the pitch of your leadscrew?

 

[waddycall]

What is the pitch of our leadscrew?

0.2”

 

[Pete.]

0.2”

5tpi? On a German mill?

You sure it's not 5mm?

 

[waddycall]

5tpi? On a German mill?

You sure it's not 5mm?

I cheated and got it from here -

 

[Agroshield]

On a German mill

Food for thought (demise of British manufacturing): the European manufacturers may have been more open to producing imperial versions of their machines than the British ones did to producing metric versions (Myford).

It would be interesting to see how many US-based Deckels were imperial. Schaublin also made imperial machines.

 

[waddycall]

I’ve checked it with a dial gauge and the thousands needle ends up back at zero whereas the mm needle drifts
After full revolutions

 

[Pete.]

Shame its not 5mm that's a perfect match for 16dp worm wheel (half a thou per tooth).
.200" is only .0036" per tooth different would probably be fine and certainly better than your randomly-worn one.

The random wear is probably down to the rapid traverse handwheel clutch stopping in the same places many times over.

 

[waddycall]

Shame its not 5mm that's a perfect match for 16dp worm wheel (half a thou per tooth).
.200" is only .0036" per tooth different would probably be fine and certainly better than your randomly-worn one.

The random wear is probably down to the rapid traverse handwheel clutch stopping in the same places many times over.

Thanks Pete. Fun one this I think but the good thing is the machines perfectly useable.
Good challenge I might take up at some point.

 

[waddycall]

Food for thought (demise of British manufacturing): the European manufacturers may have been more open to producing imperial versions of their machines than the British ones did to producing metric versions (Myford).

It would be interesting to see how many US-based Deckels were imperial. Schaublin also made imperial machines.

I think this may have been a war reparation machine but that’s just a hunch/guess based on an internet post somewhere. Maybe that would stipulate English machine spec.

 

[E T]

Like that Southbend except for the color.
Is that T-slot cross slide homemade or is it the Boxford version?

 

[waddycall]

Like that Southbend except for the color.
Is that T-slot cross slide homemade or is it the Boxford version?

Boxford I believe. I agree about the colour

 

[Pete.]

That Southbend is a bloody nice little lathe TBH despite the colour. It's in remarkably good condition.

As for the traverse gear, I can make that for you if you give me some good measurements. It will have to be cut with a 16DP hob so whilst it will have the correct diameter and number of teeth it'll have slightly thinned teeth, but that won't bother you since yours are already thinned down to nearly nothing.

My Dowding and Doll hobber has the facility for cutting such wheels built in. I'll need the gear carefully measured and I'll need the leadscrew diameter so I can calculate the proper helix angle that's all.

 

[waddycall]

That Southbend is a bloody nice little lathe TBH despite the colour. It's in remarkably good condition.

As for the traverse gear, I can make that for you if you give me some good measurements. It will have to be cut with a 16DP hob so whilst it will have the correct diameter and number of teeth it'll have slightly thinned teeth, but that won't bother you since yours are already thinned down to nearly nothing.

My Dowding and Doll hobber has the facility for cutting such wheels built in. I'll need the gear carefully measured and I'll need the leadscrew diameter so I can calculate the proper helix angle that's all.

Pete - that’s amazing! I’ll get the gear out in the next few days and take some measurements!