Pinion problem

I've owned this Warco Economy Mill from new. Over the past year or two I've found it increasingly more difficult to raise and lower the head and put it down to advancing years.

I decided to dismantle the rack and pinion today and found a sorry sight. The rack pinion is mangled, hopefully not beyond recovery. If I can remove the gear from the shaft I might be able to salvage it. But, there is always a "but", I cant budge the shaft from the housing. Ive tried moderate force to no avail. I don't want to be too brutal in case I damage the cast iron housing.

The shaft is 12mm dia. as near as I can measure. It is plane on one end and has a 6mm threaded hole in the other.

In case I can't salvage the gear I will need to source another. It is 33mm o.d., 24mm wide, 12mm i.d., 16 teeth with a 5 degree helix angle. Anyone got ideas as to where I might find such a gear.?

Iain

If the threaded hole has no other use, I would suggest it is there as an aid to removal - as in a puller.

The obvious place for assistance with removal method, or for replacement part(s) is presumably Warco. Open until 1700h today, I would think. Only a phone call away.

I don't think they are open on a Sunday! I'll give them a call tomorrow, but I don't hold out much hope as I asked them about spares for this machine a few years ago and they said that they carried no spares for this machine.

Iain

Hi Iain

Never had one of those exact assys from a Warco mill  apart but here's a couple of ideas to try to get the shaft out:

1. warm the housing sides around the shaft to expand the metal around the pin with a propane torch on highest power, and then try pushing the pin out. Support the housing side as close to the pin as possible. Sockets from a socket wrench set are handy for this. If you have an arbour press I'd suggest using that rather than hammer and drift.

2. What normally fits in the pin's threaded hole? if nothing normally does, it suggests it might be for jacking out the pin. Again a socket can be used, with a capscrew passed through the drive square hole, a washer under the head. This arrangement keeps the pulling force local to one side of the housing.

3. If all else fails the pin could be carefully drilled out and a new one made from o-1 steel or something like it.

4. HPC gears in UK have been mentioned many times in the forum as a supplier of new gears.

5. The assy shown in your pictures looks bone dry. If it has been operated dry this would partly explain the wear. I'd recommend a good coating of heavy extreme pressure grease, renewed yearly, to keep the replacement gears operating smoothly. Even axle or chassis grease from a car part store would be better than dry.

Good luck with it.

Edited By Jeff Dayman on 21/10/2018 14:51:14

Hello Iain,

Assuming this machine was built to metric standards, calculations suggest the damaged pinion is 1.75 Mod. The nearest DP value is 14 but the Mod number is a closer match

You could try one of the gear makers like HPC in Chesterfield but really a hobbed pinion would give a better fit to the worm and as a special they could make that for you, but at a high cost

Rather more realistically, do Warco sell a spare assembly you can replace the whole fitting with? I think that would be a much cheaper option all round. And, if they do, then lubricate the gear teeth with 80 or 90 grade gear oil as this has high pressure additives in it to resist the sort of wear this has suffered

A real cheats option is to knock the pin through with the remote side well supported on something solid, across the open jaws on a vice would do, I think that is unlikely to crack the housing, free off the pinion and turn it round to wear out the other side! It won't last very long but it should give you ample time to source a replacement.

Regards

Brian

Jeff, Unfortunately I have no access to either Propane or an arbour press. I'll try jacking it out as you suggest.

Brian, I've tried Warco in the past for a part, but they said they don't hold any spares. I bought the mill 14 years ago and I think it was one of the last ones they sold.

Thanks for the suggestions.

Iain

You think that's bad? You should see the pinion on my bandsaw...

Neil

If the mechanism is the same as on many drill presses, the pinion must be a helical one because rack it engages with is helical as well as the worm.

Having said that, with a dividing head (or even a gear with a multiple of the right number of teeth and an indexer), and a gear cutter, a replacement pinion could be cut in the mill, then hardened.

Edited By Mark Rand on 21/10/2018 16:20:44

Got it out with the aid of a BFH. Why it had to be so tight I don't know. I light press fit would have been enough. I've run a reamer through the holes in the casting and polished the shaft and it is now a good fit. Now I have to find a replacement pinion or have one made. If only I knew of a model engineer who could make one in exchange for a few beer vouchers...........

Mark, you are correct the rack teeth are helical, but you have to look closely as the slope is only about 5 degrees.

Iain

Hmm. Is is worth a wander around any available branches of Axminster Tools, Warco, Chester, Machine Mart etc. with the pinion in hand and seeing if any of their drill presses or small mills have a matching mechanism, then asking at the counter for spares on those models?

Flip that pinion over and grease it then it will be bearing on the un-worn faces.

Perhaps it might be time for me to look at the rise and fall on my drilling machine [bought 1983,never touched since ]

also my mill !![ later vintage ]. I would hate to find something like that .

What,s that old saying about "A stitch in time-----------------"?