Lathe change gears vs gearbox

[NikleBigHornParticipant @niklebighorn]

Posted by Martin Connelly on 21/01/2022 10:06:24:

The first thing you need is a list of the thread TPI or pitches you will need to cut and find out if it rules out any of your options. It should make it easier to narrow down the best option for you if there are some threads that can only be done with a lathe and some lathes can't do them.

martin C

This is tricky as some of the machines are std imperial, some proprietary, some metric. I also do work with 316 in metric only. So I’m not sure this helps other that it needs to be very adaptable.

[NikleBigHornParticipant @niklebighorn]

Posted by Alan Wood 4 on 21/01/2022 11:19:02:

Couldn't be faffed with all those gearbox levers, look up charts, change wheels.

Fitted a Clough42 Electronic Leadscrew to my Myford. Heaven.

This is a fascinating option and possibly a game changer. Thanks for sharing the links. What would you estimate the total cost is to set the Clough option up?

thanks

nick

[William ChithamParticipant @williamchitham75949]

My Boxford started as a non gearbox "C" but I have since upgraded it to "A" spec which is a huge improvement – the convenience for threading is nice but the real benefit is being able to play with feed rates easily. If you do go for a Boxford I'd suggest you get one with as many extras as possible – especially steady rests, thread dial, t-slot top slide. Boxford bits seem to cost a fortune, far more than Myford as far as I can see.

William.

[Alan Wood 4Participant @alanwood4]

Hi Nick

There is a full costing towards the end of my write up. The core parts total circa GBP350 assuming you use a hybrid servo. You could reduce this using a standard component. Clough42 does describe the process very well.

Alan

[Howard LewisParticipant @howardlewis46836]

Having replaced a ML7 with a lathe with a gearbox (48 possibilities) and two changewheels, (Three now having made one to halve the feed rate )

In standard trim, with the 120 /127 Idler it can cut 18 Metric pitches, 7.5 mm to 0.25 mm with one change of gear wheel – 32 instead of 40T and Imperial from 4 to 112 tpi. without any change.

Gearbox gets my vote.

Saves an awful lot time working out gear trains!

Howard.

[NikleBigHornParticipant @niklebighorn]

Thanks for all your advice, it has been very helpful. I’m off tomorrow to see an early Model A with gearbox. I’ll let you know how I get on.

Nick

[NikleBigHornParticipant @niklebighorn]

Well I’ve come home with a clean and tidy bench mounted model A with imp gearbox, powered cross slide, 3 phase variable speed, fixed and travelling steadies 3jaw, 4jaw, live and fixed tail stocks + chuck face plates and a tool box full of new drill bits and cutting tools. The bronze head bearings and lead screw have been replaced. The bad bits are a broken tooth on rev tumbler, no change gears and a sticky tool slide. The beds look clean with only a single dink and appear to be true in first inspection. It seems to be in reasonable condition. Time will tell. Tomorrow will be getting it levelled and tested.
Thanks again for all your thoughts and advice.
Nick

[not done it yetParticipant @notdoneityet]

One tooth on a gear is an easy fix. Several ways of doing it. Basic is grub screws in place of the broken tooth and filed/ground to profile. No real problem if the gear is not heavily loaded, otherwise fill with braze and recut.

[Clive Brown 1Participant @clivebrown1]

That sounds like a well equipped machine.

Re change gears, do you have the gear train between the spindle and the gearbox? For an imperial "A" machine this should be four gears thus:- 20t; 80t idler; 56t and with a 40t, normally mounted as a spacer, to replace the 20t for the coarsest pitches, ie 4 to 7 tpi.

There is normally no need for other gears unless you require metric piches..

Edited By Clive Brown 1 on 22/01/2022 21:28:22

[NikleBigHornParticipant @niklebighorn]

Posted by not done it yet on 22/01/2022 20:36:51:

One tooth on a gear is an easy fix. Several ways of doing it. Basic is grub screws in place of the broken tooth and filed/ground to profile. No real problem if the gear is not heavily loaded, otherwise fill with braze and recut.

I think brazing is the route I’d prefer. But in the short term I might just bite the bullet and buy a new one as it’s pretty worn out by the looks of it. ill post some pics tomorrow.

[John HaineParticipant @johnhaine32865]

"Tool slide" = top slide?

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