Randa lathe missing back gear

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mario, this is the backgear off my father's RandA, it shows there is 0.016" of end float when assembled. The length of the shaft is 2.263" long and the wheels are flush with the ends, the thread of the grub screws are 1 / 4" BSF. If you have found the shaft, it will save you a lot of work.

Myford change wheels are the same but as Howard has pointed out, you will have to drill a hole for the drive pin and a piece of silver steel of the correct diameter will be fine for the pin. The 60T wheel on the backgear is a slightly larger diameter than the change wheels, as pointed out earlier in this thread. The 60T backgear wheel on my father's is a press fit on the shaft and if you have to mount yours before fitting it, you will need to remove the main spindle and cone pulley to get it in. You have the New Type A RandA lathe, they are fairly good lathes for their time, but you must make sure the spindle is always oiled in the bearings when in use. I haven't used my father's one for many years now though.

Regards Nick.

P.S. I see you have it all back together and working.

Edited By Nicholas Farr on 07/07/2021 19:44:44

[Mario JonesParticipant @mariojones44715]

Nick,

Thanks again for your efforts I failed to realise the 60t back gear was a press fit it just seemed a little tight, at first I wondered if it had a small dink/burr so went round the edges of the gear with a fine file, in the end I relieved a small amount of material with a fine file from inside the gear and ran the spindle in the lathe with some light emery, it's still a tight fit but now it's possible with a little effort to remove/fit the gear on the shaft by hand.

Interestingly I note your back gear spindle has different diameters i.e. smaller where the back gear fits on and larger where it must sit in the bearing of the machine, whereas mine is the same diameter along its length

I still need another pin for the carriage arm 'not sure of the correct terminology' to run the gears in the correct order as currently it's moving the carriage/saddle 'thingy that holds the cutting piece' away from the chuck. I'm guessing this will be the same size as the one I have?

Lastly I pulled the tailstock with a drill chuck & 3mm drill bit upto the headstock chuck last night, I clamped a piece of round bar in the chuck and there is clearly some misalignment.

I had a quick play with the adjusting bolts etc on the tailstock but couldn't figure out the process of adjusting i.e. do you slacken the two clamp nuts on top of the tailstock then adjust the allen key bolts in the side, then retighten the clamp nuts? Ran out of time as I wanted to watch the football so will need to come back to this.

Oh and how did you identify my lathe is a 'New Type A RandA'? I can't find any marking on it anywhere?

Edited By Mario Jones on 08/07/2021 07:26:27

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mario, my backgear shaft is the same diameter all along its length, in the photo it is shown with the swivelling bush in place and the feeler gauges showing the 0.012" end float that the backgear has.

Two scans of adverts below, one of the "New Type A" and one of the "New Type B"

The arm for the change gears is called, the change gear banjo and new pins for the change gears can be made from mild steel easy enough. Yes you can adjust the tailstock alinement by the method you say and it is best done with a dead centre in both the tailstock and the main spindle.

Regards Nick.

Edited By Nicholas Farr on 08/07/2021 08:57:42

[Mario JonesParticipant @mariojones44715]

Fantastic info Nick! The terminology is another thing I must learn, I'm sure it will come in time.

I didn't realise the back gear spindle had the bush in place in your first photo, so that makes sense now, my back gear assembly has very slight play not sure if it's meant to be like it, or whether the shaft and/or bush is worn? Or is there away of tensioning the bush like one would do with the main spindle?

I have a couple of bars in with the bits an pieces that came with the lathe that have sharp points, I'm guessing these must be dead centres although from memory they are tapered probably to fit in the tailstock, I'll look again after work to see if they can be used for this purpose.

[Howard LewisParticipant @howardlewis46836]

Mario,

If you send me a PM with your E mail address, I'll send you a couple of pictures which will help with the terminology of parts of the lathe.

The "Bars with sharp points" are most likely centres. They have a 60 degree angle. and the back end should have a taper which matches the taper in the Mandrel and in the Tailstock.

It is possible that the Morse taper in the Tailstock will be smaller than in the Mandrel in the Headstock. If this is the case, it is quite likely to be hardened. That for the Headstock may be soft, to allow it to be trimmed up, by off setting the TopSlide by 30 degrees, should it be necessary to skim it to clean it up.

Have you thought about buying some books on the lathe, such as L H Sparey "The Amateur's Lathe", or Ian Bradley's "The Amateur's Workshop"?

Harold Hall's "Lathework, or Neil Wyatt's latest book, "Lathework" may be useful as well.

Reference books which will be invaluable are a set of Zeus Charts, and Tubal Cain's "Model Engineer's Handbook"

I bought my first set of Zeus Charts in 1958, and, grubby and dog eared, it is a regular reference source for threads and tapping sizes.

Howard

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mario, if your two dead centres are both 1MT, one may be a hard one, which you would use in the tailstock for supporting long items and the other one maybe a soft one, which you would use in the headstock spindle when turning between centres and it is normal for this to be trued up with a light cut each time you use it and that way you can be sure it is running as true as you will get it. You will of course have to remove the chuck to get to the Morse taper in the spindle and a catch plate would be required in place of the chuck, to drive the workpiece with a lathe dog, i.e. similar to these Lathe Dog A catch plate is just a flat plate that screws on in place of the chuck with a slot or a pin that catches the lathe dog, those in the link would have the right angled part sitting in the catch plate slot.

Howard has explained it already, but on these lathes, both the spindle taper and the tailstock taper are 1MT.

Regards Nick.

Edited By Nicholas Farr on 08/07/2021 15:55:02

[Mario JonesParticipant @mariojones44715]

Gents apologies for the delayed response been very busy but wanted to thank everyone for all the help to date!

[jim1956Participant @jim1956]

I’ve bought a small vintage metal lathe.
I have used small wood lathes for some time so have some experience with rotating machinery, some usable centres and chucks for the 1MT tapers in my new lathe and some test gear such as a DTI, but I’ve no previous experience with metal lathes beyond reading about them.

There obviously was something missing on the headstock and looking on the lathes.co.uk website I eventually discovered that I’ve got a RandA type B or lookalike and that a missing cog adjacent to the pulley is part of the backgear system. The closest example I could find on lathes.co.uk is the BSW RB 3x 20” with a double clasp nut. The terms Randa and backgear led me to this thread.

The pulley is obviously a modern replacement, V belt instead of flat and the pulley grub screw needs a metric 4mm allen key. Apart from that the lathe seems in good shape, bearings seem silky smooth, no damage to the leadscrew or cross slide and all the parts for a change gear train which seemed to be set up for a 24tpi cut with the 8tpi leadscrew.
The top slide and toolpost were clearly hacked in the past, the original toolpost mounting hole has the threads stripped and a length of threaded 3/8 UNC rod substituted in a new hole. The mix of fasteners did confuse me for a bit, mostly BSF, a metric grub screw but then a UNC thread as well.

The change gears have a pin connection between the collar and the cog. The gears themselves are a 5/8” bore, I found comment online that Myford 20DP 14.5 gears would probably fit so I’ve been able to buy a few Myford ML7 gears and make them fit fit with the addition of a 7/64” pin hole.

To repair the back gear I needed to either attach a 25 tooth cog to the rear of the pulley to match the existing 60T-25T-60T backgear train or else replace the three existing gears and get two matching pairs.

Lathes.co.uk had mentioned that early ML1-4 lathes used the same pin system and that the TPI indicator as part of the carriage shift on the RandA leadscrew was also the mechanism on the ML10.

Looking at spares for the ML10 on the Myford site I found a 25T spindle cog. It didn’t give any dimensions so I was unsure if it would fit but I thought it worth a punt.
Unfortunately it isn’t a direct fit, 7/8” ID instead of the 1” RandA spindle.
Since I’d bought it I decided to open it up to 1”. I drilled it out with progressively sized drills to 25mm (my biggest drill) and then got it to a sliding fit on the RandA spindle using abrasives on a mandrel. I was careful to clean it thoroughly each time before a test fit since abrasive particles on the spindle would be a real problem.

The resulting cog fitted the spindle and meshed ok with the large outer 60T gear and the collar on the ML10 cog provided clearance between the 60T gear and the end of the pulley. I did see some comment that the RandA backgears were not the same DP and pressure angle as normal Myford change gears, maybe the ML10 spindle cog is different from the change gears.

However the remaining rim on the 25T cog was very thin after taking the centre from 7/8” out to 1” and I couldn’t see how I would attach it to the end of the pulley.

My solution was to remove the collar at points round the rim directly at the teeth. A 1.5mm drill into the cog at these points to hold a pin which would go into matching holes on the pulley rim. Aligning with the teeth allowed me a larger space to drill without any danger of fouling the 60T gear.
Some metal epoxy then held the pins in place as I assembled cog and pulley together on a piece of 1” pipe as an alignment mandrel.

The design of the modern V belt pulley is such that there was no solid end towards the front of the headstock. Without the grub screw the pulley could move towards the headstock so I needed a spacer to keep it in position when the grub screw is removed.

Clearly a more accurate way to do it would have been to use a boring bar on a lathe to enlarge the 25T gear, that’s far above my current skill level, my use of a drill press is a pretty clumsy hack but it got me a working backgear.

Regards Jim

[BazyleParticipant @bazyle]

Your photo is a nice addition for education about RandA idiosyncrasies. Note the 60 on the spindle is thicker than the change wheels and the one on the back gear layshaft. This implies that the previous owner used a Myford change wheel in the back gear. Dimensions given either in this thread or an earlier one show the backgears are about 1.5% bigger than the changewheels, though they probably used a standard 20DP cutter.
When looking for someone at 3D printing one I calculated that a 61 tooth enlarged by 1% would be the best fit, though I never did make one.

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