Unimat needing a little repair

[Pete O]

One of my colleagues at work, George, is an avid collector of vintage toys and models. He told me the other day that he had bought a bloke's entire model train collection and along with it had acquired a little machine of some sort, he was wondering whether it might be some kind of lathe accessory or something. When he described it to me I said it sounded like he might have scored a watchmaker's lathe or similar or if he was really lucky it might be a Unimat.
He brought it in to work this week so I could have a look at it, sure enough it is a lovely little Unimat of approximately 1960 make, with the Selecta brand badge.
   
   
   
   
   
George was hoping that I might be interested in buying the machine but it is a little on the small side for my tastes.
Unfortunately the headstock spindle thread has been damaged and the internal thread in the chuck has also been damaged, I suspect that the chuck has been cross-threaded onto the spindle at some stage.
I told him I should be able to repair the damaged threads so I have brought it home to do that and he can then put it on the market in full working order. The headstock and tailstock threads are the same and there is a faceplate that will thread onto the tailstock spindle and provide a nice square support to run a die over the headstock spindle, I'm hoping that it will clean up ok by doing that.
There is some writing under the lid of the wooden box indicating that this was a gift to someone 'from dad' in 1960. There is also a price of 40 pounds 10 shillings (I don't have the appropriate symbols to insert for that!) which would have been a considerable sum of money at the time.

[Pete O]

Nothing's ever easy is it, the spindle appears to be a M12x1mm thread, non-standard and not amongst my tap & die collection. I'm reluctant to go out and buy tools just to do this repair for a workmate, would it be kosher to ask him to spring for the tap & die?

[krv3000]

hi yep its 12 by 1 mm their is still lots of parts for this type of lathe on ebay in the us and in the uk the one thing to watch out for is the motor they burn out with over youse as the motor is not vented by the look of the one in the pic you have one of the first ones with the cast iron bed they fetch a  good price

[Dr Stan]

(06-20-2016, 03:48 AM)Pete O Wrote: Nothing's ever easy is it, the spindle appears to be a M12x1mm thread, non-standard and not amongst my tap & die collection. I'm reluctant to go out and buy tools just to do this repair for a workmate, would it be kosher to ask him to spring for the tap & die?

While on the small side what about setting it up in your lathe and picking up the thread so you could repair it just like single pointing.  You could modify a tap by grinding away all the teeth but one for the internal threading.

[Pete O]

Sadly my lathe lacks the transposing gear to be able to cut metric threads so I don't think I can accurately fix the thread that way. One of the key missions for my new universal dividing head is to make the 127-tooth gear so I can do metric work on my lathe but that capability is a fair way off at present- especially given that I need to make several other change gears to make the 127 possible. I'm thinking I'll just acquire the appropriate non-standard tap and die for this job.

[Dr Stan]

(06-21-2016, 11:19 PM)Pete O Wrote: Sadly my lathe lacks the transposing gear to be able to cut metric threads so I don't think I can accurately fix the thread that way. One of the key missions for my new universal dividing head is to make the 127-tooth gear so I can do metric work on my lathe but that capability is a fair way off at present- especially given that I need to make several other change gears to make the 127 possible. I'm thinking I'll just acquire the appropriate non-standard tap and die for this job.

Do you have a feed rate of .0394" or very close to it on your lathe?  If so set up like the usual for threading, set the feed rate at .0394 and use your longitudinal feed (not the half nuts) once you're aligned with the existing thread.  Just remember to never disengage the feed lever until you're 100% complete, but stop the lathe, back the tool away from the work, and reverse the spindle to go back to your starting point.

BTW, go with very low RPM's and use layout dye on the existing threads so you can tell just how close to finishing you are.

[Mayhem]

Do you have a thread file? I have a spare metric one and I'd be happy to send it to you.

[Pete O]

I may well take you up on the thread file Darren, I only have an imperial one and the 24tpi is not quite close enough. I think I'll have a go at it with a needle file under the magnifier first and see how I get on. I bought a m12x1mm intermediate tap today and cleaned up the internal thread in the chuck, it was only the first turn that was damaged and it cleaned up easily- almost too easlily to justify the $48 the tap cost me  Hope I get some more use out of it in future. Closest feed rate on my lathe is .048 or something- can't remember exactly now, it's been more than 10 seconds since I looked.
At present I'm trying to get a dividing head crated up for a journey to some strange place on the other side of the continent as well as a mate's Land Rover with the clutch out of it taking up half my shed and a carport dismantled for repair after a tree fell on it, with hail forecast.  The Unimat will have to wait.

[Mayhem]

PM me your address Pete.

[Pete O]

Darren's thread file came in the mail yesterday and I spent a little time this afternoon cleaning up the thread, didn't take long at all and the chuck now screws on square. I'll give the unimat a clean up before giving it back to my colleague, will take some photos of it cleaned up. Thanks Darren for the thread file, much appreciated.