Schaublin 70 Project

[Mcgyver]

I've been doing a ground up reconditioning on little Schaublin 70 lathe, been at it most of the year. Another case of how fast I can do it in my head not being well calibrated with my physical world performance. I've never seen a lathe in worst shape, e.g. you could grab the spindle shaft with your hand and rattle it in the bearings. However being a Schaublin, there's no more worthy candidate imo for reconditioning.

The tailstock was done by lapping the bore using home made expanding copper laps, up to 1000 grit, then hard chroming and grinding the quill to fit. There's 2 tenths clearance such that, with a bit of oil on it, if you hold the tailstock vertically, the quill won't drop out. The slide was a combination of grinding and scraping. Scraped the horizontal surfaces and ground all the angled dovetail surfaces as they are so small its about impossible to get a scraper in there, and they were short enough to set up on the surface grinder. One part of the slide assembly was so bad I grabbed a piece of cast iron and made a new one.

The greatest challenge was the spindle. The bearings were destroyed its the typical watchmakers format of a double 45 and 3 degrees. This to me is a near impossible machining task and I have not figured out a super elegant way to do so - the challenge being, how to machine to adjacent tapers on a shaft, then have mate with the bearing to a tenth or two clearance? Whats the diameter of taper? relative to what? You've also have the challenge that say a thou difference along the axis in where the 3 degree tapers meet, means about 10 difference in where the 45 degree tapers mate.

How I did it was grind the shaft all over, just kissing it. Then I lapped the outboard board bearing (a conical arrangement whereby tightening it's nut reduces its diameter). I then ground a shaft to fit the outboard bearing and tightened the nut until it was clamped in place. I welded up a fixture for my face plate, and then spent half day shimming and shifting until I got the said ground bar aligned in two planes each to a tenth. this should let me bore out a pressed in piece of bronze, the new headstock bearing, and have the bore aligned with the outboard bearing. The taper attached using a sine bar and careful setting was used for the 3 degree taper. I bored the 3 degree taper, and through test fitting and measuring crept up on the 45. A lot of work - and thats just the roughing!

That was the mark II attempt. The first one was a fail as I relied on the alignment of the two headstock bearing bores. Mistake, they are quit far off. Schaublin must have pressed the bearings in then bored them and did worry about the headstock cast bores very much. My lapping of the outboard side could have, and probably did, change its axis slightly, however I measure the original inboard bearing the ID and OD were substantially eccentric.

After "rouging" it was scrape and lap. The original plan was scraping, but its obviously a real challenge getting in there. I scraped until I was getting contact in most of the bearing, then lapped. While lapping tapers is verboten because there is no axial movement between the parts, I eventually discovered that the timesave stuff for use with soft metals would abrade the bronze but would not effect the steel shaft. The eventual fit came from scraping the 45 (which accessible) until there was good contact with the 3, then lapping both with the finest grade of timesavefs yellow stuff.

As I reground the OD of the spindle shaft, I should regrind the spindle taper to ensure concentricity. This was a big setup. Figuring it out and trying different things took me most of a day. After grinding I'm getting a tenth TIR on the spindle, was hoping for a little better, but given all surfaces on the bearings and shaft are done by me in my in the homeshop, I think its reasonably good

The headstock and tailstock after getting them fit properly, need to have their bottoms scraped to align them both to the bed and each other. That is mostly done for the headstock, tailstock still needs work

Some photos and video (I'm much better with, and really prefer still photography, but I'm learning how to bore audiences with the best of them on you tube )

finished quill, the diameter is within about 1/2 a tenth end to end using an indicating mic

No that is pooched headstock bearing! Orginal was hardened steel. I'm going with bearing bronze (as some did Schuablin on some lathes)

indicating the bar - its close, but not touching new bronze bearing - its bascially a perfect extension of the outboard bearing's axis

Here's a short video of turning the bronze bore....and a long video of grinding the spindle taper and the results

 

[Susquatch]

Very impressive @Mcgyver! Well done!

I think your patience (and courage) outweighs mine by at least an order of magnitude.

I think your video skills are pretty darn good too!

 

[RobinHood]

Awesome work!

I wonder if they used jig borers / grinders to finish the original steel bearings after they had pressed them into the HS casting? One would think that with those kind of machines accuracies of tenths to sub-tenths should be achievable.

 

[Mcgyver]

thanks for kind words gents.

Robin, agreed, they had to be done after pressing in - there was too much eccentricity on the original bearing between ID an OD for it to be otherwise. No matter how accurate the machine, it doesn't explain how to get the taper right (angle is easy....it is getting the diameter dead on (male and female) at the hypothetical plane the tapers meet at that'll make one crazy - there is no good way to directly measure it and it has to be spot on). I think they had to be made on a custom made machine that would get set up with some trial and error and master male and female gauges. Said gauges would be ground almost by fit to each other - thats my theory. All which is way more than you would want to set up for a one of. It is frustrating that once, when everyone needed a watch, 1000's of people would have be very familar with this process with the 100 or more lathe manufacturers in existence. Now it seems we can do little more than guess

There are these images of Boley watchmakers lathe having the bearings done. cylindrical laps at the two taper angles. While still challenging, I can see how a dedicated machine could be construction for production. I still think its incredibly complex to figure out a methodology to accomplish this in a job shop/at home situation. I haven't succeeded at that as my strategy relied on bronze, scraping and lapping. That wouldn't work with the common steel on steel bearing found in 99.9% of watchmakers lathes. You'd have some chance with hard turning on a CNC, but its still not a lapped finish. And you can't lap a taper with two hardened pieces (only worked for me because the soft lapping abrasive didn't affect the shaft)

I will never do one like the above again, too much work for the reward. Its in part to prove I could and in part because there are so many amazing double taper lathes out there (like every watchmakers lathe) I was looking for methodology to fix them (if some knuckle dragger ran them without oil Grrr). None exists, the closest being Archie Perkins (wrote a book on using watchmakers lathes) suggestions which are best "kill or cure" and at worst are rather shade tree

If I was faced with this again, it would plunk down some dough for P4 AC's and big block of durabar and have at it. Probably would use the original shaft and sleeve it.

 

[CalgaryPT]

I've been doing a ground up reconditioning on little Schaublin 70 lathe, been at it most of the year....

Nice work. Way above my level.

 

[gerritv]

I think you were trying to link the photos from here? http://www.lathes.co.uk/boley/page7.html . Slick solution.

Gerrit

 

[kevin.decelles]

I resonated with the welding on the faceplate..... the one operation I felt I could probably succeed at in this thread Great post!

 

[RobinHood]

No matter how accurate the machine, it doesn't explain how to get the taper right (angle is easy....it is getting the diameter dead on (male and female) at the hypothetical plane the tapers meet at that'll make one crazy - there is no good way to directly measure it and it has to be spot on).

Could one use two precision balls of appropriate size (A & B) and measure how deep each one sits in it’s respective taper? It should then be a matter of geometry to figure out the exact required position from a common reference point - like the rear of the bearing. Something like this (sorry for the chicken scratch drawing):

 

[PeterT]

I had to run home from work in the cold because the pictures weren't loading on the employers machine <pant, pant, cough> LOL. Nice work!

What is the grit/abrasive of the white wheel you are getting that nice finish off?

 

[Susquatch]

and at worst are rather shade tree

Many of you guys use that term "shade tree". What does that term mean besides a nice cool breezy spot to sit on a hot sunny day?

 

[Mcgyver]

it refers to someone working on their car under the shade tree rather than in a properly equipped garage. While that's us (DIY'ers possibly under the shade tree) its used as a criticism or catagorizing of work using a poor/improper approach that will not get the job done properly. Like fixing it with a wine cork because you lost the oil drain plug.

 

[Mcgyver]

I had to run home from work in the cold because the pictures weren't loading on the employers machine <pant, pant, cough> LOL. Nice work!

What is the grit/abrasive of the white wheel you are getting that nice finish off?

Thanks Peter. That is a 150 grit wheel, J if I remember, but will check. Its only 1/4 inch wide. It was an experiment that seemed work. I wanted a great finish with minimal material removal. I like the narrowness as well, I think it imposes a little less force. My cylindrical grinder is a tool grinder so is light by cylindrical grinding standards and it has take some experimentation to get performing in the best manner. There is not a lot cylindrical grinding wisdom readily available (not exactly the longest chapter in the machining text) and what there is, is not geared toward such a light machine

 

[Mcgyver]

Could one use two precision balls of appropriate size (A & B) and measure how deep each one sits in it’s respective taper? It should then be a matter of geometry to figure out the exact required position from a common reference point - like the rear of the bearing. Something like this (sorry for the chicken scratch drawing):

thanks for the drawing. It had been mentioned to me in another discussion and should work for for the female part. Things are open so you could put parallel acros the back of the bearing and mic over it and the ball. I suppose you could grind the shaft first, then carefully measure the two tapers (mic over pins say elevated with blocks, with the shaft nose on the surface plate) and do the math on the needed ball spacing. The issue I would think is lots of sources for error. I think it will remain academic for me ......really want get this a few other machines done then get back to model engineering

 

[Susquatch]

it refers to someone working on their car under the shade tree rather than in a properly equipped garage. While that's us (DIY'ers possibly under the shade tree) its a used as a criticism or catagorizing of work using a poor/improper approach that will not get the job done properly. Like fixing it with a wine cork because you lost the oil drain plug.

I see! Around here, folks call that "Red Neck" or "Farmer". "Hill Billy" or "Red Green" is also a popular reference. Of course, as a farmer myself, I prefer Hill Billy.

So I can see why my Calgary Colleagues might prefer Shade Tree. But I've never heard that before.

My learning for the day!

 

[DPittman]

I see! Around here, folks call that "Red Neck" or "Farmer". "Hill Billy" or "Red Green" is also a popular reference. Of course, as a farmer myself, I prefer Hill Billy.

So I can see why my Calgary Colleagues might prefer Shade Tree. But I've never heard that before.

My learning for the day!

Well being from Saskatchewan, I can imagine that "shade tree" could be a foreign concept to you. Hee hee. (and being from southern alberta desert myself I think that's okay for me to say).

 

[Mcgyver]

Pretty much done, phew! The idea was spare no effort in an attempt to achieve factory new accuracy and performance. Its a no small challenge given it was a wreck and Schaublin was arguably the finest maker of lathes. (There may be equals, but I can't think of a maker that surpasses them). It took over a year and many times I had to hold my tongue just so! I did everything on the this lathe, spindle regrind and made a new double taper bearing as per above (about 3/4 of a tenth TIR), lapped the tailstock, hard chromed and ground the quill, (2 tenths clearance, you can hold the TS vertically and the quill doesn't fall out), scraped and ground the slide rest, scrape the bed, scraped the headstock and tailstock into alignment to a tenth....every surface that touches another got worked on. Had to make many missing parts as well. Really of sick of reconditioning at the moment....but nah, the biax isn't for sale...yet . I even painted it which I usually don't do...but its a Schaublin so deserved it.

 

[thestelster]

Absolutely stunning! It's more art than machine.

 

[PeterT]

Now that's a restorative work of art. Way to go.

 

[phaxtris]

wow, excellent work!

 

[whydontu]

beautiful work!