Pratt & Whitney Model C 12x30 lathe

[tailstock4]

Thanks for the pictures of your progress.

Here are a few pictures of the tailstock to show some of the changes between the early model C and the late model C. You can see that Pratt & Whitney added rollers to the underside of the tailstock. These are like fingers of a steady rest. They sit in a blind hole with a spring on the back side and an allen screw adjustment. They don’t lift the tailstock off of the ways – just lift it enough to reduce the effort and help limit wear. I don’t think these would be too hard to add. But of course, the devil’s in the details.



I also included pictures of the tailstock clamping assembly. On the late model C, they went to a cantilevered 4-point clamp that with a cam action of the handle allows for exact duplication of force and force applied equally to all four corners. I think this was an attempt to make the tailstock more repeatable when moved.



You can also see the way wipers on the tailstock. These are the same style used on the apron. They are a double felt with a bronze outer wiper. The wipers are put together in two halves. I really like the design of these wipers and have duplicated it on my Pacemaker. I’ve included some picture of the wipers I made for the Pacemaker because I have pictures of those disassembled.

 

[motormech1]

Wow, yeah I see they really up'd their game on the later models. I wonder how much of a difference the design changes made in practice. Wipers woukd be nice to have on the tailstock. I guess they could be added without too much trouble.

 

[motormech1]

@tailstock4 Oh yeah, by the way, when I pulled the cross slide hand wheel the retaining nut was missing and the shaft slid out with the wheel. Sonething tells me that shaft should be retained somehow. Lol I get the feeling somethings missing. Hopefully just something simple, nothing broken. Looks like I'll be digging into the apron afterall.

 

[tailstock4]

Wow, yeah I see they really up'd their game on the later models. I wonder how much of a difference the design changes made in practice. Wipers woukd be nice to have on the tailstock. I guess they could be added without too much trouble.

I think the changes were pretty effective and logical choices. I know this tailstock didn't have any of the customary tailstock droop. I also did a test using a tension scale with several of my other lathes on the amount of force it takes to move the tailstock. With the rollers it takes about the same amount of force that it takes to move the much lighter tailstock of a Southbend Heavy 10. The only one of the modifications I think that it would be hard to replicate is the clamping system. It is effective but a real pain in the butt to adjust. It is sensitive.

 

[motormech1]

I think the changes were pretty effective and logical choices. I know this tailstock didn't have any of the customary tailstock droop. I also did a test using a tension scale with several of my other lathes on the amount of force it takes to move the tailstock. With the rollers it takes about the same amount of force that it takes to move the much lighter tailstock of a Southbend Heavy 10. The only one of the modifications I think that it would be hard to replicate is the clamping system. It is effective but a real pain in the butt to adjust. It is sensitive.

Makes sense. I'll bet it's a pain, looks fairly complex.

 

[Beckerkumm]

My Monarch needed new glass for the sight and the old couldn't be cleaned up. From monarch they were over $100 each so I bought a few push to fit sight glasses from JW Winco for about $5 and made a new housing. The old could have been modified but I wanted to save them in case the guy at my estate sale wanted to return to original.

The tailstock is interesting. It was a time when problem solving was more important than value engineering. Dave

 

[tailstock4]

@tailstock4 Oh yeah, by the way, when I pulled the cross slide hand wheel the retaining nut was missing and the shaft slid out with the wheel. Sonething tells me that shaft should be retained somehow. Lol I get the feeling somethings missing. Hopefully just something simple, nothing broken. Looks like I'll be digging into the apron afterall.
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Here is a picture of the nut that is missing. That hand wheel and that assembly are part of the cross slide screw stop. It also provides the driving of the cross feed screw splines which are part of the telescopic taper attachment. The cross screw on mine is retained on the taper attachment cross slide housing. The lever at the bottom of the housing you're working on is used to clamp the position of the cross slide hand wheel allowing it to move about 1/2" lock to lock or 1" on the diameter.




And here are some pictures of the internal parts of that assembly on mine.



As far as taking apart the apron, if there is one thing I could recommend doing, taking apart the apron and saddle would be it on any of these old lathes. In fact I've pulled the apron apart on my 2004 Toolmex and was not disappointed that I did. Aprons collect a lot of debris and dirt and these have had close to 70 years to do it.

 

[motormech1]

I think I figured out what's missing thats allowing the crossfeed handwheel to pull the geared sleeve out. The parts manual shows a shallow hat bushing on the inside of the housing (yellow area) that would be located between the key and gear teeth (red area) when the sleeve was in it's proper place. I have it pulled out/disengaged for demonstration. Guess I have my first lathe project!

 

[motormech1]

As far as taking apart the apron, if there is one thing I could recommend doing, taking apart the apron and saddle would be it on any of these old lathes. In fact I've pulled the apron apart on my 2004 Toolmex and was not disappointed that I did. Aprons collect a lot of debris and dirt and these have had close to 70 years to do it.

Do I need to completely remove it or do you think I can get what I need done with it on the lathe?

 

[tailstock4]

Do I need to completely remove it or do you think I can get what I need done with it on the lathe?

I would remove everything. You should be able to have that whole assembly separate from the saddle. One thing that would help me is if you would back off on your pictures just a little bit so I can get a better overall picture and a feel for what might be different from my machine. Also disassembling the whole thing might let you see if you are missing anything else.