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Pratt & Whitney 12C Restoration Pictures

jim rozen

Diamond
Joined
Feb 26, 2004
Location
peekskill, NY
Phenomenal story, phenomenal pictures. Truly amazing machine. One thing I cannot figure out is how P&W ever made *any* money off these machines, given the attention to detail, and the quality of the the build (hand scraped fixed interfaces, roller or ball bearings throught) one would think they probably lost about $10K per lathe shipped!
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
Thanks, I haven't got it in its final resting place, but it was hooked to power when I bought it, so I was able to try everything out. This is the day I bought it, just before loading it up. Came with a really nice condition 12" 4 jaw bison chuck, and an older 9" Burnerd 3 jaw chuck, but no adapter for the 3 jaw. I got a good deal on a Pratt Burnerd 12" 3 jaw super precision chuck though, model 1223500 so I will probably never use the old Burnerd chuck. This lathe was used in a diesel machine shop, and they apparently used it for working on pistons. They were moving the shop and needed it out of the way, so I got it for $1,000. I feel like I got a heck of a deal on it, and everything seems in great shape, just dirty.
Looks like a good machine and intact – meaning no missing parts. It looks to be about the same age as mine. You might consider posting a serial number and maybe John Oder can give you the date. This to me is not just a nice-to-know, but also helps to document the lathe. Pratt & Whitney appears to have made many changes to the lathe as time went on and knowing the year of manufacture can help in knowing what parts will fit with what machines.

One other observation – it looks like you may have part of the optional relieving attachment, but there were also a couple of drive shafts and end gear box. I can’t see if you have a taper attachment. I’m kind of curious to see how the relieving attachment interacts with the taper attachment and cross feed.

Picture below of the relieving attachment from P&W brochure:
1660094043933.png
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
Phenomenal story, phenomenal pictures. Truly amazing machine. One thing I cannot figure out is how P&W ever made *any* money off these machines, given the attention to detail, and the quality of the the build (hand scraped fixed interfaces, roller or ball bearings throught) one would think they probably lost about $10K per lathe shipped!
Thanks. I’ve often wondered the same thing – how did they make a profit. It is certainly a window into the craftmanship of that time. Something I never get tired of seeing or working on.
 

Klinton89

Plastic
Joined
Jul 22, 2022
Location
Middle TN
Looks like a good machine and intact – meaning no missing parts. It looks to be about the same age as mine. You might consider posting a serial number and maybe John Oder can give you the date. This to me is not just a nice-to-know, but also helps to document the lathe. Pratt & Whitney appears to have made many changes to the lathe as time went on and knowing the year of manufacture can help in knowing what parts will fit with what machines.

One other observation – it looks like you may have part of the optional relieving attachment, but there were also a couple of drive shafts and end gear box. I can’t see if you have a taper attachment. I’m kind of curious to see how the relieving attachment interacts with the taper attachment and cross feed.

Picture below of the relieving attachment from P&W brochure:
View attachment 371207
Yes, I reached out to John Oder, and he was kind enough to let me know it is a late 1958, just before 1959. Mine does have the taper attachment, but I believe it may be missing a piece to lock the carriage in with the taper attachment. I have never used a taper attachment, so it's all new to me. I'll hace to keep digging in to it. Any advise from you on it will be greatly appreciated. Also, yes it has the relieving attachment, but the drive shafts are missing. I looked to see if the previous owner had them, and they didn't. The guy I dealt with didn't know anything about it. I assume it would probably be something I would have to have made, because I highly doubt I'll ever be able to find them floating around the internet. Lol
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
Yes, I reached out to John Oder, and he was kind enough to let me know it is a late 1958, just before 1959. Mine does have the taper attachment, but I believe it may be missing a piece to lock the carriage in with the taper attachment. I have never used a taper attachment, so it's all new to me. I'll hace to keep digging in to it. Any advise from you on it will be greatly appreciated. Also, yes it has the relieving attachment, but the drive shafts are missing. I looked to see if the previous owner had them, and they didn't. The guy I dealt with didn't know anything about it. I assume it would probably be something I would have to have made, because I highly doubt I'll ever be able to find them floating around the internet. Lol
You said you were missing part of your taper attachment. Is that the part that makes the connection to the shoe, the actual tool to drive it or both? I included a few pictures of them. If you need a better description of the tool I made, I can add that.

As far as the relieving attachment, I think you may be missing a couple parts more than just the drive shafts. It would be interesting to see one in use. I’m not sure how much a person would really need one. My understanding is that relieving attachments were used in the 50’s and 60’s to make custom tooling, taps, reamers, etc. in house long before the days of the internet and CNC.IMG_0429.jpgIMG_0432.jpgIMG_0425_editted.jpg
 

Klinton89

Plastic
Joined
Jul 22, 2022
Location
Middle TN
You said you were missing part of your taper attachment. Is that the part that makes the connection to the shoe, the actual tool to drive it or both? I included a few pictures of them. If you need a better description of the tool I made, I can add that.

As far as the relieving attachment, I think you may be missing a couple parts more than just the drive shafts. It would be interesting to see one in use. I’m not sure how much a person would really need one. My understanding is that relieving attachments were used in the 50’s and 60’s to make custom tooling, taps, reamers, etc. in house long before the days of the internet and CNC.View attachment 371578View attachment 371579View attachment 371580
To be honest I haven't checked under the little cover to see. I'm most likely just missing the tool to drive it down and make the connection. Having no experience with the attachment, I wasn't exactly sure how it works. I'm on the road for work till the 21st so I can't even look at it to confirm until I get back home. I like the tool you made for it. I will definitely be needing to make something like that.

As for the relieving attachment, I can't imagine a time or scenario where I will ever need it really. It's cool to have it though since I know it's not a real common piece to have.
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
To be honest I haven't checked under the little cover to see. I'm most likely just missing the tool to drive it down and make the connection. Having no experience with the attachment, I wasn't exactly sure how it works. I'm on the road for work till the 21st so I can't even look at it to confirm until I get back home. I like the tool you made for it. I will definitely be needing to make something like that.

As for the relieving attachment, I can't imagine a time or scenario where I will ever need it really. It's cool to have it though since I know it's not a real common piece to have.
The way Pratt & Whitney attachment works is as follows: You position the taper wherever you want it. You bring the carriage over the top of the shoe in the taper attachment. On the backside of the taper attachment slide on the saddle is a little clamp you have to release. This releases a little tapered pin that holds the slide secure when the taper is not in use. Once that is done, you use the tool that I made to go through the little window and engages the dogs. It then has a drawbar that engages the movable pin and holds it solid. Then you simply turn it counterclockwise to engage the shoe. Now you set the angle of the taper you want to cut.

I have no idea what Pratt & Whitney’s original tool looks like. But without some sort of tool, it would be difficult to use.

There are a couple of advantages to this taper attachment and at least one disadvantage. The disadvantage is that is takes a little longer to set all this up. One of the advantages is that the taper travel is fairly long for this size of machine and can be positioned anywhere on the bed. It also runs completely in ball bearings – not just the shoe or the slide in the taper but also the slide in the cross-slide. It makes for extremely smooth and very low friction. It also has a very high degree of rigidity. I believe the taper attachment can handle the full power of the machine.
 

Doozer

Titanium
Joined
Jul 23, 2001
Location
Buffalo NY
After reassembling the taper and using the machine later, I discovered there was a bit of spring back in the cross-slide. I isolated this to two things. One was the little taper pin which anchors the slide. It had a bit of rocking motion. I was able to re-lap this pin and replace the lock square bolt with an allen bolt. This held the assembly rigidly but did not completely solve the issue.

Further investigation turned up the two bearings that secure the cross-feed screw (which you can see in the picture). These had a little bit of spring to them. I believe I read somewhere in one of the brochures or manuals that these two bearings were duplexed. I replaced these bearings with a couple of radial bearings and made shims for the outer race to induce some pre-load and increase the stiffness. This worked to some degree, but it still had .002 of movement in the cross-feed screw. If I increased the size of the shims, it would increase the stiffness but increase drag. I wasn’t happy with this.

So what I did was to use a double row angular contact bearing. This bearing has no movement radial or axial. I did have to make a bushing and some collars to adapt to the screw. This bearing is held in place in the slide by a screw-in collar which holds it securely. This was finally successful, and movement was reduced to a few .0001’s with the greatest force I could pull on it.

This got rid of any spring-back when threading or making heavy cuts. It made the lathe more predictable. What I’m unsure of is if the bearings that was in it were original or if someone had replaced them along the way. Without a parts manual it was hard to know what Pratt and Whitney had used here. If you have this type of taper, this is a modification I would recommend.

The last picture is of the angular contact bearing I used.

I’m not sure why Pratt and Whitney chose this particular design. It requires a little more work to set up than the taper attachments on some of my other machines, but it is very rigid and very smooth. Everything is either clamped or moving in ball bearings. There are no sliding parts. I also wonder if part of this design wasn’t to make it better able to accommodate the relieving attachment.
I know this post is from back in the thread, but....
I have a square head 12C and I have also tried to correct the exact same "spongy"
cross slide condition. My shot pin seems in OK shape. Was also thinking about
replacing the square head screw with an Allen screw. I like the lapping the pin idea.
Might have to re-visit that.
Anyhow, I also took apart my ball bearing taper attachment.
It was missing most of the balls. Ha ! I think the reason they made it ball slide
design has something to do with the releaving attachment option.
Anyhow, mine lathe also has the 2 bearings. I speculated there was looseness
there. What I tried was to add a shim washer (I think between the inner races)
so that when the pin spanner bearing nut is tightened, it actually preloads the
races. Now you have to be careful not to over tighten the retaining nut, as now
it effects preload, not merely retains them like it used to.
This worked somewhat. I would tug (by hand) on the toolpost and see some
dial indicator needle movement, but it was much less. Before I added the washer
between the bearings, I had like .005" of deflection. Now I had .001" with about the
same tug force. It is still not rigid as I would like it to be.
I like your idea if a double row angular contact bearing. I will have to size on up
and try it out. I am glad you mentioned this bearing, because I was going to re-
visit the shot pin and maybe make something more rigid (and less convenient).
But now I will check out the bearings again. I would rather not have to re-invent
the wheel when working on machines (but I do, it seems on every machine I touch).

----Doozer
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
I know this post is from back in the thread, but....
I have a square head 12C and I have also tried to correct the exact same "spongy"
cross slide condition. My shot pin seems in OK shape. Was also thinking about
replacing the square head screw with an Allen screw. I like the lapping the pin idea.
Might have to re-visit that.
Anyhow, I also took apart my ball bearing taper attachment.
It was missing most of the balls. Ha ! I think the reason they made it ball slide
design has something to do with the releaving attachment option.
Anyhow, mine lathe also has the 2 bearings. I speculated there was looseness
there. What I tried was to add a shim washer (I think between the inner races)
so that when the pin spanner bearing nut is tightened, it actually preloads the
races. Now you have to be careful not to over tighten the retaining nut, as now
it effects preload, not merely retains them like it used to.
This worked somewhat. I would tug (by hand) on the toolpost and see some
dial indicator needle movement, but it was much less. Before I added the washer
between the bearings, I had like .005" of deflection. Now I had .001" with about the
same tug force. It is still not rigid as I would like it to be.
I like your idea if a double row angular contact bearing. I will have to size on up
and try it out. I am glad you mentioned this bearing, because I was going to re-
visit the shot pin and maybe make something more rigid (and less convenient).
But now I will check out the bearings again. I would rather not have to re-invent
the wheel when working on machines (but I do, it seems on every machine I touch).

----Doozer
I did lap my little shot pin and then blued it until I got good contact. I also replaced the little square-headed clamp bolt with an allen cap screw. The way I clamp it is to put a little pressure on the clamp, use a brass mallet to give the pin one tap to seat it and then tighten it up. When everything else in the slide assembly is adjusted correctly, there is no movement.

The issue you’ve had with the cross-feed screw bearing sound almost exactly like mine. I believe Pratt & Whitney may have originally had a couple of angular contact bearings on this screw. Mine had some roughness so I just pitched them. The new bearings I tried were just a deep row ball bearing. I tried them in a DB arrangement back-to-back with a thin shim on the outer race to gain some preload. I even tried a bigger spacer in the inner race like you did, but the results were not satisfactory. There was too much drag.

I finally ended up with the one-piece, double row angular contact bearings which are actually out of the Rivett headstock. If I remember correctly, I had to make an inner bushing and spacer for the outer race to provide some clearance for the inner race, but then I just tightened everything down tight. The results were amazing. I have no more than a .0001 or .0002 of movement in the cross-feed screw while pushing and pulling with quite a bit of force still maintaining almost no resistance at the handwheel. When the gib and the backlash are adjusted correctly, the feel of the cross slide is very similar to the feel of my 10EE, if that helps any. A smooth, light feel.
 

Doozer

Titanium
Joined
Jul 23, 2001
Location
Buffalo NY
Interesting, thank you.
Any chance you have a number for the bearing
that you used?? I blew up the picture you posted
and still could not see the number.
----Doozer
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
Interesting, thank you.
Any chance you have a number for the bearing
that you used?? I blew up the picture you posted
and still could not see the number.
----Doozer
I believe the bearing is a New Departure, but I'm going off of memory on that. The number on the bearing is 5205 or it could have been 5204. You can also pretty easily pull the back of the taper housing off, unscrew the little retaining ring and measure it.

I'd pull it off and measure mine for you but this would require me to remove the backsplash but I'll help as I can.
 
Last edited:

Doozer

Titanium
Joined
Jul 23, 2001
Location
Buffalo NY
I can take mine apart. Thanks for the offer though.
So the number you gave me lets me know if I am in
the ballpark of finding the right bearing, so thank
you for that. It is interesting that our lathes have some
of the same problems. I must say, the C is much better
thought out than the B. The B had vertically oriented
gear trains in the headstock, whereas the C has horizontally
oriented gear trains. Easier to fix anything that way.
I seen Kimber Zellik working on his model B, and stuff is
really hard to access.
My lathe has the FWD-REV option and the 1500 rpm option.
18 geared speeds of course, but I seen one someone has here
that has also a 2 speed motor. 36 speeds? Man, that is bragging
rights, right there ! ! ! If it's girls or gears, it will cost you trouble.
If I dig in to it and find replace the bearing, I will post it here
or in a Doozer's Shop video.

-----Doozer
 

tailstock4

Aluminum
Joined
Mar 3, 2013
Location
Oklahoma, USA
I can take mine apart. Thanks for the offer though.
So the number you gave me lets me know if I am in
the ballpark of finding the right bearing, so thank
you for that. It is interesting that our lathes have some
of the same problems. I must say, the C is much better
thought out than the B. The B had vertically oriented
gear trains in the headstock, whereas the C has horizontally
oriented gear trains. Easier to fix anything that way.
I seen Kimber Zellik working on his model B, and stuff is
really hard to access.
My lathe has the FWD-REV option and the 1500 rpm option.
18 geared speeds of course, but I seen one someone has here
that has also a 2 speed motor. 36 speeds? Man, that is bragging
rights, right there ! ! ! If it's girls or gears, it will cost you trouble.
If I dig in to it and find replace the bearing, I will post it here
or in a Doozer's Shop video.

-----Doozer
Doozer – I did some more checking, and I was able to push the taper attachment all the way forward and bring the carriage all the way to the tailstock end to check the bearing. It is the 5204 bearing. You won’t need a center spacer. Only an outer spacer to provide clearance for the inner race of the bearing on the bearing retainer side. I now have a question for you.

My machine is 2-speed, 36-speed range from 7 to 1000 rpm. I believe Pratty & Whitney to get 1500 rpm only changed the drive pulley and speed chart. Could you give me the diameters of your two pulleys and motor horsepower and rpm? All I would have to do is make a new motor pulley. This would be one way to get higher rpm’s.

Another way I have considered is pulling the motor and electrics out and installing a 5 hp Baldor Super E motor and a Hitachi VFD. If I set the parameters to 30 to 90 hz, I should have 3.5 to 1500 rpm with variable speed. I would add a tachometer to monitor the in-between speeds. Maybe this would be a good project for me to document on the forum.
 








 
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