Re-Assembly of a Pratt & Whitney 3C Horizontal Mill

In THIS THREAD I asked about Pratt & Whitney 3C horizontal milling machines as I was offered one. I actually made the deal and moved the machine last weekend. Much of it is still in boxes, especially the nice tooling selection that came with it. As the machine gets reassembled I'll add photos and text. Never having operated a horizontal mill I’m going to have my own questions to ask. So I’ll be posting them here.

It was broken down in pieces such that my brother and I could move it out of tight quarters in a basement and up some stairs. Two 90* turns involved, one at the bottom of stairs and another at the top thru a doorway.

I boxed up all the tooling and disconnected all the electrical connections and disassembled the mill as best I could a couple nights before the move. I separated the table and the knee from the mill main casting. Removed the Speed Ranger Drive as one lump. Then unscrewed the tabletop, we flipped it over and removed the Speed Ranger Hanging brackets. The cabinet went up the stairs on a handtruck. All the other pieces were horsed up the stairs by my brother and I.

At this point I have the cabinet back together, the Speed Ranger Installed, and main column assy bolted back on the table. All I plan to do is clean it up. At this point it appears to be in excellent shape. Just needs 70 years worth of cleaning. I am guessing this machine was built sometime about WWII?? But don’t really know. I worked in the Aerospace machine Shop at the U of MD in the late 90’s. I first saw this machine there. It came from some other facility on campus. A more senior machinist took ownership of the machine and he has had it since. He hunted me down and gave me first right of refusal.

Some photos of it in its current state in my garage. More to come as the reassembly progresses.

Cool!

Welcome to the "Unofficial P&W 3C Owners Group"!

Post plenty of pictures - the more documentation the better.

I see you have all the wires labeled. Please post a diagram of how to wire up the switch, if you can.

Steve

I have to say that spinning the spindle by hand it sounds as if the "permanently lubricated" bearings are dry. 65 yrs was probably far longer than the mfgr intended. I saw THIS POST describing spindle removal. Can anyone comment about the bearings. Are they open cage, rubber sealed, etc. My concern w/ removing the spindle is making sure I can be certain I can get everything clean. And I assume as long as I keep track of the tab position I can get the preload back to exactly where it was.

I have to measure to see current spindle ID runout and axial movement. The spindle feels quite solid with no movement. Bearings don't feel notchy at all. The just sound dry.

I have some light Castrol grease, and some even lighter Lubriplate grease on hand. Any recommendations for a spindle bearing grease to apply once I get to a point of re-assembly?

The bearings are open. No problem getting them clean. 2 at the business end and 1 at the pulley end.
I used Mobiltemp 32. Greg.

Thanks rustytool. How did you make certain you had the bearing preload correct when re-installing spindle?

Preload ? What's that ?
I just made a note of the position of the lock washer and nut and reassembled to the same position.
The correct way to do it ? Probably not but the bearings don't heat up and there's no runout or noise.
I figured it would better than running it with 60 year old dried up grease.
What's the serial number of your machine ? Mine is 497 and I read somewhere that puts it at 1947. Greg.

What means allows you to put the nut back in the same position? The lock-washer must be keyed to the spindle then? Is that how its done?

You asked about my S/N. Its a 6 digit number, any idea of its birth year?:

morsetaper2 said:

What means allows you to put the nut back in the same position? The lock-washer must be keyed to the spindle then? Is that how its done?

You asked about my S/N. Its a 6 digit number, any idea of its birth year?:

Click to expand...

Cross reference the bearing numbers. If they are DB duplex pairs, then the preload is built in to the bearings, and you just tighten the nut up and they will preload themselves. This is the most common set up but to be sure..
A cross reference of the bearing number will sort that out...

Dave

Dave, Yes it looked to me from the way the unit is designed the preload is taken care of and all I had to do was tighten the nut up.
morsetaper2, the lock washer is keyed to the shaft. I counted the number of turns to get the nut off and which locking tab in the washer went into which slot in the nut. But like Dave pointed out, just tighten up the nut snugly and you will be good.
I've haven't seen a 6 figure serial number before. Greg.

rustytool said:

Dave, Yes it looked to me from the way the unit is designed the preload is taken care of and all I had to do was tighten the nut up.
morsetaper2, the lock washer is keyed to the shaft. I counted the number of turns to get the nut off and which locking tab in the washer went into which slot in the nut. But like Dave pointed out, just tighten up the nut snugly and you will be good.
I've haven't seen a 6 figure serial number before. Greg.

Click to expand...

If it is a DB pair, then the lock washer is just to make sure it doesn't loosen up. Modern bearing nuts have a nyloc liner to lock them....no so the old ones...so they use a lock washer with a tab...the washer has a key "tongue" to lock it to the shaft keyway. The nut is probably castellated, and the OD of the washer has a tab that you bend over into one of the slots in the OD of the nut....and it's locked. Actually...I think it's a better design than the nyloc...the nyloc is just cheaper.....

Dave

MT2....just want to say...that is a beautiful little mill...take your time and do it right....SWEEEEEEEET!


Dave

Guys, thanks all for the bearing info.

Regarding the S/N.... my S/N ref books only offer up 3 digit S/N's. Is mine later?

Edited with a few extra entries, number listed is last S/N that Year. Below are the only entries for #3 bench millers:


No 3 bench milling machine, M-1378: 1927/sn 163, 1935/sn 295, 1947/sn 336
No 3 bench milling machine, M-1803: 1947/sn 495

Above from yr 1959 Serial Number Reference Book

Is M-1378 the earlier flat belt #3 miller? Still making it as late as 1947?

MT2, Now I know mine is a 1948, thanks.
My guess is yours is either serial # 522 or 350 with the other number being a lot number.
Just a guess. Greg.

Spent a little time today cleaning up some parts for this mill, pics above. No major surprises. I may have to remake one of the way covers. Seems the "catch" on one of them has been worn away over the years. You might see a blue arrow in the pic pointing to the spot.

Seems like its common to find shims under the gibs. There was an .008 shim behind the knee Z-axis and the Y-axis saddle. The X-axis table is still packed in a box. I wonder if its gib has a shim?

Most perplexing is the clamp for the rotating universal axis. Any amount of fiddling I couldn't get it loose. After a session with the whole knee & saddle assy in the parts cleaner I discovered what seemed to be a dowel pin in the bottom of one of the holes where the taper pipe plug looking lock-down screws go. After getting it out it all came free.

Looking at it later, I'm wondering if what I thought is a dowel pin is actually the tip of the tapered lock-down screw that broke off? On the other side there is the same piece in the bottom of the hole. But can't get that one out... errr haven't got it out yet. Ends are disfigured so can't identify a matching break on each.

Question: So are the tips of my taper screws broken off?

What's involved in getting the knee screws out? Looks like there might be straight or taper pins holding them in. And maybe some screws. There is a coat of paint applied over the original so its not obvious w/o scraping paint off.

Question: Whats the process for getting the two acme screws & dials out of the knee to clean them all up?

Yes the tips of the taper screws are broken off. I had the same problem and just made a new one.
I didn't take the screws out of my knee. Wasn't sure how and figured I'd leave well enough alone and not screw it up. I was able to clean it up well enough in place. Greg.

rustytool said:

Yes the tips of the taper screws are broken off....

Click to expand...

Thanks Greg, I figured that was probably the case. If the tips always tend to break off maybe I'll just use them as they are? Or remake them out of 4140 Pre hardened..

Snooping around in Jim Rozen's pics in the metalworking dropbox I found a photo of him stripping the knee of his 3C and some clues to how the "cranked" elevating screw might be removed. Hopefully he might chime in with more details.

Ah. Hmm.

There's a setscrew involved. The boss of the knee, that the elevating screw is mounted on, has
a setscrew that holds a sleeve. I seem to recall the setscrew has to be removed for the
bearings to come out. I can't remember if they come out as a cartridge, or if the sleeve is
the spacer between the two angular contact bearings.

Also I can't recall if you have to remove the bevel gear off the shaft, to remove the
assembly.

I do for certain now know I should have taken more photos!

Spent some time on the mill today. Want to get the knee apart to clean it up. I found the slotted head set screws jim rozen was referring to after digging under some paint. One on each screw axis. And what looks like a taper pin on each axis too.

In THIS PHOTO you can see two holes. Set screw removed from right hole. And what I'm thinking is a taper pin hole (left hole). And that there is a hole inside the knee casting where I might apply a punch & hammer to drive it out from the "inside" of the knee casting.

But using a hammer & punch on what I think is a taper pin, from both directions on each axis didn't budge either of them. Although I didn't try and press my luck with heavy blows. But when striking what I think is the taper pin things are real solid and its not budging. So before I get too hamfisted I figure I'll describe what I found and see if anyone can shed some light.

It looks like the gears at each shaft are pinned to the end of the screw too.

Went downstairs to inspect: yes, two taper pins. The one on the crank boss definitely drives out from one side, the one one
on the elevating screw bearing assembly (the two are of course linked with bevel gears) seems as though it has to be
driven out from inside the knee casting. Darn me to heck for not taking more photos!

Jim

I tried again to drive the taper pins out but they refused to budge. And I felt like I might be approaching the point I might break something. And besides, don't bearings generally get damaged on removal when you don't have direct access to drive them out properly?

So I cleaned the parts cleaner out. I had cleaned a ton of chips and crud out of the inside of that knee previously in the parts cleaner. So now with the knee disassembled even further, with the screw bearings now exposed, I ran new solvent through them to flush out whatever crud was remaining in there. The bearings were a little notchy from debris prior to this latest cleaning. But after this cleaning they spin freely. Added a little oil to them and they are really smooth now. Much much better than before. So I'll abandon the idea of removing the elevating screws, bearings, & gears.

So next is make a replacement sliding way cover, try and remove the tip of the broken taper screw from its hole, and make two new taper screws. I have some 4140 pre-hardened I can use for them. Not sure what I'll make the way cover from.