Pratt & Whitney Model C 12x30 lathe

[motormech1]

Pulled the motor out and cleaned it up to take it to the motor shop. My mill motor needs looked at so figured I’d kill two birds with one stone and take both. It likely hasn’t run in at least 20 years and there may have been a mouse living in it at some point. It has remote grease fittings plumbed with brass tubing and fittings which won’t be needed with sealed bearings but they looked cool once I cleaned it off. I forgot to take a pic after cleaning but while I was wiping it off I noticed a badge covered in gray paint and cleaned it off with some solvent. I like this old motor more and more! And talk about heavy. By my calibrated sphincter, feels like about 125 lbs. maybe more. It’s all cast so no surprise there.

 

[tailstock4]

Pulled the motor out and cleaned it up to take it to the motor shop. My mill motor needs looked at so figured I’d kill two birds with one stone and take both. It likely hasn’t run in at least 20 years and there may have been a mouse living in it at some point. It has remote grease fittings plumbed with brass tubing and fittings which won’t be needed with sealed bearings but they looked cool once I cleaned it off. I forgot to take a pic after cleaning but while I was wiping it off I noticed a badge covered in gray paint and cleaned it off with some solvent. I like this old motor more and more! And talk about heavy. By my calibrated sphincter, feels like about 125 lbs. maybe more. It’s all cast so no surprise there.
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Mine was pretty dirty also. It has a GE 2-speed 440-volt motor. When I disassembled it, I decided to replace the bearings in the motor. They ended up being hard to find as they had extended inner and outer races. Eventually I was able to find new ones of the same dimension by simply going to double row ball bearings.

I love these old motors. They may not play well with VFD’s, but they can run in any condition or load all day and be within a few degrees of ambient. I guess that’s how so many of them made it for 60 or even 80 years.

 

[motormech1]

@tailstock4 I was planning on running mine with a VFD for phase converting but run it at full speed and just use the gearbox. Do you ever feel like you want more speed selections with yours?

 

[tailstock4]

@motormech1 - As far as speed selection goes, no. With a 2-speed motor it has 36 speeds (7 to 1,000 rpm) which are more than enough speeds for me. I did have plans for variable speed using a 5 hp Black Max and the original pulleys. I was considering this mostly for the advantage of reaching 1,500 rpm. But this modification is a low on my priority list.

One thing to be aware of is the input shaft speed should be no lower than 500 rpm or higher than 1,000 rpm because of the oiling system.

Really, 1,000 rpm works pretty well if I stay with positive tooling or high speed steel. I still occasionally use its original Lantern tool post that came with the machine. This type of tool post still has some advantages.

I've included a picture of the Lantern tool post. If you look closely you can see the center scribe mark which was probably put there a long time ago.

 

[motormech1]

Good to know about the oiling system. Wonder if it could be converted to an electric system or something so it wouldn’t be speed dependent. Oh well, that’s pretty low on my priority list right now. Lol

 

[tailstock4]

Good to know about the oiling system. Wonder if it could be converted to an electric system or something so it wouldn’t be speed dependent. Oh well, that’s pretty low on my priority list right now. Lol

Maybe so. I did something similar on a Smith & Mills shaper that had a gravity-fed open oil system. I installed two small electric oil pumps - one as a backup for the other. It is wired in such a way that the machine won't start unless these pumps are running. One word of caution, it turned out to be more difficult to design an automated oil system for a machine tool than what I originally had thought. You not only have to account for speed, but also temperature and oil viscosity. I had to make my own meter valves. After some experimenting it eventually worked well.

 

[motormech1]

Is the P&W a relatively low pressure system?

 

[tailstock4]

Is the P&W a relatively low pressure system?

I've never actually measured the pressure. Mine has a pressure relief valve. My guess would be 30 lbs. or so.

 

[tailstock4]

Maybe so. I did something similar on a Smith & Mills shaper that had a gravity-fed open oil system. I installed two small electric oil pumps - one as a backup for the other. It is wired in such a way that the machine won't start unless these pumps are running. One word of caution, it turned out to be more difficult to design an automated oil system for a machine tool than what I originally had thought. You not only have to account for speed, but also temperature and oil viscosity. I had to make my own meter valves. After some experimenting it eventually worked well.

I know this isn't a Pratt & Whitney but some of the issues would be the same. There is a lot more to it, but here are a few pictures of that rebuild.

I have learned through the years that if I make changes to these old machines, I had better be sure of what I'm going to do and give it a lot thought because I know the original manufacture did. Eventually I usually find the reasons for their design choices.

 

[motormech1]

I have learned through the years that if I make changes to these old machines, I had better be sure of what I'm going to do and give it a lot thought because I know the original manufacture did. Eventually I usually find the reasons for their design choices.

I definitely agree. Especially considering we have tech like VFD’s, etc. that was never part of the design. An oil system change would definitely have to be extremely well thought out move. I highly doubt I’ll ever need to run the lathe over 1000rpm so it’s more of a mental exercise.