P&W 12x30 Model B - Need help badly

Good morning,

Yesterday I was turning down a gear blank and the lead screw stopped turning. It has been making a banging noise when I engage the feed lever for a little while now and I thought the tooth was worn. Now the toothed clutch won't engage in either direction. The feed lever still moves but the lead screw isn't turning.

What happened? I can only imagine a gear broke, but it was running and the lead screw was turning when I was cutting the blank and when I went to take the next cut it had stopped. I didn't hear any unusual sound during that time, either.

Also, what is the disassembly procedure to get to that area of the headstock? Everything looks like it has to come off before something else.

I'm a one-lathe shop and I'm stopped now. I'm on bended knee here. Thank you very much for any help you can provide.

A quick search turned up some information that may help.
Bill D.

http://www.practicalmachinist.com/v...g-pratt-whitney-12x30-model-b-spindle-205188/

Welcome to forum

Tell us more. Normal ops would have lever high and to right on apron in one of three positions - forward, neutral or reverse - lead screw and feed rod rotational direction - and it would stay in that one position unless you needed to back up - as in threading

As suggested, controlling the single tooth clutch

If feeding as in NOT threading, you would be using the apron clutch to engage and disengage feeds - if long feeds, the clutch knob centered in the carriage hand wheel

If you have been engaging and disengaging feeds with reverse-fwd-neutral lever - especially at high speeds, you may have successfully destroyed your single tooth clutch

Carl repaired his - possibly you will want to search his posts

http://www.practicalmachinist.com/v...y-12x30-model-b-ready-turn-once-again-158090/

Thank you kind gentlemen. Normally, I engage the feed lever and leave it engaged. The previous owner (yeah, I know, let's blame the old guy) would leave the lathe spindle running and engage the carriage feed lever when he needed it. It made an awful noise. I'm sure the clutch was unhappy.

When the lead screw and feed rod stopped rotating, moving the feed lever produced no movement at the single-toothed clutch. It didn't try to engage. I thought the lever that moved it in and out of engagement had broken. With the above information, I'm about to plow in. Wish me luck.

Thanks again.

Here are some snippets from 20" parts book (bigger Model B with same features) The J568 items are the "pins" that get tired of being beat on

You can see this lash up is in that portion of the head stock just above the ways - meaning it has to come off and get situated where you can work on it - from the bottom

Yes sir, I see that. I'll have to figure out how to get it up and get the lifting points identified.

I pulled the top cover to see what's what. The clutches are engaging but there is no output to the shafts. How is that possible? Is the feed select lever broken? This is getting more and more deep into the machine.

One more thing I found. The oiler up on top that oils the three bearings is not putting out anything. It is dry. I'd like a little wetness up there. Any suggestions on that one? I checked the oil and it looks perfect, like it's never been used. Now I know why.

One more thing, where did you get that manual?

Thanks.

I own the 20" manual - bought it from P&W in 1978

Note the shaft with the shifting fork is visible out side on both ends. Get a helper to wiggle the apron lever up and down while you eyeball the end of that shaft. If it rocks there is nothing wrong with the linkage

If the J568 pins are ripped off or damaged enough the clutch elements can engage all they want but no power will be transmitted

Let's worry about the oil later. I will say the pump is down low near back wall of bed - maybe it lost its prime some time ago

Here is the op manual for your 12". Do not know if anyone has a parts book

Pratt & Whitney Co. - Publication Reprints - Model B Operator's Manual | VintageMachinery.org

RexTWD said:

Yes sir, I see that. I'll have to figure out how to get it up and get the lifting points identified.

I pulled the top cover to see what's what. The clutches are engaging but there is no output to the shafts. How is that possible? Is the feed select lever broken? This is getting more and more deep into the machine.

One more thing I found. The oiler up on top that oils the three bearings is not putting out anything. It is dry. I'd like a little wetness up there. Any suggestions on that one? I checked the oil and it looks perfect, like it's never been used. Now I know why.

One more thing, where did you get that manual?

Thanks.

Click to expand...

Okay, now for the embarrassing part. The single tooth clutch on the side that drives the carriage toward the headstock is toasted. It's not completely sheared, it just looks sort of like my dog's head when I pull the skin back - badly worn with lumps and no good driving edge. Also, the feed select lever is having difficulty engaging. I haven't tracked this down yet, but that appears to be part of the problem. I can get it engaged by working it in but it needs work. Hopefully the old girl can get through the next few jobs before I have to pull it down for a big repair.

The oiling issue is bothering me, though. When I plugged the holes and blew in some air I could hear it coming out down below the gear train. I have no idea what is going on. Any suggestions on this one?

Thanks for all the advice and the links. I know now that when I have to do so I can get it broken down for a rebuild.

As you may know, power comes thru rear wall of bed and heads on up to spindle. Right where the gearing passes thru rear wall is the pump (at least on 20") with a pick up on the bottom.

So - level of oil has to be high enough for pick up, and since pump has to suck it up from there. it could lose its prime . I have no idea of how to restore prime except take apart upper plumbing and pour in oil. Oil on that machine in that area needs to be ISO 46 such as Mobil DTE Medium

As far as upper right lever on apron, get it engaged and don't touch it - use apron clutch instead

RexTWD said:

Okay, now for the embarrassing part. The single tooth clutch on the side that drives the carriage toward the headstock is toasted. It's not completely sheared, it just looks sort of like my dog's head when I pull the skin back - badly worn with lumps and no good driving edge. Also, the feed select lever is having difficulty engaging. I haven't tracked this down yet, but that appears to be part of the problem. I can get it engaged by working it in but it needs work. Hopefully the old girl can get through the next few jobs before I have to pull it down for a big repair.

The oiling issue is bothering me, though. When I plugged the holes and blew in some air I could hear it coming out down below the gear train. I have no idea what is going on. Any suggestions on this one?

Thanks for all the advice and the links. I know now that when I have to do so I can get it broken down for a rebuild.

Click to expand...

Thank you sir. I'll dig deeper.

My Model B 12 x 30 has a sight glass tower on the back giving a visual indication of the oil level. Hopefully yours is the same. If the oil level is well up to the mark the pump should self prime OK. You need to release the top of the tower to vent it so the oil can find its level. With the top screwed down its well sealed and the indicated level probably won't change. I know mine didn't move in 3 years of storage despite the actual level being low. Naturally Muggins didn't realise that the top had to be loosened and overfilled it. Removing the excess was bit of a game. I took the top off the clutch housing and pulled it out 1/2 litre at time with big oil syringe. So if you are having priming troubles and need to overfill the system its pretty practical to pull the excess out that way.

If your level tower has been knocked off and replaced with a plug, its pretty vulnerable when the machine is moved, you will need to dipstick it. The oil level should be about 4 1/2 inches below the top cover joint of the clutch housing. The bronze plate with adjustment details is a bit higher. Don't recall if there is a straight run making it possible its possible to dipstick down through the bronze plate or not.

Blocked output line(s) may well stop the pump self priming. A clear output path is important whilst its trying to clear the air bubbles. Blockages seem to hold the air enough that it just compresses enough to backpressure the pump. I had to clear the top distribution holes with a probe two or three times to get free flow but at least nothing was fully blocked and everything up top was wet. The B seems easy on its oil. Mine looked really good but sniff test said it was old, very old.

Clive

P&W 12x30 lathe lubricants.

[QUOTE:


Default Re: P&W 12x30 lathe lubricants.
Please repost question in forum so all can benefit from any replies




Quote Originally Posted by cobalt blue
I see in old thread where you recommend Mobil DTE Medium for the headstock.

Not mentioned in this thread, is recommendation for apron. Is Mobil Vactra 2 a good bet for this reservoir?

Also, what is good for all remaining oil cups and manual oiling points?



Stan aka Cobalt Blue

Not mentioned in this thread, is recommendation for apron. Is Mobil Vactra 2 a good bet for this reservoir?

Also, what is good for all remaining oil cups and manual oiling points?

Click to expand...

Looking in 12 X 30 Model B Circular 429-2 dated February 1943, I can only assume apron oils itself but not the ways.- oiling them via apron is not mentioned

If this is the actual case, you manually oil the ways with, say, Vactra 2, but in the apron reservoir you could use either Vactra 2 or DTE Heavy Medium. Same in all oil cups

I would imagine most ALL old way oiling systems that have not been apart recently to MAKE THEM WORK AGAIN no longer work anyway - making putting way oil in the apron for that purpose somewhat useless.

John,

From the 12x30 Model B Lathe Operators Instruction Book.

"Lubrication, Apron. A reservoir at the lower left hand side of the apron supplies oil to the apron, the carriage and the cross slide ways. This oil is distributed by a pump to the various working parts."

I interpret this to mean the carriage "ways" and the cross slide ways.

Assuming Vactra 2 is satisfactory for the rolling element bearings in the apron, then the Vactra 2 would be good for the ways as well.

Your point is well taken that any lathe of this age that has not had the pump R&R should be supplemental oiled on the ways manually.

Further discussion in the manual mentions manual oiling points on the cross slide ways that must be used when performing relieving operations. Presumably the pump is not actuated when relieving. Someone here that has been "in there" could perhaps enlighten us on that.

Stan aka Cobalt Blue

Not sure about the B, but the Model C Lathe has a piston type pump in the apron same as the gear box for feed thread selection and range. They are activated when the clutch handle I'd engaged and disengaged.