Joining the Pratt & Whitney 3C family

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

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discodan
Posts: 118
Joined: Mon Oct 22, 2018 10:08 pm
Location: Annapolis, MD

Re: Joining the Pratt & Whitney 3C family

Post by discodan »

One thing I just thought to ask is if you have a brass ring that fits on your draw tube that measures 0.1345" thick? I wonder if that is to space it out to compensate for some of the extra length of my collet?
SteveM
Posts: 7763
Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

Re: Joining the Pratt & Whitney 3C family

Post by SteveM »

discodan wrote: Fri Oct 26, 2018 1:25 pm One thing I just thought to ask is if you have a brass ring that fits on your draw tube that measures 0.1345" thick? I wonder if that is to space it out to compensate for some of the extra length of my collet?
My guess is that you are correct. The spacer is the prior owner's "adjustment" for the collet length.
Drawbar_a.JPG
On mine, the adjustment was that there were two nuts on the end, the inner of which was machined to center on the spindle and the outer one jammed up against it.

BTW, I knew I had a drawing of the collet. Here it is:
PW4_Arbor_Drawing.JPG
Here's a pic of my mill:
PW_Mill.JPG
That was before I got an original switch and overarm, and before I pt it on a "proper" bench.

Now that I have the lathe, I need to look at making a longer bench for the pair.

One of the best vises to use on this mill is the South Bend drill press / shaper vise. It's 4" wide, an inch deep and fits on the table.
SB_DP_Vise.jpg
Even a 3" kurt is too big for most operations if you don't have a swivel (the vise will only fit in one direction without one).

Most of the time, they are pricey, but occasionally, you get lucky.

Steve
John Hasler
Posts: 1852
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Joining the Pratt & Whitney 3C family

Post by John Hasler »

25 degrees is a long way from the 34 degrees of an R8. An R8 in that taper will tend to close tightly only near the very end. Between that and the loose back bearing I don't see how you can avoid a lot of deflection under side load.
discodan
Posts: 118
Joined: Mon Oct 22, 2018 10:08 pm
Location: Annapolis, MD

Re: Joining the Pratt & Whitney 3C family

Post by discodan »

It is interesting comparing how our machines are similar and different. I have the original switch on mine but it is not hooked up to the motor, so I need to see if I can confirm that it works and is able to operate my motor. I am attaching pics of my draw tube, which looks original, but doesn't appear to be adjustable like yours. I also added pics of my Craftsman variable speed motor and the unknown maker 3 1/2" vise with swivel that I got at Hershey. I just used it last night to cut down the height of the t slot nuts from Shars.
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discodan
Posts: 118
Joined: Mon Oct 22, 2018 10:08 pm
Location: Annapolis, MD

Re: Joining the Pratt & Whitney 3C family

Post by discodan »

Pics of my switch. The date on the little label is Feb. 1947.
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SteveM
Posts: 7763
Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

Re: Joining the Pratt & Whitney 3C family

Post by SteveM »

That is an original drawbar; he just added a spacer. I have the original too. If you notice, there is a bearing on that so that it's not a lot of friction when you tighten it.

That vise is very similar to the South Bend drill press vise, so it should do decent.

The original motor was 3/4hp, so you could upgrade at some point, but the adjustable speed is nice. Only issue is that at low speeds, it won't have any power. A good solution is to set up an intermediate shaft with a dual pulley, so you have a high and low range. be sure that there is some overlap so that you cover the full range of speeds.

The spindle speeds with the original 2-speed motor with the variable speed drive are 125-375 in low and 250-2,250 in high, so be sure whatever you do, you don't go much faster than 2,250.

That switch has a zillion contacts because it is meant to switch a 3-phase 2-speed motor. By using a voltmeter on ohms, you can figure what contacts do what.

Your switch is missing a small conical ramp with a hole in the top for the reversing switch plunger to go into. It prevents you from starting it my accident and from going from forward to reverse without pausing at stop.

Steve
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