P & W grinder - I think - info?

Picked up this little Pratt and Whitney bench top machine as shown in the photos. It was part of the stuff in the Ada Ohio sale discussed here a while back and a few of you may have seen it if you visited.

I believe it is a grinder. No model number on it. No idea what collet or tool taper the spindle takes either. The knee goes up and down, the table traverses left/right, and the head moves fore and aft. All these travels are rapid requiring only a portion of a twist of a dial or lever, and there are no calibrated feed dials. There are locks and travel stops on all axes. It appears to be in reasonably decent condition. Looks like the V belt pulley may be an adaptation, but may be not.

Any info is appreciated, and especially comments on its utility.

A couple more photos.

Um. Probably not a grinder. More likely a milling machine.

Pratt & Whitney always specialized in "smaller" machine tools for the toolmaker - although as time progressed their tools became larger, more varied, and more specialized.

A similar grinder has been mentioned on this board at. https://www.practicalmachinist.com/...-help-308478/?highlight=Pratt+Whitney+grinder

Given that this has the "raised lettering" classic cast Pratt & Whitney brass plate I would put this one before 1885 - but the "type study" for Pratt & Whitney has yet to be published - I'm guessing on a change-over date. Earlier has the brass plate - later has cast in lettering or a stamped plate. That much we know.

Joe in NH

Similar, but a mill - from 1911 catalog - page 111

Precision tools : Pratt & Whitney Company : Free Download, Borrow, and Streaming : Internet Archive

Joe in NH said:

Um. Probably not a grinder. More likely a milling machine.


Joe in NH

Click to expand...

Thanks Joe.

I originally thought it was a little bench top horizontal mill too. I offered to buy it based on a poor photo of another machine where this one appeared in the background with a bunch of other stuff - no details really visible. After getting it I realized that there were no calibrated feed dials on any axis. Several pre 1900 machines I have had did not have calibrated lead screws or dial either, but this machine seems in very good condition for something that old and does not really seem to be from that era. Also, all the feeds are very coarse moving the axis through full travel with less than a full turn. I thought that might be more characteristic of a grinder than a mill, but I have little to no experience with grinders so...........

I have seen P&W collets before. Was it common for them to use their own proprietary collets in spindles, or did they use something standard?

My Nichols has four manual feeds (head up/down plus standard knee and table motions), two of them with no calibrated dials when the rack-and-pinion table feed preempts the leadscrew. The two rack-and-pinion feeds are both less than full turn, although for the table motion that's because you have to reposition the lever to avoid interference with the saddle. Even if you discount that interference, full X travel is only about one full turn.

Hand production mills of a certain vintage were usually fixtured and hard-stopped for a dedicated single operation. Think slitting a bushing, or gang-milling the sides of a rod end. So the uncalibrated manual feeds weren't usually a problem.

Guys, it's an OLD Pratt & Whitney hand miller. The old ones like this didn't have dials on the feeds, just hand levers. As has been mentioned, they were made for specialized operations. One just like this was mentioned over on the OWWM site back in 2017
Not a Milling Machine . . .or is it? - Old Woodworking Machines and the same discussions went on as to what it was. It is just a small milling machine.

I talked to the seller a lot about this one and was going to get it but decided my wife would do harm to me if another machine showed up here! Cute little machine.

Irby

It's a beauty! Pratt & Whitney Precision Bench Millers

Pratt also made a really useful tool and cutter grinder R8. Plus some excellent Jig Bores.

Federal Mogul down in Malden MO where they used to grind carbide burrs had several R8's When regrinding end mills the R8 and Monoset would set side by side in most tool rooms. They were fun to rebuild.

What I liked about it was the headstock was movable with a leadscrew. I hadn't seen that in a small mill like this before,

Irby

View attachment 245294

Earlier this year I picked up a P&W 3C bench mill, which is larger than yours but has a similar look and color. I have mine partially pulled apart to do a little cleaning. Mine uses the proprietary 4pn collet, which has a body (also called the back bearing) diameter of 1.000". There is a smaller 3pn (body diam. of .650) and a 5pn (body diam. of 1.312. Let us know the diameter of your spindle.

OK - I have very limited instrumentation here so rough measurements with a dial caliper and T gauge.

Max inside diameter of Spindle Nose 1 inch
Max Spindle thru bore diameter 0.775
rear collet back bearing diameter 0.650
back bearing to nose bore diameter 0.755
spindle nose to collet rear bearing 2.375
collet rear bearing length 0.5
Approx collet body length thru bearing 2.25

I found one reference indicating the collet would be a 3PN. Other references give the overall length of this collet's body as 2.063 - which is too short to get thru the rear back collet bearing journal area. Of course it is possible this journal area is a bushing that was pressed into the spindle bore and it has moved away from the spindle nose.

A 3C collet fits pretty well and sticks thru the rear bearing enough for a draw tube to get a good purchase on the collet threads, but the head diameter is way too small and the collet ends up recessed deep into the spindle nose.
Anyone know the diameter of the head of a 3PN collet? or the 1/2 angle of the taper?

a very rough first pass measure of the spindle bore taper 1/2 angle gives about 13 or 14 degrees.

At this point I agree - this is a very small horizontal milling machine for production use where a fixed setup would be normal and rapid manual table movement from stop to stop would be the normal. That said, setting the other axes to a precise location would be challenging given the rapid feeds and no provision for fine adjustments.

Inside the column there is provision for a hanging counter weight to balance the weight of the knee and table. The chain and sprocket are there but the weight is gone.

Overall the machine seems to be in really excellent condition for its age.

I did notice that there is a sliding pin at the rear spindle bearing casting area that should slide forward and engage holes in the rear face of the spindle pulley. The V belt pulley currently installed has no such holes. Also, my impression is that most older machines designed for flat belts and step pulleys have slopped surfaces in the head casting under the pulley somewhat matching the contour of the step pulley. This mill does not - wonder why? I am also currious as to why there is no provision for an over arm support.

I weighed it on the bath scale - which like most tells lies - it reads out at 121 lbs.
Table travels are approximately X = 7-1/2, Y = 2-3/8, & Z = 4-1/2.
This gives a very small work envelope for what I do. Since I am cutting way back on the antique machinery collecting aspect of this hobby, and since I have lots of projects including two other larger horizontal mills, this machine is probably not a good fit for me.

IT is Cute as heck - couldn't leave it behind - but probably should have.

How close are you to Dayton?

Irby

View attachment 245485

Here are the measurements from my 3pn. The 3C is close but longer and has 26tpi instead of the 3pn 24tpi. I calculate about a 21.92 degree angle. I did notice the diameter of the threaded portion of my collet is .641 instead of the .645 I see in charts of collet dimensions.

One other thing. On my 3C mill, the 4pn collet only sticks out about 1/8".

Here are some other dimensions for a P&W 3PN:


Irby

Irby, that is interesting. Where did you find that? I use two sources, one being the Hardinge catalog and the other Xtronix and they both agree on the shorter 2.063 length. I have an actual collet that appears to be 3pn although there are no markings saying so. But it fits all of the dimensions from my two sources except a slight difference on the threaded portion diameter.

Actually that was a figure from this forum I had bookmarked a while back. It came from this thread: https://www.practicalmachinist.com/vb/general/3-pn-collets-235772/

So is this figure's length wrong? I'm a Hardinge collet person myself (or at least 3C, 4C, and 5C), and have no P&W collets here.

Irby

I did find another source that refers to Pratt & Whitney No. 3, whose measurements don't match what I have and then a P&W New Style No. 3 that has the measurements of your picture. So maybe there were multiple versions??

View attachment 245491

Thanks all for the responses.

In searching the web I found 3 different length dimensions stated for the 3PN collets, thus the request for a measurement.

I am now convinced that this is a hand miller intended for production use. As received, it had a shop made holder for 1/2 inch shank tools and it had a big box of mounted grind stones with it suggesting it was being used as a grinder.

It is in very nice condition for its age, if it is any where near as old as suggested.

I am in the Columbus OH area.

It is too small for my use so if someone loves it - PM me.

I didn't see these pages in John's link (although I may have missed them)

From my 1917 catalog:





I'd adopt it in a sec if it was closer. I have a soft spot for those little mills, and P&W stuff in general.