Pratt & Whitney Model No 3 "chase threading attachment"

Hi all of you,

I need a bit of help here. (don't we all) Years ago I bought a lathe that happened to be a P&W No3 bench lathe. I fell in love with it right away. After a couple of years I found out what it was and that the "wooden" bed that came with it was not original. Finding out that there was a little milling machine brother was even a bigger thrill. Now years later and watching ebay close every day I have the biggest part of the family together! Always looking for little bits and pieces. There is nothing around here, the Netherlands, so that makes it harder. But not long ago I managed to by a, long desired, "chase threading attachment" on ebay. I found out that that was not complete either.
I have got only one master thread, so I am looking for more and I am missing most of the change gears, which is not a big deal. But what is a pity is that I do not have a clue as what the gear that is attached to the headstock spindle looks like or how it is attached??? Is there anybody out there who can supply me with pictures or measurements so I can make something myself?? I would probable be able to reinvent the wheel but why bother!
Any help would be greatly appreciated.
Many thanks,

Melle Wondergem
Amsterdam

Er, there was a man here who owned one of those, with threading attachment
(chasing setup, fed to compound via a linkage of universal joints) and I am pretty
sure that I was so intruiqued by this I saved the photo on my computer at work.

Will hunt it up monday and try to post it.

In the meantime for your viewing pleasure:





Oh. Hold the phone here. There are some thread chasing setup photos
in the dropbox - don't know if the one I have is different - I'll still check. But:





Now your setup might possibly a backmounted chaser type?

Here's what the similar Hardinge set up looks like. May give some ideas.


Note the bed plate with hardened wear strip for the follower to ride on.





On the Hardinge, the gear on the spindle is twice as wide as the other gears, and it is a smooth slip fit onto an extended part of the spider for the lever collet closer. The outboard end of the hardened spindle is a smooth straight stub with a thin keyway in it. The spider is also hardenened & slides over this and has a key that fit the keyway. The spider also has an external keyway. The gear is bored for a very close fit over the spider shank, and there is a loose key that fits in to retain it. So the gear is assembled to the spider, the key slid in, and then the assembly is slid onto the outboard spindle stub, and the collet closer installed to retain everything.

Lathe in photos is mine, and I use the chase threading extensively. Mine came with piles of gears and 5 thread hobs, though there were only 3 different pitches. I made and hardened one for a particular product I make to turn 7/16" x 14 pitch square thread screws. It is reatively easy to make a hob if you have another lathe with leadscrew threading. I used O1 for the first hob, but would probably use A2 to make others. Skip the oil quench and opprotunity for distortion.

The hobs have buttress threads. This is important: If the driving face of the thread is not vertical (90°), then the location of the cutting tool and hence the accuracy of the pitch depends on how deeply the follower is engaged, depending on the slope of the driving face.

A friend has one very similar for sale, with tons and tons of 4c tooling but not so many gears. One thing about gears on a chase threading: There are no thread dials, so it is easiest if the hob is the same pitch as the desired screw pitch. If not, use a hob that is a divisor of the desired pitch, not a multiple. For instance, I use a 10 pitch hob for 20 pitch threads for collets I make and sell for mortice machines. If you try to use a 20 pitch hob and make 10 pitch threads, it is almost impossible to do it with any speed without double threading. If the hob is the same or a whole number divisor of the pitch, chase threading is a _very_ fast method to production single point both ID & OD threads.

Edited: Note, i commented that the spindle gear is twice as wide as the rest of the gears. This is not obvious in the post above because i cut down one of mine to allow a compound gear to fit beside it for some threads. It is double wide at the base for fit and stability, but I reduced one side to clear a large compound gear in a previous set up. I do keep some of the double wide, since sometimes the next gear is better set to one side or the other.

smt

Since there are two replies showing two completely different attachments for cutting screw threads, I will comment. I don't have a P&W catalog and don't know their terminology. But my Hardinge Cataract catalogs use this terminology:

The "screw-cutting attachment" drives a shaft that connects to the longitudinal feed screw on the slide rest.

The "chasing attachment" drives a master screw, or hob, mounted on a T-slot on the back of the bed.

Larry

The photos Jim posted are of a friend of mine's lathe, and he adapted that attachment from some other manufacturer's lathe (can't remember which one now). P&W made only the hob-style (rear mounted) attachment, which they referred to as the "threading attachment" in their catalogs.
I used to have one of the gears you are looking for, but I think I sold it a few years ago. I will check to be sure.
Andy

Andy FitzGibbon said:

The photos Jim posted are of a friend of mine's lathe, and he adapted that attachment from some other manufacturer's lathe (can't remember which one now). P&W made only the hob-style (rear mounted) attachment, which they referred to as the "threading attachment" in their catalogs.
I used to have one of the gears you are looking for, but I think I sold it a few years ago. I will check to be sure.
Andy

Click to expand...

Thanks for providing the clue to jog my memory. Your friend adapted the geared power feed attachment from a Hardinge Cataract bench miller to make his screw-cutting attachment for a P&W lathe. One of the rarest Cataract accessories there is, and only the second I ever saw. I have the other one.

Larry

Dang I'm pretty sure I've got another photo of a PW setup at work that I nabbed
off the internet. Maybe an ebay auction?

Can't remember if it is leadscrew cutting or chase cutting. I'll post it when I can.

There was a No. 3 lathe on eBay recently that had a chase screwcutting attachment.
As I said, the only threading attachment shown in any of the No. 3 lathe brochures I have seen was the chase style, as below:



The 3C lathe's threading attachment was of the driven-slide rest style.
Andy

Jim, were you thinking of the Stark that has been posted here by the owner iun the past? (photos cribbed from metalworking dropbox)





Or maybe it was this one?





smt

P&W Chase Threading

Melle,

The grey P&W No #3 that Jim posted is my lathe. The driveshaft arrangement is not original to the lathe. P&W never offered this type of threading attachment with their No 3 lathe. I set it up using parts to provide a drive for a fussee cutting attachment for clockmaking (set up pic attached).

The chase threading as posted by Stephen Thomas is my Stark #4 . The chase threading attachment is partially original. I had to cut all the gears myself and also make the master hobbs. This is the only type of threading attachment that was offered by P&W for the No3 lathe.

It is very rare to find one of these attachments complete. If you want one you probably will have to figure on fabricating many parts yourself in addition to making the change gears. I currently not at home so I don't have access to all my photos and info.

Thanks to Jim & Stephen for posting the pics of my lathes.

Joe

Hi guys,

Sorry for my late reply, this blog thing is new to me. I wanted to ad some pictures as well but I could not manage. I ll keep trying.

First, thank you all so much for your enthusiastic and quick replies with so much info. And of course the wonderful pictures.

Jim, what a nice machines you have got. I have got the same setup but with the older type miller. I am the one that bought the one that was for sale from Sobel Machinery and I still feel privileged to own it. I have got a question for you. My lathe has lost his oil cups and on the pictures it seems that your lathe has got the original ones. I am planing on making my own. Would you be able to shoot some close ups and maybe ad a few measurements for me. If not, no hard feelings I understand. Thanks for your help so far.

Stephen, thank you so much for you additional info, priceless!! It is nice to hear how it works for you and it underlines what I have read elsewhere that it is a pretty accurate way on cutting threads, which appeals to me. It is going to take a while before I will have it up and running when I still need to make some bits and pieces, but exciting stuff!

Larry, Andy,
You are right, to be accurate, I have a back mounted chase threading attachment. An original one! As in the catalogs. I have one of the old sales catalogs as well and it even has some hand written prices in it as well. But I don't know from which time the are exactly. But exciting enough, it has got prices of most of the accessaries. Nice reading, practically what is on the website Lathes.co.uk.
Andy, please tell me you did not sell it! I would love to know what the parts looks like.

Joe, what a gorgeous little lathe your stark lathe. Really nice. And the threading attachment looks the same. Well all most.

Well guys, my problem remains, so far. When you take a look at Jim's picture of his lathe's headstock you can see that where the gear that powers the attachment is fitted there is only a bare piece of tube that is the spindle.
There is no keyway or any other way of fixing the gear from rotating on the spindle. At least, that is on my spindle. You could make a gear on a split ring that fits the spindle tightly, with a screw to tighten it even more but even that could slip eventually! Any bright idea's out there?? Making a keyway is going to be difficult since the spindle is hardened.

Guys, again, thank you so much for your thought's, pic's and help. I really appreciate it.

By the way, here some bad pic's taken with my phone. My lathe is now being given some tlc, the bed is being reground and scraped. It's going to be costly I guess,but it's worth it!

All the old Hardinge spindles have keyways, needed both for threading gears and for lever collet closers. Ditto my Levin lathes.

But Derbyshire and the American Watch Tool lathes, and others, have plain spindles. A couple of Derbyshire lathes I own had two holes drilled through
the spindle 180 degrees apart. The lever collet closer part had mating set screws. Holes are much easier than keyways, even in hard steel.

I used the split bushing in the gear, pinned on one side of the split and with a set screw on the other, to mount a threading gear to my Derbyshire
lathe. The plan for that arrangement is in the Levins' book Practical Benchwork for Horologists. Cutting threads on a watch lathe does not put much
torque on the spindle gear, so I have no worry about slipping.

Larry

Still haven't had a chance to look and see if I still have one. But, as I recall, it had a split sleeve with a screw to tighten it down on the OD of the spindle.
Andy

Sounds like you purchased a p&w milling machine from sobel? The only one I ever
saw him ship was a full-up bench model with the underneath drive - which
incidentally had an IBM brass tag on it, I'm honestly not sure how Janusz Wilczinski
managed to sell that to him. But there you are.

You must have purchased that machine long before he closed up as I don't ever
recall seeing it there in his shop.

Anyway I would be happy to shoot some close-ups and do a quick sketch of
those oil cups for you. Give me a few days.

Jim

Here are some pictures of my thread chasing lathe bought on Ebay last year

Here are some pictures of my thread chasing lathe bought on Ebay last year. The yoke is broken but will be repaired shortly, and I am missing the change gears. I have been looking for the measurements to recreate a complete set of change gears, if anybody has them I like to get them. in the meantime, I will take a look at the spindle shaft and see how the spindle gear is affixed to the shaft, Thanks

Larry, thanks for the tip, the two holes thing might be just what I'll do when all else fails. I would love to make something up that is original but if that is no option than this will be.
A thought: I do not understand though that P&W, making such sturdy and well made machinery, came up with something that might slip!
I have the same thing with the angled head for the milling machine of theirs.
When I want to put a mill in a collet and tighten the drawbar there is no sensible way of locking the spindle! I know you should never over tighten things, and I am mister over tightening but this is silly. When end mills start slipping or you loose your thread then what? I know, I know, by then you over powered the machine anyway but still....

Andy, Jim: I appreciate your help immensely, and I would love all the info and sketches that I need to get this stuff made but ....take your time aye, this thing has been under my bench for ages now. And I certainly do not want to rush anybody. But I do like the shared enthusiasm, try to talk to your partner about this stuff !!

Jim, I bought the miller from Sobel just befor the old man died. I must have been the last one in the store, Aladdin's cave. It had been on ebay for more than a year and I do not understand why nobody bought it, it had everything with it!! So I talked to his son and had it shipped.

oldmasheentuls, That's IT!!! I have got the same thing and Andy seems to be right in how it is connected! When you have some time I would love more info. As for the gears you are thinking of making, from the sales catalog I know that the attachment came with 6 gears. It does not say with how many teeth thou, and if you ever find out let me know as I need to make them as well. I have got two that came with the attachment, a 90T and a 48T. And it seems to be Module 1. I was hoping they would have Module 0,85 which the gears that came with the miller's dividinghead have but no. The gears on the machine that you have got look like they are both the same, how many teeth have they got?

If anybody is interested I could scan the catalog and try to post it for everybody's benefit. Maybe next weekend or so, I'll have some time.

Thanks again everybody, keep it coming!

Melle

From the photo, yep, a split clamp definitely. My suspicion is, given the application
there's no way it would ever slip on the spindle.

P&W No 3

Melle,

I had to make all the gears for the Stark. I also have a P&W universal dividing attachment. Looks you have one on your mill. I also had to make all the gears for it including all the gear banjos for attaching the gears.

All the gears for these machines will be DP gears with 14-/2 deg pressure angles. If your gears are close to Mod 1 it's probably 24 DP. Most Mod gears are 20 deg pressure angle and won't mesh with 14-1/2 deg gears. When I get home next week I'll check the DP on the P&W dividing attachment.

I also have a spare orginal P&W no 3 headstock. I'll get some pics of the end of the spindle for clues as to how the gear was attached. I know I have the original sales brochure for the P&W lathe and milling machine. Jim's right about the split clamps. The pic definitely shows it. I've used them before and they won't slip.

The Stark catalogue provided a complete list of the gearing required for various threads on the chase cutting attachment. I also have this in my files. The P&W will be identical or very close.

I remember that miller at Sobels. At that time it was part of his "museum" i.e. items that were not for sale. Eventually when Peter, his son, took over everything was for sale.
Joe

Melle,

I would love to get a scan of the pratt & whitney catalog.

I am reading your post correctly, You seem to be saying that the gears for the dividing head are not the same as for the thread chasing attachment. is that correct.

I had been thinking that they would be the same given that the milling machine and the lathe were sold as a manufacturing unit. I to have a #3 miller, the early version with overhead drive with a dividing head. I am missing the banjo's and the gear set, and am looking to replicate both.

Can anybody confirm that the gears for the dividing head are different than for the thread chasing attachment?

Thanks very much for any help that anybody can provide.

P&W No 3

oldmasheentuls,

I have an original No 3 Lathe & No 3 Mill catalogue. I've got PDF's of them but I won't be able to access them till next week. I'll send them to you ASAP.

All of the 7" lathes probably have about the same DP gears for chase threading since it's really a space issue. I'll check my Stark gears and the gears on the P&W dividing attachment. I have some Hardinge change gears for their 7" lathe chase threading. If I remember correctly the holes were either 1/64" larger or smaller than a "standard" hole size. They didn't want you to buy a competitors change gear for their lathe. All the 7" Bench lathes differed by similar details.

Joe