Requesting information on P&W "C" taper attachment parts...

Hi all, I have a Pratt Whitney model C with the later model plain taper attachment... as shown in this from the parts manual.



I am missing parts 6, "swivel stud," 12, "taper shoe," and 13 "swivel stud washer."

I'm fixing to make them, however from the end-view drawing I can't tell what the plan-view shape of part 12, taper shoe should be... is it round? Or is it, as I think may be the case, rectangular? Is it steel, or perhaps bronze for better wear characteristics? Also, why does the swivel stud centerline appear to be offset from the center of the taper shoe? Seems unlikely to be unintentional...

A couple pics or any explanation from someone who has one of these would help a whole lot.

Thanks!

Salem Straub said:

Hi all, I have a Pratt Whitney model C with the later model plain taper attachment... as shown in this from the parts manual.

I am missing parts 6, "swivel stud," 12, "taper shoe," and 13 "swivel stud washer."

I'm fixing to make them, however from the end-view drawing I can't tell what the plan-view shape of part 12, taper shoe should be... is it round? Or is it, as I think may be the case, rectangular? Is it steel, or perhaps bronze for better wear characteristics? Also, why does the swivel stud centerline appear to be offset from the center of the taper shoe? Seems unlikely to be unintentional...

A couple pics or any explanation from someone who has one of these would help a whole lot.

Thanks!

Click to expand...

I have no drawing, parts nor recall ever seeing one of these "in the metal", but.. if I had to "reverse engineer it", under my OWN roof?

Here's what I THINK as to how it is meant to function:

- part 15 would be a hardened and ground dowel-pin, press-fit into EITHER the (un-numbered) bed bracket, OR the collar, part 14, but not BOTH. One end needs to be free to rotate. I'd probably anchor it to the bed bracket, which has less metal to over which to distrubute wear that the run-length into part 14 provides.

- Part 15 would serve as the vertical "axle" for part 14.

- Part 14, Iron or steel, would carry an eccentric insert, part 12, in a hard bronze.

- Part 12 would be free to rotate within part 14, but be locked to vertical shaft 6 with a pin or setscrew. I might use a spring-roll pin?

- Part 13 would be a hardened and ground steel disc or washer. It would free-float, not bearing at all, UNTIL either of vertical free-float of part 6 & 12, OR wear brought parts 6 & 12 lower in the housing, part 14, thereby coming into bearing of modest load. Either way, it would then limit further vertical down-travel that might bring vertical shaft 6 into interfering contact with the top of the dowel pin, part 15.

In use, part 14 would be rotated to adjust the pivot center of shaft 6.

The detail shown at the left side "may" be a boss meant to provide purchase for a hook spanner to manually make that adjustment. Or it may be provision for oiling?

CAVEAT: It is not 100% clear (no locking clamp nor fasteners?) if that whole assembly is meant to be "locked".. or if it is meant to be able to free-float in response to the slide-guide rail being locked ELSEWHERE. Specifically by part 10 against part 6.

ALL of the above is a "SWAG", and an incomplete one at that, rendered from a distant screen and keyboard as it has been.

Hopefully you can "blend" bits and pieces of it with what you have in front of you ... and make even BETTER sense of it, overall?

Also, why does the swivel stud centerline appear to be offset from the center of the taper shoe?

Click to expand...

Likely because the shoe has a gib on the "thick" side, though not shown here

Well, the shoe has a gib, that's something anyway... so it must be rectangular as well. Other than that, making the swivel stud should be pretty straightforward. Looks like the shoe is held to the stud with a counterbored bolt and washer combo from the underside.
Looks like I have some forging Herculoy to size and then bandsawing a simple block with gib from that in my near future.
I do have a friend fairly nearby with a PW model C 14" lathe, I'll have to ask if it's got a taper attachment and if so arrange a visit to inspect the assembly.

I haven’t used my model C taper attachment yet but the bracket is sitting on the floor. The only pictures I can post from my phone are low resolution thumbnails. Shoot me a PM with your email and I’ll try to get them out later tonight.

Salem Straub said:

Looks like I have some forging Herculoy to size and then bandsawing a simple block with gib from that in my near future.

Click to expand...

Email me the raw size you need. I keep a small stash of Aluminum Bronze & Nickel-Aluminum Bronze around. Moses B Glick drops, most of it.

Also about 980 lbs of decent CI, thanks to another PM member who parted out a big ole hor-bore with detachable rectangular bedways!

Hobby Shop said:

I haven’t used my model C taper attachment yet but the bracket is sitting on the floor. The only pictures I can post from my phone are low resolution thumbnails. Shoot me a PM with your email and I’ll try to get them out later tonight.

Click to expand...

Thanks a lot! PM inbound.

thermite said:

Email me the raw size you need. I keep a small stash of Aluminum Bronze & Nickel-Aluminum Bronze around. Moses B Glick drops, most of it.

Also about 980 lbs of decent CI, thanks to another PM member who parted out a big ole hor-bore with detachable rectangular bedways!

Click to expand...

Far out, Thermite! I'll take some measurements tonight when I get in there.

Oh man, the mail lady just brought me a set of used rubberflex collets, 1/16" - 5/8" in the mail for my Jacobs collet chuck! I'm gonna go do some recreational turning at least...

Salem Straub said:

Far out, Thermite! I'll take some measurements tonight when I get in there.

Oh man, the mail lady just brought me a set of used rubberflex collets, 1/16" - 5/8" in the mail for my Jacobs collet chuck! I'm gonna go do some recreational turning at least...

Click to expand...

LOL! Very useful creatures, those are!

I have TWO.. one for the 10EE(s) on D1-3 mount. Another that came in the door with the ex-Milacron "French Gal", HBX-360-BC, on HER proprietary mount.

"Fortunately".. when I got the first one, I laid in 3-plus sets of all the 9XX collets and their short-slug rubber "butt plugs".

One set as-new, one damned good, one imperfect, but still serviceable.

Get yours whilst you still can! They are not rebuildable as easily as my Burnerd "Multisize" all-metal ones are!

Man, those Cazeneuve HBX 360 lathes are crazy cool. Lucky to get a good collet setup with it!
As for the butt plugs, I'm thinking of getting a cheap gauge pin set so I'll have something on hand for any conceivable size of small work that may come up. Plus then I'll have them to use as styluses (stylii?) in my Deckel pantograph.

Salem Straub said:

Man, those Cazeneuve HBX 360 lathes are crazy cool. Lucky to get a good collet setup with it!
As for the butt plugs, I'm thinking of getting a cheap gauge pin set so I'll have something on hand for any conceivable size of small work that may come up. Plus then I'll have them to use as styluses (stylii?) in my Deckel pantograph.

Click to expand...

Good stuff to have.

But the Jacobs / Ortlieb / Burnerd / Crawford systems NEED a rubber plug a skosh over the size of the workpiece.

It is then loaded in compression by the arse-end of the blades to resist them "tipping" away from, rather than following, the taper of the forcing cone as they are forced rearward down the forcing cone's walls.

Unlike "spring" collets, they neither "hinge" at one end - or both - nor "buckle".
They just slide, acting as sets of partnered wedges.

The action is more obvious with the Burnerd Multisize or Crawford Multi-Grip, as they are all-metal.

More expensive, too, but.. also 100% rebuildable by a(ny) really good grind shop, hence lower risk bought used than Rubberflex can be.

Even so, the Jacobs goods are uncommonly durable.

EG: Not BAD.

Just not as nice as Multisize!