WTB: Acme Tap 7/8" - 5 Left Hand

[Uglydog]

Long shot, but thought I'd ask if anyone has a good Acme Tap 7/8" - 5tpi Left Hand they'd like to sell.
Am working on the rebuild of the crossfeed of a Pratt Whittney 12x30C and need to fab a nut.

Thanks for digging through your crates of surplus acme taps.
Daryl
MN

 

[mattthemuppet2]

Would a 1"-5 LH work? I have one you can borrow for postage

 

[Chipper5783]

7/8” - That’s a reasonably large hole, single point thread it (I’ve done a 5/8” Acme nut - it was a pretty small boring bar and the tool ground to the minimum protrusion).

 

[Uglydog]

Matt, thanks for the offer but I need 7/8".
Chipper, Yes, a single point is a real option.
Another, real option which is a strong possibility is to make a tap. I've not done that before would be fun.

Daryl
MN

 

[mattthemuppet2]

no worries. I've got 3/4-6 and -8 too, but I imagine those won't help either

one option if you're making a tap is to make a series. First V pitch rougher like you see on some large pipe taps, then a stub acme and then the full acme thread form. That will reduce the cutting forces on what will be a pretty honking tap. I've done 1/2-13lh acme through bearing bronze (SB9 tailstock extension) that wasn't trivial with a single pass tap.

 

[Uglydog]

Matt,
Good suggestions.
I'm plan to complete the compound rebuild then come back to the cross slide feed screw/nut.

Thank you,
Daryl
MN