What the heck uses 1/2-8 LH 2 start ACME?

rke[pler

Diamond

Joined

Feb 19, 2002

Location

Peralta, NM USA

• Sep 13, 2011

• #1

Twice now I've found 1/2-8 ACME taps on eBay, and both times they show up as double lead taps. Now, 1/2-8 LH is pretty freaking rare (only used in a 10EE tailstock) but apparently double lead is not so rare as single start. So what uses the double lead?

 

Cole2534

Diamond

Joined

Sep 10, 2010

Location

Oklahoma City, OK

• Sep 14, 2011

• #2

Could be a double square thread form, at first glance they do look somewhat similar.

If that's the case, I saw a smaller example on a centrifuge in a lab once.

 

I

i_r_machinist

Titanium

Joined

Apr 12, 2007

Location

Dublin Texas

• Sep 14, 2011

• #3

Gate valve stems. Very Common. Bitch to cut.
i_r_

 

rke[pler

Diamond

Joined

Feb 19, 2002

Location

Peralta, NM USA

• Sep 14, 2011

• #4

Cole2534 said:

Could be a double square thread form, at first glance they do look somewhat similar.

If that's the case, I saw a smaller example on a centrifuge in a lab once.

Click to expand...

Nope, these are labeled taps from North American, HW, etc. Either way it looks like ACME, with a tap the tooth form is easy to see and there's a big difference from ACME and square.

Best I can tell is that it seems to be used in some smallish CNC drives and such.

 

rke[pler

Diamond

Joined

Feb 19, 2002

Location

Peralta, NM USA

• Sep 14, 2011

• #5

i_r_machinist said:

Gate valve stems. Very Common. Bitch to cut.

Click to expand...

I meant to mention that thought, spaced it when I found the oddball CNC use.

Any value to these? I've got a bunch of them to either return or sell. They're TiN coated and look pretty good, can't tell if they were used or not.

 

W

willbird

Banned

Joined

Jul 19, 2005

Location

North(very) West(very) Ohio...near exit 13 on OH t

• Sep 14, 2011

• #6

Well LH stuff can can lay around at a company for years. I know a guy here local who has some of the old Mohawk inventory...they stocked RH and LH of a lot of tools for customers, the accounts went away, the inventory lingered, the RH stuff sold over the years, the LH gathered dust. Looking at the stock 20 years later might lead you to think LH endmills were once very common ;-).

 

R

rhinsen

Aluminum

Joined

Feb 9, 2009

Location

Mo,usa

• Sep 15, 2011

• #7

taps

When I was in the Navy we made 3/4-10 LH double start valve stems in stainless all the time. The taps would be used to make the nut in the bonnet of the valve. The BT's ( Boiler Tenders ) or MM's ( Machinist Mates ) would use a cheater on the valve handle to close and tighten the valve. If the valve leaked they would tighten until it broke the handle off.
I was a Machinery Repairman on tenders and we got to make all sizes of fun things like that.

Rick Hinsen

 

P

paulwag

Plastic

Joined

Dec 12, 2017

Location

madison

• Dec 3, 2020

• #8

Im looking for a good used 1/2-8 double lead tap if you know of any

 

rke[pler

Diamond

Joined

Feb 19, 2002

Location

Peralta, NM USA

• Dec 3, 2020

• #9

paulwag said:

Im looking for a good used 1/2-8 double lead tap if you know of any

Click to expand...

Right or left hand?

 

M

Mark Rand

Diamond

Joined

Jul 9, 2007

Location

UK Rugby Warwickshire

• Dec 3, 2020

• #10

Steampunk Shay locomotives.

 

P

Peter Neill

Stainless

Joined

Apr 30, 2006

Location

Suffolk, England

• Dec 3, 2020

• #11

Pretty sure that the cross slide leadscrew on my Colchester Bantam is about that size or very close - and definitely a 2 start, left hand thread. I had to replace it about 10 yrs ago, and seem to remember it was something like this.

 

rke[pler

Diamond

Joined

Feb 19, 2002

Location

Peralta, NM USA

• Dec 3, 2020

• #12

Mark Rand said:

Steampunk Shay locomotives.

Click to expand...

Naah - I'd know that use.

 

sfriedberg

Diamond

Joined

Oct 14, 2010

Location

Oregon, USA

• Dec 3, 2020

• #13

willbird said:

the inventory lingered, the RH stuff sold over the years, the LH gathered dust. Looking at the stock 20 years later might lead you to think LH endmills were once very common ;-).

Click to expand...

Absolutely! Sam Mesher in Portland, OR, has the remnants of a large stock of WW II tooling. You would not believe the LH taps and drills, the odd-DP bevel gear cutters (bevel cutter tooth form is narrower than standard spur cutters), all sorts of stuff that would be hard to find if you were looking for it. On the other hand, anything that you might reasonable expect to use was sold decades ago! I spend a couple of hours pawing through their shelves of "vintage NOS" one afternoon, and didn't find a single thing I had any use for, although I did make a mental note that if I needed large carbon steel taps, there was a mother lode.

 

J

john.k

Diamond

Joined

Dec 21, 2012

Location

Brisbane Qld Australia

• Dec 3, 2020

• #14

Think the Colchester is 10 LH 2 start.......I made one some years ago to renew the bronze nuts in a Bantam.....Anyway ,a suitable tap lives in every piece of silver steel---but take my advice and make the tap a long one with a transition from V thread to Acme ,or it will break cutting tough bronze.....Or two taps ,one V, one Acme.........................Tracy Tools in Devon ,England used to carry all the taps for renewing lead nuts in UK made lathes.

 

B

Bill D

Diamond

Joined

Apr 1, 2004

Location

Modesto, CA USA

• Dec 3, 2020

• #15

My Harrison m300 crossslide screw is something like 12mm by 10TPI. For native English gearing.