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View Full Version : .664" -32 tap???



rubes
05-07-2009, 07:21 PM
So I got some of these (http://www.mcmaster.com/#5966k14/=1rxavf)smaller 3/8 ball nuts to fit under the cross slide on the CNC mini lathe I got from S_J_H. Boy is it a tight fit. Anyway, the thread is called out as .664"-32, anyone ever seen a tap of that size? I guess maybe this is my first excuse to use the 4jaw on my 9x20 and thread the bracket that way.
http://img503.imageshack.us/img503/7632/smallnuts8049064.jpg

lakeside53
05-07-2009, 08:45 PM
Wacky... not a standard fractional or metric size.

What is the thread form?

ptjw7uk
05-08-2009, 01:53 AM
Nearest I can figure is a metric 17mm x 0.8 as dia is only 5 thou bigger at 0.669. Tried a search but cannot find tap with that pitch I would email the supplier to find the tap as I assume they must make one.
It does seem a bit strange to me as to why the have chosen such an odd size.

Peter

rubes
05-08-2009, 08:20 AM
It is a "V" thread form, so I should be able to thread the part on my lathe. The Thomson catalog shows a separate flange available, but it's not shown on the McMaster site (the square nuts come with a flange though). I just realized I have a contact at one of the Thomson distributors through work, so I'll see if I can "sample" a nut and flange. I hate doing that for my own projects though.

JCHannum
05-08-2009, 09:34 AM
There really is no standard for threads. Fasteners are made to standards to facilitate interchange. Those threads may be incorporated into other applications, but machine parts and such follow no fixed rules. The 60 degree thread form is more or less accepted and used in most cases, but that too is not cast in stone.

mbensema
05-08-2009, 01:07 PM
that is a standard N-03 inch series bearing locknut thread size. Here is the dimensions you will need to turn them.

http://www.nookindustries.com/pdf/LockNut.pdf

lakeside53
05-08-2009, 09:18 PM
Interesting.. but weird that they (the ball screw guys) would specify the MAJOR diameter instead of the pitch diameter...

DR
05-08-2009, 09:38 PM
Interesting.. but weird that they (the ball screw guys) would specify the MAJOR diameter instead of the pitch diameter...

I don't recall seeing threads that were not specified by the major diameter? Have you?

BTW, I bought a piece of tooling for one of my lathes. The shank was threaded 5/8-23. I called to ask why. Because then anyone wanting to duplicate it would need a CNC to thread it.

JCHannum
05-08-2009, 09:51 PM
My Sheldon will cut 23 TPI. It is double 11-1/2TPI, a common pipe thread.

lakeside53
05-08-2009, 10:05 PM
I don't recall seeing threads that were not specified by the major diameter? Have you?

.

Good point... :D But.... for example.. a 1 inch x 16 doesn't have a major diameter of 1.000 for a 2A (or was it a 3..?) thread. I'm too lazy to go look it up but I cut it yesterday at 0.9xxx as per the Machinery Handbook.

S_J_H
05-09-2009, 12:57 PM
Rube,
that is going to be much cleaner than the original setup.
I you need a hand cutting that thread let me know. Can do it on my SB9 if you want.

Steve

rubes
05-09-2009, 09:22 PM
Thanx Steve...it looks good on CAD so far, but it's going to take some doing to make it fit. I understand why you didn't do it in the first place. I should be able to handle the threading...just need to stop being such a slouch.

And thanx for the dimensions mbensema.