Logan Cross Feed Screw & Nut

[mjhenks]

Need some ACME tap help.

As mentioned before I have to replace my cross slide nut. My screw major diameter (OD) measures @ .441" and the Minor (ID) is .336" The old nut Minor ID measures @ .341"

I believe and a quick search seams to confirm that ACME is measured on the Major diameter so I figured I had a Left Hand 1/2-10 screw.

Got a 1/2-10 left hand tap today and it is bigger than my screw and will not thread into the old nut. It Major measures .526" and the minor about .417".

What am I missing?

 

[hvontres]

Well, checking the table on page 1609 in my 24th edition Machinery Handbook shows that a 7/16 Acme has a Major diameter of 0.4375-0.4325. My Cross feed measures 0.490 Major, which is only 0.005 under the minimum
I'll bring in my nut tomorow to compare.

 

[mjhenks]

Thanks Henry.

Turns out that Left hand 7/16-10 ACME taps are not that common. Especially two stage ones. I know the Southbend guys have the same issue.

Anyone have one or know where to get a two stage unit? www.tracytools.com in the UK has single stage as does a seller on Ebay.

 

[stevecmo]

Have you seen Jim Shroeder's excellent post on using Acetal for nuts? That's the method I'll be using as I work my way down my "to do" list.

http://www.hobby-machinist.com/showthread.php?t=11166&highlight=acetal+nut

 

[mjhenks]

I ended up finding someone who has the right tap and having them tap some blanks for me to later mill to size.

See post #73 in the below thread for details.

http://www.hobby-machinist.com/showthread.php?t=20631&page=3&p=190586#post190586

Matthew