Machinist

[Lawrence London <lfljvenaura@gmail.com>]

http://www.practicalmachinist.com/vb/general/radius-root-thread-question-279311/

Got a print the other day to quote. There is a thread call out that reads:

1-1/2-8 un thread class 2a
smooth and radius root
(fully formed threads)

this part is a tension rod in a press. made from 4142 pre heat treat cold finished

I was planning on running these on cnc with laydown Kennametal inserts. but do not know what type of insert to buy to cut the radius root.

Was thinking a unj profile.
any ideas questions??

The J profile should only be used when it is mated with J threads. Major / Minor diameters may not clear unless both rod and nut threads are J. Use UNR thread spec instead. The R specifies root radius also, but is slightly smaller than J radius.

I used a kennametal J insert. If I recall correctly, J threads are used for overhead lifting devices