Any engineers - threaded bush feasibility?

[Wrightpayne]

I’m trying to engineer a solution to a particular problem, one option is to make a threaded bush to drop a female threaded hole from 1/2” UNF to 5/16” UNF. The threaded bush would have 1/2” UNF on the outside and 5/16 up the middle.

Looking at thread tap tables the 5/16 has a max (thread top) diameter of .3125 and 1/2” a min (thread bottom) of .4459. This equates to a total difference of 3.38mm, so a solid ring of 1.69mm between the outer and inner threads.

So the question, can this be physically made with the small amount of material between the inner and outer threads?

I’ve also looked at helicoils but for a given internal thread, the outer thread / hole tap seems to be a special size e.g. I cannot find a helicoil which uses a tap size of 1/2 UNF.

The fixing bolt is not normally under any load.

Regards

Ian

PS - I have a spare 1/2” bolt so may just try tapping it!

[rj]

If it's not unde heavy load  can't see the problem.

I did an M12x1.5 to M10x1 adaptor for my oil pressure sensor a year back or so. No problems at all.

Even if your bush breaks at one of the threads it won't give up. To let the inner thread go it would need to expand - and would be held in place by the bigger diameter "hole" so nothing would happen; just imagine how a Helicoil works.

[Mechanical Moz]

I know this is 1/2" UNC external thread but that has a smaller minor diameter than UNF so yes it can be done.

https://www.ezlok.com/ezlok-insert-329-524

[ScottR400D]

Yes, done it several times. Did some in magnesium FR upright. No problems. 

Time-serts are what I used. 

[Nick T]

Can you get a helicoil to fit?

[rj]

It wouldn't have the right thread on both sides

[rj]

Double post

[Nick T]

Is there enough material to take to larger hole out to a size that will fit the 5/16 UNF Helicoil?

 

[Wrightpayne]

Solution sorted - new boss with 5/16 thread being welded in.

Thanks everyone.