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Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 2:32 pm
by Alpha1
I did not realize you can buy internal/external carbide metric inserts by tpi or whatever they are measured by. I have just purchased some internal ones to cut a 27x1 internal metric thread.
You learn something new every day. You can buy the inserts for any thread for example Whitworth or unf etc. Cool or what.
Re: Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 4:47 pm
by Mattnall
Do you mean helicoils and similar? They are great if you have to repair a thread especially in aluminium.
Helicoils
Re: Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 7:31 pm
by Alpha1
Mattnall wrote:Do you mean helicoils and similar? They are great if you have to repair a thread especially in aluminium.
Helicoils
No I mean carbide inserts for cutting internal threads on the lathe.
Like in the attached picture they fit onto a tool holder.
Re: Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 8:51 pm
by Mattnall
Ah, sorry.
Also great.
Re: Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 10:43 pm
by Alpha1
Re: Internal and external metric threading inserts.
Posted: Mon Sep 28, 2020 10:50 pm
by The Gun Pimp
Alpha1 wrote:I did not realize you can buy internal/external carbide metric inserts by tpi or whatever they are measured by. I have just purchased some internal ones to cut a 27x1 internal metric thread.
You learn something new every day. You can buy the inserts for any thread for example Whitworth or unf etc. Cool or what.
There are always plenty for sale on Ebay - half boxes etc for a fraction of new price.
Re: Internal and external metric threading inserts.
Posted: Tue Sep 29, 2020 7:37 am
by Ovenpaa
Also, check out Posithread UK for the finer and more obscure inserts. I had to machine 48TPI for a revolver earlier this year and have gone as fine as 60TPI for an elevation shaft on a sight.
Internal threading is interesting, if I have to machine to/from a shoulder such as on larger thread protectors for barrel tenons I machine out instead of in, less chance of smashing things. You can screw cut both in forward and reverse and from both sides of the work piece.
TIP - Inserts are cheap, barrels are not. I only ever use a corner for a single barrel, so do the job, mark the corner you have used with a black marker pen and rotate it to the next position. The only exception for me is production runs of the M8x0.75mm thread on stainless for our OAL gauges where I end to do runs of 40 threads per corner.
Re: Internal and external metric threading inserts.
Posted: Tue Sep 29, 2020 4:53 pm
by Alpha1
Hmm interesting.
I never thought to screw cut in reverse. I take your point on using one corner per cut thread.
