Threads on Commando cylinder head studs

[Geoff]

Do any of you engineering egg heads out there know what threads are used on rear head stud on Commando. I have a stripped thread in head & have tapped hole out to a bigger M12 !! thread, and am torn between making an insert to accept the original stud, or a new stud with M12 one end & turned down to original size & thread. Any advice welcome

 

[hewhoistoolazytologin]

I juat had all three done two weeks ago...BSF 20 sounds right.

 

[Geoff]

Many thanks, will probably go with insert as otherwise I need to get a cycle thread die & that sounds a bit 'ard!

 

[hewhoistoolazytologin]

RGM does all three for like 19 pounds.....inserts will allow replacement of the bolts...should ever there be a reason. Mine were done here....inserts from a firm called "recoil"....must be as good as Helicoil....and now I can torque them up so they feel snug.

 

[L.A.B.]

As Geoff has said that he has already drilled and tapped the hole to M12, using a wire thread insert may now not be possible otherwise I would have suggested the same thing.

 

[hewhoistoolazytologin]

M 12????

Quess when he gets it back together....THAT bolt won't pull out again.....but won't he have a bit of bother with getting a M 12 nut to go up into the holes below the barrels, and getting a wench/socket on it? Could be time to look for a good alu welder who can get it back to where you can use a Helicoil...or?

 

[L.A.B.]

It is Geoff's intention to make his own insert (his original question was whether to make an insert or a stepped stud) and use the original stud. So no need for an M12 nut! (It is only the rear stud that needs fixing).
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Geoff,
My only concern would be that tapping the hole to M12 may not be large enough as there would be practically no metal between the internal and external threads of the insert??

 

[hewhoistoolazytologin]

Spose it's possible...but he has to be better than me, with a lathe...that's a tough trick for any machinist...and the 12 might be, as you said, a bit small....but if he is that good...and I'm sure he must be, to even consider it.....he'll know what he has to do....

 

[L.A.B.]

There is an exellent alternative to wire thread inserts: broken link removed self tapping inserts.

 

[hewhoistoolazytologin]

L.A.B.

Thanks for the link.....the product I have been looking for was listed, and the manufacturer is here in Germany.....already requested a Catalog.....Thanks!!!!