Guys,
Can I put a M12 helecoil into what was a 7/16 unf hole.
One of the brake caliper threads on a pair of 2.8i bilstein struts is damaged and I don't think its repairable without helecoiling or similar.
I believe it will be fine as after the new oversized hole is drilled there is non of the old thread left.
But need a logic check
also what material are the 'cast' pats of ford struts
Cheers

JP

Sounds ok to me, and I believe the base of the struts that look "cast" is cast steel.

If the helicoil process is carried out correctly there should be no problem.
 
The M12 helicoil drill diameter is 12.3mm.
7/16" diameter thread if completely stripped is 11.1mm.
 
So the 7/16" thread diameter is well under the drilling and tapping diameter for the M12 helicoil. Even if the 7/16" thread is completely stripped.
 
Probably the biggest problem will be to exactly align (square) the drill and tap for the helicoil to the original hole.
When drilling keep the drill speed to an absolute minimum and use a small amount of oil so the hole doesn't come out oversize. Good idea to drill to a depth of only about 1mm first then check the new hole diameter before completely drilling.
 
Not sure about the legalities being a brake component. Others on the forum might know more.
 
Agreed, the strut bases are a very good quality cast steel so drilling and tapping a good thread will be no problem.

As a Qualified RWC Inspector & VACC SMM, I can assure you a well re-produced thread/helicoil where clearances and anchorage have not been compromised, will always "pass" scrutiny over anything "untoward" done/not done in the same repair........PeterM has described to a T what I didn't have time to elaborate.......cheers  ;-)

Thanks Guys,
Will tend to this on the weekend.
Had to make a tool to extract the bushings from deep inside the strut casing as I'm using konis. what a head job!
to discover the ID of the bilsteins is 44mm and the OD of the inserts are 44mm unpainded! tight fit. Might need to relieve both a bit and use heat. My concern is if I heat it and get it halfway in before it binds Ill never get it out...
 
JP