Helicoil thread repair help.

[busastars]

My RD350 has been bodged by the last owner. The one exhaust stud was missing but in its place was a bolt.

The problem is the cylinder is cast ally, the thread should be m8 and he wound an m10 bolt in it and has pulled all the thread out.

I would be gessing the hole size is 10mm, realy I want an m8 helicoil in but is it gone to far, what size drill is used for an m8 helicoil before the tap is done, can you buy just the taps seperate and what size would I need as I know the helicoils are cheap but a helicoil kit is expensive and I do have access to the wind in tool.

 

[Paul.]

21/64th's, according to my chart, or 8.3mm

 

[busastars]

21/64th's, according to my chart, or 8.3mm

Im gessing my hole is to big to go for an m8 helicoil then. Maybe an option is to use an m10 helicoil and get a stud made with m10 one end and m8 the other?

 

[Paul.]

An M10 is a letter Z drill, or 7/16" , 11.1mm
the tap is a special, it will be marked STI, Steel Thread Insert, you can buy single size repair kits with a drill, tap, insert tool, and a few inserts for about £15.00 or less

 

[Garreth]

Is there enough meat in the casing to drill it further down and tap it M8 - and use a longer stud ? Or weld the top of the whole up and tap it out M8 ? Or tap it out to M12 and use a M12 - M8 stud ?

Otherwise you'd be into repairing the thread with a helicoil or similar. We use "Wurth Timesert" kits at work - like a helicoil but a solid insert, not a helix. Dearer but better in my opinion.

Garreth

 

[irondarren]

I good bodge, and it depends if you can get away with. Tap it out to take a 12mm bolt, cut a piece of 12mm threading, drill it out with a 6.8mm drill through the centre of the studding, tap an 8mm thread in the studding, screw the 12mm threading in the hole and fit an 8mm bolt. If that makes sense. A make your own heli-coil

 

[andypocock]

I good bodge, and it depends if you can get away with. Tap it out to take a 12mm bolt, cut a piece of 12mm threading, drill it out with a 6.8mm drill through the centre of the studding, tap an 8mm thread in the studding, screw the 12mm threading in the hole and fit an 8mm bolt. If that makes sense. A make your own heli-coil

Just what I was going to suggest. I much prefer a sleeve to a heli-coil if there is room.