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Post by upchurch on Jan 27, 2019 17:14:31 GMT
HONDA SUPERDREAM CYLINDER HEAD, BROKEN OFF EXHAUST STUDS.
Has anyone any 'hands On' experience of Drilling Out broken off Exhaust Studs?
What are the best type of Drills to use?
Boron or Tungsten?
What is the best Tap Size for cutting a new Thread?
Any Info gratefully received.
Regards
Wilf
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Post by BritPete on Jan 27, 2019 17:44:13 GMT
The thread on the Exhaust studs is a standard 6mm thread (6 x 1.0) drill size varies, my tap kit has 5.0 mm in it but other sources say 5.2 mm drill
Not done a SD before but others I have done ground flat - centre punch then start at 3mm and increase size of hole
If the other stud is still OK and you have a sacrificial exhaust manifold clamp/rose you could try using that as a guide for the drill, fixing it on the other stud
Be interesting to know how you get on as SME has a snapped stud but has a little thread on it
I was going to soak in Oil then modify a Die Holder so I can thread further down the stud and then lock 2 nuts together then try to get it out that way
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Post by davefirestorm on Jan 28, 2019 2:26:19 GMT
Good quality drill ie no cheap rubbish.5mm is core diameter for 6mm thread.Follow advice given regards centre drill and starting with a small diameter drill at first then I would use a a left hand drill of around 4.5mm the force generated may be enough to unscrew the stud
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Post by JonnyHonda on Jan 28, 2019 6:17:09 GMT
As previously said, I would certainly try I small 3mm hole and then a left hand bit or an Ez-out on a hammer action drill.
With any luck the heat generated by the drilling of the hole will aid release.
Failing that, it's probably a heli-coil Job,
I take the head is off and you are not trying this on the bike?
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Post by wealdenrust on Jan 28, 2019 14:26:34 GMT
I agree with Firestorm about a left hand drill because the action of the drill is going to bring the broken stud up and out naturally, if you get lucky.
The best thing to do first is to file flat the end of the broken stud close to the casting it’s siezed in so you can determine the centre and crusually the start point for the drill.
Getting the start point right is going to help you most of all.
The material of the drill is not a worry. HSS is fine. The main thing is that it’s sharp!
My advice is take your time.
Get the centre spotted in the dead centre of the stud.
Use a LH drill if possible.
Start with a smaller drill if you want but I would go straight for it.
5.1 dia is std for tapping in Ally. So 4.5 (as previously advised) up to 5 is ok.
Follow the direction of the deepening stud implicitly.
If all fails drill out totally and helicoil.
Don’t panic!
It’s always difficult but satisfying when completed.
Good luck.
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Post by davefirestorm on Jan 29, 2019 4:17:05 GMT
Also if enough of broken stud is sticking out you could weld a bigger bolt to it but reckon not a lot of space available,and if the stud comes out and threads no good you could put 7mm thread or even 1/4 UNF with appropriate thread on new stud. Is the head still in situ or removed
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Post by upchurch on Jan 29, 2019 15:40:36 GMT
DRILLING OUT BROKEN OFF EXHAUST STUDS
Many Thanks to those who replied to my enquiry regarding
Drilling Out Broken Off Exhaust Studs on Superdream Cylinder Heads.
Very Useful Tips
Much Appreciated.
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Post by davefirestorm on Jan 29, 2019 19:52:17 GMT
Let us know how you get on removing the studs Wilf
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