Helicoil/Timesert Help needed.

[Moo.]

So, bought a Suzuki DR600 and previously one of the exhaust studs had snapped and has been drilled out with a M7.5 drill bit. I want to fit a Helicoil in there, but unsure what size helicoil i need.. (Also need to find the right pitch for the exhaust stud..) Anyone know what size helicoil would fit?

Or, do i just tap the hole out to M8?
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A2 Passed 18/6/10

[Fisty]

M8 tap stick an 8mm stud in it. Should be a 6.8mm hole but there should be enough meat there to get an exhaust stud to bite.
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Quietly and consistently taking the piss.
TL1000R | Hayabusa | ZXR400 | TL1000S | Bandit 400 V
Fatter and faster than Fret

[Pete.]

The tapping size for a M8 x 1.25 roll tap (a.k.a thread forming tap) is 7.5mm.

Buy a roll tap and put a full M8 thread in it.

https://www.guhring.com/documents/tech/charts/formtapdrill.pdf

This WON'T work if the hole has wandered off the stud and some of the steel stud is in the hole.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Moo.]

[Pete.]

Yes, like that. M8 x 1.25. Use copious amounts of lube.

Will the M8 clear through the hole in the pipe clamp?
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Moo.]

[WD Forte]

[Moo.]

[Pete.]

Ok, probably why the hole is straight then

Roll taps are unforgiving. They form the thread by moving the metal rather than removing it. They use a special high-pressure lube to keep the flanks of the tap from friction-welding to the metal. The best I can think of is to use EP90 oil (Extreme Pressure) as a tapping lubricant. If it starts creaking back out and add more oil.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Pete.]

[Moo.]

Cheers Pete. I've got some EP90 gear oil I can use, I'm guessing it operates like a normal tap? But its going to be alot harder..
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A2 Passed 18/6/10

[davebike]

Tapping size for M8 1.25 is 6.25 to 6.5mm 7mm is just about do able but 7.5 will give a rather loose thread but may get away with it I no go there

thread depth is 1/2 the pitch thread is on both sides so subtract Pitch from size add a bit for Clarence for tapping size
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Dave
NC750Xdct + others at work !
davebike1@gmail.com

[Raffles]

[Aff]

Using a form tap seems like a bit of a faff.

I would just drill both the head and the clamp out to 8.3 and put an M8 Helicoil in there.

You need to drill the clearance anyway.
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Current Bikes:Honda 929RR Fireblade, Honda CD200 Benly (Project), Stomp Z2 140
Electric Bike Project

[Pete.]