SAFEST WAY TO DRILL OUT A HOLE & FIT A HELICOI

[sTe140Ve]

I need to fit a Helicoil into the crank case of my T140 to repair the thread that receives one of the cylinder base studs, but I can foresee a problem. I dont have a pillar drill and I am sure a hand held power drill will cause the drill bit to bite into the existing hole resulting in the drill being snatched from my grip . Does anyone have a tip to enable me to safely drill out the stud hole?

Added later - I guess a hand reamer is the answer!!

[Hunter]

Not an easy one by any means, but you need some kind of drill guide such as a piece of steel with the correct size hole for the drill bit attached to 2 of the other stud holes,this should act as a pilot for the bit and cut out much of the snatch.

[L.A.B.]

By using a hand drill, what's most likely to happen is that the drill bit will wander away from the hole centre, or you will not drill the hole perfectly square to the joint face, -or both!

As Hunter has said, a drill guide (preferably bolted/clamped accurately in place?) that's had its guide hole drilled by a bench drill will give you a much better chance of getting it right.

As for the drill being wrenched out of your hands, I suggest you use a battery powered drill with the torque control set to roughly the mid torque position to start with, and increase the setting if necessary, also use a lubricant (such as engine oil) on the drill bit.  

[Rex]

[ I am sure a hand held power drill will cause the drill bit to bite into the existing hole resulting in the drill being snatched from my grip . Does anyone have a tip to enable me to safely drill out the stud hole?
Shouldn't be that bad; you're going up a couple of mm in hole size. Do it very slowly and carefully, and in the smallest drill increment sizes possible. Make sure the case is securely clamped though.

[52t-bird]

Hello,If you are not confident in doing this then dont do it! Having a helicoil done proffesionally is much cheaper than replacement crankcases and or proffessional repairs of a messed up job. If you get it wrong it could be a disaster! There is also no shame in giving a job to the pros if you do not have the proper equipment to do it.Much as it is a simple job to drill out a stud so much can go wrong with expensive consequenses such as spark erosion if you snap off a drill,in my humble opinion and with the greatest respect if you have to ask what to do you shouldnt do it!Sorry to be negative but there have been many times when i wish someone had told me this!!! Regards David