Drilling for Helicoil

I have to put a Helicoil, 5/16-24, in the aluminum insert that goes inside the windshield frame, after-market, on a T-bucket. The Helicoil requires a 21/64 drill, 0.3281. I can't find one locally. I have an O size drill bit, 0.3160". A little too small. The other option is 11/32, 0.3437. A little large. Would either work or keep hunting? Too ****?

Bill

 

get the correct sized drill bit , you will be sorry if you don't

i can't believe that somewhere in your area there isn't a 21/64" drill bit...have you checked Fastenal? Lowes? all the local hardware stores? your buddies garage?

 

I can mail you one if you an't find it, but surely this isn't a hard find? And, don't call me Shirley.

 

isnt a 21/64 drill bit in a usual drill bit index ***ortment?

jeff

 

Before you do the helicoil, take a look at this method. http://www.timesert.com/

I found this on the Pontiac forum. Supposed to be superior to helis, especially for soft aluminum. And doesnt take as large a hole.....

 

Lowes has them. Should have tried there. Posted too quick.

Bill

 

Yep, Sears, Depot & Lowe's have it for sure.

 

I've preached the TimeSert here quite a few times. Far superior to the Helicoil...

 

add a +1 for the timesert here as well. I have done some beautiful repairs with them - my helicoils now sit motionless, lost to the ages

 

Timesert and then forget it.
PK

 

Well, I spent the last 40+ years as a machinist, including 24 on commercial airliner overhaul, and we used heli coils on all sorts of stuff that you can't just coast over to the curb and stop! Used them in all sorts of metal from steel to aluminum and magnesium with good result.
But I did bookmark that link ti timesert and I'll give it a look later.
Dave

 

Never used a Timesert. the guy isn't right when he says a Heli-coil will go in loose and need staking. That's just a lie. But the Timeserts look pretty interesting. A 3/8-16 Heli-Coil uses a 25/64 drill bit. What does the Timesert take?

 

I've also used nothing but Helicoils for the last 45-years or so and have never had a problem or failure with them. Not saying Time-Serts are not as good, just saying Helicoils always have done the job for me.

 

I have used both heli-coils and Time-Serts for many years. Both are good, but given a choice, I'd go for the Time-Serts.

 

LongT, Machinist for more decades than I want to remember. Listen carefully, your 21/64 is .328", the letter O is .316", you subtract the .316 from the .328 and you have .012", NOW take half of that and .006" is the amount from either side that will be SMALLER than the dimension you optimally wanted. Then consider the material you are using, only aluminum, keep your tap well lubed with a good product like Tapmatic, or even WD-40, go slow and you wont have any problem. Hope that theory helps alot of HAMB ers out there. .006" of an inch- "PER SIDE" smaller on drill size, you could even safely do in mild steel, good luck brother with your project!!

 

I agree with Bulldogmafia, if you have to it will work. Someone here praised Timesert to death a few years ago and I bought some. They work great, but the kits are expensive. They use an STI tap, same as heli-coil for the same thread.

 

Buy a complete drill index, 1/64" - 1/2"

And don't loan it to your cheap *** friends.

 

I actually did that math before I asked. I thought it would be OK but figured I'd ask. Got the 21/64 at Lowes. Home Depot didn't have them.