I have to helicoil a stripped hole for a 5/16-18 bolt. I have the helicoils but nowhere can I find info on the proper size drill bit and tap to use. Screwing this up would be very, very bad. Please help.
Starrett sells/gives away a chart for the proper drill size. With the heli coil, you should have received instructions on proper drill size.
Nope. I got a box of the coils from NAPA but nowhere on it does it say anything about the sizes of taps or drills. BTW, what is "Starrett".
Helicoil I have always purchased Helicoil stuff in a kit. It would have the tap and inserts as well as a little plastic key to install the insert. The drill size is specified in the kit, usually a number size rather than inch dimension. The taps are not standard sizes either, I think you need the one made for the helicoil, not a standard 1/4-20 or whatever. Look for the thread repair kit with all the stuff.
I just did a littel research on this, and it's a special tap; you can't just grab a standard one and go at it. You apparently can't get the tap in a regular tap and die kit
I have here a chart from the Carbide Depot that says a size Q drill is for 5/16-18 helicoil taps Double check on that
Thanks, but I guess I still need a special helicoil tap? What am I saying, of course I do. It would be silly to think that I could use one of the many taps I already have. Thanks again
Just... Quit fighting it and go back to the auto parts store and get the KIT. It should at least have the tap a few coils and a note with the correct size twist drill. If it's a nicer kit you should even get the twist drill. Expect to pay about $20+. You may me able to get the tap seperatly from a place (Ohh the irony) like www.mscdirect.com or some other industrial supply house. good luck..
Who's fighting it? The NAPA by my house didn't have the kit in that size and I just thought I could just use one of my taps. Who knew o No:
Kast time I needed one, the machine shop owner just threw me the kit and told me to bring it back when I was done. He even had a block of steel that was tapped with the special tap at a perfect 90 deg angle to use as a guide so the hole would be square when done. I returned everything the next day clean and in good shape and told him I used two coils. I asked what I owed him and he said don't worry about it! This really blew my mind as this was the same shop that charged me $100.00 just to mag inspect a 4 cyl tractor block!!! Ken
