Okay, first a digression: buy a set of torque wrenches, and use them. Don't gimme that crap about how you have been wrenchin' fer forty years and you know the right torque by "feel". It's bullshit. I can "feel" the right torque if I just used a torque wrench on a bolt and torqued it to the exact same torque from the same moment arm, otherwise I'm like every other wrench on this planet -- I overtorque small bolts, and undertorque big'uns. My use of torque wrenches tends to bear that out -- my torque wrench always clicks long before I think the bolt is "tight enough" on small bolts, and on large bolts I'm always sayin', "is this damned torque wrench gonna ever friggin' click? Is it broken or somethin'?" Of course it ain't. I just haven't torqued the big bolt enough yet.
My recommendations for torque wrenches: Sears "click" types. First of all, you can get'em calibrated by Sears Roebuck & Company, though if you properly care for them by putting them away in their cases with the dial set to zero between uses, they generally don't need calibrating more than every five years or so. These make a little "click" noise when you reach the set torque. You may not be able to see a dial or lever when your ass is buried deep under a car hood, but you can damn well hear the "click". Furthermore, get a set. I got a little inch pounds one, a medium-sized one that goes to about 50 foot-pounds, then a big'un that goes all the way to 150 ft/lbs. Deal is that big torque wrenches are no good at the low end of their scale, they're just not very accurate down there, so you need small torque wrenches to handle those. But when you're torquing lug nuts to 100 ft/lbs (gotta do it evenly so that you don't warp the brake rotor)1, you damn well need that big friggin' wrench. And yeah, they're expensive. So what. Don't buy cheap tools, that's how ya get busted knuckles. (Sorry, Ornery Bastard, had to steal yer tag line there).
Anyhow, back to the thread repair. What kind of thread repair you use depends on what you're fixing. Me, I'm going to take that cross-member that I broke a bolt off in the other day, drill that bolt out of there, and then put a thread repair coil in there. If it was a spark plug hole or a brake cylinder bleeder hole I'd use something different -- a Timesert, which is a solid repair that won't leak like a Heli-coil or its clones. But for a general frame tube that's expensive overkill. Anyhow, here's a Heli-coil kit, a Makita drill, a bench vise, and a left-handed drill bit for drilling out a bolt broke off in a hole: Now, one thing you'll find out, pricing thread repair kits, is that they're expensive. The good part is that you can re-use them and just buy coils. That particular Heli-coil kit is so old that the packaging has yellowed, but the tap and insert in it work just fine. As for the Makita drill, a word of advice -- have a second fully-charged battery available if you're using a battery-powered drill. This is my only drill that will hold a 31/64 drill bit (needed for the Heli-coil kit), so that's what I gotta use. Finally, it's a lot easier to work on a piece if you can get it up on your bench. Obviously that won't work if you're working on the frame of a car, but here I took a bit of inner tube and stuck that frame tube on my bench and started drilling, first punching a small indention with a punch then drilling like my life depended on it: Until finally, I drilled all the way through: Once through, I moved up one drill bit size at a time until I was up to the size specified on the Heli-coil packaging, then tapped new threads into it to wind the Heli-coil into. Note: I used the can of cutting oil in the pump can below the bench to lubricate the tap, those things are expensive ($55 for a Helicoil kit nowdays, and most of that is for the tap!). Said cutting oil actually being 80w gear oil :-). Note that I'm using a high-tech tap wrench on this tap, but you'll see a "real" tap wrench later: Once the hole is threaded, then you put the coil on its inserter so that the tang is resting against its end: And then screw it into the hole using the inserter and a tap wrench (from my tap and die set, duh). Until finally it's all the way in! And then you have to break off the tang on the bottom using a punch and a hammer. Luckily I have a punch set from Cheap Chinese Tool Company in the second drawer from the top of my rightmost tool chest-of-drawers (which used to be a bedroom chest-of-drawers before I retired its ugly ass to the garage). One whack with the hammer, and the tang was history. And now the end result: Yay, my (replacement) bolt screws in! And now I'm ready to put this cross-member back on the bike until its replacement gets here. Beats bein' out of commission for a week!
-- Badtux the Wrenchin' Penguin