Brake drum shoe clearance gage, where can I get one?

Hi All:

Needing to do a brake shoe adjustment to .76mm clearance between lining and drum.

I was going to buy one of those "drum clearance gage tools" that measure diameter of drum and diameter of outer lining so that I can ensure .76mm gap.

I was flabbergassed that AutoZone, Car Quest, Napa and Advanced Auto Parts don't carry this tool. The manual says to use this tool.

Anyone know how much this tool costs and *where* I can get one? Don't know if the Chevy Dealership would sell this tool?

Is there another tool I can use as an alternate? I *guess* I could carefully use a ruler to measure diameter of inner drum and then carefully subtract .76mm from it's width and then turn the adjusting screw until the outer lining diameter length = that value? Just seems kind of "risky" though as it would be (most likely) inaccurate.

thanks...

thanks, I was just going by the following:

So that there's less than 1mm gap perhaps? Would it hurt if I measured it to about a 1mm gap?

Also, on step 25, they say: Install the drum and wheel, tightening the lug nuts to 100 ft. lbs. (136 Nm). Adjust the brakes using the procedure given in this section. Be sure to install a rubber hole cover in the knock-out hole after the adjustment is complete. Adjust the parking brake. Where/what is "knock-out" hole that they're referring to and where to get this rubber hole cover? Maybe just reuse the existing one.

thanks

Never mind. I figured this out. Did not realize that they meant adjusting with the drum on and sticking a screwdriver thru the hole on the backing plate to do the adjustment. I know where that hole is.

thanks.

I agree too. I have done it that way for many years except I do it until they drag a bit and leave it that way as they will seat in some/ Also I would step on brake hard a time or two while still on jack after you adjust them and then recheck them.