Howto make 6 inches into 12

[Kurt in NJ]

With Hershey coming I figured I would share a method I thought up to measure brake drums with the cheap harbor freight 6" caliper---

Using any known size in the range you want to use this method you come up with a number to set the calipers at---then zero it

The older one in the picture the correction factor for 12" is 2.704---if you want to measure an 11 inch drum you use 1.704

I mark the correction number on the caliper, I have a newer "pittsburg" 9.95$ with coupon that the correction number is 2.717 for 12", I havn't checked at the store to see if it is close enough to use on others of that series

the brake drum in the picture is quite thin at .168 over 11 inches, the drum surface is only .020 thick