How to 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

[ford38v8]

Shucks, I thought you had found a way to fool the wife.

[51 MERC-CT]

Interesting, have been using basically the same method for years except I have the overall length of the caliper (when at zero) marked on it.
Then just take a reading and add that to the overall length, that's your dimension. No correction factor required for different size drums or anything else you want to measure. I have 3 different length calipers marked with their lengths on them.

[Brian]

I just use a 12" rule. One can read a rule to .005". You can soon see if the drum is oversize!

[KiWinUS]

I have a hand held piece of aluminium cut @ 12inches I take with me to swap meets , its tooo easy !

[Bob G/Spanaway]

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I cut pieces out of an old tape measure.
If you're careful cutting to length and measuring the pieces they're very accurate.

[Bolts]

Thanks for the tip Kurt.