My Pete rebuild

[Rawze]

(07-16-2018 )Nostalgic Wrote:  https://www.mcmaster.com/#20365a15/=1dqk9pr

Here's a budget depth micrometer that would be a lot more accurate. You know, even between skilled machinists, the guy twisting the ratchet can affect readings up to .0005"

If I had the cutter, this is the only type of depth gauge I'd use for measuring the counterbores.

If you're Starrett loyal, It's a little more of course, but if you're like me and like tools to match.

https://www.mcmaster.com/#2051a42/=1dqk633

More accurate than a genuine B&S? -- No, but the measurements required for liner protrusion, all will work. Like you say, it is the person taking the measurements that you have to worry about lol. If someone wants to start measuring a 4"+ depth to less than a 0.00025" accuracy then they need to start taking into account temperature and several other factors while taking their measurements. I have had to deal with measurements and corrections of less than 3 microns in the past on industrial machinery.

I remember once a long time ago helping someone figure out why the straight cuts they were making were ending up with a few micron radius. They blamed the machinery and said it was impossible to cut, but I showed them why all their cuts were on an arc after heating the metal by 10 degrees with a hair dryer.

Come to mention it, I once watched a 65+ foot long, 20+ foot diameter pipe (part of a large ball mill) grow by more than 0.065" to one side by mid day after the sun hit it while doing some precision machining out in the Nevada desert (at a gold mine). The job required a flange be cut all the way around on it to less than 0.002" accuracy. It took a couple days of measuring temp + time of day + growth to come up with a program on the CNC machine to follow it so an accurate cut could be made.

-- Pics of one of the end caps if memory serves me right (I took these pics a long time ago)..