precisionworks
Flashaholic
This job shows some measuring tools that aren't familiar to everyone. The job involves reducing a .8750" OD to fit a .7895" blade bore. My target dimension is .7890", so the two parts fit together nicely without much play (the blade turns at 12,000 rpm, so the fit needs to be close).
Diamond blade (4.5") resting on top of Inside micrometer. This one came from J&L or Enco, around $50 on sale, and it repeats well. Even has decent feel for a Chinese mic. Digital calipers are almost useless for this type of measurement, as the jaws on even the best ones are so springy that you have very little feel for part contact. For comparison, this bore was first checked with my Mitu digital, which read .7910". The ID mic read a consistent .7895". That's a big enough difference to cause fitment problems on this job.
The "jaws" are two hardened pins, and the mic includes a ring gage for setting. Graduations are large enough that it's easy to split thousandths.
There are times when a conventional micrometer will not work. The body of the mic prevents using it on this job.
A vernier caliper is an ideal tool for this measurement. Starrett made this Model 123, about $50 on eBay. The vernier scale allows accurate measurement to .001", and a screw adjusted slider lets you feel when you have light part contact, just like tightening down a micrometer on a part.
The vernier also has long enough jaws to work around the chuck. The two parallels, behind the part, space the part out enough to give tool access - they are removed before starting the machine.
The dial indicator (right of tool post) is held by a FlexBar arm. Really nice for getting around near the headstock. The other dial indicator is the depth limit.
Indicator with mag back.
Finished part on left.
Like so many jobs running multiples, it took 45 minutes to set up & find the correct diameter setting, and 15 minutes more to run all five parts.
Diamond blade (4.5") resting on top of Inside micrometer. This one came from J&L or Enco, around $50 on sale, and it repeats well. Even has decent feel for a Chinese mic. Digital calipers are almost useless for this type of measurement, as the jaws on even the best ones are so springy that you have very little feel for part contact. For comparison, this bore was first checked with my Mitu digital, which read .7910". The ID mic read a consistent .7895". That's a big enough difference to cause fitment problems on this job.
The "jaws" are two hardened pins, and the mic includes a ring gage for setting. Graduations are large enough that it's easy to split thousandths.
There are times when a conventional micrometer will not work. The body of the mic prevents using it on this job.
A vernier caliper is an ideal tool for this measurement. Starrett made this Model 123, about $50 on eBay. The vernier scale allows accurate measurement to .001", and a screw adjusted slider lets you feel when you have light part contact, just like tightening down a micrometer on a part.
The vernier also has long enough jaws to work around the chuck. The two parallels, behind the part, space the part out enough to give tool access - they are removed before starting the machine.
The dial indicator (right of tool post) is held by a FlexBar arm. Really nice for getting around near the headstock. The other dial indicator is the depth limit.
Indicator with mag back.
Finished part on left.
Like so many jobs running multiples, it took 45 minutes to set up & find the correct diameter setting, and 15 minutes more to run all five parts.
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