Do you need to accurately check bore size......and don't have a bore gage. Try this!

Thanks,
yeah, that should work fine, looks like it should be very accurate.
I've never even seen that set up......I got to have one.
on my way to Ebay to see if I can find a Starrett 196
Dan
 
The back plunger indicator comes in 0.001 and 0.0001" resolution. The older kits were in a wood box, newer ones in foam lined. New around $300 but way better prices used. Lots of different ways it can be set up. The indicator tips may be be weird threads on the older ones so nice if the kit comes with different tips.
 
Danzo187 said:
I'd attempt this is by making a plug gage. But then you have the problem of is the plug truly round, am I too fussy?
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If you turn the plug gauge on your lathe (I set my compound over by a few degrees to get the taper), you should be OK.

I machine my plug gauges by setting my caliper jaws to the desired diameter and frequently check the gauge as I make it.

One useful trick to get very fine control over the ID is to set the compound over by a few degrees and advance it -- the resultant depth of cut is proportional to the sine of the angle times the amount you advance the compound. However, this is problematic if you are boring a pocket rather than a through-hole because you may lose the actual depth of the pocket --- in this situation, you have to advance the carriage into the work so moving the compound messes things up. A DRO on the Z axis could manage this (if you know how much you moved your compound). A CNC lathe could do it pretty easily but how many of us have such a thing?
 
Danzo187 said:
Yes, bore gages are expensive, if you need to measure a bore size to within .0001 use the three-pin gage method, all you need to do is use this.
3 PIN GAGE REVERSE CALCULATOR
https://www.holecalc.com/reverse
input (2) any diameter pin gages, enter the bore size and accuracy up to .0000 calculate, the calculator will give you the 3rd pin size you'll need to measure bore.
hope this is a help to new machinist, simple and helpful. Enjoy
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DEFINITELY helpful! Thanks!
 
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