toolnuts
Cast Iron
- Joined
- Sep 27, 2009
- Location
- washington
Hello all,
I am in the process of lapping my granite surface plate,
so I thought about making a repeat-o-meter.
The first one is mine and the second one came from Boeing surplus.
Boeing's you can change the spacing for USA spec., or metric spec..
Things I learned doing this.
Don't use a bandsaw because the blades are never quite square with
the table. Secondly, the welds are hardly ever perfect. My bandsaw cut
was .025" on one side and .005" on the other. This made the spring
constant to small and it was lowly damped IE: the dial oscillated
to much. I added a feeler guage to the bottom side to decrease the
oscillation.
If I were to do it again I would use a slitting saw or wire EDM to
make the hinge spring.
I used Tom's idea of using ball bearing feet that were ground down
after insertion.
Also, the reason I used the Federal guage is because I had it already.
If I didn't, I would use a zero setting electronic guage to eliminate the
zeroing function. The guage I used had a long moment arm which also
adds to vibration. If you go with the zero setting electronic guage
you don't need the zero setting arm, but you need to make the guage
holding arm thicker ( otherwise you get a tuning fork effect). Remember
you are trying to measure .000020", it doesn't take much to vibrate .000020".
Best Regards to all,
Paul
I am in the process of lapping my granite surface plate,
so I thought about making a repeat-o-meter.
The first one is mine and the second one came from Boeing surplus.
Boeing's you can change the spacing for USA spec., or metric spec..
Things I learned doing this.
Don't use a bandsaw because the blades are never quite square with
the table. Secondly, the welds are hardly ever perfect. My bandsaw cut
was .025" on one side and .005" on the other. This made the spring
constant to small and it was lowly damped IE: the dial oscillated
to much. I added a feeler guage to the bottom side to decrease the
oscillation.
If I were to do it again I would use a slitting saw or wire EDM to
make the hinge spring.
I used Tom's idea of using ball bearing feet that were ground down
after insertion.
Also, the reason I used the Federal guage is because I had it already.
If I didn't, I would use a zero setting electronic guage to eliminate the
zeroing function. The guage I used had a long moment arm which also
adds to vibration. If you go with the zero setting electronic guage
you don't need the zero setting arm, but you need to make the guage
holding arm thicker ( otherwise you get a tuning fork effect). Remember
you are trying to measure .000020", it doesn't take much to vibrate .000020".
Best Regards to all,
Paul
