Ken Whitney
02-14-2011, 11:07 AM
Harbor Freight sells a 24" aluminum caliper that I have found very useful around the lathe.
I use it to set the 10% bowl blank thickness without doing any "hard" math. First, get the diameter of the blank:
182681
Since the caliper is scaled in both metric and imperial units, it is easy to reset the caliper to 10% of the diameter using the metric scale. I sharpened one of the arms of the caliper and use it to scribe the 10% line. It clearly marks the 10% line and provides a stop for potentially wandering bowl gouges.
182682
I also use the caliper to check bowl depth. I first read the overall depth of the bowl blank:
182683
I then measure the depth using a stick and metal rod:
182684
I can directly read the bottom thickness off the caliper:
182685
If you can remember your 10% thickness number you know your target depth. Or use one caliper for depth and one for diameter, and save the brain cells for something more important:)
The calipers run about $10 and can easily be cut to shorter lengths, if needed. They are adjustable as well, and the reference arm can work loose so it pays to recalibrate occasionally.
I use it to set the 10% bowl blank thickness without doing any "hard" math. First, get the diameter of the blank:
182681
Since the caliper is scaled in both metric and imperial units, it is easy to reset the caliper to 10% of the diameter using the metric scale. I sharpened one of the arms of the caliper and use it to scribe the 10% line. It clearly marks the 10% line and provides a stop for potentially wandering bowl gouges.
182682
I also use the caliper to check bowl depth. I first read the overall depth of the bowl blank:
182683
I then measure the depth using a stick and metal rod:
182684
I can directly read the bottom thickness off the caliper:
182685
If you can remember your 10% thickness number you know your target depth. Or use one caliper for depth and one for diameter, and save the brain cells for something more important:)
The calipers run about $10 and can easily be cut to shorter lengths, if needed. They are adjustable as well, and the reference arm can work loose so it pays to recalibrate occasionally.