Eureka!!!!!! ( or I must be getting old0
When I bought my first checkering file a few years back, stock was a bit thin everywhere and I ended up buying a 30 lpi model. I have been thinking about buying a 20 lpi version because that seems to be a little bettter suited for what we do. I was trying to find the best price and for some reason decided to rummage though my file drawer to find my old 30 lpi file. Imagine my surprise when I found an unopened 20 lpi file that I had ordered from Jantz about 9 months ago as part of a big corby bolt and assorted parts and metals order and then forgotten about it because I had gotten really busy with work, etc. I tried it out today and it is actually a little trickier to use than the 30 lpi, but it does the trick. Attempting to "clean up" the jumping with a 60 degree triangulate file did not go quite as well. that may take some practice. it really wasn't necessary on the 30 lpi file. The spacing with the 20 lpi file is 50% greater than with the 30, but the actually groves do not appear to be 50% wider, so they could tolerate some opening up.