H-M Supporter Gold Member
- Jun 12, 2014
I had made a set-true type ER40 chuck many years ago, but wanted to add a screw in stop system for the back of the chuck so when repeating parts they would all be the same length. When I made the ER40 chuck I threaded the back with a 1.25-20 thread, which is the same as the outer thread of the 5C collets. Stop system is 5.5" of CR1018 bar stock that I had, through drilled with a 3/4" MT3 drill and then bored out one end to 1.001" to a depth of 3" with a 5/8" carbide boring bar, and threaded that end. CR1018 is a bit more challenging to get a good finish/threads, but depends on the inserts/speed. The threads were cut at 600 RPM, boring at around 1200 RPM with a sharp positive rake CCMT insert. The center adjustment rod is 3/4" O1 steel, it can be flipped for different tips, and also threaded for additional size tips. I milled a flat fon the adjustment bar for the 3/8-24 allen set screw and milled the head flat so it locks in securely without digging in. I also have a through the spindle stop system, and use that if I need to adjust the part depth with the chuck mounted. Was a nice afternoon project.