I'll second what Harold says about inserts. Years ago, I needed to slightly reduce the diameter of the wheel-mount flange on a set of Strange Engineering drag racing axles. These axles were for use in a Dana-Spicer 60 series rear end, and were made from E4340 steel, arguably the toughest steel available for high-stress applications. After receiving the forged blanks, Strange would spline the inner ends and turn the bearing surfaces and wheel flanges close to finished size. The axles were then heat-treated, bringing them up to about Rockwell 55C-58C. Final dimensions of the bearing surfaces and wheel flanges were achieved by grinding, which gives you some idea how tough these things are.Harold_V wrote: ↑Sun Jun 16, 2019 1:57 amThat's an interesting comment, one that needs to be read and understood.
Those who have the intestinal fortitude to read my ravings are all too familiar with my admonition to avoid that trap. Not doing so robs an individual from learning one of the most valuable lessons that is to be learned in the shop--the one of grinding cutting tools. That skill, above most others, will permit a guy to take cuts that most likely would not have been successful with insert tooling. It's hard to understand, and many will argue the point, but the harsh reality is the use of HSS tool bits on light duty machines is far better than the use of carbide (there are exceptions).
Thanks for your contribution.
Anyhow, due to a miscommunication on my part, Strange finished the wheel flange OD to the wrong size, about 3/16 inches larger in diameter than needed. Despite having an assortment of large hammers at my disposal, the disc brake rotors wouldn't fit, the weekend was only a day away and I was trying to get the car on the track. As I was working for a large railroad industry supplier at the time, one with a very well-equipped tool room, I decided to take the axles to work and cut down the flanges after hours, since at the time, the tool room worked on two shifts. I knew, of course, the axles were very tough but also knew I could cut them with carbide, as long as work and tool were flooded with coolant and the lathe was sufficiently substantial.
It helped that the tool room had a Lodge & Shipley lathe big enough to sink a small ship—it had a 96 inch bed and if memory correctly serves me, a swing of 24 inches over the ways. The machine was massive, so I knew nothing was going to deflect when I started taking bites out of the axles. So I mounted an axle between centers, put an insert-type carbide cutter into the tool post and went to work. Much to my chagrin, I could not come up with any combination of feed and speed that would keep the damned cutter from chattering and making a mess. I had the tip as close into the tool post as possible, everything was cranked down tightly, etc. What was I doing wrong?
Finally, I swallowed by pride and went to the tool room foreman's office for help. The first thing he said was "Don't use those (expletive deleted) replaceable inserts. They're no damned good!" Taking his advice, I went to the tool crib and got a large cutter with the carbide silver-soldered in place. A little grinding got the cutting edges where I wanted them, along with a nice radius on the tip, and I was off to the races, so to speak. I got the accuracy I needed and a nice finish to go with it.
I must say, though, the chips were coming off almost red hot, even though I had plenty of coolant flowing. Heat-treated E4340 is sure tough!