(12-08-2013, 12:19 AM)TomG Wrote: What speed would you use with a carbide parting tool on mild steel?
Tom
On an open lathe I've got to keep it lower than I would on an enclosed CNC. I have several different widths, from 1.5mm to 5mm. The deeper I have to go and the tougher the material, the wider (and stronger) a tool is required. Generally I don't use coolant or oil because it's over so quickly.
My "go to" width for probably 70% of my cutoffs is 4mm, but that's for work over 1" diameter. I use the little 1.5mm one for small diameters and thin walls to minimize burrs.
As for cutting speeds, I try to get above 200sfm in most materials, but not much more than 500sfm. Of course I don't have constant surface speed on my old lathe as a CNC or a Monarch 10EE might have. This means you start at a given speed but are down to "zero surface feet per minute" at the center.
Here's a short demonstration of cutting off 1-1/8" diameter 1117 with a 4mm cutoff. I start (and end) at 1200 rpm, which works out to abut 350sfm. Feed rate is set at .0057" per rev, and remember that depending upon machine feed per rev is generally half in cross feed as set for longitudinal.
Most home shop guys really should just learn to be successful with the HSS blades first, and your video helps immensely. Other instructional videos on that subject are all over the map on center height and grind. Yours takes the "black art" out of the process.
Investing in an insert cutoff is intimidating because of all the choices and the cost. There are single-ended and double ended inserts, spring clamp or screw clamp, and holders can be blade, monoblock or modular.
The big thing about carbide insert parting is to not be afraid of it and FEED the damn thing. Wider tools want to chatter and the natural tendency is to slow the feed. Do the opposite. The good quality carbide cutoffs can take it.