Thread: Depth of cut HM35 Mill

I don't think there's an absolute depth of cut, it depends on the material being cut, the size and type of the cutting tool and so forth.

I work on the basis that the machine will tell me when I'm trying to take too much material off, the tool chatters and the machine complains noisily until I back off the cut a bit.

Just for the record Im using an 1 1/2" 3 tiped square face mill using TPKN 160308 tips on mild steel.

There is a bit more to it than just depth of cut.
First you need to ascertain the surface cutting speed for the material.
Mild steel 100 SFPM.
100 x 4 / cutter diameter = 100 X 4 / 1.5" = 266.6 RPM
Carbide inserts can work at higher RPM than standard cutters so 300 to 400 RPM should work ok.
Next you have calculate a feed rate . If you dont have an automatic feed then hand feeding will be by feel.
Depth of cut can also be discovered by just trying a few thou cut and increasing each cut until the machine starts to complain a bit then stop it and back it off a bit as has already been explained by Gavin.

Have been running at 960 RPM with 3mm DOC feed by hand (typically over a 100mm length 50 mm/min ,was just wondering how deep people have gone ,guess I will sneak up on it would like to be able to take 5mm roughing passes.

I don't think a HM-35 machine would handle a 5 mm cut in steel well at all .
It would place a lot of strain on the machine and inserts and you would have to feed so slowy that at 960 RPM a lott of heat would build up in the steel and inserts leading to possible premature tool failure.
Face mills can use higher feed rates than standard cutters by as much as 200% but heat buildup is still a limiting factor.
Cutting soft material at 960 RPM with carbide inserts is quite possible but if you apply that same additional RPM above normal to much harder stuff then problems can result quickly.
The faster the RPM the more impact is developed at the cutting point of the insert.
If a mill spends too much time removing light cuts at high RPM because the depth of cut is too deep and as a result the feed rate too slow then heat will become a problem.
I think you are over estimating the capacity of your mill.

Start with light cuts first and work up from there eventually you will find the capability of the machine with that cutter for a certain material .