(04-09-2015, 10:33 AM)PixMan Wrote: The tool nose radius as it relates to feed rate has a profound effect upon the surface finish you get. Also, it's often critical to use at least the size of the tool nose radius as your minimum depth of cut. That's primarily true with carbide inserts because they need heat in the process to get a shiny finish in most materials, soft steels in particular.Hello KEN
Those inserts which have a molded-in chipbreaker (top form geometry) will have a range for depth of cut and feed rate and feed rate in the materials which a particular grade and coating were aimed at. In general terms a larger tool nose radius will get a smoother finish than a smaller radius if both are run at the same feed rate per rev. The profile shape of an insert (90º, 80º, 55º, 35º) and the approach angle of its holder have an effect too, just much less pronounced.
If you are using CNMG and WNMG negative rake inserts, tell me what materials you are turning, and the amount of stock removal you wish to get per pass. Also, the spindle power of the machine will matter with negative rake inserts. I would hope you have at least 3HP on the lathe to use negative rake inserts effectively. I can help with chipbreaker selection and grades when I learn more about what you are trying to use and what materials you are cutting.
Your machine certainly appears to be right for these inserts, I simply don't understand the bit about "keep in low"! If that's what they want, why is the lever option there at all? Perhaps they want it in low only for threading? You definitely want higher speeds and feed rates. I can't quite see the top information plate in your photo, but it appears you have a specific gear arrangement for turning feed rates. See if you can find in your machine's documentation why the notation about "Keep In Low."
Ken
Always good to hear from U.
We have usually tried to maintain an 0.10mm depth of cut when taking a finish pass. And also experimented to see if there was any difference in applying Cutting Oil direct to the part, which seemed not to make any difference. Now that U mention that Carbide Inserts need the heat to generate that polished finish, it all comes together.
The materials we generally turn are the usual lot of salvaged "unbeknown" scraps and some special boughts comprising Mild steels, BMS, Tool steels including and not exclusive to Silver Steel, 303 SS, 316 SS, a little on our 4 Grade Knife Steels,and the usual lot of NFM's viz Brass, Bronze and quite a bit of Aluminium. We are really not hurried to take heavy cuts and at the most have taken 3.0 - 3.5mm heaviest cuts, and this too, not often times. Looking at the machine specs, it says Spindle Drive Motor 4P/8P, 3PH 3.3/2.2 kw or 4.5/3kw 4P, 3PH 90W !!! I will only be able to check out the Motor on Saturday to really get the exact specs and revert with the correct info. Do bear with me. In the interim I am pretty sure it is a 3HP Motor, if not more.
Have attached 2 more pics of the machine to give U a better idea. Will also research that bit on the "Keep in Low" reason in the Manual, which I highly doubt has any further elucidation, and I think my best bet would be to contact and find out from the Sellers personally. Will let U know, either way.
Thanks a stack
aRM