feeds and speeds

[JpBinc]

Hello all
I was wondering if anyone has any input on how to calculate feeds and speed for different cutters. I have done some reading and it seems like it is a little bit of magic in finding the right numbers. What methods do you use???
Thanks
JpBinc.

[tobyaxis]

The only method to use is experience with a mix of Manufacturer Recommendations and Feel.

What are you cutting?
Mild Steel, Hard Steel, Stainless, Aluminum, Titanium?

What Tool type?
Single point Lathe tool, or End Mill?

What type of Setup; Vise, Fixture, Lathe Chuck, Hard or Soft Jaws?

All these Variables and more have to be considered when Machining.

As a rule of thumb if you get chatter or squeeling turn the RPM down Gradually in 5%-10% increments or the Feedrate Up until the cutter is Happy. You will develope a feel and know when a cutter and Machine is Happy.

My opinion on Chatter or Squeeling: It is the Cutter (on a Mill) or the Bar (in a Lathe) bouncing instead of Cutting. Hence you have to find the Sweat Spot or Optimal Feeds and Speeds in a given application.

I hope this Helps you.

[cdlenterprises]

The formulas for feeds and speeds are:

RPM = CS x 3.82 / D
where CS = cutting speed; D = dia. of the cutter(mill) or the part(lathe)

Feedrate = RPM x FPT x # flutes
where FPT = chipload or feed per tooth.

The CS values can be manufacturer specific and can vary depending on cutter geometry, coatings, etc. A good place to look for general starting points would be the Machinery Handbook. Hope this answers your question

[BobWarfield]

Buy a copy of one of the popular machinist's help software. ME Pro is the one I hear most recommended in places like Practical Machinist. They say it's dead on.

Best,

BW

[JpBinc]

Thanks for the input. I am cutting alu, brass, steel in a vise (china ripoff of a kurt) on a seig x3. I converted to cnc with information from this site. This is the best forum out there. I am starting to understand that there are so many variables that there is not one sure answer without testing it. However I was really looking for a starting point to experiment with. Many thanks for the answers.