speeds for milling?

oscer

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Hi folks, I am trying to teach myself how to run a milling machine and I have a speed chart out of a Bridgeport manual on my tool box.It apears to be for hss tooling, for example, low carbon steel-90 sfpm. If I go to carbide end mills, which I'm seriously considering, is there a multiplier for this table? I think I downloaded the manual from this site it was for a 1966 mill.
I burned out a 1/4 " hss end mill pretty quickly today using this table but it was used slightly before a friend gave it to me. I had pretty good results though with a 1/2" end mill.
Another question I'd like to ask is, do you use misters on your mills? Where do you buy them and do they save you much money in tooling?
Thanks for any help on these matters and I'm sure there will be more to follow.
 
There are many variables involved in determining the optimum spindle speed and feed rate. Much depends on the machine and workholding method. Cutter geometry, material, flute count if end mill are only part of the equation. Here is a discussion of some aspects of milling speed selection:

http://its.fvtc.edu/MachShop3/speedCalc/SpeedRPM.htm

In general, if you have enough rigidity, carbide can be run from 4 to 10 times as fast in the spindle, which necessitates an increase in feedrate to maintain the chipload per tooth (or edge). One of the main things beginners do wrong is to feed too slowly. That overheats the end mill and allows the edge to break down, the material to work harden, and ultimately ruin the cutter.

As far as mist systems, I use a KoolMist system on the BP, with mist coolant, not soluble oil. I recommend mist on end mill work, but not on inserted cutters.
 
Those charts were made up for production uses, and for newbie purposes should- for all practical purposes be ignored.

I think a good mantra for 'newbies' on both lathes and mills should be "If you think youre going slow enough, slow down some more" Going slower will still make chips and give you a 'feel' and an 'ear' for the tool and what its doing - its easy enough to gradually ease the feed/speed up as you learn. This will hold true across the board for the different cutting tools.

Speed and feed (especially speed) for me was one of the most difficult things to rein in.
 
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