could someone recommend a quite, around 2hp or so, AC spindle motor to engrave steel plate, with a recommended bit. would like to be able to cut into soft steel, around 0.040" deep in one pass.
Material is standard mild steel (structural).  It doesn't have to be variable speed, just have the power and rpm to do the job at around 20-40 "/min feed rate.

Scott

Have you figured anything out for this? What size and kind of bit do you want for this? and is that ipm or mm/pm?

Chad

dont know, that is why I am asking for recommendations.

Ok well I will make some guesses.

If you want to do 20-40 IPM in mild steel .04 deep with (1/8 , 1/16 ,1/4 ,1/32 ,2mm ,4mm, 6mm "rolls dice" 1/8 inch) then you will have to use a spindle running 12000 rpm and higher probably a lot higher. I would recommend good flood cooling, and depending on speed and feed either 2 or 4 flute carbide. Depending on... you are getting into "high speed" machining. The smaller the bits you use the faster they have to turn to keep the chip load reasonable especially at high fees rates like this in steel, especially at that depth. Depending on the size of the bit it might not be at all possible to go that deep in one pass at any ware close to that speed, or at all.  If this were wood there would be no problem but this kind of speed in steel is going to take a lot of experimentation and very high rpm.
 
For example on our metal mill with a 1/8 inch bit cutting 1/8 deep in 2025 alum with mist cooling with the speed cranked all the way up to 5600 rpm I start breaking mill bits at 12 ipm. If it were mild steel I couldn't go much over 2 or 3 ipm (maybe). 

Cooling is going to be critical! At that kind of rpm and feed any heat = broken bit.

Spindles: http://www.hsd.it/home.asp  or http://www.pdscolombo.com/products.htm

Just found this:

 Fully guarding the machine and offering a remote video system for monitoring performance will also reduce operator fear and anxiety. High-speed milling is quite foreign to many of today's operators, and running a spindle at 25,000 or 30,000 rpm is vastly different from running at the 2,000 or 3,000 rpm that operators understand.

To assist in determining certain feeds and speeds for a selected machine, Tables 1 and 2 are reprinted with permission of the Robb-Jack Corporation and represent their recommendations for using their particular end mills for machining three different materials.

Table : Table 1 - Recommended feed rates for two-flute solid carbide end mills in aluminum (based on unlimited available horsepower).

DIAMETER   CHIP LOAD   FEED RATE AT   FEED RATE AT   FEED RATE AT
(INCHES)   PER TOOTH   6,000 RPM      10,000 RPM     20,000 RPM
1/8        0.002             24.0         40.0            80.0
3/16       0.004             48.0         80.0           160.0
1/4        0.008             98.0        160.0           320.0
5/16       0.008             98.0        160.0           320.0
3/8        0.012            140.0        240.0           480.0
1/2        0.016            190.0        320.0           640.0
5/8        0.016            190.0        320.0           640.0
3/4        0.020            240.0        400.0           800.0
1          0.020            240.0        400.0           800.0
DIAMETER            CHIP LOAD   FEED RATE
(INCHES)   R.P.M.   PER TOOTH   (IPM)
1/8        2,000     0.0007     16.8
3/16       8,500     0.0012     20.0
1/4        6,000     0.0017     20.0
5/16       4,900     0.0025     25.0
3/8        4,100     0.003      25.0
1/2        3,000     0.004      24.0

Table 2 - Recommended feed rates for roughing a slot in 6AL titanium (340 Brinell) with a two-flute solid carbide end mill (up to 5/16-inch diameter) at 400 sfpm. These recommendations apply to a depth of cut not to exceed one half of the cutter diameter. For cutters over 5/16 inch in diameter, depth of cut should not exceed one quarter of the diameter. For finishing cuts or profiling operations, use a four-flute end mill at double the listed feed rates.


Chad

Hi All,
How do you run these R.P.M.s and those feed rates ?
10/15 thous. deep,less?
I cannot get anywere near that,end burns up,vib,noise,etc.
1/4 or less maybe for O.D. depth, feed rt.
Machine is B.P. retro/2 hp.apx,52 IPM.feed.
 
 Bear