Engraving spped question?

[jaysteel]

Hello all, I have a engraving speed question, but I might be in the wrong area maybe not so I'll ask. I have laser but I need to engrave some seals on delrin, I don't want to use the laser to engrave them because I want to try to engrave the seals all at a precise depth and I want to do it with something besides the laser.
I have a new in the box sherline 5400 cnc mill that I'm going to use - the seals are 3 "s round. Here's the question the spindle shipped with the machine spins at 2800 rpm, probably not fast enough for engraving. So sherline sells a 10,000 rpm pulley set - by adding the additional pulley I'm quite confident the machine will engrave what I need. But sherline also is touting a high speed air spindle - they claim it's designed specifically for engraving and is capable of speeds up to 54,000, a huge difference (of course a huge difference in price as well).
I want a to do a great job and don't mind paying extra for the air spindle if the results are going to be superior.
So your thoughts, Gentlemen?? Thanks, Jeff

[Tweakie]

If you are going to be using flood coolant it will be different but most use air jet and perhaps mist, therefore, there is quite a close relationship between spindle speed and feed rate in order to avoid welding the material being cut to the cutting edge of the tool.
I don't know the optimum cutting speeds and feeds for Delrin but it will be available on one of the CNC machine forum sites. The 10,000 rpm would be my first choice as I think it would be a more versatile option for milling, engraving etc. However, if you were going into jewellery making and other small, fine work then the 54,000 sounds good for those little engraving points.

Just my 2 cents.

Tweakie.