[drxlcarfreak]

Hey guys,

I am running a FLA standard machine with the skateboard bearings, upgraded nema 34 servos and a 2.2kw spindle. I recently started using an actual decent end mill instead of ebay brand ones and was blown away with how much more material can be removed as well as the reduction of post processing work I need to do to the parts. So naturally, I am now planning to go all out and get some bits that can cut sheets of plywood in a single pass instead of the 1/4" bits that flex too much to do that at the appropriate chiploads. I threw all of the specs into the Gwizard feed and speed calculator for a 3/8" compression bit and it looks like my 2.2kw spindle has become the limiting factor, only letting me do about 1/4" DOC with a 3/8" bit to have the correct chipload. My question is, before looking into upgrading my spindle and vfd to be able to rip through material, is there a reason the standard spindle size people on here run is 2.2kw? Is that the limit we can use safely with skateboard bearings, or is it just because that size spindle is readily available?

Thanks!

[ger21]

There are multiple reasons why 2.2Kw spindles are so popular.
1) They were the first affordable spindles available to the masses.
2) They will work on commonly available 20a-30a 240V circuits. Once you get to 4-5Kw, you may need a 50 amp circuit to power it.
3) They're still relatively small and lightweight. Larger spindles can weigh 40-50lbs or more.

While not ideal, you're skate bearings are far from the weakest link. Getting anywhere near a proper chipload will have your machine flexing all over the place.
On an industrial machine, to maximize tool life, we run 3/8" compression bits at 700ipm and 16,000 rpm.

I would not make 1/4" passes with a compression bit if you want it to last long, as you'll weaer out the tip. I'd use a down cut to rough the part oversize, then follow with a single pass with the compression bit. You can use a dull downcut for a long time and still get decent results for roughing, and you'll get a lot more life from your compression bit.

[MARV]

I may be way off base here, but my review of G/wizard a couple of years ago seemed to favor metal working with regard to suitable range of feed speeds, chip loads, etc. My understanding of cutting tool geometry over the years has been that "end mills" (cutters long associated with metal working) and similarly shaped "router bits" (for woodworking) were fundamentally different. Hook angles, back clearances and gullet depths are what set these cutting tools apart. Don't get me wrong, in a pinch, most end mills will cut wood well enough (I think). But cutting tools designed for the task will always perform better. As a reference, I would suggest using the feed and speed calculator that is on the Onsrud Cutter website (as far as I know, its still there). And yes, those are parameters generally used in industry, but you might be able to extrapolate to meet your HP limitations. Regarding suitable use of skateboard bearings: my only experience comes as a former (and much bloodied) skateboarder. Hope this helps.

[drxlcarfreak]

Fair enough, that makes complete sense and kind of figured that, but wanted to ask. I had assumed that the weak link would be the skateboard bearings as I have crunched a couple before wracking the gantry, but it is just held together with aluminum extrusions and bolts, so that makes sense.

I have been messing with 1/4" bits so long, I was surprised how quickly the spindle runs out of head room when moving up to a larger diameter bit.

This was my first shot at compression bits and figured I just needed to cut deeper than the upcut portion, but that makes sense. That is exactly what I did except I used the compression bit for every pass, but you are right. I would much rather dull out a $30 bit than a $90 bit.

With that in mind, I think the best plan for me would be to stick with 1/4" bits instead of upgrading to 3/8" since with either one I will be doing multiple depth offset cuts and then a final full depth pass. With the plywood I had a bit of fuzzing with the bit I used and looked at Vortex's site a bit more and saw that they have a chip breaker bit specifically to combat this, except the smallest bit available is 3/8". It is kind of what lead me down the rabbit hole of trying to further optimize cuts. This is the bit series I am talking about: https://www.vortextool.com/wood-tool...pbreakers.html

Complete thread change and this is now probably in the wrong section, but is there a comparable bit in a different brand available in 1/4" diameter?

[drxlcarfreak]

I may be way off base here, but my review of G/wizard a couple of years ago seemed to favor metal working with regard to suitable range of feed speeds, chip loads, etc. My understanding of cutting tool geometry over the years has been that "end mills" (cutters long associated with metal working) and similarly shaped "router bits" (for woodworking) were fundamentally different. Hook angles, back clearances and gullet depths are what set these cutting tools apart. Don't get me wrong, in a pinch, most end mills will cut wood well enough (I think). But cutting tools designed for the task will always perform better. As a reference, I would suggest using the feed and speed calculator that is on the Onsrud Cutter website (as far as I know, its still there). And yes, those are parameters generally used in industry, but you might be able to extrapolate to meet your HP limitations. Regarding suitable use of skateboard bearings: my only experience comes as a former (and much bloodied) skateboarder. Hope this helps.

That may be true, I just saw that there are wood/composite options on the calculator as well and went with it. It seemed to be the only calculator I saw that took tool deflection and spindle HP into account, even if it was a bit off it kind of gave me peace of mind. I am using wood specific bits. I guess to your point, Vortex actually doesn't say end mill anywhere, and searching their website, it does say they specialize in non-ferrous router bits. I guess I was using the wrong terminology for the bits. My bad, I just assumed router bits were specific to lesser quality/toleranced bits like the type you buy at Lowes.