New table running! Q about bit feed speeds and bit durability

[psantangeli]

My 42x36 wood router is working! I've cut a few things on it, and it seem solid and accurate (at least accurate enough for me!). I used 20mm VXB shafts and bearings, a xylotex system and 2 TPI rods from McMasterCarr. It's geared primarly to through-cutting wood (though I'm doing a bit of drilling and will probably end up cutting some dado's with it). It's a low-profile gantry with overhead leadscrew drive. (I'd probably switch to dual leadscrew with belt drive on X if I had to do it over again - but it works, so I'll wait until it fails first). The spindle is a 30,000rpm porter-cable trim router.

I haven't pushed the speed on it yet. I'm sure on Y it is capable of in excess of 100IPM, and in X it will probably get up between 60 and 100. In practice though, cutting speed is the big limiter for the things I do, not slewing speed.

A couple of questions:

- I am cutting Finnish Birch ply (baltic ply). I'm using a cutting depth of 0.17inches per pass and a feed rate of 12IPM. Does this sound right to people? The results seem reasonably free of burning and are smooth, and the machine does not struggle at all. What speeds are other people using for similar materials?

- I'm using 1/4" Spiral Upcut bits, solid carbide. How long should I expect these to last (measured in either feet or cutting time)? I've noticed that though the wood is not seemingly burning as far as I can tell, the bit I've started with has gone quite black. If it weren't still cutting well, I'd assume it was toast.

Pete

[ger21]

Heat is what dulls router bits. Cutting slowly and high rpm's causes the bits to get hot. If anything, you should get some bit cleaner and try to keep it clean, which will extend bit life. When cutting wood, you really can't go too fast, and faster is usually better than slower. Do some test cuts and keep increasing speed until the quality of cut decreases, or the router or machine doesn't like it.

If your machine is stiff enough to not flex, you should be able to cut with the depth you mention at over 100ipm, or whatever you're machine is capable of. I'm not sure if the trim router has enough power for that, though. On a commercial router I've cut Baltic Birch with a 1/4" upcut spiral at about 150ipm and 18,000 rpm, with .25 to .375 depth of cut.

[psantangeli]

The machine is definitely flexing. Just wasn't sure how much you could push a bit. Switching to the dual X drive will fix %90 of the flex. Maybe I should move that project up in the priority list a bit :-)

Thanks for the great info!

Pete