Duration of Router Bits

[MeticulousMaynard]

@madgrizzle

So my understanding is that for plywood, we should be striving for 0.011 to 0.013 inch chip loads. With a feed rate of 47 ipm (which I understand is the current limit), a single flute 1/4-inch bit, the required RPM is about 4000, which is too low for the router. If using a 2-flute bit, you need an RPM of 2000… even worse (please correct me if I’m wrong, this is all new to me).

Just curious, where are you getting your chipload recommendations from? I’ve been using the Onsrud chipload tables to get my values. I know these are intended for Onsrud’s tooling, so far it has served as a pretty good starting point. According to their tables, 0.011-0.013 is nearing compression bit territory. Up/downshear bits at 1/4" diameter need somewhere between 0.005 - 0.007. This still means that at the Rigid R2200 router’s minimum RPM of 10,000 the Maslow should need 3,000mm/min (118 ipm). If the spindle speed could be reduced to about 3000 rpm, then the Maslow’s maximum feedrate of 900mm/min (35 ipm) would be okay. Last I checked, that was the max feedrate set in the firmware, but it could have changed. Also, all these calculations are for two flute bits. I have yet to get any of my two flute tools to cut without screaming as they go, so I’ve stopped using them for now.

So far the best solution I have come up with for running bits at an optimal feedrate is to use single flute bits. The single flute bit I bought from the Maslow store has lasted me about a month of weekend work. I just noticed it was getting dull last weekend. I dialed the tool into 12000 rpm at 500 mm/min (20 ipm) cutting around 6mm (1/4") with each pass.

We have been going over options to increase the machine’s max feedrate in this thread.

@vertex

Does anyone know how warm a router bit is after an hour of work?

You should be able to touch the bit after any amount of cutting (WITH THE SPINDLE OFF!!!). If it is noticeably hot to the touch, then the feed and speeds are wrong.

@JaceD

Good call, @mooselake. I don’t think the cutting forces would be very large with a shallow depth of cut, but I can definitely see them being large enough to overcome the small portion of the weight that’s normal to the sled, especially if the depth of cut was higher. Still waiting for a machine so I can’t speak from experience just yet, but downcut bits would be a good way to avoid sled lifting. I guess Maslows are primarily used for cutting out 2D shapes right now (profiling ops), which downcut bits are well purposed for.

Gotta change my perspective a little here. Sorry for the poor assumptions.

Scratch that @czimm74 … use downcut bits!

While I have not gotten the feed-rate right for my two flute downshear bits, I have not had any trouble with it pushing the sled off the work-surface. I hadn’t seen any comments about downshear bits on this forum so I wasn’t sure if that was something that I should pursue further. I’ll just need to find a supplier for single flute downshears or get more work done on increasing the max feedrate to pursue this futher. I would prefer to cut with downshear where possible, since it gives me much better top edge quality.