Bit usage?

I built my MPCNC back in February-ish. I’ve cut quite a bit of MDF since then, and my 1/8" end mill burned up the last time I cut stuff. I was hearing some chatter starting in the cuts leading up to the burn out.

How often are ya’ll burning up bits? Was this because my IPM was too high, or does this happen more often on the smaller bits we use in the DW660’s ?

I’m starting to wish I kept a better log of how many hours I had on the bit. I think I’ll start a spreadsheet and start tracking cut times.

MDF is tricky, too slow or to high of rpms can burn it as well. There is a ton binders in MDF that tend to burn easy. Your bit might be okay and just covered in residue not truly burnt. I am not an expert on these things, I still have some of my very first bits. Usually I will chip them by hitting a screw or otherwise break them.

I have a single flute bit I have been using to cut LowRider pars out of 1/4" MDF and I think I push it pretty hard, it still seems to be going strong after 20 hours or so of cut time (really pleased with this I figured 5-10 max). I run that at full depth plus a litte so 9mm DOC, at a 3 speed setting on the 611, and 9mm/s I think. So, sorry I don’t have an answer but I am watching to see if some others do.

What are you feeds,speeds, DOC?

The answer is yes. All those factors play into how fast a bit gets dull. I think our main issue is RPM. The Dw660 spins super fast for what we are trying to do which is one of the reasons why the single flute end mills seem to be working better for people. At a high rpm it gives the bit time to actuallu cut and pull away the material before the next cutting surface comes around. Rpms, speed, feed, and materials all come into play. I am not sure there is a good way to estimate how long they should last. Just pay close attention to how its cutting and you should be able to tell when its time to change bits before they burn up. You play the same game when turning steel on a lathe or mill. Watch and listen to how it cuts and try to get the most out of each bit or insert before it breaks or burns up.

I’m sure that when it gets dull, it will heat up a lot more too. So you might have just dulled the thing (which will happen in time, no matter what) and then it was working harder, getting duller, leading to exponentially more problems.

I’m using the 2-flute 1/8" end mill bought on this site.

30-40 IPM (depending on project)

.1" DOC

Mostly cutting MDF, some 1/4" ply

Friday night I was doing cuts at 40 IPM in MDF and towards the end noticed chatter getting a little worse. Figured I was running a little fast, so on Sunday I did the rest of my cuts at 30 IPM. No chatter at the beginning, but after an hour or so I started to get slight chatter and suddenly the machine started skipping steps. That’s when I killed the process and noticed when I backed the router out that the end of the bit was black all the way up to the DOC that it was up to.

That is pretty fast and shallow, try moving slower and deeper to utilize more of the bit cutting surface that should make it last a lot longer, with the two flute you really need to slow down the rpms. The single flute I still run really slow rpms.

Thanks. I’ll try that.

Wife just called that the new bits arrived. I’ll adjust the gcode tonight and give it a try on Friday.

I’ll also add…

The other day I did a trochodial pocket at .25" and 30 IPM that cut really nice.

I always break my bits cause the tip of my single flutes chips on a screw. I am pretty abusive on my bits :frowning: You can sort of feel how sharp your bits are just by feeling them in your hand. Not the most scientific test but you can tell easily which ones are sharp and which ones are just downright dull. The sharp ones really bite, the dull ones just slide across.

I always break my bits cause the tip of my single flutes chips on a screw. I am pretty abusive on my bits :frowning: You can sort of feel how sharp your bits are just by feeling them in your hand. Not the most scientific test but you can tell easily which ones are sharp and which ones are just downright dull. The sharp ones really bite, the dull ones just slide across.

Yeah deeper and slower is the way to go, you are really only using the first .25" of your bit, so when that gets dull its trash, if you go deeper and slower you will get more life from the bit, and much faster cut times even moving slower. Couple that with a full depth finishing pass you will have amazing tolerances and surface finish.

So, when doing aluminum, do small DOC and slow speeds, but when doing MDF or other woods, do full depth and slow speed?

The PVC tests I’ve done with the chipper bit worked best at .06"DOC and 30IPM

I would always do as deep as possible on all materials and only vary the feedrate, and rpm. Tricoidal/adaptive helps with more dense materials like aluminum. A lot has changed with the software in the last year, much more is possible now.

It is a complicated process but it comes down to haw many passes you would need to take, desired tolerances, material, cutter type, etc. You might want to get a single flute, it is pretty much the only cutter I use besides a carve v-bit when necessary. We have high RPM “spindles” two flute is just not ideal and has a much smaller sweet spot in terms of settings.

heh. I should have made this post before ordering my new bits then :frowning:

now that I think about it… I did buy the parts to make the speed control for the DW660. I could go ahead and finish building that. That might help some.

Tonight I got up to a .3" DOC and 10 IPM. I tried to go .6" DOC at 3 IPM, but the bit grabbed and dug into the board.

At the smaller DOC the router bit had a nice hum to it, so I think I’ll stick with this. I’m also going to try to bump up the speed on the finishing pass, since it’s barely biting anything off.

I will saying using the finishing pass did leave a nice finish to the piece.

We really need to convert you to metric.

The finishing pass shouldn’t go too fast, the name of the game is accuracy, not speed usually. If you need speed skip the finishing pass.

7.6mm to 15.2mm is a huge jump, more than double the load on the bit because it is hanging out further and twice as much is getting cut at once. I think the deepest I go is 9mm in pine, I made a video of it.


Funny enough… when I design for the 3d printer, I use metric.

I’m still a bit stuck on imperial for the CNC machine because the stock I buy is listed as such and the designs tend to be larger, which my tape measure measures easier.

I keep meaning to buy a metric only tape measure. I have an english/metric combo, but the metric is on the bottom, which isn’t very helpful. I would get a kick every time someone else tried to use it.

I bought a tape that is half metric, My life is easier now.

I was just messing with you , I just google the conversions that I don’t have memorized. I learned big things (construction) in feet and inches. Working with 3D printers, and being in college at the same time everything small was done in metric, and when it wasn’t the math gets much harder. So I just understand what .3mm is much more readily than what 1/16". If Imperial was done in decimal .125" it wouldn’t matter as much I don’t think. Going to the hardware store for prototype stuff I have to bring my metric tape now. I know all my tolerances and offsets in metric for CAD.

Chemistry ruined me, metric or nothing in that subject.