The 1/4" bits I’ve been using have long shanks for use in standard routers. When using them with my CNC spindle, I stick them in a collet - off the spindle - leaving a comfortable amount of the bit exposed. Then, I mark the shank sticking out of the top side of the collet, remove it, put it in a vise and cut it off with a hacksaw. No chatter!
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I haven’t done any tests at lower feed rates yet (still at work), but I do believe I will be trying tonight; I’ll post my results.
I had used a 1/4" 2 flute spiral upcut bit, but like you said the edge on MDF was tearing out pretty badly. Besides the chatter, I think the straight bit is the way to go on MDF.
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I’m cutting MDF all the time on my machine but I wont use a 1/4" bit anymore - I end up with cuts like yours.
I only use 1/8" bit and the only way I can get acceptable edges is to take shallow passes.
Ok I ran a few more tests, I think slowing down the feed is helping, but something still seems off.
Here the set up for the video below:
Bit: 1/8" Straight 2 Flute
DOC:0.06"
Feed rate: 40ipm
(again sorry for the poor video quality, I neeed some better lighting in the shop)
I might try another test going slower still, but it’s starting to look more and more like a spindle upgrade is in my future. I don’t want to be waiting hours for my cut to finish!
So from my vague understanding of feed rate calculation, if I have higher RPMs a can have a higher feed rate, is this correct?
The power rating of the spindle needs to be included in that calculation somehow. The spindle needs to have enough torque to maintain the desired speed when under load and the load will increase the faster the bit is moving through the material.
On a side note, I saw in another thread that someone had upgraded their X-Carve with a 2.5 HP router. That is about 1,864 watts of power. At 110 volts a router that size would draw almost 17 amps (actually closer to 20 after considering the heat losses of the motor). That is getting really close to the capacity of a typical household 20 amp breaker.
Thanks for the info! I’d more than likely consider upgrading to a 800w spindle and VFD, it’s starting to look like a pretty common upgrade now.
Is there an 800w spindle that will fit in the 300w holder?
No, I’d need to get a new mount. I guess the Dewalt mount Inventables sells holds a 65mm spindle with minimal shimming.
I would try a much lower IPM (like 10 or 20, find one that works) and then maybe increase the DOC in increments.
Aiming for the same amount of material being taken away, but less lateral power on the Z-axis, and more use of the RPM.
(in a way 
)
Thanks I will give this a shot!
i have chatter issues as well going across the grain along the X axis in hardwood at a depth of .0625" and at max rpm with a 60 deg v-bit.
Since my spindle is doing the “needs a jump start” thing now. i will probably opt for either the 24v or 48v quiet cut if the thing dies like some have.
I havent decided yet.
I ran a bosch colt on a piranha and had no cross grain chatter issues, even with a deeper DOC.
On the stock spindle I can SEE the arbor shifting in relation to the motor assembly so there is a fair amount of play there. I can also see excessive play in the shaft when I manipulate it by hand with the motor off.
but it is just a basic spindle to get us started after all.
would you be better off calculating 80ish % of max spindle speed it is bound to bog down some while cutting or has the manufacture taken that into consideration?
That is probably good advice. The Max rpm is not always the rpm with the best torque. I try to run my 300w 24v spindle between 12000 and 13000, and I find that gets the cleanest results.
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