Ben wrote:
Thanks so very much for taking the time to respond - it’s really appreciated.
I’ve now got the 600watt one you purchased in my cart - https://www.aliexpress.us/item/1005004547167176.html?gatewayAdapt=4itemAdapt
Is this the one you’d purchase for an all rounder best option? I don’t want to
gold plate the thing, but don’t want to be replacing weak components in too
short of a time either.
I don’t have any time on the spindle, so this is book learning/logic
A brushless motor gives you more consistant speeds than a brushed DC motor (like
the 500w one). A brushless motor also gives you more power (much more power at
low rpms, a brushed motor gets low rpms by reducing power)
The AC motors with a variable frequency drive like you had posted earlier, are
commonly used in bigger machines.
I prefer a separate chuck so it can be replaced. If you manage to damage the
chunk and it’s part of the shaft, you end up replacing the motor. That said, if
you can get 3 full kits with the chuck built in for the cost of one with a
replacable chuck, that makes up for a lot 
it needs to be <67mm diameter to fit the maslow.
after those considerations, more power is better
I must admit, I’m now thoroughly confused! I’ve been reading that higher RPMs usually mean cleaner cuts, but there’s obviously much more to it than I’m seeing.
the right speed is better. If you spin too fast for your feed rate and bit, you
spend a lot of time with the bit rubbing against the material rather than
cutting. This rubbing heats the bit, destroying the temper of the edge, which
dulls the bit quickly, which makes the cut ragged (and generates more heat)
If you spin to slow, the bit can’t cut out enough material with each flute and
you will break the bit or wander from your cut line.
there is a science for feeds and speeds (look up machining feeds and speeds).
For a given cutter, each cutting flute can cut only so much material before the
gullet between the teeth fills up with material, but you want each tooth to take
a noticable bite of the material (when you do this, a lot of the heat goes into
the chip you take off, not into the bit). So the more flutes you have, the
slower you should spin. The slower the machine moves, the slower you should
spin. If the machine isn’t super ridgid (which the maslow very much is NOT), you
want to take a smaller cut, if only in depth, to reduce the forces on the
machine. Professional Machinists are trying to balance tools wearing out and
breaking against spending more time to get the job done, so their calculations
are aggressive, assume that the machine is ridgid enough to handle the forces,
and that time is your biggest priority. For hobbiests, time is not as much of a
priority, so we usually opt to back off and go slower than the calculations
suggest (our machines are not as ridgid as well, so we can’t cut as
aggressively)
you can really get bogged down in this, and when cutting aluminum you probably
should at least try, but wood is very forgiving (especially soft wood like
pine). So if you just think of ‘chips not sawdust’ you will do a pretty good
job.
If you are getting dust (and especially if the wood is getting burnt), slow down
the rpm, use a bit with fewer flutes, and/or speed up the feed rate. This can
dull bis really quickly, so expect it have have some extras around.
if you are trying to cut too much, the machine will flex and the path will
wander a bit. Take shallower passes and/or more flutes, higher rpm, slower feed
rate. worst case, you will break a bit (especially with small bits), so expect
it and have some extras around.
when you are cutting aluminum, it’s common for the heat to get too high and weld
the aluminum dust/chips to the bit, so expect it and have some extras around (so
you sense a theme here? )
If the spindle doesn’t have enough power, you can deal with that by making more,
shallower passes.
As a general rule, it’s better to be spinning a bit too slow than too fast.
this is a long answer, but I hope that by explaining the reasoning rathe than
just giving a short answer, you can understand the logic and adapt it to your
own situation.
David Lang
