Has anyone used a larger facing bit for aluminium, or do folks stick to 1/4" to face off their stock?
I have a 1-1/8" carbide tipped Amana surfacing bit. Would this be too big for a makita to handle? And/or Makita can’t go slow enough?
I’m not sure I’d try a bit that large on Aluminium, does Amana recommend it for metals?
You’re right about speeds, you’d need to slow down the RPM to keep the temperatures down on the workpiece without coolant.
I’d be concerned that it might well vibrate horribly in Aluminium at that size too.
I’ve had decent results with a 10mm 3 flute when surfacing, but I had to slow it down to keep the temperature down and get a clean finish without coolant. At 24kRPM I got ridges between passes. I think I ran it at about 15kRPM after some testing. Also tramming errors really show up in Aluminium and the wider the bit the more visible they are.
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Good points. I will stick to a 1/4" since it’s the biggest I got.
What bit, speeds and feeds would you guys recommend for cutting various shapes from a piece of .025" aluminum sheet?
Check out Winston’s videos here (the first four ones) for recommended feeds and speeds for aluminium:
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Curious, how does high RPM give rise to ridges? I may be facing a similar problem.
I would guess it’s due to vibration at higher speeds raising a small edge as the bit wiggles a hair side to side?
I’m not entirely sure but what I believe was happening was heating of the workpiece.
There’s a good chart on this page
showing how machining temperature changes with cutting speed. That chart is showing how, once you go fast enough the temperatures actually come back down but I think I was sitting in the high temperature zone and heating up the cut and the workpiece.
I was using this cutter
Which when you use the sides removes material really fast, but when facing there are three flutes on the material with variable radius from the center, giving a range of surface speeds from about 200m/min to 600m/min at 20kRPM which seems to be right in the range of ‘hot’ for hard aluminium based on the chart. The workpiece certaintly got very hot during the machining, so hot it started to lift off the glue & tape by melting the adhesive.
So far as I can tell the ridges I got were workpiece material being pushed around on the surface due to softening at high temperature rather than being cleanly sheared off by the cutter.
When I dropped the RPM a little the finish was less ‘smeary’, the workpiece was colder and the ridges were gone.
I’m open to corrections from those who know more.
Makes sense when a little thought is given to it.
I use Apt-Tools here in the uk. I find them very reliable.
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Yep,
I’ve also found APT to deliver really quickly and produce really consistent tools for surprisingly good prices, got quite a collection.
Have you tried their DLC coated in Aluminium yet? They work pretty well for me.
Not until you mentioned it above. Probably because I’ve been milling silver using 0.4mm bits. I, too, have quite a collection of APT bits in bits; getting the feeds n speeds right has been troublesome but ramming the spindle into the bed due to incorrect Z setting the main reason - darned if I know why as I’m pretty sure that in some instances I have properly zeroed before starting.
I’m going to give these DLC bits a spin; I like the reference to dry milling.
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I’ve been using these the past few years. As recommended by @Vince.Fab.
1” and 3/4”, 15-18k rpm, .01-.5 mm DOC depending upon desired depth of material to be removed.
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Nice! What make/model? Nice they have inserts.
I guess you guys are running custom spindles? Or did you buy a 3/8" collet for makita/carbide routers? Do they offer 1/4" shank versions?
I have a 1/4", 1/8", 4/7/8mm collets. Hate to buy another just for a face mill.
3/8s collet for the Makita, its decently cheap and I bought one for around $10-15.
Not just for facemill usage but 3/8s tooling can be very handy in high doc/high stress apps
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Was it from Elaire or just elsewhere? Amazon?
EDIT: Oh, wow there is an official makita one https://www.makitatools.com/products/details/763619-3 ?
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yup, go offical and use two wrenches to tighten always.
The split style collar takes a bit more force to really clamp
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Oooof, backordered for ages it looks like. Makita in town said maybe August. Online looks thin as well, I’ll keep lookin!
Is the tolerance on the 3/8 good enough to get a good surface finish?
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