1/16 (1.5mm) Bits, Breakages, Feeds & Speeds

Mostly Printed CNC - MPCNC Troubleshooting
1

After breaking 4 bits yesterday, I wanted to get some advice on other feeds/speeds people have used on 1/16 or 1.5mm bits or similar.

Project was through cut of 7mm plywood. It’s some home decor type pieces for my wife’s business, which would normally be done on a laser cutter (which I don’t own). It’s mostly text and some smaller simple drawings. Fairly small hence the small bit. 300 - 70mm items.

MPCNC Specs

  • 600x600mm cut size

  • 100mm Z

  • RTO700 clone.

  • Bit - 1.5 x 3.175 x 8mm 2 flute straight from https://www.endmill.com.au/2-flute-straight-carbide-end-mill/

  • 8mm/s & 1mm DOC / ~15000 rpm - heavy chattering, and then the bit snapped.

  • 8mm/s & 0.7mm DOC / ~15000rpm - no issues except someone forgot to put tabs on some cut out pieces and the bit snapped when it encountered the entire 7mm side of a loose part…

  • Bit 3… may have not been paying attention and driven into clamp…

  • Bit 4 was a Bangood cheapy roughing mill approx 1.4mm. It seemed to be cutting fine but may have encountered some vibration from the plywood not being quite flat and snapped after

Now not all of those were feed/speed related but I have broken the same bit previously experimenting with feeds and speeds. I believe it should handle 1.0 - 1.5mm DOC but I am not sure on feeds. I want to compare what feeds/speeds other people have used and work from there.

I am also going to try raising the piece closer to the gantry as has been suggested elsewhere in forum.

2

You need some upcut bits. Straight will clog the cut area and as you found out, break.

3

Yep. Single flute if you can find them.

4

Didn’t realise it had been three days since I posted. You forget how much time new babies can take up.

I have ordered a couple of 2-flute upcut 1.5mm X 3.175 X 12 bits. I can’t find a single flute bit in that diameter and length locally.

Would these 3.175 X 3.175x17 single flute be alright? https://www.endmill.com.au/1-flute-up-cut-carbide-end-mill-for-plastics/

I think they are a bit longer than the Kyoceras but I can’t get those here in Aus.

I’ve also tightened a few belts and bolts. The 130mm gantry bolt was pretty loose causing some wobble in the gantry. Which I noticed after some pretty good blowouts with a 6.4mm down it but (longest bit I had left and needed something cut out for anniversary.)

I also noticed that some of the feet aren’t planted fully on the base, so will fix that as well.

Are the any recommendations for Aliexpress bits that anyone has tried? I eventually want to mill acrylic and aluminium, but I was to have a stockpile of bits to play with.

5

The lead times are so long and prices are so cheap I wound up ordering a large assortment of bits and haven’t been disappointed yet. It’s good to have a few quality bits from V1 so you can judge the difference.

Anything single flute… I find I use the ten pack of square single flute 3.175mm bits the most. I also got a 90 degree carving bit I like a lot. Also some smaller bits for doing detail work… those work best not much longer than the stock you are cutting or they break. With thin stock I had trouble with the bit lifting the work so I grabbed a few compression and down cut bits but haven’t tried them yet. They also sell surfacing bits which I got but haven’t used yet.

Make sure to get 3.175mm shank and not 3mm there is a lot of metric on there