What to look for in bits?

[Boyan Silyavski]

Its a repeated question when somebody starts.

The answer:

Sizes:

you need 3 major sizes:

3mm or/and 1/8"

6mm or/and 1/4"

12mm or/and 1/2"


Flutes:

You will need 2 flutes cutters mostly. 1 flute cutters are specific material and you dont need them at the beginning until you know what you are doing and why exactly are needed. They are not a necessity if you have HF spindle.

In rare occasions 3 flute cutters are perfect, like straight cutters for wood, special ones for aluminum. You dont need them at the beginning.


Material:
Carbide. Given the current prices of cutters, dont buy HSS except for special jobs, making custom cutters of them and bigg cutters that you need for 1 off jobs.


Type:

for the 3mm you need 3 lengths. Short/stub , 10mm and extra long 16mm. All 3 degree spiral. Buy this x10 and even more. learn and test with these as they are cheaper to break.


for the 6mm you need same, 3 lengths- stub,~ 22mm,~ 35mm , same as above, spiral.

12mm- only straight and here even carbide tipped will do the job. Dont buy spiral, they are expensive and you can not resharpen them yourself. $$$. best would be insert bits. You need here 30mm long and 50mm long, plus 20mm wide and 50mm wide for surfacing.


Thats all you need for a couple of years untill you know what you are doing exactly


Eventually for composite materials you willneed 2, 3 and 6mm diamond shaped like chipbreaker bits

for engraving you need only 60degree bits for normal jobs. Eventual 90 degree for rare jobs and 3 degree for fine engraving. best 6mm shank / 1/4.




Of course you will need more stuff but that will cover all normal needs. HSMAdviser and starting to understand whats happening is better investment than buying blindly bits. I have a box worth >1k$ in small bits, have bought all possible and then narrowed things with time, so i know what i am talking about.


Ball nosed bits are another territory, you will need all possible nose tips 0.5 to 6mm if you are to dive in 3d machining, and possibly make your own shank adapters or you will need some serous cash invested.


For example I could meet all normal orders in plastic,aluminum and composite with the following bits, all quality brand micrograin carbide. : 1mm ball nose, 2mm spiral 5mm LOC , 3mm 16mm LOC spiral, 3mm ball nose, 6mm straight flute 22mm LOC, 6mm ball nose, 6mm 60 degree V cutter , 12mm 30mmLOC instert bit CMT.

[magicniner]

1 flute cutters are specific material and you dont need them at the beginning until you know what you are doing and why exactly are needed. They are not a necessity if you have HF spindle.

But don't forget that single flute cutters can (with a little practice) be easily re-sharpened off-hand with a suitable grinding wheel.

[Boyan Silyavski]

But don't forget that single flute cutters can (with a little practice) be easily re-sharpened off-hand with a suitable grinding wheel.

I am a big fan of resharpening as it saves money. Thats the reason i have bought myself fine diamond plates to resharpen the flat bottom surfacing bits. And thats why i use straight 6mm bits for wood. If you mean straight 1 flute bits, yes, positively are easy to resharpen.

But to tell you the truth from the moment i bough insert tooling, i could say only WOW, quality and life time are not achievable by any other bit. So i always try to do the job with the insert, unfortunately the smallest cutter is 12mm 1 flute, but its incredible.

[CrazeUK]

Its a repeated question when somebody starts.

The answer:

Sizes:

you need 3 major sizes:

3mm or/and 1/8"

6mm or/and 1/4"

12mm or/and 1/2"

......

Wow, thanks for that. This needs to be a sticky!

Its a great place to start.

I did forget to mention this is just a "hobby" machine, alo a learning machine in advance of my friend ordering a industrial capacity one.

The only Collect i currently have is 6mm (they are expensive on the Kress), I am looking into getting a 3mm one too.
I bought a whole load of Carbide and HSS bits of ebay (cheap and cheerful with a range of sizes) to get me going.

Even with the 2 flute, I have already broken 3 x 3 mm bits (once out of stupidity, moving the head whilst i was aligning the bit to a whole).

I did find swapping the 4 flute to 2 flute made a massive cutting difference.
Someone mentioned getting a single flute for acrylic?

I am still getting a bit of a problem with melted acrylic piling up around the bit, this then suddenly grows as more is backed up.

Is there a correlation between temperature of the bit vs the build up of melted material around the bit?

As for sharpening, i think i will avoid that for now, this machine is a steep enough learning curve for now! lol

Thanks again, this is awesome.

[Boyan Silyavski]

Acrylic needs brand new sharp cutters and sturdy machine so the cut is excellent. On small machines is best to scratch it rather than digging in it, or it will melt easily. One flute are nice but not all a center cutting, meaning not very good for drilling holes as the tend to go off center.


here bellow is a general suggestion for cutting acrylic using 3mm / 1/8" / cutter