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Discussion Starter · #1 ·
First of all, I'm sure everyone asks this kind of question, but my search didn't turn up much. It seems to me there should be a pinned thread on the subject?

My long awaited CNC router is finally ready to be picked up! But I don't have any cutters for it yet.

I want to be prepared to do most things, from 2D cutting to 3D carving, all on plywood/ MDF/ HDF.

My machine is a ShopSabre 23, which has a 5" gantry (spindle lifts up 6" above bed) and a 1.7kw air cooled spindle. It comes with 1/8, 1/4, and 1/2" collets. Cut speed is around ~300ipm. (I don't know if the machine's specs will affect bit selection all that much, but just in case.)

Simply put, what are the types of bits that are essential and most useful? Also, what bits are not very useful?

Also, what shank size should I pick? Is there a rule of thumb for deciding? I will have up to a 1/2" collet, but I don't know if/ when the larger diameter shank is a good idea?

If left to my own devices, I would just order few down cut bits, compression bits, straight flutes, bullnose cutters, tapered spirals, etc. I do plan to buy a 2.5" fly cutter w/ inserts, but I haven't decided on anything else yet.
 

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Discussion Starter · #3 ·
For clean cuts in plywood a downcut spiral bit, 1/4"d or 3/16"d. In hardwoods upcut spiral bits usually do fine. For 3D carving the finish passes you'll need ball end bits. The smaller the bit then the finer the finish, but also the longer the job will take. If you've got a heavy duty machine rather than a hobby machine then 1/2" and 3/8" diameter bits can also be handy rough cuts and large pockets.
Thanks. The machine is a bench top size (30x40" bed), and it is built like pro machines. Welded steel frame, servo motors and ball screws on all axis, etc.

Have you bought bits you thought you needed but ended up not using? Or bits that were surprisingly useful?

Is breaking bits an issue? I know that will depend on rpm, feed rate, and depth of cut...but as a newb I'm wondering if I should worry about having multiples on hand.

I'm just trying to anticipate what bits I am likely to need, so I can have them on hand when the need arises. My project has been on hold since March, which is when I realized the only way forward was for me to buy my own CNC machine. I want to be as prepared as possible when my machine is finally ready to go. (Hopefully in 2 weeks, but anything could happen...)
 

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Discussion Starter · #6 ·
So just to update, I ordered a few bits. I didn't go too crazy, as the price is a bit sobering. But at the same time, the investment is a waste if I handcuff myself by cheaping out and not buying the cutters I need.

Mostly I got 1 of each, except small ones that seem more likely to get damaged. They all seem reasonable for what I'm trying to do. I'll try to remember to update this list as I go.

2.5" fly cutter/ spoil board cutter w/ carbide inserts (I got the vacuum table option, so this one was kind of necessary, though expensive)
1/4x 1 1/2" ballnose
1/2x 1 1/2" ballnose
1/16 x 1/4" ballnose (2x)
1/4x 1 1/4 down cut spiral
1/4 to 1/18 ball nose tapered spiral
1/4x 7/8" compression
1/8x 7/8 up cut spiral (2x)
 

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Discussion Starter · #7 ·
Has anyone ever come across a 3/16" or 5mm tapered spiral bit? I'm looking, but haven't seen anything. I don't care what the shank diameter is or the cutting length, but ideally the overall length would be 3.5", but no longer than 4".

I am cutting contours, not fine detail. So the larger diameter bit would give a smoother finish and allow a larger step-over.

I'm searching right now, but the bits I'm seeing jump from 1/8 to 1/4" (or 3mm to 6mm...which is effectively the same sizes.)

When I first started looking at bits, it seemed the selection of bits was endless. But now I'm looking for something specific and I can't find it.
 
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