I’ve used a router for years; even made my own Norm Abram router table. Have also used TurboCAD to help me create some of the stuff I’ve made. But I’m stumped with one particular thing that’s critical to using my Shapeoko Pro. Do the edges of the bits cut like a conventional router bit, or are the flute just for chip evacuation?
Outside of some specialty bits for the CNC (which are essentially high speed drill bits), you can assume the CNC bits will cut when moved horizontally into the material. So, for CNC bits the flutes are cutting edges.
Not all CNC bits are made for plunging - there are some that should only be used to cut horizontally. You’re unlikely to run into one like this though unless you are looking for a specialty bit.
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Routers used for manual work work exactly like the cnc router bits. Think about cutting a 1/4" slot on a router table. Yes the bottom flutes cut but so do the side flutes. If the router bits did not cut on the sides you could never cut a slot. As Michael said drill bits do their cutting at the bottom and the flutes only extract the chips but drills are not the same as router bits. The only cutting in a drill bit is at the bottom because as they cut down the hole is already cut and you only need to evacuate the chips. Router bits from your router table will work in a cnc except for bits with bearings. It is never a good idea to use bearing type bits in a cnc. The reason is because they cannot plunge and while cutting eventually you get to the bottom. People do use bowl bits that are curved at the bottom on their CNC for a round bottom or for cutting juice grooves on cutting boards. You can use core bits but if they have bearings try to avoid them because of the depth of cut issues you can run into.
I use several Whiteside 2 flute up and down 1/4" bits and they work great but the side flutes cut as well as the bottom flutes.
The v7 CC has a new keyhole tool path that you have to cut the full depth of the keyhole and then plow forward for the smaller diameter but this is a special toolpath. Using bits that cut the full depth of a slot are very hard on 1.25 HP routers and on the belt driven Shapeoko’s. That is why most bits only cut a few thousands per depth of cut so compensate for the lack of power in trim routers. With more powerful routers and spindles you can cut deeper but you are still limited by the limitations of belt driven cnc systems. Even the Pro and HDM have limitations of depth of cut although they have greater power to move forward there are limits to cutting aggressively. When you go to industrial type cnc machines they can plow through wood and metal much easier because of the horse power they have the robust nature of their rails and bearings. Even on a table router you should never exceed 1/2 the diameter of the bit in the plunge or you can burn wood and/or bog the router down. A 2-3 horse power router has your human horse power pushing them along but the horse power of the router motor is still the limiting factor.
For Carbide Create, tooling needs to be able to plunge/center-cut.
Endmills are 4x as good at cutting horizontally as they are plunge-cutting though.
Router bits can be used so long as they:
- are capable of plunge cutting
- don’t have bearings
- are used at feeds and speeds suited to their geometry and the dust collection’s ability to clear chips
- are used w/ toolpaths suited to their geometry
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Thanks. I thought they were the same, but some days my eyesight gets a bit fuzzy. Brain, too.
Hey Will: I’ve never tried my router table bits, so, if I want to do a 1/4" or 1/2" round over on a rectangular frame I’m assuming I do the setup on the line or maybe with a small offset - however, how do you calculate/set the depth of cut because most of those do not go to a center point. I may have something coming up that I would like to try that on rather than going over to my router table to do the job manually.
When you set up a custom tool you can set the depth of cut per pass. So either set it to the full depth and set the depth of cut to the same as the full depth. You could say you want a 1/4 round over set the depth of cut to 1/8" and set the depth to 1/4" so it will make two passes. You can make the passes smaller depth and just hit pause and stop when the round over looks good.The trick is to set the offset so you get the round over the correct distance from the edge. Do not use router bits with a bearing at the bottom. That could cause your router to stall if it hits a corner because the bearing cannot cut just the router bit. If you only have bearing roundover bits you can take the bearing off for the use on the cnc.
I treat roundover tooling similarly to V endmills.
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