Cutting Circles

[bigjeff (Jefro)]

At times I have a problem cutting accurate circles. Such as coasters. I do a simple 4" circle every thing is good in CC but when my Shapeoko Pro cuts them they are not round they are kind of bumpy around the circumference.

[mhotchin (Michael Hotchin)]

• Check belt tension
• Check set screws on motor pulleys - both tight, one over the ‘flat’ of the motor shaft.

[WillAdams (William Adams (Carbide 3D))]

In addition to the mechanical considerations, where possible avoid slotting and add geometry and cut as a pocket

Making vacuum hose adapters

While cutting up vacuum extension wands for this is expedient, it’s a bit problematic given that Shop Vac recently filed for bankruptcy, was bought at the last minute, and production hasn’t caught up. I need a receptacle for the Sweepy 2.0 dust fitting — one option would be to purchase one from Woodcraft, but Carbide 3D sells blocks of HDPE: which looks to be just barely big enough for things to fit. Measuring the hose fitting I get a diameter of ~63.5mm — offsetting that twice we arrive at…

and/or

Adding geometry to cut as a pocket with a finishing pass

One technique which is often suggested to avoid slotting is to add geometry around a part which one wishes to cut out and cut as a pocket down to tab depth — here’s one technique for that. In this case, the project is a bevel gauge which will be cut out of 0.0625" (~1.5mm) thick aluminum: [bevelgauge] Due to the narrowness of the angles, an 0.03125" endmill has to be used, so after importing and scaling the file (we will be cutting out one which is 3") we select the perimeter and offset it tw…

and consider leaving a roughing clearance and taking a finishing pass.

Also see:

Best Bit for full cut through

One which has a cutting flute length equal to or greater than the thickness of the stock — pretty much any tool should work. Big thing is the toolpaths — if cutting out, rather than just cutting a slot: [image] Offset to the outside by endmill diameter plus 10% or so: [image] [image] [image] Then cut as a pocket: [image] down to tab height or the penultimate pass: [image] then move the contour down to below the pocket and start cutting at the bottom of the pocket: [image] and…

[Tod1d (Tod (with 1 'd'))]

@WillAdams

where possible avoid slotting and add geometry and cut as a pocket

The problem is that CC will not cut this as a series of shallow pockets, it will cut it as 2 deep slots.
If you’re lucky the slot away from the material will cut first.