First attempt at letter cutouts

[Griffwood1 (Jay Griffin)]

This is my first attempt at letter cutouts. Not sure how to avoid the blowout.
Used the 102 bit with default settings.

This is birch sanded plywood.

Appreciate any suggestions.

Also tried 2mm contour with a 112 bit and it blew out as well.

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

Did you add geometry and cut as a pocket?

Leave a roughing clearance?

Perhaps try a V carving first?

[CullenS (Cullen Simpson)]

I have had good luck with a compression bit.

[Griffwood1 (Jay Griffin)]

I am new to this… what do you mean add geometry?

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

See:

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.

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…

[Cadefoster84 (Chris H)]

Get yourself a downcut bit, makes a world of difference. Or a compression bit as Cullen suggested if your stock is thick enough to take advantage of it.

[OShag (Dave)]

I agree with Cadefoster84. I have had the most luck with downcut bits when I want the top surface to be as clean as possible.

Think of upcut bits as throwing the waste material up. They will clear material out of the tool path and will leave the bottom looking nice (for a pocket). But that action can pull up on your top edge like you’re seeing. Downcut buts throw waste material down into the path but leaves the top surface nicer. Sometimes you need more passes at shallower depths to allow the waste to clear.

Most of what I do is a finished top surface so I like the downcut bits for that. Good luck - plywood is plywood and sometimes doesn’t hold up well. Mostly because of how it’s made and some are better than others in terms of gaps in the material under the “show” surface.

[CullenS (Cullen Simpson)]

I just completed a project where I used a downcut for the first pass in plywood and then switched to an upcut for the remainder. It left a nice surface and then was more efficient at the profiles.

[Griffwood1 (Jay Griffin)]

Thank you everyone. I am learning lots from the comments.

[Griffwood1 (Jay Griffin)]

Downcut bit for the WIN! Thanks again.