Inventables Community Forum

Which bit upcut or down cut

Trying to cut some delicate pieces with a spiral upcut bit and the piece breaks on the last pass. Would I have a similar problem if I used the spiral down cut bit? Material is flat and clamped down good. See image, antlers break .

well a downcut bit will push down towards the wasteboard, which is a more solid surface vs the upcut bit pulling it up into the air. So there is a lesser chance of breakage with the downcut BUT i suggest using the double sided blue tape & CA glue method to hold smaller pieces down since the tape will also help against horizontal forces that a moving bit will also place onto the workpiece.

It’s kinda hard to tell from the photo whether that is plywood, or just veneered mdf. You might also have better results by thickening up the areas where the antlers are touching the mating areas… and/or making the antlers wider in general by applying a small offset to them.

So by CA glue and blue tape, the tape adheres to the work piece and it’s glued to a separate spoils board? Never tried this. The photo is 1/4" Walnut, keeps breaking with the grain. I understand the grain is a weak spot.

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2 layers of blue tape, one on workpiece, other on spoilboard, ca in between to adhere the backs of the blue tape. need a clean spoilboard so blowing off or freshly vacuumed will help it stick to the MDF… and the low tac of the blue tape makes it easy enough to get off of the workpiece after the carve.

For solid wood, yeah, you’re definitely going to have issue with along the grain weakness… I try to keep my 1/4" walnut no smaller than about 1/3" in the smallest areas… I’ve gone smaller, using mdf and tend to setup like 3 duplicates on the carve to get a single good one that isn’t snapped.

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Hi Armen,

How about rotating the walnut 180 degree and slow down your feed rate and plunge rate.
let’s not forget put a few extra tabs.

180? or 90? 180 would keep the grain direction the same :man_shrugging: 90 would make the thin bar across the name portion quite weak.

at lease someone is paying attention, just the wrong person . also using the ca method will work to hold 1/4" walnut down.
but when you go to remove from the waste board. the intricate project will break .

Thanks for the suggestion. As is, 40IPM takes 1hr 2min. I need to make 4 total.

the down cut or a compression end mill, will give you a clean cut on the face. This will work the best.

If using the tape method, then instead of carving out pockets, you can cut the perimeter only (Outside the line, or Inside the line) and that will make it a faster overall cut time.

I do these from 1/4" walnut using a 2mm downcut and the rifles never break on me. I use 0.8mm depth per pass. . :man_shrugging:

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