Tapered ball nose or engraving bits for Zank inlay. ???

[FixitMike]

I’ve seen a number of posts and UTube videos where the claim is made that a Zank (VCarve) inlay is cut with a ball nose or engraving (flat end V) bit. I don’t understand how this can work. In the picture below, I show a Zank inlay female base cut on the left and the matching male insert on the right. I used a bit with a .125 flat on the end to exaggerate the effect. Note that the male insert has sharp upper corners, while the female base has flats in the valleys where the corners are supposed to fit. NO WAY! Using a tapered ball nose will have similar results

Can someone explain why people are using those bits for Zank inlays? I realize that if the flat or radius were to be quite small, one could clamp the two pieces together hard enough so the wood is distorted, but that is not the way to do things.

[adze_cnc]

 
Yeah, I'm unconvinced too. It really does come down to "if it doesn't fit you haven't hit it hard enough".

Attached is a file using the tools, toolpaths, and geometry from the recently posted video link.

This is a simulation of the inlay plug:
 

 
The edges are nice and crisp as they are "outside" cuts. The bit flare at the bottom doesn't matter as it will be between the plug and socket piece in the "air gap".

But the socket part does not have the same crispness on the inside edges as it is being cut with a TBN. Fine it comes to sort of a point a the tip of the star where some material could be bashed into it. But, you'd probably just sand it off anyway.
 

 
This is the tightest shot I could find of the results and all the star's points are rounded and all the inside corners are rounded too. Despite video guy's assurances that they are pointier than if you were to use a v-bit.
 

[wb9tpg]

Try cutting the male part with a pocket tool path.

[FixitMike]

Try cutting the male part with a pocket tool path.

Same result. Sharp corners that won't fit the female. May I suggest you take the time try your suggestion before you submit it. The answer will be obvious when you look at the 3D view of the toolpath.

[wb9tpg]

So you've tried it and it didn't work?

[FixitMike]

So you've tried it and it didn't work?

Right. The 3D Preview shows that it will not work. It was not necessary to actually do any cutting. The 3D preview of the carving when I try the pocket toolpath with the same engraving tool indicates that it will not work. The male insert has the same sharp upper corners that will not fit into the female base.

My CNC is retired and I have to rely on the 3D preview. I have found the 3D picture to accurately reflect actual results as long as I haven't made a mistake in setting up the bit or use settings not suitable for the machine.

If you got a different result I would like to see it.

FYI: I have 40 years experience employed as a Mechanical Engineer designing machinery, including 26 years designing parts for CNC machining. 12 years using Vectric VCarve.(after I retired).

[Leo]

So you've tried it and it didn't work?

FYI: I have 40 years experience employed as a Mechanical Engineer designing machinery, including 26 years designing parts for CNC machining. 12 years using Vectric VCarve.(after I retired).

Mike, you and I have similar experience and background. Mine is a bit more focused on the shop floor, but I have significant time in front of a computer screen.

I have not tried it, but I have made several Zank inlays and I am 100% sure if I try it with a TBN - it will not work.

[Aussie]

Yes you are all correct there is no way to avoid the rounded corners.
Does it really matter !!...unless you are doing large stars of course.

I can't get this detail using my 30 deg vbit at the depth I want to carve thats why I use my TBN

Just my 2 cents worth... I am happy with my results

[LithgowShedder]

I have yet to try it, but would rounding off the outside edges to the same radius as the tip of the ball nose not worK? You would lose that nice crisp sharpness, but at least you might avoid the gaps at the points.