Checking V Bit Angles

[Paul Z]

There have been many users who have had difficulty getting V Carved cuts to come out properly only to find that their V bits are not the angle they are advertised to be. What follows is a process to determine the bit angle of an approximately 90 degree bit by examining cuts.

The .crv file contains a triangle which has been toolpathed with bits defined as 85 through 95 degrees. Make cut files for your machine and cut a piece of scrap.

The "85" cut shows what happens when the bit angle is larger than the toolpath bit angle. Notice that the corners are bowed out a little and that the top edge looks bowed up.

The "95" cut shows what happens when the bit angle is smaller than the toolpath bit angle. Notice that the corners are bowed in a little and that the top edge looks bowed down.

I would suggest that one find the lowest number angle that looks OK and the highest number that looks OK. Average these two and that’s the angle to specify for this bit when using V Carve.

I hope this helps to save time and material while minimizing frustration.

Paul Z

Brian - 11/12/2009 Copied to technical archive and non-technical responses removed - original topic can be found here -> http://www.vectric.com/forum/viewtopic.php?f=3&t=2164

[CLyon]

Helpful, clear and pragmatic! I have become very fussy about verifying the angle of each critical bit before layout and cut. It has saved me some heartache - and helped me identify suppliers wo can measure angles.

Thanks

[TReischl]

Excellent method, Paul! It sort of reminds of the way an inkjet printer gets setup when the ink cartridges are changed. Nevermind fussing around, just pick out the best looking one.

[Paul Z]

Part of the reason I created the test was that I had a bit which had a very accurate 90 degree angle between the faces of the bit. Unfortunately the carbide was attached to the bit after the 90 was made and the faces were not 45 degrees to the center of the rotation. This procedure will allow a bit to be used even through it may be "off" for several reasons.

Paul Z

[Tony Mac]

Taking this to an extreme - a customer who will remain nameless recently cut his first VCarve Pro job using the wrong cutter and wondered why the results didn't look correct - although it did create an interesting result!

The pictures below show what a toolpath calculated for a 90 degree V-Bit looks like when cut using a 60 degree V-Bit.

Tony

[tsalaf]

Another way to measure the included angle of a V bit.

1. Make a short cut at a known depth.
2. Measure the distance from long edge to long edge, at the surface of the stock.
3. Use your CAD program to calculate the angle from the depth and width of the cut.

Don't forget to account for the flat bottom of most V bits when drawing the cross section of the cut.