V-carve corners

[drueth]

azlogger

Before I use any V bit I measure it with a test cut. I have found many bits to be as much as 5 deg. less than what they should be. To make this a little easer I have found Lay out a 2" inch square and inside of that a 1" square Set your flat depth to 0.25 Do a V-Carve tool path. Measure the flat depth if it is less than 0.25 adjust your zero start and recut the square. If it is more than 0.25 it will through off the next step and you must adjust your zero start up and make a new test cut. If the flat depth is good measure how big the two square are, if the outer is smaller than 2" and the inner is more than 1" you bit is less than 60 degs. If the outer is greater than 2" and the inner is less than 1" than your bit is greater than 60 deg.. It also pays to cut back your pass depth and feed rate until you get a good clean cut. I now have a collection of 2x4 with squares all over them. looking at your post my guess is your 60 deg. bit is some were around 56 deg.

PS this will also work for an EM bit. The flat depth does not matter here as it will for a V bit.

Good luck.

[azlogger]

One thing to note with your cutting of two squares is that many V-bits (and I'm pretty sure all of them would have to) have a flat end. The V-bit I was using has a .015" flat on the end. So this will get your flat depth off and the bit will appear to be more than 60.

I took a pass at the router table with the bit I had used, and as near as I could tell, the top of the groove was .460", figure the bottom was .015", and the depth was .375". Trigonometry says it's 61.364 degrees.

I'm going to make another clock identical to the first, only I'm thinking I'll do the vcarving first this time. That way it's more equal and doesn't have the problem of cutting with both sides of the bit part of the time, and with only one side the rest of the time. It will cut with both sides the whole time. And I'll set the pass depth to 1/8".

Thanks for the replies!

[azlogger]

Actually I won't be making another clock right off. I don't have enough wood!

[drueth]

azlogger

Like I said I use 2x4 or what ever scraps I can find to make test cuts to zero in the proper degrees of the V bit. and how V-carve need to be set. If you set the bit to zero as best you can and make test cut an change the include angle ( use the edit tool button) lay out four test squares and do the first at say 65 deg, 62.5 deg, 57.5 deg and 55 deg you will see how much the cut will change and the problem you have pointed out is affected by changing the degrees setting.

You have point out one thing I did not take into account and that is the bit most likely has a flat spot and does not come to a to a true point. The one thing I am sure of is if you lay out a square at say 1" and it is not 1.00" than you start depth is off or your bit angle is off.

[azlogger]

I have been always zeroing my Vbit .015" above the surface. Otherwise the Vbit is too deep, and in places like this clock, the letters come out .015" too narrow. In normal vcarved letters, they come out .015" to wide. So lines less than .015" wide, the bit is above the wood and does not cut.

Essentially what you are doing with the squares is setting your program to think your bit has a sharp point right at the depth where it actually has a flat end. I have no problem with this, except that I think you may have issues at different depths. If your flat depth on the squares is 1/4", then at 1/2" deep you will get a narrower cut than intended and at 1/16" deep it will be wider that intended. I will follow this post with a picture that shows what I mean...since I don't think I described it any too clearly...

[ohiococonut]

Just an FYI.

I have two 60 degree bits that come to a point. One is the 60 degree sign making bit sold by Rockler. The carbide is ground on the backside so it comes to a point. The other is a carbide triple wing 60 degree bit made by Whiteside.
Both can be used for fine detail carving.

[azlogger]

Orange is your actual bit. Black is what you are telling the program the bit looks like.

Just an FYI.

I have two 60 degree bits that come to a point. One is the 60 degree sign making bit sold by Rockler. The carbide is ground on the backside so it comes to a point. The other is a carbide triple wing 60 degree bit made by Whiteside.
Both can be used for fine detail carving.

I'll have to check em out! I like the idea of a three wing, and I'm sold on whiteside