Lock Miter issues...

[Bryan Mills]

So i've read all about these joints and the bits used to create them and have taken my time in setup and testing, but I'm having a problem that i don't quite understand.

The bit height is correct, of this I am sure, as you can see in the photo.



however the issue is with the second piece that gets cut...there's a small but unacceptable flat area on the edge of the piece cut vertically.



The only way to get rid of this, is by adjusting the fence back further. Since the edge of the other piece is already being cut right to a sharp edge, moving the fence back would mean that the cutter would now narrow the first boards width by the same amount as the flat you can see, and it would mean that the edge of that first board would no longer ride on the face of the fence making good result impossible.

Is there something I'm missing or is it simply possible that the bit is too small for 3/4" stock even though the manufacturer says it is possible...

[Bill Huber]

Your bit height is off, this link is from Whiteside and it shows you just what you need to do. If you notice the part on the right in the last picture is not cut correctly, it should come to a point on the edge and not have a flat on it at the top edge.

http://www.whitesiderouterbits.com/L...structions.pdf

[Mel Fulks]

There are a number of treatises on this subject. Here's mine .I like to run vertical pieces first ,intentionally leaving a little smaller flat spot toward face side than the inside . I do not cut to a sharp point, I leave a tiny flat. What that does is help stop tear out ,and means that your cutter height adj for horizontal cut will be zero or UP. Much better than not knowing which way to go. It also means your material does not need to be over size. If you are making a 5 inch box get material exactly 5 inches, when assembled it will be slightly oversize for sanding and the tiny notch at corners will disappear.You will find horizontal cut will need some fence adj.

[Bryan Mills]

How can the bit height be off? Look at the first picture...if I raise or lower the bit at all, the two pieces will no longer line up. Does that not matter?

[ken masoumi]

Is it possible that the two pieces have slightly different thickness?

[Bryan Mills]

No, i should have mentioned that I supposed. They are the same thickness...

[Mel Fulks]

I've seen some real capable guys go berserk trying to use those things . Save some samples and put your own notes on them. The method I posted requires that you run ALL the vertical pieces first .THEN CHANGE to do horizontal pcs. I have not seen the way shown in link work without moving fence when going back and forth between vertical and horizontal,but I don't see that mentioned. I do agree that in their set up you don't have to move cutter head . But that way ,tear out can be bad.

[Bryan Mills]

From everything i have read, you should not have to change anything to cut the pieces once the setup is right. I'd like to try and accomplish it that way if I can. The Whiteside instructions don't really tell you much...

I'm not using an Infinity cutter...but here's their instructions

http://www.youtube.com/watch?feature...&v=v-_bGkR2SKM

[Mel Fulks]

Just watched it. The camera is cut off before he runs the second piece ,and he does mention that the fence might have to be moved. Poor instructions. He should have had the 2 fence positions marked with tape,or pencil; left the camera running and showed the change. I've also seen guys buy those cutters and NEVER get them to work ,again poor instructions.

[Bryan Mills]

I can see there may be the need for a small adjustment sometimes, but I literally can't find ANY info on the internet that says this is needed once you have the setup right. Not to mention that we're not talking about a small flat that requires a small adjustment, it's large.

This can't be normal...

[George Bokros]

I believe the reason the two pieces in the first picture line up is because they are both cut flat on the table, am I correct? If so they will always line up. I have never used that bit but I believe I am correct, if not please tell me so.

Thanks

George

[Bryan Mills]

Yes George you are correct, they are both cut flat on the table, but one is upside down when they are mated. That means that if the bit height is not perfectly centered to the work piece thickness they will NOT line up.

[Phil Erup]

Yes George you are correct, they are both cut flat on the table, but one is upside down when they are mated. That means that if the bit height is not perfectly centered to the work piece thickness they will NOT line up.

If you do the same test on two vertical pieces with proper alignment, you should then assure matching centered sides.

[Mel Fulks]

I thought I was on the Internet ! This thing doesn't look like an etch a sketch to me. Much of what you are reading is coming from the same incorrect sources. I might be out voted ,but I am not wrong! I have used those cutters ,usually on shapers , for decades and would like to help you . The manufacturer just wanted you to buy the cutter,THEY are happy. How far you have to move the fence is dependent on how thick the material is. If you look at your own pictures you will see that the fence must be moved. Once when I was asked by a contractor to make some newel posts he gave me a drawing showing butt joints.I showed him the lock mitre cutter and told him I would mitre them. He said " every shop I deal with has one of those cutters, they don't work". Changed his mind. As I said before many never get them to work.

[Jim Kirkpatrick]

Yes George you are correct, they are both cut flat on the table, but one is upside down when they are mated. That means that if the bit height is not perfectly centered to the work piece thickness they will NOT line up.

The bit height is fine. Where you are going wrong is the vertical pieces is not held tight against the fence, or table. Review your technique and make sure it is both flat against the fence and flat against the table. I wrote a tutorial about it a while back here:
http://www.sawmillcreek.org/showthre...ght=lock+miter