Lock miter bit setup using a height gauge

[Dave Cav]

A while back I remember reading an article in one of the WW magazines about using a height gauge for setting up woodworking tools. One procedure they went over in some detail was setting up a lock miter router or shaper cutter. I just got my Grizzly lock miter shaper cutter today, and of course I can't find the article. I looked through the table of contents of the last couple of years of FWW and PW and nothing turned up. Anyone else remember the article and remember where it was?

Thanks
Dave

[Gary Curtis]

Your router table will handle this job better if you first have a high fence. My approach to adjustments is to avoid measuring things whenever possible. In keeping with that, I crafted some soft plastic blocks. I made cuts using the Lock Miter bit with one block making a horizontal pass. A second block was cut held vertical against the fence.

A few tries were needed to get two blocks forming a perfect joint. Fit the blocks together. Various heights are needed until you get the joint right. You want no offset, and no overhang in the corner. Toss all trial blocks and keep the good set.

To use the blocks, switch off on the router and nestle the blocks (in the correct orientation) into the cutting edge of the bit. Adjust bit height until the plastic blocks fit snugly --- flat against the fence, and vertically against the fence. This will calibrate vertical bit height and horizontal fence position. You can dial in a high degree of accuracy. Even if you are older, like me, and eyesight is a challenge.

These height blocks are then stored with similar gauge blocks used with other bits. No numbers involved.

[Michael Weber]

Dave, I believe that was in FWW some months ago. It turns out that in a later issue a reader takes them to task because the procedure won't work for all lock miter bits. Something about some bits not being equally divided or asymmetrical or something. He noted in particular that it would not work with his Katana brand lock miter bit (the one I have)

[Myk Rian]

Your starting point is to measure from the center of the cutting edge. Same distance from the fence out, and to the top.
That distance is 1/2 the stock thickness.
http://www.woodshopdemos.com/cmt-lm5.htm

[Mike Schuch]

I have the Grizzly shaper cutter with a 3/4" bore. I use the adjust and test fit method with excellent results. Make sure your spindle is perfectly perpendicular and you should be able to dial it in with a few test passes.

[Matthew Bradburn]

FWW #218 p. 36

[Dave Cav]

Thanks guys. I found the magazine later last evening. My wife had rearranged the front room and chosen that particular FWW to decorate the coffee table.