Lock miter router bit?

[JDuke]

I have had a lock miter router bit in a drawer for years and never used it.

Yesterday I had a box project that I decided to try it on.

The box would require the locking miter bit to cut end grain as the box is only 2.75 inches deep and about 12.75 inches long and just over 6 5/8 front to back.

I tried the bit on some scrap and it seems that holding a piece that’s 12.75 tall and 2.75 wide is going to be problematic when running the piece upright against the fence.
I couldn’t get it to feed smoothly.

Most of the videos I’ve seen on lock miter bits shows them cutting with the grain.

Is there some trick to getting these lock miter bits to cut end grain well, or am I just trying to use it wrong?

Thanks in advance
Duke

[fredhargis]

I've never tried one on end grain, but I can't imagine they wouldn't work. Just a guess, but I'd bet the blowout on the exit end would be bad, so maybe use a push block or something to back the work piece up. It is a big cut, so maybe slow down the router speed a little???

[Cabinet Monkey]

No trick really, it's the wrong tool (bit) for the job.

You'd be just as well off with a splined miter (biscuit) or even a brad nailed miter and they'd be much faster and safer and easier to make.

[jteneyck]

You just need to clamp the narrow parts to a wider board so that it feeds straight across the table and/or fence and bit w/o tipping, etc.  The backer will prevent blowout on the trailing edge of the cut, as well.  

John

[MstrCarpenter]

I've used one on 3/4" birch ply.. Made 1' x 1' x 1', 2', & 3' tall cubes for art displays. All corners mitered; including top to sides, so there was plenty of end grain there. Add an aux. fence tall enough for safety and control before setting the bit depth and distance from fence. Use a tall push block to keep the narrow piece vertical, similar to what you'd do to cut a raised panel drawer front on the T.S..

[Kizar_Sozay]

What I do with difficult bits is to do a series of cuts at increasingly deeper passes until I reach the final config.  The way I do this is to set the horizontal depth of cut at the finished line of the fence.  Then I shim behind the fence either with some thin wood stock near the cutting head and again at the end of the fence.  Once I've done that I remove the wood shims and replace them with playing cards.  That way I can sneak up on the finished cut.

Another trick I use is because I like a little bit of the original wood to show, maybe 1/8" so the finished miter is not on the point.  This is done by lowering the bit to the desired level and make one side of the miter, Then raising the bit to fit, leaving a bit of the original stock a bit off the point.  This takes a bit of fiddling about.  Once you have it down save a piece of each as templates so next time you just fit the template to the cut. With a little bit of "off the point" jointing I can then break the edge. To me its a cleaner look.  Hope my explanations are clear.

You can also use a biscuit cutter, I'm sure there is a video and the PC instruction book shows how.  I'd make a jig to hold the pieces.  I also made a spline jig where I can clamp a piece at a 45 and use the fence on the saw to slide the jig and work piece past the blade.  Once you make a pass, flip the work piece over and do another pass to center the spline cut.  Then cut the splines to the width of the centered cut.

[JDuke]

What I do with difficult bits is to do a series of cuts at increasingly deeper passes until I reach the final config.  The way I do this is to set the horizontal depth of cut at the finished line of the fence.  Then I shim behind the fence either with some thin wood stock near the cutting head and again at the end of the fence.  Once I've done that I remove the wood shims and replace them with playing cards.  That way I can sneak up on the finished cut.

Another trick I use is because I like a little bit of the original wood to show, maybe 1/8" so the finished miter is not on the point.  This is done by lowering the bit to the desired level and make one side of the miter, Then raising the bit to fit, leaving a bit of the original stock a bit off the point.  This takes a bit of fiddling about.  Once you have it down save a piece of each as templates so next time you just fit the template to the cut. With a little bit of "off the point" jointing I can then break the edge. To me its a cleaner look.  Hope my explanations are clear.

You can also use a biscuit cutter, I'm sure there is a video and the PC instruction book shows how.  I'd make a jig to hold the pieces.  I also made a spline jig where I can clamp a piece at a 45 and use the fence on the saw to slide the jig and work piece past the blade.  Once you make a pass, flip the work piece over and do another pass to center the spline cut.  Then cut the splines to the width of the centered cut.

I sold my biscuit jointer a while back, sometime after I got a festool Dominoe.  I guess I could use the domino.

[Hank Knight]

Start with a 6" wide board. Run the piece, full width, through the router. Then rip your 2.75" pieces from the 6" wide piece. The 1/2" extra width lets you get rid of any blow-out you might experience at the end of the lock miter cut.

A little different, but related issue: I've found that cutting cross grain with a lock miter bit will frequently splinter the long grain at the edge of the cut. This is especially bad with plywood; the top layer of veneer splinters badly. Solve this by scoring through the top veneer at the exact edge (or as close as you can get) of the 45º cut with a sharp knife and a straight edge.

It's sometimes helpful, particularly on end grain, to remove some of the waste with your table saw before you run it through the lock miter bit. Don't remove all of the 45º waste because you will remove the little tongues that mate with the other board.