Replies

1. 
   holz | Jul 03, 2003 04:36am | #1

   There is a good article in Wood Magazine (February 1996, Issue 86, Page 10) on using a lock miter bit.  I made a 9" tall fence for the router table, and a "sled" to slide along the top of it.  The sled has a piece attached so that your workpiece is absolutly perpendicular to the table.  The workpiece is clamped to the "sled" and moved slowly across the bit.  Critical part, of course, is the careful setup for both cuts, and the Wood article covers that.

   Fred

2. 
   forestgirl | Jul 03, 2003 04:54am | #2

   As Fred alluded to, the set-up is extremely important.  Once you get a sled that's a reliable and steady 90* to the table, you can evaluate your set-up technique.  The one suggested that I've thought was very straightforward is where you cut two test pieces in the horizontal, and flip one over.  The should fit together flush.  It's relatively easy to see that way what adjustment is needed.

   My only experience along these lines is with a drawer lock bit, but it's a similar challenge.  The lock miter is next!

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

1. 
   PelhamPete | Jul 03, 2003 04:00pm | #3

   ForestGirl wrote:

   <As Fred alluded to, the set-up is extremely important.  Once you get a sled that's a reliable and steady 90* to the table, you can evaluate your set-up technique.  The one suggested that I've thought was very straightforward is where you cut two test pieces in the horizontal, and flip one over.  The should fit together flush.  It's relatively easy to see that way what adjustment is needed.>

   Does this help you set-up for both the blade height AND the fence setting?  If so- this is a great tip!  This bit/joint has always really annoyed me with its set-up complexity and fussiness.

   Well- if this works, it will almost be like I just got a couple more router bits (I bought both the large and the small sizes and used them only a couple of times as a result of the time-consuming aspect of set-up).  Thanks ForestGirl!

   -Peter T.

1. 
   forestgirl | Jul 03, 2003 07:39pm | #4

   Peter, without physically having a MLB here, I can't be sure, but I think that method does fix both the bit height and the fence distance.  Even if it doesn't, simply fixing one of the two settings makes it much easier to figure out the other one by trial and error (my experience with the corner lock bit).  When you're trying to establish both distances simultaneously, it's sort of like a dog chasing its tail!  You can get the height perfect, then set the fence a little closer than you expect it needs to be, and cut/nudge, cut/nudge, cut/nudge until you hit just the right spot.

   With my little PC690, the other thing I found was that I couldn't make the entire cut with one pass, so I set my GripTite at the spot where the fence back needed to be for the final pass, pulled the fence in and started working my way back (moving only one end of the fence).  When the fence got to the GripTite, that was the final pass.

   [PS:  clarification -- the GripTite works for me because I use a steel router top]

   MLCS and some of the other bit companies sell set-up blocks for their MLBs but once you get it figured out, you could make your own out of a hard wood like oak or better yet out of a high density plastic.  Then it's just a matter of thicknessing your stock consistently.

   There's no doubt these bits take extra time for set-up.  They're great for making several duplicates, but questionable for one-offs.  Maybe a set-up block makes the one-offs do-able, I dunno yet.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

   Edited 7/3/2003 1:48:09 PM ET by forestgirl

2. 
   forestgirl | Jul 03, 2003 08:12pm | #5

   PS:  If you stay discouraged and decide you don't want the bits around, LMK!  I'll be in the market in the next couple of months.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

3. 
   stancalow | Jul 04, 2003 01:39am | #6

   Thanks Fred and F-G

   I am able to set up the bit height and fence OK, but had a problem making a sled that held the veritcal pieces square (on three axes) to the bit.  I have a good jig for the horizontal workpiece, but not the vertical.  Your posts made me realize that it would help to have a taller fence (duh!) to help with two of the three axes. 

   F-G  I too have a PC 690 in the table.  The instructions for my lock-miter bit say it must be cut in one pass.  I can do this but, get some burning.  I am getting a speed control to see if that helps.  You already know this, but if you get one, get a good quality bit.  The first one I  tried, I must have damaged with some oak, because it started vibrating like a veg-o-matic.  It scared the heck out of me so I threw it away. 

1. 
   forestgirl | Jul 04, 2003 06:57am | #7

   "It scared the heck out of me so I threw it away."  You are a smart man, I like that!  I guess when I get one, I'll have to mount the larger plunge router in the table, which I've been pretty tempted to do anyway. 

   Let us know how it goes when you get everything going and try again.  I'll look forward to any tips you pass along!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

1. 
   jagwah | Jul 28, 2003 07:41pm | #9

   In listening to all your post am glad to hear all the concerns. The lock mitre is just another big bit, albeit a nasty little bugger.

   I've used the bit for a number of years but not necessarily for box construction. I find it a most excellent joint for column construction or table leg construction.

   I built a writing table for a client that I designed the legs so that they were a four sided taper. They tapered 4" at top to 1-1/2" at bottom, accepting a walnut foot. The material was mdf and painted a high gloss hunter green.

   Sorry the cabinetmaker wants to share to much information. Anyway because I wanted to paint the legs the mdf was a better choice. I had never used the lock mitre on mdf. As it turned out it did well but care is needed with the interior rib. Once it glues up it makes for a great leg.

   As to the columns and my reason for the post- Once I realized I needed a perfectly smooth table surface, lots of finger boards and a long infeed and outfeed tables, it's easy to handle the vertical pieces.

   I do use a 3-1/4 hp pc router in my table though.

   Edited 7/28/2003 12:43:04 PM ET by Bob

4. 
   cheapwood | Jul 28, 2003 05:06pm | #8

   I built a simple fence using .75" x 12' x 24' melamine coated particle board. Bottom piece and upright three section piece (fence); with replaceable two fixed and center spline indexed piece. Bottom section, right and left fence pieces are screwed together. On the back to stiffen and help secure the fence at right angle I added a "lean-to" enclosed dust hood with 2.5" hole for shop vac; also screwed to the melamine fixed fence pieces. Cut out 3"semicircle in front edge of bottom piece to allow for dust collection and to provide clearance for the bit.  I put together and disassembled the contraption several times during its construction but I figure it'll be useful for many projects.  Assemble the "unit" then with suction on slowly fed the fence into the lock miter bit.  Here's the key part: attach a disposable 24" x 4-6" strip of .25" smooth hardboard with double sticky tape to the right and left melamine fence surfaces, back it up with a scrap of plywood and ease the bit through the fence from behind and you'll have a nearly zero clearance uninterrupted, smooth opening across which the vertical pieces you are mitering will travel.

   I tried to cut the vertical pieces before adding the masonite "travel strip" but kept hitting the cut edge of the left section of the three piece fence.

   After adding the Masonite strip I used a push block to feed the pieces through and another to hold the piece against the Masonite fence.