Is there something wrong with the lock miter bit that I just purchased? Yeah, I know these things are tricky to setup, but I can’t see how setup would cause my particular problem.
The tongue and grove bottom out before the miters come together.
I attached a couple pictures showing the problem.
Replies
The pictures didn't show.
Bruce
Ok, trying again to post the pictures...
Sir.. I use the lockmiter bit alot.
I have no direct answer for you except both pieces of the wood must be the same thickness (unless you want it different and have accounted for it).
I made a bunch of 'patterns' in different thicknesses of wood I usually use to set the bit height for the 'next time' I use the bit for another project.
A lockmiter bit is wonderful BUT takes some time to set it up correctly.. If two different thicknesses I use two different setups on different router tables. Yes.. I use two whiteside bits...
Edit: I forgot to mention. I run one stick Horizontal and the other Vertical...
Edited 4/26/2009 11:09 pm by WillGeorge
Well, I can digitally reproduce the results using CAD by shifting the centerline of tongue/groove feature off of the centerline of the miter. This assumes that the bit's profile was ground incorrectly. I called the manfacturer's tech support and they haven't had any other calls regarding a non-conforming profile...
Has anyone ever seen an incorrectly setup lock miter bit produce results similar to the pics I previous posted?
(For reference, the bit I'm using is a Skil part number 91703)
outside of the fact that I think that these bits are the devils own work, offering marginal advantage at substantial effort, I think this is a case of RTFM,
Pix 1 ain't how the sucker is spossed to be used, and if you look at pix 2, the corners don't line up.
printed the picture and cut out the two parts, and they look like they will line up if they are aligned correctly.
This kind of stuff is exactly why I sold my interlocking mitre cutters. lots of effort and frustration for marginal (if any) gain,
one board with a 32" bow in it at the aim of achieving a perfect mitre joint is not only defeated, but no amount of clamping can rectify it without causing other problems.
One bit of dried glue or a piece of sawdust and things won't and indeed cannot align.
There are times when you have to work with precision and certainty, dead flat, perfectly straight, and all that.
But you have to increase your waste factor to allow that some boards, even when milled perfectly true , will bow when they achieve stability in their new thickness , or a perfectly straight board will bow when ripped to width due to release of tension, and both those things will set things askew when it comes to using this bit.
Couple those eventualities which can occur with machining errors, (dished down router table, dull bit, out of square/curved fence, variable feed pressure and then toss in a few pieces of sawdust under the piece, and you get the idea that your efforts are ALWAYS at risk of not achieving the desired end. There's at least half a dozen variables which you have to not just minimize, but totally remove, and you have to do it with two pieces, or in the case of drawers, on 8 cuts.
Can be done, but is it rational given that this is a simple mitre joint.
Far more effective to rip a spline slot on each joint.
An ordinary 3/4" board, when mitered yields over 1" of glue joint, friggin near impossible to break when dry. . I gotta really figure out what advantage would be gained in using this on legs. And I I am equally puzzled as ti the advantage in drawer side construction, given that the "interlocking" pieces constitute short grain, which we all know is prone to breaking off in stress.
Is the advantage in alignment of pieces when gluing? hardly, as the interlocking feature makes slight adjustments out of the question. A less than precisely 90 degree angle on the end cuts would compound itself 4-fold in glue up. No advantage there to my mind. Force the issue and you've got broken interlocks. Great stuff that!
Oh these bits do work, and can work well, but I'll repeat myself and say that the effort to set them up and feed them material machined suitably to produce the desired effect is simply not worth the time and effort, particularly when the risks of a blotched glue up are considered.
That's just my thoughts.
Eric in Calgary
Here's a leg I made this w/e with a MLCS bit. I also got the setup block; really helps. I would have to think that your thickness is greater than 3/4". The MLCS setup block will let you setup drawers for 1/2" sides and 3/4" ends, but the thicknesses have to be right on for the joint to work.
View Image
Edited 4/27/2009 4:10 pm ET by knuts
I use the lock miter joint quite often and it appears to me that the fence was set so that the bit did not cut deep enough into the wood.
As one other respondent mentioned USE SET UP BLOCKS
Make a set for each thickness of wood. That is the only way to quickly set up and make lock miter joints.
One other tip, I use a double fence to keep the wood being cut tight
to the fence around the bit. Feather boards allow to much play.
Hope this helps
Moksha
Just had another thought. You're not pre-beveling the edges, are you? My instructions explicity say not too.
No, I just take a squared off piece of wood and run it through. If the setup is correct the cutting process shaves a bit off the total width of the board, in other words the bevel or angle does NOT end up exactly where the squared up edge of the board began. Try moving your fence back and taking a deeper cut. Align the fence
to be equal to the deepest point on the bit. Normally I cut lock miter joints on ####large shaper; which gives
a much wider range of possible stock thickness. However, no matter what the thickness of the stock, you have to max out the cutter to get a tight joint. When you get the set up right it should look like the attached pictures.
Oh, man, the cat's meow those joints. I've used the lock miter joint on...hmmmm....3 different projects. Got 'em lookin' pretty good, but nothing as tight as in your pics!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Forestgirl,Have to say that part of my ability to get the things tight and exact stems from the fact that they are being cut on a 5 Hp shaper with a five wing large diameter cutter. Plus the double fence on the shaper allows the material to be fed through the cutter in a more precise way. So, the results are primarily due to the machine and not the operator.But thanks for the compliment. Moksha
Is that double-fence approach safe on a router table? I have a stock feeder for my table saw, suppose it could be adapted to the router table.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Forestgirl,There is no doubt that it is not the safest procedure; as there is no where for the stock to go but through the blade or back out from whence it came. I use the double fence on lock miter joints and cutting stiles for cabinet doors all the time. My safety factor is that I stand in such manner as to allow for the kick back to pass me by. I use the same technique on the router table - especially when I am cutting with a 45 degree bit. Some bit shapes tend to push the stock away from the bit more than others and those I lock down with a double fence rather than
feather boards. I just shot a couple of pictures of the fences on the router table and shaper to illustrate how they appear in use.
I've not had much kickback on the router; but, that shaper can kick back extremely hard.
Moksha
Thanks for the pics, Moksha, I'll keep 'em bookmarked for future reference. I've only had router-table kickback once, fortunately I already had great respect for the possibility and was well out of the way.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
All I can say is I use my Whiteside LockMiter often. Mostly on Plywood for cabinets. I use my standard old fence with a 'bit' of height added to do the Vertical half. The Horizontal is flat on the table. I said before. MAKE a test pattern or purchase one from the manufacturer! I make mine.
I will say that things change a bit when going from your cheep setup wood to the real job.. A scrap of the final wood used to tweek things does the trick.
EDIT:
I forgot to say I do it with a PC 1.5 HP router! That big old bit, once up to speed, works and works!
Edited 4/30/2009 7:49 pm by WillGeorge
"I will say that things change a bit when going from your cheep setup wood to the real job." For my work, once I get the joint set-up where I want it, I run some very tight-grained old oak through to keep as set-up blocks. I guess plastic -- what, UHMW? -- would be even better.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Forest.. I GUESS all I was trying to say is a LockMiter Bit is wonderful if you set it up right!
OK, you are a Woman and a wonderful God made thing..
I am just a man.. Well, I was once!
AND you said... I agree except for! For my work, once I get the joint set-up where I want it, I run some very tight-grained old oak through to keep as set-up blocks.
I make my final setup blocks for the 'normal wood' used.. All woods cut differently. And you may still have to 'tweek' a bit to get perfect!
OK, I have 'some' patience for this setup,
Edited 5/2/2009 9:26 am by WillGeorge
For anyone interested, I've an update on my lock miter problem and now have an explaination for why I'm getting a gap.
I had the profile of my suspect bit measured using an optical comparitor (I have access to one at work). Using those measurements, I drew the bit profile in CAD (Figure 1 in the attached Word doc). In order to see the results of theoritical cutting operation I also drew the two pieces of wood positioned as they would be when routed (figure 2). I extruded the wood profiles and positioned the pieces together (figure 3).
The CAD assembly results match exactly to the picture of the actual results. Examining the sketch of the bit profile, I noticed that the center of the tongue and groove feature is not aligned with the miter cutting edges. This causes the t&g to bottom out before the miter comes together. Just to verify, I adjusted the CAD sketch of the bit so the center of the t&g was aligned with the miter edges. As expected the resulting assembly was then perfect.
So, lessons learned:1) Not all lock miter problems are user setup errors2) Don't cheap out and buy router bits from the local home supply store
Hopefully the store or Skil, the bit manufacturer, will refund my money...
I'm glad that you've resolved the question, excluding the pending refund/replacement, that is.It seemed to me all along that it had to be the bit profile causing the problem. With the right profile, the joint should fit together, even though there might be an alignment problem created by improper setup.
I appreciate the comments.
No, not pre-beveling. And, yes, it does seem that the bit "isn't cutting deep enough" but the bit is cutting the entire profile, corner-to-corner, so there's no way to make it cut deeper.
Once I set the bit height to be centered, I played with the bit protrusion from the fence. To minimize the number of variables, I kept comparing two horizontally cut pieces, but no matter how the fence was set, the gap between the mitered edges was alway there.
I'm still thinking that the bit profile was ground wrong, so... I have access to an optical comparitor at work so I can easily take very precise measurements of the actual profile of the bit's cutting edge. Then I can re-create the profile in CAD and hopefully get to the bottom of this. We'll see...
That has to be the probem. The 'lock' cut is not deep enough because it's preventing the joint from closure.
Just a suggestion - take the bits back and buy a whiteside or frued or anything but skil! Man - an optical compari - rometer! Let us know how that turns out.... ChrisPS - mean to be humorous!
My bits ARE take the bits back and buy a... Whiteside ..
(ALL of my GOOD biti are! Whitesides!) BUT I would have to say the lock miter works wonderfully if the stock is square and square!
Make sure you have the right size miter locking bit. They make two different sizes. If you get the larger one it gives your a deeper cut.
"When the job is perfect, we're almost done."
Gap in mitre joint
The shaft of your router is not at right angles to your router table.
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