FMT - bad guide?

I purchased a FMT from Leigh a few months back - I've been happily making joints with it since I got it. Very easy to use, and a snap to get correctly sized moritises and tennons. Usually. Today, I tried to make 5/16" x 1/2" M&T's. No way, no how can I get these things to fit. I can get either the width or the thickness correct, but not both. Do I have a bad guide?
Can someone measure their guide? The dimensions of my guide are 0.700 x 1.161 (measuring at the base, the widest part of the bevel). I'm also using the Leigh 5/16" bit that came with the jig.
Next up is a phone call to Leigh - I'm sure they'll be able to determine what the issue is, but since it's the weekend, I thought I'd ask here.
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OK, The measurements on my 1/2" X 5/16" guide are very close to yours. I've included all of the measurements that I took.
Outside guide = 1.161 X .696 at the bottom edge (your measurement position - so there's only a few thousandths difference in our readings) 1.090 X .619 at the top edge
Inside Guide = 0.345 X 0.146 at the bottom edge 0.350 X 0.225 at the top edge
I included the readings for both the inside guide and the outside guide surfaces as the relationship of the two are required to get a good M&T fit. If all of these readings are close to yours then your problem is not being caused by the template.
To try to isolate the source of the problem try the following tests;
1. Use the stops to lock the top plate tightly in one position and then make a mortice and a tenon and then check the fit. If they are OK, then your problem is likely that the position brake on your top plate is sliping during the cut whenever you are using the top plate to cut more than one mortice & tenon position or when cutting a larger M&T than the template size. This is the problem that I was having.
If the mortice & tenon made in the cut above do not fit OK, then the source of the problem is somewhere else.
2. Is your router shifting in it's mount? Are you using screws to attach the router directly to the plate or are you using the rail system to attach the router. The rails can allow shifting if they are not tightened down really good. The rails will bend when they are tightened correctly.
3. Are the clamps holding the wood parts tightly so they cannot move during the cut?
4. Is there any side play in the router shaft bearings or runout in the bit. Can you feel any side play in the bearings? Can you see any bit runout when the router is slowing down?
Isolating the source of your problem before you call Leigh will help in getting it resolved quickly. If it's being caused by their fixture I'm certain that they will make it right for you. They are great people to deal with.
If I can help with anything else, you can e-mail me directly or respond here.
--
Charley


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I measured the inside guide and got measurements very close to yours. So, apparently, the guide is not the issue. Not suprising, really.

I do the same. The top isn't moving. I've not used this particular template before, so this was the process of cutting a mortise, cutting a tennon, and adjusting the depth of the router platform pin. In other words, I'm not cutting multiple pieces.
Usually, with the use of my digital caliper, this is a one, perhaps two step process: cut the mortise and tennon, and if they don't fit, measure the difference in thickness vs. width, divide by two, and adjust the depth pin accordingly. I usually make the tennon slightly smaller to allow for the glue.

This is a good question, one I'll have to check. I have the new Hitachi router (the funky green Darth Vader one :-) ), and I had to use the rails to lock it down. It's held pretty tightly, but I'll check anyway.

Absolutely.
Nope, brand new router purchased just for this jig. Again,I've used this same setup to make joints in larger pieces, and the fit has been perfect, after one round of adjustment.

Absolutely, I agree. They've been nothing but helpful with other problems I've had.

I appreciate the offer. I'll check out the jig, and report back on what I find. I'm certain it has to be user error, but trying to determine what the user error is, especially then the user might be defective (!), could be tricky :-)
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So, I went back into the workshop, and very carefully checked what I was doing. No go. The workpiece was just large enough to handle a 3/4" wide tennon, so I stepped up to the 5/16" x 3/4" guide, so I did that. Very quickly, I had perfect joints. Pretty small shoulders, but that's OK.
I called Leigh today, and after a short conversation with Barry, he told me that out of all the standard guides for the FMT, the 5/16" x 3/4" guide was incorrectly manufactured. I was the third person to notice this issue. Ha, I have all the guides, and I just had to pick the one that was broken :-(
Anyway, they're shipping the corrected guide to me.
Charley, you may want to run a test cut with your guide - if you haven't used it before, you may find that it doesn't work.
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I think you meant to say that the 5/16 X 1/2 guide was the one that was made incorrectly. You then switched to the 5/16 X 3/4 as a test. Right?
Most of the work that I've used my FMT on so far has been 1/2 inch M&T but I bought all of the guides for possible future use. I bought the FMT for a very large project (about 1400 M&T) that I had last year, and then ended up buying a new router just to finish that project, because the Ryobi RE600 that I had been using was way too heavy and was crippling me. The replacement, a Dewalt DW618, is about 4 pounds lighter and bolts directly to the FMT (a big plus). It was a real pleasure to finish the project with the DW618, which has now become the favorite router in my shop. The RE600 has a new permanent home, in a router table, where it belongs.
I'm going to test my 5/16 X 1/2 guide this afternoon, and I'll call them for a new one if it's wrong (I expect that it is, as mine is a year older than yours). From your discovery, and the fact that they have been shipping FMT's for several years now, Leigh likely has quite a few of these templates to replace. Unfortunately, I don't think they have any idea who owns them all as many were not bought direct from Leigh. Everyone else is going to have to find out the hard way that they have a problem (or read this thread).
--
Charley


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D'oh, fingers way faster than my brain. Yes, the 1/2" guide was incorrectly manufactured. The 3/4" guide is fine.

1400? Good lord....what on earth did you build?

The Hitachi is pretty heavy, but man, what a nice router. It doesn't bolt to the FMT, but it's very, very secure with the rods. I have no worries. I did look at the Dewalt, but I got a really good deal on the Hitachi...

Hey, let me know what you find. It was really nice to hear that I wasn't going crazy this morning when I talked to Leigh.... :-)

Well, that's the beauty (and the curse) of Usenet. Lots of info, you just have to know how to find it.
Good luck!
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