Leigh FMT

[Michael Simpson Virgina]

I just got a Leigh FMT and have noticed that all the joints seem to have some slop along the length of the joint. If I use the pin adjustments I can create loose or tight joints but not enough to remove the loosness in the length of the joint.

If I adjust it so there is no length slop the width of the tenon is way too tight.

Has anyone else come accross this problem?

[Leo Vogel]

I'm not sure I understand your question, but remember the mortise must be a bit deeper than the tenon or it will not fit correctlyl.

[Michael Simpson Virgina]

No the depth is fine. And that is part of the procedure when you cut the mortise. Its as though the length of the mortise is a bit too long.

Say I have a 5/16 wide mortis that is 2" long. When adjusted properly it is nice and snug on the faces but will slide about 1/16" along the length. The joint still works but this could make through tenons a problem.

If I make the tenon real tight I can reduce the length slop to about 1/32".

The jig may be setup to do this to keep the hydrolic effect in control.

[Rick Markham]

I will have to go play with mine to see how it works... Honestly it is a tool that I bought, unpacked and haven't used... Oh wait, I said I would never admit to that :D

[Michael Simpson Virgina]

I would normaly use my Domino but needed a joint like the one shown here.

[Sam Babbage]

I've not got a FMT so I'm only hypothesizing. Some folk consider that tenons should always have a bit of lateral slop in them, through tenons can be wedged to 'fill' them.

[Michael Heffernan]

I have the FMT Pro and haven't noticed that much lateral movement with a properly fitting M&T. Mine are pretty snug and even all the way around.
Not sure what would cause this on your unit. Best to give Leigh's tech support a call. They will be able to help diagnose the issue.

[John Piwaron]

Maybe the FMT should give a close fit all the way around a tenon, but in my opinion, having a bit of movement slip the tenon side to side isn't any big deal. In fact, it may be a help. For a place for excess glue to go and a bit of help in aligning the parts. The important part is that the tenon and mortise are the same distance from the face of the assemly. It's very nice that the faces of the two parts are exactly coplanar when assembled.

[Leo Vogel]

Michael - I noticed when I first started using my FMT that if I cut the mortise with a little too much pressure on the router, that it would produce a somewhat sloopy mortise. I now cut the mortise with a more gentle touch (don't slam against the ends of the mortise) and they come out perfect. What type of wood are you using?

[Michael Simpson Virgina]

For this project its Yellow Pine.

[Philip Rodriquez]

I have the Pro. I always get that piston fit! How deep are you going? perhaps that is the problem?

+1, call Leigh!

[Leo Vogel]

I too get the piston fit. Be sure you are using a good spiral bit and that it is square to the router. What brand router are you using?

[Michael Simpson Virgina]

Using a Festool 1400 and the router bit that came with the unit. I am thinking that I took too much play out of the right pin. It seems that play on this pin would yeald a looser face and this allow me to dial in with the left pin.

[Mike Heidrick]

You could look up Al from Sandal Woods. He is a FMT expert.

sandal_woods@bbwi.net

[Michael Simpson Virgina]

That was it. When setting up the jig it says to have a little play on the right pin. I had the play dialed out.

I now have perfect dialed joints that go pop when you pull them appart.


I was hesitant at first to purchase this jig as I was not happy with the Leigh D4R dovetail jig. It takes quite a while to get it dialed in every time I set it up and my results have been less than spectacular.

The FMT while it takes a while to get use to is pretty easy and quick to set up. I think I spend more time moveing the clamps around when going from the tenon cut to the mortise cut.

Thanks all for your comments. Just knowing you all were getting good cuts let me know I was doing something wrong.

[Al Navas]

Thanks for your faith in me, Mike! :)

Michael,

Edit to add:
Congratulations! I guess I piddled around too long preparing my response, and you figured out the problem while I was editing. Sorry about that! But I am happy you solved this problem!!! ----- Al

Meanwhile, the following is what I suggested:


I wonder if your FMT Pro might need a little tweaking, to ensure your router is sitting perfectly perpendicular to the work piece? I suggest you take a look at Appendix II (http://www.leighjigs.com/data/FMT2008-App1-4.pdf), starting on page 55. I wonder if something is a bit off that might be corrected using one of the steps in the procedures in this Appendix.
If it were me, I would also go through the procedure to re-adjust the play in the right-hand pin, so it feels "just right", not too tight nor too loose.
I wonder if you might have checked the runout on the router?
Have you tried a different router bit? Using a good set of calipers, how is the diameter of the bit along the length of the cutters?
Have you tried establishing a dialog with the folks at Leigh's Customer Support? They are terrific, and will likely think of stuff I might have missed.

Once you get this dialed in, you will not be likely to use anything but the FMT Pro. In fact, everything will start to look like a candidate for mortise and tenon joinery. :D

Al

[Al Navas]

... I think I spend more time moveing the clamps around when going from the tenon cut to the mortise cut...
Michael,

I got around the issue of moving the clamps too much by simply bying some more of them:

http://sandal-woodsblog.com/wp-content/uploads/2009/09/workholding-clamps.png

You can search my blog for the phrase "fmt workholding consistency"; there you see some more photos on how I have achieved the highest accuracy and consistency using the FMT Pro.

Once again, congratulations on solving the issues you had!

Al

[Michael Simpson Virgina]

Where do you get the leigh clamps. I could use a few more. IMO the jig should have come with a couple more. Well maybe not, then the jig would cost $1500.

[Al Navas]

I ordered mine directly from Leigh, Michael. However, you might want to check with Highland Woodworking, or with Woodcraft, as they are both distributors. If they don't have them in stock, they could probably order them for you. I believe they run under $20 each.

The other clamps you see in the photo are the newer Surface and Bench hold-down clamps, which I use to secure "stuff" to the bench, including the mounting ply boards that I use to mount the dovetail jigs and the Leigh mortise and tenon jigs. They are the same type of clamp as the ones used on the FMT Pro and the DT jigs.


Al