DIY sub-base for Leigh FMT? - Router Forums
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post #1 of 21 (permalink) Old 08-21-2020, 01:46 PM Thread Starter
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Default DIY sub-base for Leigh FMT?

Hey everyone,

I picked up used Leigh FMT mortise and tenon jig recently. Unfortunately, it is missing the sub-base to mount the router on. I called Leigh and the sub-base is available for about $300CAD. Before I take the plunge on a new one I thought I might try making one to at least get started playing around with this thing. So I was wondering if anyone here has one and would be willing to take some measurements for me so I could figure out the rough size and placement of the pins and the router?

Thanks very much.
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post #2 of 21 (permalink) Old 08-21-2020, 01:53 PM
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WOW they sure are proud of them. Good idea to make your own.

https://www.leightools.com/fmt-pro-features/
Herb

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Last edited by Herb Stoops; 08-21-2020 at 02:04 PM.
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post #3 of 21 (permalink) Old 08-21-2020, 05:20 PM
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the FMT and the FMT Pro are different animals...
also, is it sub base for the router or for the jig???...
which is it???...

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If only new layers hadn't been added....

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post #4 of 21 (permalink) Old 08-22-2020, 07:12 AM Thread Starter
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Thanks for the replies. As I said in my original post I'm "missing the sub-base to mount the router on". What I'd really like to know is the distance between the two guide pins on the bottom of the universal sub-base that fit into the joint guides as shown in the photo below. I think I can make some good estimates about the rest of the sub-base dimensions from there.

Thanks again. I've also attached a couple pics of the used FMT I bought.
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Last edited by impala; 08-22-2020 at 07:16 AM.
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post #5 of 21 (permalink) Old 08-22-2020, 08:30 AM
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Welcome Andy, Can you describe the part or a picture of it for clarity?
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post #6 of 21 (permalink) Old 08-22-2020, 09:16 AM Thread Starter
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Sorry if I did not explain what I'm looking for very well. Here's a picture that may clear things up. I purchased a used Leigh FMT mortise and tenon jig at a local Habitat ReStore, but it is missing the Universal Sub-Base that attaches to the router as seen in the photo. I would like to try making a sub-base, but would like to know the distance between the Left Guide Pin and the Right Guide Pin. The pins appear to be tapered to fit in the Joint Guides, but I have a mini-lathe and think I can make something that fits.

Hope that helps a bit. It would be great if someone can let me know the distance between the pins.

Thanks again.
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Last edited by impala; 08-22-2020 at 09:36 AM.
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post #7 of 21 (permalink) Old 08-22-2020, 10:55 AM
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With the bolts in, inside distance is 9-11/16", outside is 10". Appears to be a 5/16 threaded adjuster that screws into those holes.
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post #8 of 21 (permalink) Old 08-22-2020, 05:32 PM
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So to add to the detail......
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post #9 of 21 (permalink) Old 08-22-2020, 06:44 PM Thread Starter
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Thanks for the the pics and measurements Steve. It looks like you have the FMT Super, but hopefully the specs are the same as the Pro/Original. Doesn't look like it would be too hard to make something similar.
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post #10 of 21 (permalink) Old 08-23-2020, 11:10 AM
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The left pin in your first pictures is a tapered pin, with an adjustment knob on the top side of the plate to move it in and out. It is used to fine adjust the dimensional relationship of the tenon to the mortise, to get the desired perfect fit of the tenon to the mortise. An 1/8 of a turn of this knob will change the mortise and tenon fit by about 0.001". Once set, you can create mortises and tenons of the exact size relationship to fit together perfectly.

I have an early model FMT jig, but I have a knee problem that will keep me from getting to the jig to be able to measure it for a while, so I hope you can find someone else who can provide your needed measurements. They need to be quite accurate, not only for the pin spacing, but the pin to router bit center measurement as well. It would be best to make the plate from aluminum, since moisture changes in a wood plate might seriously affect the accuracy of the jig. The taper on the pin is going to be hard to measure too. It's this accuracy that is likely the reason why a replacement plate is so expensive.

How in the World did the seller manage to loose the top plate to his FMT? He likely still has it attached to one of his routers and it is some place in his shop. Maybe you could help him search for it (and maybe find some other goodies in the process). If not, deducting the cost of a new top plate should be part of the pricing for what is left.

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