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Leigh Super FMT Jig
Frame, mortise & tenons plus economy
Text, photos and video by Tom Hintz
Posted - 12-15-2009
The Leigh FMT Jig has been on the wish list of many woodworkers for years. However its price point kept many of us with shrinking budgets on the outside looking in. The Leigh Super FMT Jig was designed and built to fill that economic gap and like all Leigh "Super" grade products, does so while maintaining a surprising level or functionality.
The Leigh Super FMT Jig is capable of creating more than 70 sizes of mortise & tenons from miniscule 1/16" x 1/8" to oversized 1/2" x 5" versions. The Leigh Super FMT Jig kit includes a 5/16" joint guide set but 1/4", 3/8" and 1/2" sets are available (21 guides in total) as accessories. Leigh also offers 6 specialty guides: 4 square tenon guides, 1 louver guide set and an Y-axis mortise guide.
An easy to use adjustment system makes perfect joint fit easily attainable. Thanks to the front-mounted and hinged front mounting plate, the Leigh Super FMT Jig also makes angled or compound joints as well. Single, double, (tandem and side-by-side) triple and quadruple joints are also easy to make on the Leigh Super FMT Jig.
The Leigh Super FMT Jig reviewed here is equipped with the ACSMTV Accessory Kit that includes the Vacuum Box, two hose adaptors, 3 HSS bits; 1/4"(part #168), 3/8"(part #173-500) and 1/2"(part #180) and 16 guides; 8-1/4", 4-3/8" and 4-1/2"(part #6720). This kit sells for $219.00 (12-9-2009) but for that investment substantially increases the range of joints the Leigh Super FMT Jig is capable of creating.
The Leigh Super FMT Jig is made from heavy gauge steel where the original Leigh FMT Jig features a precision-machined aluminum core. Though certainly a price reducer, the steel components are precisely manufactured from noticeably heavy steel plate to insure durability and rigidity. All of the Leigh Super FMT Jig components are cleanly fabricated.
The base has pre-formed mounting holes for securing the Leigh Super FMT Jig to a board. That makes clamping the jig securely to a work surface much easier and faster. Leigh even includes bolts for attaching the board!
The top plate to which the router is mounted is also made from heavy steel plate that has been precisely formed and fitted with adjustable guide pins that follow the joint guides. Adjusting those guide pins is tool-free and allows for tiny changes that let you fit the joint as you like. The top plate also has provisions for mounting most of the popular plunge routers on the market today. We look at these features closely a bit later in this review.
The front plate is mounted on a hinge for making angled mortise and tenon joints. The front plate can be angled up to 30-degrees from vertical and is locked in any position within that range using finger-operated locking knobs on either side of the Leigh Super FMT Jig body. There is an adjustable stop that lets you be certain that the front plate actually returns to zero (vertical) every time.
The front plate is formed with multiple holes designed to work with the included pair of specially designed f-style clamps that make holding stock easy and secure. These clamps use a familiar twist handle that makes applying sufficient pressure to secure a large range of stock sizes tightly. The clamps can be easily relocated on the front plate to accommodate most stock sizes and shapes. The moveable arm comes off of the main bar, which is then inserted through the front plate. A strong magnet built into the fixed arm holds that portion of the clamp in place making them easy to use.
A side stop fence is also included that makes repeat cuts quick and easy. This fence attaches to slots in the front plate and its position is easily adjusted to accommodate various stock widths. The bottom edge of the side stop fence works like a T-square to make setting up for square cuts very quick. You can also set the side stop fence to virtually any angle needed using angle gauges.
The Leigh Super FMT Jig is compatible with the vast majority of popular plunge router models in use today. See the link at the end of this review for the Leigh web page that contains links to more information on this jig, including a full list of compatible routers. All necessary hardware for mounting most routers is included as well as diagrams on which mounting holes are used for the various routers.
A nice feature of the Leigh Super FMT Jig router mounting is that perfect alignment is assured by a pair of centering tools that are included. One tool has 1/4" and 1/2" shanks, the other 8mm and 12mm diameter shanks. The large end of the alignment tools fits the bit hole in the router plate. When installed in the router and placed in the bit hole, these tools insure that the spindle centerline is exactly centered on the bit hole.
Oblong washers on the mounting bolts are assembled to contact the outer edges of the router base during the initial setup. These washers are essentially bumpers that then locate the router when it is returned to the Leigh Super FMT Jig. That means that the router can be removed quickly for other shop uses, yet returned to the correct position on the Leigh Super FMT Jig just as quickly.
Most routers are retained with a pair of bars that pass through the fence attachment holes in the router base. Those bars are secured with clips that apply pressure with a knurled finger nut at each of the four positions. This tool free router attachment is secure yet fast so your router is always available for other tasks.
Guides and Control
The top plate of the Leigh Super FMT Jig body is actually two individual plates that allow the operator to limit front-to-back and side-to-side movements independently. This separation of the limiters makes it possible to cut oversized or multiple mortise and tenons very accurately. The top plates are secured with a single pair of finger-operated knobs that lock both plates at the same time.
A snap-in sighting reticule makes aligning the top plate with your layout marks very fast but remarkably accurate. If you mark the center point of the mortise and tenons accurately, the Leigh Super FMT Jig will cut the joint exactly where you want it. The sighting reticule even has a built-in magnet so that it can be stored on the end of the Leigh Super FMT Jig where it is out of the way but always handy. That magnet is housed in an extended upright tube that also blocks the movement of the router plate if you forget to remove the sighting reticule before making the joint.
The top plate has a pair of adjustable tapered pins that interact with the guide plates and a fixed slot. Raising or lowering these tool-free tapered pins increases or reduces the travel around or within the guide plates in tiny increments. It is possible to make joint fit adjustments under 0.001" if desired!
The guide plates simply click in and out of a holder on the left side of the Leigh Super FMT Jig top plate. Each guide plate controls the mortise and tenon cuts for that size making the process easier. The right side guide slot remains constant regardless of guide plate being used. The precise manufacturing of these guide plates and their simple but secure mounting insure the remarkable accuracy of the Leigh Super FMT Jig.
Part of the ACSMTV Accessory Kit used with the Leigh Super FMT Jig reviewed here is a dust collection shroud. That shroud has to be installed during setup but Leigh incorporates the mounting studs into the base so all I had to do is place the shroud over the studs and secure it with the included nuts.
Leigh includes adapters that make it possible to connect most shop vac hose sizes up to 2-1/4" OD. Because the dust port exits to the rear of the Leigh Super FMT Jig, its use in no way interferes with the use of the jig.
While the Leigh Super FMT Jig looks somewhat complicated to use, the User Guide Leigh includes makes the process easy to understand. This is a very well written and heavily illustrated guide that literally walks you through the entire process from assembling and setting the Leigh Super FMT Jig up to actually cutting joints. Leigh has always done a great job with their User Guides and continued that tradition with this manual.
Leigh also retained their spiral binding of the User Guide. This feature is overlooked by many but is important. The spiral binding is more expensive to produce but allows the Guide to lay open on the bench without having to fold pages or weight it down. This makes actually using the Leigh Super FMT Jig User Guide AS you work simple. That means more of us will actually use it!
In the Shop
Setting the Leigh Super FMT Jig up for the first time is a simple process because of its design, plus most of it is assembled at the factory. The longest (about 1/2-hour) task was mounting my Bosch 1613 plunge router. Using the included hardware and instructions I had my router installed and aligned precisely much faster than I anticipated.
Actually using the Leigh Super FMT Jig is easy if you read and follow the well-illustrated user guide. This instruction manual covers common single and less common multiple mortise and tenon arrangements. Using the stops as described and working in the sequence the manual spells out actually makes it tough to make a bad joint.
I started out making single mortise and tenon joints and only had to make two fit adjustments to get a perfect slip-together fit. I found later that once I had set the tapered adjustment guide pins that joint fit carried over to other joint sizes as well. I had to make tiny adjustments on the first double mortise and tenon joints but that was more to please me than necessary. The joint actually closed up with a little persuasion after the first cut. The ease with which you can fine-tune the joint fit encourages you to make the adjustment to get it right.
With the ACSMTV Accessory Kit the only real limitation with the Leigh Super FMT Jig is your imagination. This jig is way more capable than we are. The user just has to think up the joint pattern that best fits the job and more often than not, the Leigh Super FMT Jig will cut that joint perfectly.
The only note I would add relates to the dead-on accuracy of the Leigh Super FMT Jig. I found that I had to increase the mortise depth slightly (about 1/8" usually did it) to get a fully closed joint. At first I was not sure why the joints would not close because the mortise was the same depth as the tenon length. Actually, that was precisely the problem. When glue was applied, the close fit between the mortise and tenon was scraping a some amount of glue off of the sides of the mortise and the gap I was seeing was the amount of glue now trapped in the bottom of the mortise. I have always cut my tenons a bit shorter than the mortise depth when using my mortising machine but forgot that when using the Leigh Super FMT Jig. I will remember now....
If you like to use mortise and tenon joints - or have been afraid to try them - the Leigh Super FMT Jig could be the tool for you. It brings traditional Leigh quality and engineering horsepower to your shop with a budget-saving price of only $449.00. (12-11-2009) However, that is the suggested retail price. I expect the "street price" will come down a little as the Leigh Super FMT Jig gets into full distribution.
If you are considering a jig for mortise and tenon joints, the Leigh Super FMT Jig or its more sophisticated brother the Leigh FMT Jig should be at the top of your must see list.
See my review of the Leigh FMT Jig - Click Here.
Visit Leigh Jigs Super FMT Jig info page - Click Here
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