Powermatic PM-TJ Tenoning Jig Review

The ultimate professional tenoning jig for precise repetitive tenoning.

Powermatic PM-TJ Tenoning Jig

Powermatic PM-TJ Tenoning Jig



Mortise and tenon joints have exceptional strength, in large part because of the ample glue surface they provide. As a result they resist racking and twisting forces better than most other joints. Which is why they are one of the most commonly used joints in woodworking. However, in order for the joint to work successfully, it's important that the tenons fit snugly into the mortises.

When you only need a few tenons it's often just as efficient to cut both the tenons and mortises by hand. However, when you need lots of them, a tenoning jig used with a router table or table saw is the way to mill the tenons – you can complete the job more quickly and with greater accuracy. Similarly, you can cut the mortises using a mortiser, or with drill press and chisel.

Powermatic has introduced an innovative tenoning jig that anyone who processes a lot of tenons will want to take a close look at. The PM-TJ is a professional duty tenoning jig that can be used on any conventional table saw for processing straight tenons, as well as half lap and bridle joints. While the PM-TJ can cut angled shoulders on tenons, it cannot be used to cut angled tenons. Note that you'll cut the tenon shoulders on the table saw before using the PM-TJ to cut the the tenon cheeks.

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Ensure your table saw is perfectly aligned

In order to obtain accurately machined tenons with the PM-TJ you need to ensure that the saw blade is parallel to the table saw miter slot, and that the blade is precisely 90-degrees to the table top. You also need to remove any blade guard. However, the riving knife can remain in place, as long as it's a low-profile style that rises and lowers in tandem with the saw blade.

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Nicely packaged

First impressions are important, and I like that the PM-TJ comes nicely packaged – plastic wrapped and protected in form-fitted polystyrene trays. It virtually eliminates any damage to the contents during shipping.

The included user manual clearly outlines how to assemble and use the jig. Additionally, there is an excellent 5-1/2 minute video that shows how to configure the jig.


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Minimal assembly required

Assembly is pretty minimal. Three screws attach the miter guide bar to the bottom of the PM-JT. A couple of screws attach the work stop to the fence, while the stock clamp just slides in to a T-slot on the back side of the fence. Before tightening the screws that attach the guide bar to the jig you'll want to confirm that the face of the fence is square to the blade. The whole process only takes about 5-minutes, and Powermatic thoughtfully includes all the tools you need to do the job.

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(A) Main handle; (B) Auxiliary handle; (C) Stop #1 cam lever; (D) Stop #2 cam lever; (E) Fence locking knob; (F) Micro-adjust; (G) Clamp T-slot

The photo above shows the main parts of the PM-TJ. As you'll find out during the assembly process, the jig is very well machined, primarily out of aluminum and steel. At just over 5" wide, the main handle is a decent size. The auxiliary handle is a tad narrow, though I rarely use it. The stop cam levers are large enough to easily manipulate.

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Large, rigid fence (work stop removed)

At almost 10" long and just over 6" high, the aluminum fence provides ample support for just about any size of work piece on which you'll want to cut a tenon. There are six holes tapped in the face of the fence, so you could add a higher sub-fence if cutting tenons on particularly long stock. The longest stock I've used with the PM-TJ (without adding a sub-fence) is just under 40".

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Work stop with integrated angle indicator

For most tenons the work stop will be set perpendicular to the top of your table saw. However, it can be tilted, via a knob on the back side of the fence, when you need to cut angled shoulders on tenons. The stop features a magnified angle indicator, but I can barely read the hash marks. I find it much quicker and easier to use a sliding bevel. Once locked in position the work stop is very secure.

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Fence in the 'zero' position with #1 stop locked in position

As well as ensuring that your table saw blade is parallel to the table saw miter slot, and 90-degrees to the table top, it has to be parallel to the jig fence. If not, your tenons won't be of a consistent width. You fine tune the alignment by means of a bolt that connects the jig to the miter guide bar. Mine was slightly out of alignment, but it only took half a minute to set things right. The user manual clearly outlines the adjustment process.

Once the jig fence is set flush to the saw blade, the #1 stop is locked in position. Until you install a different saw blade you can forget about the #1 stop – you won't have to readjust it.

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Adjustable stock clamp

The adjustable clamp provides a very secure method for holding stock up to 3-7/8" thick. I find that the 1" diameter clamp head provides ample contact surface with the stock and the sliding head operates very smoothly. You can reposition the clamp anywhere along the fence, and secure it in place by means of a a locking lever on the back of the fixed clamp arm. A very effective clamping system.

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(Top) Chisel positioned between #1 and #2 stops; (Bottom) Stock positioned between #2 stop and handle

While you can manually position the fence to make tenon cuts, Powermatic has designed a system where you can use the width of chisel you'll use to chop out the mortises to set the width of the tenon cuts. You simply position the hollow chisel, mortise chisel, or bevel chisel between the two stops, snug up the #2 stop, and then lock it in place. Then place the tenon stock against the #2 stop, pull the jig handle flush up against the stock, and lock it in place. That's it. You can then cut the tenons. All that's left is to cut one face of the tenon, turn the work piece 180-degrees, and cut the other face.

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Tenon width matches chisel width precisely

Right off the bat I was able to cut tenons that precisely matched the width of the mortising chisel. The process is very intuitive, and you'll only need to do it once to get the knack of it.

If you're using a mortiser to cut the matching mortises, and find that the 
tenon doesn't fit snugly into the mortise, the fence is either too close, or too far, from the blade – the user manual shows you how to use the micro-adjust feature to recalibrate the zero point between the blade and the fence. The process takes only a few minutes.

If, like me, you cut mortises using a drill press and chisels, it's probably a good idea to cut all the mortises first. Then cut a test tenon to check the fit. You'll want to chop those mortises carefully to ensure that the tenons fit snugly. Of the several dozen I've done so far, only a few needed to be fixed – to do this I glue a shim on the tenon, and then use a shoulder plane to adjust the fit. It goes fairly quickly. 

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The ultimate table saw accessory for repetitive precision tenoning
 
If you do a lot of tenon work, then this is a shop accessory you should really consider. It makes quick work of the repetitive task of batch cutting tenons, and the results are consistently precise. It's the ideal match for anyone using a mortiser, and in any kind of production environment the PM-TJ will give you a solid return on your investment in short order

KEY FEATURES:

  • 12" x 13-3/4" footprint
  • 6-1/4" x 9-5/8" aluminum fence
  • 3-7/8" stock clamping capacity
  • 1-1/4" clamping rubber head on 3/8" threaded rod
  • 5-3/8" main handle, 1-1/4" secondary handle
  • Fits conventional 3/4" x 3/8" miter slots
  • Micro-adjust system
  • 17 pounds
  • 1 year warranty

COMPANY:Powermatic
MODEL:1799000
PRICE:$329.99 US
MADE IN:China
SOURCE:Dealer Search

Author: 
Carl Duguay
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