|Review by DynaBlue||posted 10-01-2011 06:56 AM||6932 views||1 time favorited||13 comments|
Disclaimer: I’m not a professional reviewer and these opinions are mine and mine alone!
Retail Price: $149.99
I first saw this jig in magazine adverts about two months ago and have had a couple people ask me about the jig, but I hadn’t actually seen one until last night. I was able to procure the jig, spent last night reading the directions and checking out the General Tools Website videos, and today I tested the jig over several hours with the following results.
The jig specifies that it is capable of handling stock from 1/2” to 1 1/2” thick; so I took some undesignated project wood and spent an hour or so milling it flat and square in 1/2”, 3/4”, 1”, and 1 1/4” thicknesses. I ripped pieces at 1 1/2” (face framing), 2 1/2” and 4” wide. The manual states that you can do long pieces but doing so would not allow you to cut the tenons at the same time as the mortise. Not a big deal, but aligning the long piece on the jig as designed would be challenging at best. More on alignment later.
I unpacked the jig and familiarized myself with the basic controls while comparing it to the manual. The manual is well thought out, and I found no major discrepancies when applying the instructions to the jig. The main pieces of the jig consist of the following:
the jig itself;
reasonable quality guide bushings and centering cone; (Also a hex key and a bushing wrench which aren’t shown. The bushing set differs slightly from what you might be used to in that the center hub of the bushing screws in place vs. removing the entire bushing from the router. This is important when using a bit other than the 1/4”.)
a bit, which the manual states is a spiral upcut bit but instead is a straight flute cutter.
Also included is an alignment tool which I will show in a later picture.
The jig seems to be a decent quality bit of aluminum with adjustable heavy plastic guides for both the mortise and the tenon openings. There is a ribbed centering fence below the jig which allows you to adjust for nominal stock thicknesses in quarter measurements (3/4, 5/4, 6/4, etc). As shown in the picture it is set for 4/4 stock or 1” thick:
Opposite the centering fence are the face clamps which secure the workpiece against the centering fence. They are a ‘U’ shaped bracket with two knobs to allow you tighten from the back side of the jig. A minor complaint is that if you turn one knob too much more than the other you bind the face clamp and have to back off a bit. So I found you turn one knob a full turn and then the other. Turn the knobs until you’ve lightly secured the workpiece in the jig in preparation to align the workpiece both vertically and horizontally.
To set the workpiece to the proper height there are two positioning bars in each opening. In the above overview picture they are deployed in the mortise opening and retracted in the tenon. In theory the bars, when deployed, allow you to gently butt the workpiece up against them and ensure that you have correct vertical positioning below the top surface of the jig. In reality they flex too much to be of much value, and even very light pressure against them easily allows the workpiece to fail to square up relative to the top of the jig. That failure to square up is something that I didn’t recognize until I was setting up to cut my final set of joints; using an engineers square against the bottom of the centering fence corrected the problem (no, the picture shows BEFORE I used the square to er…square up the stock to the jig):
Also visible above is the method for aligning the mortise and tenon; they align in identical manner. Before placing the stock in the jig, you mark the centerline of the intended joint on the mating surfaces, and then you are supposed to align that line to the stamped marks in the M&T openings. The problem comes in that the workpice is about 3/8” below the surface that have the stamped marks, and parallax error can make it tricky to ensure that you are cutting both pieces in exactly mating places. Enter the alignment tool, a small metal guide which is supposed to allow you a better shot at both aligning the center mark with the jig and also assist in ensuring the joint length guides are the same. The problem with this tool is that it is nearly useless as the tab which extends down towards the workpiece still doesn’t get close enough to help eyeballing position:
Additionally, the tool is not long enough to reference against the sides of the jig so it is easy to misalign.
All of these can be overcome, but only once you know about them. They don’t seem to add to the EZ part of the jig.
The next step is setting the length of the mortise and tenon. A stamped arrow (visible in the above picture) on the jig allows you to set the graduated scale on the guides. All four guides need to be adjusted to the same setting. The black plastic guides are dovetailed into the side of the jig and seemed to stay mostly square to the edges. The aforementioned hex key is used to loosen and tighten the screws that lock the guides once properly positioned. A chart in the manual shows what the actual M&T length will be based on the guide setting vs. the bit being used. In general when using the 1/4” bit, the length will be 1/8” less than the guide states; 3/8” will be exact, and 1/2” will be 1/8” longer.
One of the last steps in prep is to set the depth of the plunge cut. The manual states you add 1/2” to the depth to account for the bushing (ie, a 1 1/2” plunge to make a 1” deep cut) and recommends setting the mortise slightly deeper to accomodate glue. Checking the actual length of a cut tenon showed it to be about 1/16” shorter than desired, again, probably not a big issue.
When cutting the mortise, you will always use the 1 1/8” bushing, but when cutting the tenon, you will switch the center of the bushing as indicated in the manual; a process that only takes about 15 seconds.
With my first workpiece in place, I set up the jig as instructed. I used a 1/4” bit, the 1 1/’8” bushing and a 3/4” piece of stock. The mortise went fine, but the tenon exhibited the ‘fence or flash’ which is mentioned in the manual as sometimes occuring:
The flash needs to be cut off with a saw, and the manual cautions you to be careful so as not to ruin your nice shoulder. I haven’t used any of the more expensive jigs, and they may do the same thing, but I can certainly see this as a potential nagging issue. So I decided that 1/4” tenon isn’t appropriate for 3/4” stock, and I set up for a 3/8” tenon. The recut seemed to go okay until the fit:
This is the first indicator of the positioning bars not actually squaring up the workpiece, and I attributed that to me probably placing too much pressure against one of the bars and causing the non-square result. The joint is also not flush at the end which is a factor of trying to adjust the mortise and tenon length guides. All the guides are supposed to be set the same (ie, all to 2 1/2” mark). However, the adjustment is done by eyeball, and if eyeball fails, you are supposed to use the alignment tool again. The diamond cutout in the alignment tool is supposed to allow you to match up to the stamped arrow and more precisely set the guide length. This works on one side of the jig, but if you look at the pictures the top edges of the jig aren’t equal; one is wider than the other. On the narrower edge you can either put the edge of the alignment tool against the jig which covers the scale (in hindsight I guess you can see through the diamond, but I still don’t see how this helps much if at all because there isn’t a good way to actually match the stamped arrow to the alignment tool) or you can align the diamond with the arrow without really registering against the edge of the jig so you’re back to eyeballing, the thing the alignment tool was supposed to help with. Additional testing of the jig showed that at the 1” minimum length setting the alignment tool was too wide and covered the centering stamp marks completely, forcing you to rely on eyeballs. Either the edges should be equal width or, alternatively, put all the template scales on the wide side of the jig instead of alternating narrow and wide.
Joint #3 seemed like it was going really well until I hit it with a square (I still hadn’t identified the flexing positioning bars yet) :
Knowing that any tool has a learning curve I continued on and went for #4. This time I paid close attention to the positioning bar pressure and tried again. The very first thing that happened was the mortise piece shoved out of the jig and notched the endgrain:
I started looking into why this happened, and what I found was that the entire jig body flexes as you tighten up the face clamps. What I found in retesting was when I cinched in the mortise piece and then the tenon piece, the mortise face clamps had loosened. I didn’t think I was tightening too hard, but apparently I was wrong. So it becomes a balancing act between tight enough to hold during routing and too tight. Probably some sandpaper stuck on the centering fence and the face clamps would be quite beneficial. This happened on a later piece of wood; so even when I was mindful of the problem, I was still sometimes unsuccessful at avoiding it.
I tried some 1/2” stock and ended up with the flashing issue; so careful attention needs to be paid either to matching bit/tenon/stock thickness or to your sawing skills after you finish routing:
I set up my 1 1/2” face frame stock and found out that the mortise side of the jig simply won’t clamp it because the face clamp and centering clamp don’t extend high enough to capture the wood. It seems that 2” is about the miminum width that the jig can work with; so if you’re looking do to M&T on narrow stock, you will either have to mill it wide and rip narrower after cutting the mortise or find another way to cut the mortise.
As I mentioned before, all tools have learning curves, and this jig is no different. Applying all the work-arounds I’d discovered, I was able to make a very nice fitting M&T on the seventh try. It was square, flush on the faces and ends, and loose enough without being sloppy. As they say in Eternal Optimist School, “Seventh times the charm!”
I would have to say that my final impression of this jig isn’t as favorable as I was hoping when I started. It is not a bad product and it will get the job done provided that you are willing to work around several limiting factors but it certainly isn’t an ‘unpack and go make a perfect M&T joint’ device. I have started brainstorming ways that I might increase the accuracy of set up while eliminating eyeballing, parallax and flexing bars. If I come up with something reasonable I’ll post more pictures. I am confident that ingenious woodworkers will start to adapt this jig and that feedback will hopefully lead to product improvements.
- At $150 it is much cheaper than other jigs designed to do the same thing;
- Does the job IF you are willing to work around several little problems
- Jig won’t cut face-frame sized stock;
- Frame will flex if face clamps are tightened too much;
- Clamping mechanism can loosen up if frame flexes;
- Alignment tool seems more like an hastily made afterthought rather than a helpful addition;
- Positioning bars are too flexible to be of much use in squaring up the stock without use of an actual squarel;
- Too much reliance on eyeball measuring for joints that must be precise;
- Flashing around tenons when using particular bits and stock thicknesses requires additional hand tool work
- Adhesive sandpaper on the centering wall and face clamp surfaces would improve grip without requiring excessive tightening;
- Redesign the alignment tool to: – Lengthen the center mark tab’ – Lengthen the cross piece to snugly fit between the jig rails; – Narrow the cross piece to allow use when the tenon length is set to minimum;
- Ensure both jig top rails are the same width to allow the alignment tool to work equally well on both sides;
- Put the length guide scales on the same (wide) side of the length template to allow the alignment tool to work ‘as is’;
- Include a chart in the manual specifying which bit/stock thickness combinations are most prone to flashing;
- Redesign the positioning bars to make them more resistant to flex and to be of more use in squaring up stock.
Thanks for reading,
-- Mistake? No, that's just an unexpected design opportunity....