How to center the tails board on a PorterCable 4216?

Use the left side of the jig for corners 1 & 3, and use the right side of the jig for corners 2 & 4. Once set up properly, you won’t have this issue anymore.
The jig has built in guides on the front, that adjust with an allen wrench. You only need to set the offset once.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

That is a tough nut to crack. The best solution that I’ve found is to use a set of feeler gauges to measure the gap until it is the same on both sides of the board. What is needed is a vernier adjustment on the stops because it is super difficult to move them just a few thousands of an inch.

Even then I sometimes have problems which I work around by taping a couple of pieces of sand paper to my work bench and then use them to sand the edges of the finished box.

-- Joe

Joe, There’s a much larger gap than that when centering the tail board. It’s more like half an inch. But if I’m off by 1/16th of an inch (for ex), then the mated pieces will be off by 1/8” on every corner, alternating between the top and bottom of each corner.

pinto, I hadn’t even noticed that there’s a guide on the right.

I’ll have to experiment with that to see if I can figure out what you mean. Centering is still an eyeballing, right? And could still be off a bit? Does that approach just eliminate the “offset doubling”, and any mistake is marginal, assuming I’m not an idiot and get the board pretty close on each end?

Guess I don’t understand what you are talking about. Just noticed that you said 4126 which I misread as 4216.

-- Joe

Oh that WAS a typo. You’re right. It’s 4216.

When you cut through tails, you line the guide up all the way to the left. You then center the board between the leftmost opening and bring the guide over to meet it and lock it down. That’s the registration for the tails and then the pins later. Because you’ve centered the board edge between the leftmost opening, and the board’s width is whole inches + 1/4”, the right edge is automatically centered in an opening as well.

It’s that centering that I’m messing up, because it’s by eye. The instructions don’t mention the guide on the right, so I’m curious about it. But … I don’t see how I couldn’t still mess it up by being just a little off on each centering and in opposite directions. I’m probably just being stupid.

Here are the specific instructions. Step 4 (and Figure F4) is the one I’m talking about.

I only have a Leigh but I’m sure the concept is the same. You mostly work on the left side. You align the horizontal and verticals with test boards…those test boards don’t get enough attention but if they are perfectly square and relatively flat, you should be able to set-up the machine (one of the rare “follow the instructions” on blind faith).

I stared and questioned my Leigh instructions for a long time, not understanding how and why it works. It does (concluded that the most important part of the machine is that manual!!!).

ok…while I was typing you were too.

Referring to Figure 4, measure the distance from the edges of the workpiece to the edges of the template fingers, and adjust the position of the workpiece until the two measurements are the same. I’ve used digital calipers as well as feeler gauges and for me the feeler gauges work best. When you get the workpiece centered, moved and secure the offset guide against the workpiece.

-- Joe

guess I’m glad I bought the Leigh! you guys have to go through this stuff everytime you use it?

Leigh runs you through an extensive set-up procedure to ensure the horizontal and vertical boards align properly. After that you only need to move the fingers around depending on your layout. Of course periodic checks/adjustments are prudent.

@Todd, I’m not trying to be a smart a.. here but that is exactly the reason I got rid of my 4212. I decided it was too finiky and complicated to fool with. I’ll bet I read the instructions 20 times(and yes the extra ones on the internet) and I still could not get it right. I bought an Incra and have had better success and a lot less frustration.
Good luck I hope you get it worked out.

-- Don't rollerskate in a buffalo herd

I’ve had the same problem when I was getting used to this jig… I always test scrap wood joints before making my real cuts. Here’s what I do:

Make test joints with scrap wood the same thickness and width as your real work. Measure the width of your furthest left and right tails, note the measurements. (Left and right refer to when your work is in the jig, not in assembly.)

If the left side is larger than the right, you have to move the stop block to the left. Put in a piece of wood, flugh against the stop block, lock down the wood. Loosen the stop block, put in a feeler gauge that is half the difference between tail widths, then move the stop block back so the feeler gauge is tight. Lock down the stop block.

If the right side is larger than the left, you have to move the work to the right, so you move the stop block to the right. Take the difference between the tail width, put the right feeler gauge between the block and scrap wood, lock down the wood, pull out the gauge, and then move the stop block right until it’s flush with the wood.

...Or, you could perfect your hand cut dovetails. Which is what I should be doing now…

Hope this helps!

Like your way better than mine, Coldfoot.

-- Joe

Pintodeluxe has it right. I have the 4212. I made the same (or very similar) mistake the first time I used it. Again: corners 1 & 3 on the left side, corners 2 & 4 on the right. There should be stops for the wood on the right side that are mirror images of the ones on the left. I admit that PCs instructions are confusing.

I haven’t made any dovetails since, but I did spend some time thinking about the problem and it suddenly came to me. I really don’t understand how the left/right side plays into this, but I will experiment with it the next time I make some.

But what did occur to me is that I need a spacer to register the piece in relationship to the template’s outer tooth. And what size would that spacer be? 1/4”, of course. I happen to have the Kreg spacer blocks/bit height blocks (forget their real name) and tried it out. I really think that will solve the alignment problem, guaranteeing I’m centered.

The manual just isn’t clear enough about the offset guides, and you really sort of have to read the entire manual (including the parts that don’t appear to apply) before the ones on the right side get mentioned. There are two colors of guides in the kit. One color is for one type of dovetail, one color is for the other types (half blind vs. through). It is necessary to adjust the guide on the left according to the instructions and then adjust the guide on the right, using the same (mirror image) principal. Once adjusted, you don’t have to adjust them again unless you remove them to switch colors. When properly adjusted, (that’s why you create lots of test stock that is the same thickness and width as the boxes you are making) the jig handles the offset and does the exact job of the spacer you are discussing. Frankly, I use a dial caliper for as many set-ups as I can, including this one where you need to achieve “centered”. Keep in mind that ends 1 AND 3 are done on one side and ends 2 AND 4 are done on the other side. If you follow that practice, the corners will match up EVEN IF you haven’t achieved “center” as long as you attach the #3 SIDE corner to the #3 front (or back). Marking the sides as suggested in the manual is a really big help to avoid confusion and error. I find this jig really easy to use as long as I keep my parts straight.