Inconsistent Results PC 4212 Please Help

[Adam Potack]

I need some help. I have a PC 4212 dovetail jig. I set up the jig and router (PC) made some test cuts, adjusted until I had everything fitting good (half blind dovetails). However each dovetail I make varies from just right to needing the pins filed to fit, to too loose. This happens with pieces cut from the same board. What am I doing wrong?

Thank You,
Adam

[Cliff Rohrabacher]

I'd guess that you are pushing on the router up against the guides in your effort to keep it under control and down. If so then, that amount of push causes the jig to deflect a tad but, never the same amount twice.

[Adam Potack]

Thank you. I will give that try.

Adam

[Alan Tolchinsky]

Make sure you have the bushing exactly centered on the router. I found the tips in the manual (or on the side of the jig ) to be useful.

[Steve Clardy]

I run the router right to left for less tearout.
Then I reverse going back through the cuts.

When I first started using mine a couple years back, I found I had the same thing. Going through the motion twice eliminated my problems.

[Rob Young]

Two more suggestions:

1) Be sure your work pieces are not cupped or twisted. The clamp is strong enough to take out a bow or twist right at the clamp but it won't take one out of the end of a board.

2) Be sure the template is level and not bowing as suggested in another post. Light hands and a light touch on the router should be all you need.

Good luck figuring out your problem. Please report back when you think you have the solution. I too have a 4212 and while I haven't had the problem you are describing, I'd like to add your lessons to what I have learned. That way I can move forward into making bigger and better mistakes! :)

[Chip Lindley]

The above causes for mis-alignment just about cover it. I would add, that if the bar clamp does not hold your stock SECURELY, there may be a slight movement left or right due to the grab of the router bit. I had this problem with an old half-blind DT jig, and everyone was puzzled until I figure it out. Gluing sandpaper to the hold down bars prevents ANY slippage!

[Adam Potack]

Thank you all so much for the advice. I will work on all of your suggestions this weekend. I will let you know how it comes out.

Thanks Again,
Adam

[Don Bullock]

Adam, I'm no expert on dovetail jigs, but I was reading an article in American Woodworker about them this morning. One discovery that the author made may apply to your situation of inconsistent dovetails. He noticed that's it's important for the router base to be exactly centered on the collet. If the base is off-center the bit won't be centered in the templet guide because it mounts to the base. Misalignment can cause problems with the fit of the dovetails because the orientation of the router for the successive passes through the template may be different causing differences in the cut from one template finger to the next. He further suggests that even with the base centered exactly it is important to orient the router the same way for each pass. Just my $.02

[Adam Potack]

Thanks Don. Can't wait to try this again.

[Adam Potack]

Thank you all for the advice. My dovetails while not perfect are now acceptable and consistent.

Thanks Again!
Adam

[Rob Young]

Good to hear. What did you find to be the issue after reading all our various posts?

[Adam Potack]

I don't know which issue was causing my problem, I think I had a few problems going on at once. I incorporated all the suggestions, ran a test cut, made some adjustments to the jig & bit depth. Ran many samples until I was satisfied. The one issue that was not causing a problem was twisted or cupped stock. I was using 1/2" baltic birch and it seemed to be straight and true.

Thanks again, I do not think I would have been able to figure this out on my own.

Adam

[Don Bullock]

Great Adam. I'm looking forward to seeing pictures of your project once it's finished.