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I bought the premium self centering dowel jig from Rutlands and I have been testing it on pieces of 18mm plywood, however it seems that it is not quite centered correctly.

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I did contact Rutlands directly who quickly sent me a video from the manufacturer on how they centre the jig themselves. It looks like they unscrew the 2 bolts on the non-handled plate and screw/unscrew the piece that the 2 bolts hold down securely, allowing this plate to be moved forwards/backwards.

It seems however that after performing this 'fix', the middle plate when tightened on a piece, is not parallel... It feels like the plate with the adjustment bolts is loose and can rock about the main threaded screw.

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Does anybody have experience with this type of jig and correcting it?

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  • I'd hardly call myself an expert on self-centering jigs, but I can't see that this is actually one! If you look at the various designs for this they all employ some sort of rocking action or mechanism, where either the entire jig (single-hole) rotates, or the two outriggers rock into position and it's this that ensures they find centre. This is an adjustable jig yes, but self-centering? No, I don't think so.
    – Graphus
    Feb 15 at 5:12
  • @Graphus I think you're thinking of a different style of jig. This one is self-centering because the two sides have threads of the same pitch but in opposite directions, so that turning the center screw always moves each side the same distance in opposite directions.
    – Caleb
    Feb 15 at 22:08
  • @Caleb, yes I am very much thinking of a different style of jig as being the classic self-centering design. "the two sides have threads of the same pitch but in opposite directions, so that turning the center screw always moves each side the same distance in opposite directions" except that in this case it doesn't apparently LOL
    – Graphus
    Feb 16 at 9:33
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It feels like the plate with the adjustment bolts is loose and can rock about the main threaded screw.

I haven't seen this particular one, but there are a lot of jigs produced in this style and I'm pretty sure they all work the same. The center hole in the middle plate contains a grub screw that compresses a spring which pushes a ball into a groove in the center shaft. The handle-side plate is threaded, so not adjustable, but the non-handle side has a threaded bushing that's screwed to the plate. The two smooth outside shafts just keep everything lined up.

So... I'd remove the screws holding that bushing in place, and then turn the handle until the handle-side plate contacts the center plate. Then install the non-handle side plate and slide it so that it also contacts the center plate, and clamp it in place. Finally, install the threaded bushing, screwing it onto the center shaft until it's snug against the plate. Install and tighten the two screws to lock it in place.

Now the two sides should be parallel to each other and to the center plate, since they're both contacting the center plate, and if you turn the handle to open the jig they should both move the same distance away from the center plate. They may have a bit of play from side to side, but that should disappear when you tighten the jig on a piece of stock.

If you've done all that and the side plates and center plate aren't all parallel, I'd suspect a defective jig.

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    Hi Caleb, I got further instruction from the company that pretty much outlined what you just said. Basically loosen greatly all bolts but don't remove, place the centre dowel plate as best you can in the centre of a parallel board and clamp tightly. At this point it should all be centred and set up, then just to tighten all the bolts back up.
    – physicsboy
    Feb 16 at 10:38

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