Leigh Dovetail jig problem

[Aled Dafis]

I've bought the Leigh D4R D/T jig home from school over the holidays so that I could get used to using it before the mad rush that next term brings with it.

My first impressions of the jig are very impressive indeed, it's very well made and fairly straigtforward to set up. I have come up against one problem however, when cutting my first joint, I found that one side of the dovetails consistently had a gap of about 0.5mm on the left hand side of the pin, across the board.

The gap doesn't show up too well in this pic, but it's definately there.

So I went about checking the guide bush concentricity and set up. The guide bush seemed ok, so I tried another joint just to see whether it was down to user error. Much to my surprise, joint B also showed the same error, so I'm either consistently out, or it's the jig.

The gaps are a bit clearer here. But on the right this time as the joint was photographed the other way round.

And in close up...

So any guidance would be most appreciated.

Cheers

Aled

 

[Bluekingfisher]

I'm not going to be any help Aled but i have just bought a 12" Leigh super jig. I haven't even had the chance to get it out of the box yet.

i will keep an eye on your thread for my benefit too. I hope you get lots of advice or at least you manage to figure it out.

Just a thought, is the bush centred bang on in the router base, maybe there is a little burring or some debris keeping it from centre? could you fit it the other way round, My router base has only two mounting holes so easily swapped around although I know some router bases have 3 holes which could then cause you problems. At least, if the gap is then on the other side when you make a joint either the bushing is not centred or aperture of the bushing could be out of shape, just a thought

 

[Steve Peacock]

Hi,

I don't have the Leigh dovetail jig - and my memory is very fuzzy - so I'm not much help.

However, here is some stuff from an article that I downloaded from the net on machine-cut dovetails:
(It may not actually be relevant to your jig ... but maybe it will help)

"Setting up to rout machine-cut dovetails is always a trial and error effort. There’s usually
lots of fiddling around with test pieces and adjusting of the jig to get a perfect fit.
TOO LOOSE. If the joint is so loose that the pieces wiggle around when they’re put together, the depth of cut is too shallow. Increase the depth of cut about 1/32" and try again.
TOO TIGHT. If a trial cut is so tight that the pieces can’t be tapped together, the router bit is extended out too far from the router base. Decrease the depth of cut about 1/32" and try again.
TOO DEEP. If the pins on the drawer sides go too far into the sockets on the drawer front, the sockets are too deep. To correct this, move the template forward (toward you) by turning the stop nuts on the studs counterclockwise. (Be sure to adjust the nuts on both ends of the jig.)
TOO SHALLOW. If the pins don’t go far enough into the sockets, move the template back (away from you) by turning the stop nuts clockwise.
OFFSET. If the top edges of the two pieces aren’t flush when you assemble the joint, the problem is either with the offset of the stop blocks (it should be 7/16") or the fact that the pieces weren’t tight against the stops.
OTHER PROBLEMS. Most other problems are usually caused by the pieces not being clamped down in the jig so they are flush across the top, or because they move outof position as they’re being routed."

Steve

 

[Aled Dafis]

Hi,

I don't have the Leigh dovetail jig - and my memory is very fuzzy - so I'm not much help.

However, here is some stuff from an article that I downloaded from the net on machine-cut dovetails:
(It may not actually be relevant to your jig ... but maybe it will help)

"Setting up to rout machine-cut dovetails is always a trial and error effort. There’s usually
lots of fiddling around with test pieces and adjusting of the jig to get a perfect fit.
TOO LOOSE. If the joint is so loose that the pieces wiggle around when they’re put together, the depth of cut is too shallow. Increase the depth of cut about 1/32" and try again.
TOO TIGHT. If a trial cut is so tight that the pieces can’t be tapped together, the router bit is extended out too far from the router base. Decrease the depth of cut about 1/32" and try again.
TOO DEEP. If the pins on the drawer sides go too far into the sockets on the drawer front, the sockets are too deep. To correct this, move the template forward (toward you) by turning the stop nuts on the studs counterclockwise. (Be sure to adjust the nuts on both ends of the jig.)
TOO SHALLOW. If the pins don’t go far enough into the sockets, move the template back (away from you) by turning the stop nuts clockwise.
OFFSET. If the top edges of the two pieces aren’t flush when you assemble the joint, the problem is either with the offset of the stop blocks (it should be 7/16") or the fact that the pieces weren’t tight against the stops.
OTHER PROBLEMS. Most other problems are usually caused by the pieces not being clamped down in the jig so they are flush across the top, or because they move outof position as they’re being routed."

Steve

Thanks Steve, but I think you'll find that these instructions are for the simpler half blind dovetail jigs like this one

Which I also have at school. :wink:

Cheers
Aled

 

[jasonB]

What shank cutters are you using, I usually use the 8mm as I found the 1/4" ones chattered and cut oversize particularly on the cut in if you don't do it in stages, climb cutting helps here. This may be why you have an oversize cut on one side.

Are you correctly fitting the boards with inside faces and outside faces the right way round if not you will get an asymetric joint. inside facing you for tails, outside facing for pins.

And make sure its clamped firm and not moving away fron the edge stop

Provides you are not rotating the router the guide bush won't affect this even if its out of ctr.

J

 

[andy king]

Hi Aled,

As I recall, you still have to fine tune a Leigh jig for through dovetails, and its a case of moving the pin cutting side of the guide in or out to make the pin profile wider or narrower.
There should be a scale on the side of the pin/tail comb that allows for fractional adjustments of the comb to suit - moving the pin side slightly forwards should tighten the joint as I remember.

hope this helps.

cheers
Andy

 

[jasonB]

You do indeed have to fine tune the fit but this affects both sides not just one.

J

 

[Aled Dafis]

Thanks for the advice guys.

I've been doing some more investigating/experimenting this afternoon and found that the problem was actually with my tails as opposed to the pins as I first thought.

The problem was that when I cut the tails, the router actually cut a very small taper on one side of the joint as the cutter exited the work (the show face). I then tried to cut the tails with a backing board in place so that the cutter wouldn't jump as it exited the workpiece, and thankfully it worked, the tails were parallel and the joint went together just nice.

Cheers
Aled