Leigh D1600 - an independent review by John Bullar

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Independent Review of the Leigh D1600 Dovetail Jig

© John Bullar 2005

previously published in The Router magazine

It's a real Leigh - only smaller. Based in Canada, Leigh Industries Ltd have manufactured a succession of dovetail and other jigs for routers since the early Nineteen Eighties, building themselves a strong reputation in the process. At 400 mm (16 inches) wide, the new D1600 is geared to narrower boards than its Big Brother the D4 is, but shares many of the same functions, with a similar mechanism. The D1600 enables you to cut through dovetails, half-blind dovetails, sliding dovetails and variants on these using a medium to large sized router. The joints have infinitely variable spacing and you can fine-adjust them for tightness of fit. Assembly of the jig is straightforward and fairly quick. Leigh supply tools for assembly and adjustment but you will have to find your own sturdy baseboard before you can clamp the jig on your bench, also a spacer board to hold up the rear clamp.

The spiral bound manual of 120 pages has hundreds of diagrams plus a clear description alongside each for assembly and operation of the D1600 with measurements in imperial and metric units. A DVD also comes in the pack, which provides a good foretaste to ease you into the Leigh system, but it is not a substitute for the manual. The D1600 body is an aluminium extrusion with CNC machined fittings and front and top clamping surfaces. Machined side stops provide joint alignment while milled circular grooves here provide a high friction surface, allowing the timber to be gripped with only a moderate pressure from the clamps. Cam levers each end of the clamp bar press the wood onto the body and prevent slippage. The clamp bars themselves bow quite alarmingly with only a moderate pressure. The Leigh instructions suggest that a 2mm bow at the end is normal and this is reached with a very light pressure on the cam, resulting in a somewhat uneven force on the timber. However, once the jig is bolted down and timber clamped in place the finger assembly provides a solid base to run a heavy router on. To use the D1600 you need to fit a guide bush on the base of your router then feed the cutter shaft through it. Wile routing you feed this bush between the fingers of a template assembly on top of the jig. By flipping the finger rail over, you position the cutters for both mating sides of the joint. Unlike the comb type templates on simpler jigs the Leigh system allows you to slide fingers individually to achieve the ideal joint spacing. The position of the guides is fine tuned on a scale at each end to adjust the fit. When tightened in position the finger tops are smooth enough to avoid giving the router a bumpy ride. Unlike the larger D4 jig, the pins are not split into pairs so, while you can vary the tail width, the pin width is fixed by the cutter size. This does however simplify operation. With so many non-standard router bases to fit, guide bushes must be a real headache for router jig designers.

The two-piece bush supplied by Leigh fitted beautifully to my Makita 3612C with quick fit base. Leigh's steel flange plate with its brass guide bush, clips into the router base and fits it a treat - even better than Makita's own bush and with just one-third as much sideplay. Leigh's cutters have tungsten carbide tips supplied by Sandvik. The edges are finely honed on diamond wheels and cut very cleanly. Their 8mm steel shanks make them stiffer and less prone to vibration than the more common ¼ inch (6.4mm) type. Of course this does mean that ¼ inch routers cannot be used, but these would not be powerful enough for cutting dovetails in any case. An 8mm collet reducer is supplied to allow you to fit the Leigh bits in a half inch router. I particularly liked the shouldered design of the reducer, positioning it correctly in the router chuck and allowing easy removal. The only thing that lets the Leigh bush down is that it is very awkward to tighten the two parts together. The brass bush has a knurled backing ring that must be screwed up tightly on its collar - but here I found a problem: there is nothing to hold the collar by while you tighten the ring. Despite a slot milled in one edge of the brass collar there is no corresponding peg in the steel flange plate, which the manual showed fitted to other adaptors. Gripping the guide bush itself with pliers would inevitably distort it so I found the guide bush could work loose, potentially allowing the router to wander. It may be advisable to apply Loctite adhesive to the bush unless Leigh come up with an improvement. The manual describes in detail how to move the router between pins and proposes you should back-route (or climb route) some of the cuts. Routing dovetail sockets must be done in one pass and decent sized ones spit out wood chips and dust at an alarming rate. As the cutter slides between fingers a stream of debris sweeps across like machine-gun fire, plastering your clothes and producing a slippery matting on the floor.

For cutting half-blind tails any wider than the minimum, it is necessary to bridge the gap between adjacent fingers to create an edge for the guide bush to run on. Bridging pieces need to be cut with a hacksaw from the supplied lengths of T section plastic strip. The Leigh produced a pleasingly tight fit - some might say a little too tight, but because the cuts were so smooth, straight and precise, with a light tap the tails engaged in the sockets superbly. The precise width of the pins is infinitely adjustable by moving the finger rails fore and aft against a sliding scale. This means it is always possible to make the cut a little tighter or looser. I was worried that infinite adjustment might require infinite patience to adjust - something I sadly lack, but maybe I was getting the feel of this jig because this time I found it quite straightforward.

The results were excellent with precisely matched clean-sided tails and sockets.Leigh's experience of a quarter of a century designing and making various dovetail jigs is shown to great effect in the D1600. The components are precision machined and the gauge of materials is sufficient for medium duty. Assembly is straightforward so long as you follow the manual, which is clear and well illustrated. The sharp bits with their sturdy 8mm shanks together with the precision fitting guide bush all add up to a very positive and chatter-free action while routing tails. Dust extraction is not provided as standard but is very necessary so ask for the router vacuum attachment. The many adjustment possibilities on the D1600 system mean that some time and patience may be needed for correctly setting it up, but this will be rewarded with first rate results. While there are some much cheaper dovetail jigs on the market, for the versatility and precision offered, the Leigh D1600 is good value for money.

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Independent Review of the Leigh D1600 Dovetail Jig © John Bullar 2005 previously published in The Router magazine
	It's a real Leigh - only smaller. Based in Canada, Leigh Industries Ltd have manufactured a succession of dovetail and other jigs for routers since the early Nineteen Eighties, building themselves a strong reputation in the process. At 400 mm (16 inches) wide, the new D1600 is geared to narrower boards than its Big Brother the D4 is, but shares many of the same functions, with a similar mechanism. The D1600 enables you to cut through dovetails, half-blind dovetails, sliding dovetails and variants on these using a medium to large sized router. The joints have infinitely variable spacing and you can fine-adjust them for tightness of fit. Assembly of the jig is straightforward and fairly quick. Leigh supply tools for assembly and adjustment but you will have to find your own sturdy baseboard before you can clamp the jig on your bench, also a spacer board to hold up the rear clamp.
The spiral bound manual of 120 pages has hundreds of diagrams plus a clear description alongside each for assembly and operation of the D1600 with measurements in imperial and metric units. A DVD also comes in the pack, which provides a good foretaste to ease you into the Leigh system, but it is not a substitute for the manual. The D1600 body is an aluminium extrusion with CNC machined fittings and front and top clamping surfaces. Machined side stops provide joint alignment while milled circular grooves here provide a high friction surface, allowing the timber to be gripped with only a moderate pressure from the clamps. Cam levers each end of the clamp bar press the wood onto the body and prevent slippage. The clamp bars themselves bow quite alarmingly with only a moderate pressure. The Leigh instructions suggest that a 2mm bow at the end is normal and this is reached with a very light pressure on the cam, resulting in a somewhat uneven force on the timber. However, once the jig is bolted down and timber clamped in place the finger assembly provides a solid base to run a heavy router on. To use the D1600 you need to fit a guide bush on the base of your router then feed the cutter shaft through it. Wile routing you feed this bush between the fingers of a template assembly on top of the jig. By flipping the finger rail over, you position the cutters for both mating sides of the joint. Unlike the comb type templates on simpler jigs the Leigh system allows you to slide fingers individually to achieve the ideal joint spacing. The position of the guides is fine tuned on a scale at each end to adjust the fit. When tightened in position the finger tops are smooth enough to avoid giving the router a bumpy ride. Unlike the larger D4 jig, the pins are not split into pairs so, while you can vary the tail width, the pin width is fixed by the cutter size. This does however simplify operation. With so many non-standard router bases to fit, guide bushes must be a real headache for router jig designers.
	The two-piece bush supplied by Leigh fitted beautifully to my Makita 3612C with quick fit base. Leigh's steel flange plate with its brass guide bush, clips into the router base and fits it a treat - even better than Makita's own bush and with just one-third as much sideplay. Leigh's cutters have tungsten carbide tips supplied by Sandvik. The edges are finely honed on diamond wheels and cut very cleanly. Their 8mm steel shanks make them stiffer and less prone to vibration than the more common ¼ inch (6.4mm) type. Of course this does mean that ¼ inch routers cannot be used, but these would not be powerful enough for cutting dovetails in any case. An 8mm collet reducer is supplied to allow you to fit the Leigh bits in a half inch router. I particularly liked the shouldered design of the reducer, positioning it correctly in the router chuck and allowing easy removal. The only thing that lets the Leigh bush down is that it is very awkward to tighten the two parts together. The brass bush has a knurled backing ring that must be screwed up tightly on its collar - but here I found a problem: there is nothing to hold the collar by while you tighten the ring. Despite a slot milled in one edge of the brass collar there is no corresponding peg in the steel flange plate, which the manual showed fitted to other adaptors. Gripping the guide bush itself with pliers would inevitably distort it so I found the guide bush could work loose, potentially allowing the router to wander. It may be advisable to apply Loctite adhesive to the bush unless Leigh come up with an improvement. The manual describes in detail how to move the router between pins and proposes you should back-route (or climb route) some of the cuts. Routing dovetail sockets must be done in one pass and decent sized ones spit out wood chips and dust at an alarming rate. As the cutter slides between fingers a stream of debris sweeps across like machine-gun fire, plastering your clothes and producing a slippery matting on the floor.
For cutting half-blind tails any wider than the minimum, it is necessary to bridge the gap between adjacent fingers to create an edge for the guide bush to run on. Bridging pieces need to be cut with a hacksaw from the supplied lengths of T section plastic strip. The Leigh produced a pleasingly tight fit - some might say a little too tight, but because the cuts were so smooth, straight and precise, with a light tap the tails engaged in the sockets superbly. The precise width of the pins is infinitely adjustable by moving the finger rails fore and aft against a sliding scale. This means it is always possible to make the cut a little tighter or looser. I was worried that infinite adjustment might require infinite patience to adjust - something I sadly lack, but maybe I was getting the feel of this jig because this time I found it quite straightforward.
	The results were excellent with precisely matched clean-sided tails and sockets.Leigh's experience of a quarter of a century designing and making various dovetail jigs is shown to great effect in the D1600. The components are precision machined and the gauge of materials is sufficient for medium duty. Assembly is straightforward so long as you follow the manual, which is clear and well illustrated. The sharp bits with their sturdy 8mm shanks together with the precision fitting guide bush all add up to a very positive and chatter-free action while routing tails. Dust extraction is not provided as standard but is very necessary so ask for the router vacuum attachment. The many adjustment possibilities on the D1600 system mean that some time and patience may be needed for correctly setting it up, but this will be rewarded with first rate results. While there are some much cheaper dovetail jigs on the market, for the versatility and precision offered, the Leigh D1600 is good value for money.