Liegh Finger joint jig - Super Jigs - sweet!

[Will Blick]

After a 8 month wait, today I got my Leigh F18, Finger Joint template for the Super 18. It makes 5/16" and 5/8" Finger / Box joints. I am nursing a few injuries, so I won't use it for awhile.... regardless, I was curious to see how consistent the jigs finger spacing was. I also measured the thickness of the fingers, the accuracy of both are critical for tight fitting box joints....

Using a very accurate Fowler digital tester, remarkably, all the spacings tested are within .01mm, or .0004". Quite impressive, you get what you pay for when it comes to machined parts. This template IIRC is $199, which sounds a bit high, but precision machining is not cheap.

Any poor fitting box joints will be a result of user error, router concentric problems, or guide bushing adjustment issues, certainly NOT the Leigh Template. Kudos to Leigh for building such high quality products.

[Bryan Berguson]

Leigh makes some super (no pun intended) jigs! I got a new D4R last October. Love it!!!

Those Canadians make another jig that I just puchased and I think I'm going to love it as much as the D4R - Dowelmax. Our Northern friends make great tools! :D

I think you're going to LOVE making some boxes with that new template! Enjoy!

Bryan

[Cliff Rohrabacher]

precision machining is not cheap.

Well, the machinery is not cheap but almost any CNC machine these days can cut to within 80 Millionths of an inch without much difficulty.

[Will Blick]

> almost any CNC machine these days can cut to within 80 Millionths of an inch without much difficulty.


I think "any" CNC Machine is a big stretch.... to hold that type of precision over 24" is the most elite mills..... Trying to hold more than .001" in a final part that is 24" long is still a challenge, as even at .001" final part precision, you often need a mill that is much more precise probably close to .0001", and you must control other variables such as material temperature, air temp, cutter speeds, cutter wear, clamp pressure, etc.


I am not arguing your accuracy numbers, but high precisioned CNC mills are very expensive. They have to bill the machine out on an hourly basis based on its amortized cost and operating cost. Looking at this F18 template, it appears to have spent some significant time being milled....... Overall, I would suggest the quality vs. the price is very favorable.


On another note, I toyed with leighs new ebush - an elliptical guide bushing. It enables you to vary the width of cut by rotating the elliptical bushing. This provides almost infinite adjustment over a .02" range - which is the max. change in the ebushs thickness when rotated 180 degrees. So assuming you can set 20 increments over the 180 degrees, this allows for .001" adjustment resolution. Not so bad, as it takes very little effort, and you can do it on the fly (no disassembly). Tweaking the ebush allows will account for small differences in router bit widths, wear on bits, etc. Of course this feature comes with a small price, you must learn to keep the router very square for all cuts, i.e. not allow it to rotate, or you will produce varied size cuts. Overall, a brilliant concept IMO.


Even the instruction manual for the template is excellent.

[Will Blick]

BTW, why is their two terms for these joints? Which is more accurate, box, or finger joint?

I always thought finger joints were not straight, slightly angled, and used to join straight boards, as seen here

http://www.coastaltool.com/a/amana/images/55392_profile.gif

[Will Blick]

Forgot to mention... in addition to the fixed spacing 5/16th and 5/8ths, i.e. insert board, cut all fingers - DONE....

the jig allows other size fingers by sliding the jig and changing index pin position, i.e., cut the board, then move the index pin, cut same board again, etc.... the jig will allow additional finger sizes.... as small as 3/32" (impressive), then in 16th's, finger sizes can be.... 2, 3, 4, (5), 6, 8, (10).

Of course, the (5) and (10), (5/16th & 5/8th) are the default sizes on the jig, i.e. cut all fingers at once, i.e., no re registering the index pin and cutting the same board again....

Since it's not clear in the Leigh literature.... the Leigh Super Jig finger joint jig (F18 and F24) offers a total of 8 different size fingers.

[Eric Haycraft]

> almost any CNC machine these days can cut to within 80 Millionths of an inch without much difficulty.


I think "any" CNC Machine is a big stretch.... to hold that type of precision over 24" is the most elite mills..... Trying to hold more than .001" in a final part that is 24" long is still a challenge, as even at .001" final part precision, you often need a mill that is much more precise probably close to .0001", and you must control other variables such as material temperature, air temp, cutter speeds, cutter wear, clamp pressure, etc.


I am not arguing your accuracy numbers, but high precisioned CNC mills are very expensive. They have to bill the machine out on an hourly basis based on its amortized cost and operating cost. Looking at this F18 template, it appears to have spent some significant time being milled....... Overall, I would suggest the quality vs. the price is very favorable.


You would be amazed at the speed that some of those mills these days. A good pallet based system could probably churn out a set of 20 of those templates in under half an hour. The machines are well over 1 million dollars, but can typically have at least double the throughput of what previous generations of machines would be able to do. Something like these templates are probably machined on a pallet based machine. Essentially the machine has multiple pallets and a pallet carrier. When one pallet is in the machine being milled, another pallet is in a loading/unloading bay for the operator to load and unload. Each pallet could hold dozens of these templates to be milled at once. These newer systems can hold tolerances well below .001 and even allow for rotation of new tooling in without stopping. Because they are so fast, the costs to run them per part are actually quite small. They also allow for almost 0 setup time so the machines only need to sit idle if it is being serviced.
I worked at a manufacturing co that purchased one of these machines. It could churn out parts cheaper than they could be imported for and paid for itself in no time.

[Will Blick]

Eric, interesting info.... I know Leigh doesn't have such equipment, and they make these in-house on a Haas. But your point is well taken... if the volume is great enough, the speed of these high-end machines can really drive down part costs.... After set-up, I guess its almost a cookie cutter approach.