Jointech and Box Joints

tdubnik · Post by **tdubnik** » Mon Aug 24, 2009 11:51 am

I experimented with box joints using my Jointech and router table. I was making 1/4" equally spaced box joints using a 1/4" spiral upcut bit and the appropriate template.

The spacing on the joint seems good but the fit of the joint seems a little loose. There is no friction at all when assembling the joint.

My question is: What causes this? Is it something in the Jointech setup or is my router bit off size?

curiousgeorge · Post by **curiousgeorge** » Mon Aug 24, 2009 12:34 pm

I would guess that it is the router bit that is a fraction off size. That's usually the case, unless you are using top of the line bits.

charlese · Post by **charlese** » Mon Aug 24, 2009 4:18 pm

tdubnik wrote:I experimented with box joints using my Jointech and router table. I was making 1/4" equally spaced box joints using a 1/4" spiral upcut bit and the appropriate template.

The spacing on the joint seems good but the fit of the joint seems a little loose. There is no friction at all when assembling the joint.

My question is: What causes this? Is it something in the Jointech setup or is my router bit off size?

It's an adjustment. You have to move the pin just a very small amount (a tap) away from the cutting bit. If it gets too tight - tap it back toward the bit.

The grooves are set by the diameter of your bit. The fingers are set by the pin's distance from the cutter. Fingers can be adjusted to fit any size of cutter.

tdubnik · Post by **tdubnik** » Mon Aug 24, 2009 4:29 pm

charlese wrote:It's an adjustment. You have to move the pin just a very small amount (a tap) away from the cutting bit. If it gets too tight - tap it back toward the bit.

The grooves are set by the diameter of your bit. The fingers are set by the pin's distance from the cutter. Fingers can be adjusted to fit any size of cutter.

Chuck,

I think what you are describing would work with a normal box joint jig but I don't think it works with the Jointech. On the Jointech there is no pin to adjust. It works like the Incra system where you use a template and move the fence to fixed points to create the joints. It does not reference off of the previous cut.

I think curiousgeorge has it right and I may need to get bits specifically designed for either the Jointech or Incra system.

tdubnik · Post by **tdubnik** » Mon Aug 24, 2009 5:38 pm

charlese wrote:It's an adjustment. You have to move the pin just a very small amount (a tap) away from the cutting bit. If it gets too tight - tap it back toward the bit.

The grooves are set by the diameter of your bit. The fingers are set by the pin's distance from the cutter. Fingers can be adjusted to fit any size of cutter.

Chuck,

I've been thinking about your comment and how it applies to the Jointech. It seems to me that if I can figure out how much my bit is off I can create my own template that matches my bit. The Jointech has a micro adjustment so I can move the fence a precise amount. I'll have to think about this a little more but I may give it a try in the next couple of weeks.

Thanks!!!

dusty · Post by **dusty** » Mon Aug 24, 2009 6:36 pm

tdubnik wrote:Chuck,

I've been thinking about your comment and how it applies to the Jointech. It seems to me that if I can figure out how much my bit is off I can create my own template that matches my bit. The Jointech has a micro adjustment so I can move the fence a precise amount. I'll have to think about this a little more but I may give it a try in the next couple of weeks.

Thanks!!!

This may seem obvious but then maybe not!

The bit that you use must be matched "exactly" by the spacing between cuts. Is the bit exactly .250"; I doubt it..

charlese · Post by **charlese** » Mon Aug 24, 2009 8:40 pm

Yes! The diameter of the bit shouldn't matter one little iota! Like Dusty said, the width of the cutter and the distance to the pin/fence must be exactly equal. I suppose the systems that will make set-ups to the nearest thousandths of an inch should be adjustable to turn another thousandth.

The box last box joints I made were done using not measurements - just a ¼" brass block. I'm not even sure my wobble dado blade was dead on to ¼". It was just a matter of adjusting the pin by tapping on the side of the jig. When originally set up it would make wonderful box joints for about 6". Any longer than that the pins would no longer match. A side tap was all I needed to get a box joint 13" long. That tap probably moved the jig .0005" (half of a thousandth).

If you can adjust your jig to that amount - you are probably home free!

Note: all measurements using one of those Incra or Jointech devices depend greatly on the basic set-up from the saw blade or router center.

tdubnik · Post by **tdubnik** » Tue Aug 25, 2009 5:33 am

The Jointech and Incra type systems are a little different than a normal box joint jig in that none of the cuts reference previous cuts. The initial setup determines where the first pins or tails are cut but the bit determines the fit. Errors in the fit are NOT cumulative and do not get worse just because you are making a wider joint. A setup that is off by .005 on the first kerf will still be off by .005 on the last one.

The Jointech locks to a lead screw and has a .001 fine adjustment. The joint is made by unlocking the fence and sliding it over to the next position on the template, locking it down and making the cut. The positions on the template are precise and do not change. For the 1/4" box joint I am trying to make, the spacing is 1/2" for both the pins and tails. In other words each movement of the fence is 1/2" and the starting position determines whether you are making pins or tails.

In my case it seems that the kerfs are about .005 too wide for the pins making for a loose fit.

My thoughts for correcting it go something like this:

The Jointech has slots for 3 templates on top. The box joint only uses 1 template and slot. I plan to have the box joint template in one slot and putting a blank template in another slot. I would then go to the first position on the box joint template and use the micro adjust to move the fence .005 to make the pin .005 wider. I would make a mark using the Jointech cursor on the blank template at this position. I would then go to the next mark on the normal template and repeat the process until I have all of the appropriate marks on the blank template. If this works I should have a new template that matches my bit. What I haven't figured out yet is whether the micro adjustments will have to be cumulative or not; i.e., the first adjustment is .005, the next one is .010 etc. A couple of test cuts should determine this pretty easily.

dusty · Post by **dusty** » Tue Aug 25, 2009 7:22 am

It is not suppose to be this difficult!

The templates (I have an Incra but I think this is true of the Jointech as well) are based on precise measurements and should not need tweaking. Incra accuracy is advertised to be 1/32". If I move the fence correctly, I am able to move the tails or pins in 1/32" increments. This is plenty accurate for good fitting box joints. Positioning depends on my ability to move the fence per the instructions.

That all having been said, if my bit (or blade) is not accurately dimensioned, I cannot cut pins and tails that fit together.

What you describe should work but only if you make a very accurate replacement template. Would it not be a lot easier to obtain a router bit that is .250".

Bottom line: "Pin width" must equal "tail separation". Kinda close does not count.

tdubnik · Post by **tdubnik** » Tue Aug 25, 2009 8:01 am

dusty wrote:It is not suppose to be this difficult!

The templates (I have an Incra but I think this is true of the Jointech as well) are based on precise measurements and should not need tweaking. Incra accuracy is advertised to be 1/32". If I move the fence correctly, I am able to move the tails or pins in 1/32" increments. This is plenty accurate for good fitting box joints. Positioning depends on my ability to move the fence per the instructions.

That all having been said, if my bit (or blade) is not accurately dimensioned, I cannot cut pins and tails that fit together.

What you describe should work but only if you make a very accurate replacement template. Would it not be a lot easier to obtain a router bit that is .250".

Bottom line: "Pin width" must equal "tail separation". Kinda close does not count.

dusty,

Maybe I'm expecting too much. The joints actually LOOK good but there seems to be no friction when I put them together. When I build joints through other means I always strive for a friction fit without having to bang them together.

Jointech works like the Incra and moves in 1/32" increments and also has a micro adjust that moves in .001" increments between the 1/32" positions. It would certainly be easier to get a bit that measures .250" but how would I know that until I buy one and try it? The bit I'm using now is a Freud 1/4" spiral upcut bit but it doesn't actually measure exactly .250. The nearest woodworking store to me is 60 miles away so I do most of my buying online. This prevents me from measuring a bit before I buy it.

There's also the challenge aspect. If I can successfully create this template I may be able to create others that would be unique to me and not everyone with a Jointech or Incra system would have. I enjoy things that make me think and that I can craft without always resorting to buying. The prime example in my case is the Kerfmaker I analyzed and built myself or the Pro Planer control box I rebuilt with the suggestions from the forum members here.