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Discussion Starter · #1 ·
I know that this subject has pretty much been beaten to death but what I going to suggest has not quite been pin pointed.

First of all, repeating the issue of the accuracy that is affored by the fence positioner is of not all that important.

We probably all realize that if several cuts were made from the same material that the width of the cuts will vary by several thousandths which unsecores the fact that you cannot cut wood to an exact dimention of .001" over and ver again.

But since you can set the fence itself to within .002" of a previous setting, you can reset the fence to make cuts that with the same tolerances as you got in previous cuts. I suppose that when you think about, any change in temperature and humidity will nagate thais concept. Certainly cutting materal of a different species can also effect the ability to repeat a cut. However, as we all agree, the difference would be of no particular importance.

I asked Mark Mueller about this and he pointed out that it takes a little practice but with some care and practice that he can keep his tolerance within about .004", again so what? I agree that such accuracy is not really that important, but I sure do like to have the potential.

Now when it come to cutting dovetails. I found that my dovetail bit is not quite able to make the cuts wide enough to allow the fit of the pins and tails to be makde with out having to use a mallet with more force that I would like. So what I can with the LS arrangement is this. After making a cut I move the fence forward .005" and run the bit through the cut one more time. Next, I move the fence rearward .010" and cut another time. Next, I move the fence forward .005" which is back to the original position. By doing the fit of the pins and tails during assembly is nice ans snug without having to use the mallet. This is where the LS concepts shines for me. On the other hand if one were fortuanate enough to find a bit that would make the cuts the correct width without doing what I have described above unnecessary.

Since I have never used any other dovetail jig, I have to wonder if the issue of the fits exist or not. I would think that if the bit used is not quite wide enough that the problem would still be an issue. I'd like hear from anybody if thay have any thoughts on the issue.

Jerry
 

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Jerry, you are over thinking this and making it harder than necessary. You just want to increase your dovetail cuts by a few thousandths. These can all be from either side of the first dovetail cuts. You don't need to remove a little off each side. Take it all off one side in just one additional pass, avoiding the time needed to make a third pass.

With your system, once you have determined the increased size necessary for your dovetail cuts, why not just do it in two passes If you need .005" or .010"more clearance, just offset your jig by .005" or .010" and repeat the cuts a second time. You will remove the .005" or .010" from just one side of each dovetail cut, making the position of your total joint slightly off from it's intended position, but with all of the joint offset by that amount it won't matter. The joint will still fit together, saving you from needing to make the third pass.

I have a Jointech system, which is much like the Incra. On this jig, I make a second pass after adding a few thousandths to the position and it opens up all of the dovetails by this amount. This works fine with the Jointech, so it should work fine with the Incra as well.

Charley
 

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With an Incra system, you adjust the fit of dovetail joints by adjusting the height of the bit.

With through dovetails, you make a pass on the edge of two boards, space the fence a certain amount, take a second cut, and then test the fit, if it's too loose or too tight, then you need to raise or lower the bit. To really blow your mind, the distance BETWEEN the two test cuts affects the height of the bit AND THE FINAL THICKNESS OF THE WORKPIECES. You want thicker box sides, you space your test cuts differently, or use a wider dovetail bit. I can't imagine using an Incra LS Positioner without owning a thickness planner.

Test cuts determining the thickness of your board is one reason other dedicated dovetail jigs are easier to use for through dovetails, you can use any thickness board you want, not so with an Incra Positioner.


In woodworking there is always more then one way to accomplish something.
 

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Discussion Starter · #6 ·
Jerry, you are over thinking this and making it harder than necessary. You just want to increase your dovetail cuts by a few thousandths. These can all be from either side of the first dovetail cuts. You don't need to remove a little off each side. Take it all off one side in just one additional pass, avoiding the time needed to make a third pass.

With your system, once you have determined the increased size necessary for your dovetail cuts, why not just do it in two passes If you need .005" or .010"more clearance, just offset your jig by .005" or .010" and repeat the cuts a second time. You will remove the .005" or .010" from just one side of each dovetail cut, making the position of your total joint slightly off from it's intended position, but with all of the joint offset by that amount it won't matter. The joint will still fit together, saving you from needing to make the third pass.

I have a Jointech system, which is much like the Incra. On this jig, I make a second pass after adding a few thousandths to the position and it opens up all of the dovetails by this amount. This works fine with the Jointech, so it should work fine with the Incra as well.

Charley

Charley,

Thanks for the tip, makes sense to me and since you have already done it the way you have described, that's good enough for me. This is how we learn from each other and why this forum is such a great tool.

Jerry
 

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Discussion Starter · #7 ·
I remember that in the demo that they do say that to tighten or loosen the joint the adjustment has to do with raising or lowering the bit.

The first bit that I had that got with the set that came from Incra, Whitesides, I did raise and lower as per the instructions. After a lot of practice I purchased a second bit and it wat with that bit that I do the drill that I described, or so I recall, but that has been over two years ago maybe more. I have not been in the shop doing much for the past two years due to this darn health issue. The good news is that I have started to feel much better lately and will have to go cut some dovetails and try to follow the instructions and see if has been operator error or not.

Charley, do you think that Terry has spotted the problem or not, let us know.

Jerry

a
 

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I think you have to take into consideration the fact that when you raise or lower the bit to tighten or loosen the fit, you also change the length of the joint. This, of course, can have an impact on the finished fit due to the possibility of no overhang for sanding. The Incra LS/TS system is consistently precise cut after cut and dialing in the same precision for changes is simple and error free. I would not even consider another fence system for my shop.
 

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Discussion Starter · #9 ·
I think you have to take into consideration the fact that when you raise or lower the bit to tighten or loosen the fit, you also change the length of the joint. This, of course, can have an impact on the finished fit due to the possibility of no overhang for sanding. The Incra LS/TS system is consistently precise cut after cut and dialing in the same precision for changes is simple and error free. I would not even consider another fence system for my shop.

I agree with you n/a about not ever wanting another fence system. While the fence position can be set to a precise position we can't cut wood to the same precision, but we can get it close enough for government work and that's good enough for me.

Jerry
 
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