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if sanding th eslots is what you want to do, i'd employ that technique using the incra miter slider bars as the sandpaper carrier. that way, you can start out as snug as possible and gradually tighten the miter slider bars with their adjustable feature until they slide uniformly within the slot. i had a similar issue. i didn't bother sanding anything. i got a second miter slider and, with two of them steadying the sled, there was no slop whatsoever when i employed this technique to construct the sled.:

https://www.ridgidforum.com/forum/t13945/

absolutely 90° to the blade:
 

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I just don't see a way around removing material, since I can't add material to the middle of the slots! With either 1 or 2 runners, if either slot is too tight to travel in once place but not another, and they're adjusted to be able to travel the entire distance in the slots without binding, some slop is inevitable. If I understand it correctly, Niki's sled idea was basically to have the runners hugging the sides of the miter slots closest to the blade. If we knew that the biding was being caused by excess material on the sides of the slots furthest from the blade, Niki's solution might work. The fact is I don't know where the excess material is, I just know that there's some there, on both slots, and in roughly the same places. I will probably have to use the Incra sliders because the Craftsman bar behaved slightly bent and twisted when I laid it on the table surface.

At first, I didn't want to use the Incras because I didn't want to get them dirty(4 bars were $100, I wanted to keep 'em spiffy). Now, I don't want to use the Incaras because they aren't the same width on the bottom as they are on the top. They're 19.08mm wide on the tops, 19.11 - 19.15 on the bottoms. Doesn't sound like much, but it's enough to keep the sliders from coming out of the table saw at any point other than the front or end of the saw when adjusted for perfect fit. I certainly don't want to reinforce that into the actual table surface. I'm leaning toward just returning all of them since that's not a problem I anticipated when I bought them. Looks like Kreg bars might be the way to go.



I was hoping that the length of whatever bar I use that's sliding in the "good" areas of the slot would lend straightness to the material removal process in the bad areas. Kinda like a jointer, a long enough bar in the back would ensure a straight slot up front.



Have you watched this video? http://youtu.be/UbG-n--LFgQ?t=21m
yes, i've watched that video about the 5 cut method and decided niki's method was easier and less pretentious. you should know that the incra miter sliders do come out of my miter slots easily ANYWHERE along the miter slots they ride in. your comment about not using them because the bottoms of the sliders are wider than the top of the sliders thus preventing easy removal from the slots does not bear out in my application. like you, the miter slots in my CC dedicated TS vary slightly in width along their length. that's why i think niki used two runners. any variation in slot width is compensated for by the two runners and how they are applied to the sled.

i would humbly suggest rethinking the kreg miter bars. they adjust only at specific points along their length with set screws that are side mounted. this can, according to wood magazine when they last tested miter bars, make their adjustment for a snug fit tedious. incra miter sliders exert pressure from "within" the miter bar along a portion of the length of the slider. i found them easy to install and adjust, especially with their top mounted adjustability.
 

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Yeah, I don't think I can expect to get 24 holes so precisely drilled in the center of the pre-drilled holes in the jig bar that the position of the miter bar isn't going to shift when the screw head is pulled into the wedge-shaped hole. IF The countersink in the jig bar and hole in the sled base were drilled at the same time by the same bit, it wouldn't be a problem. But getting them to line up after the fact seems impossible.

what about getting a brad point drill bit that's the same size as the through hole in the kreg fixture bar and use it to mark the pilot hole for the sled attachment screws?




A flat area and a flat bottomed screw is the only way I can see to keep the screw action limited to just bringing the two pieces together and not shifting them.

in principle, you're right. what you're describing is how the incra bars work.
or how about using a machine screw with a tapered head that matches the countersink of the miter bars? drill a flat recessed hole to receive the nut in the bed of the sled, with a slightly oversized through hole for the machine screw? that way, there's no need to drill the miter bar, and the oversized hole will allow for some wiggle room to facilitate any alignment issues. this could work pretty easily in 3/4" material since most nuts that small are less than 3/8" thick.

BTW, what do the instructions that come with the kreg bars say about the problem you're anticipating?
 
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