Anyone ever done this? Comments/Suggestions?


I've Googled the group (not exhaustively however) and can't find any reference to the use of these 'casters' to replace miter slot bars and was wondering if anyone has ever done this before. Also would like suggestions for other WW applications (besides work infeed/outfeed support) for these casters and/or comments or criticisms of my idea for utilizing them.
Recently came into a bunch (as in lots and lots) of 'ball casters' or 'ball transfers' or as Woodcraft calls them 'ball bearing work rollers'. They had obvious WW applications for large/long work support. . Woodcraft sells a flange model but these are stud mounted with a threaded bolt out the back. Various styles are available at McMaster Carr. In the process of utilizing some as an outfeed support, I noticed that they set into and rolled nicely in the miter slots of the TS. The photos here http://photobucket.com/albums/v697/mike72903 show a simple sled that uses four of the rollers as guides in the slots instead of miter bars. A box joint jig I designed to utilize the sled is installed on the sled front. The sled is remarkably stable as long as some downward pressure is applied while pushing straight forward. There is absolutely no detectable side to side slop and absolutely zero binding along the length of the slots. It glides along with no effort even with heavy pressure. The rollers on one side were mounted in slots so they would align perfectly with the slot before final tightening. A couple of already noted disadvantages are: If you push with a twisting, non-centered or sideways motion without applying enough downward pressure it can come out of the slots. Also, you lose about an inch of cutting height because the base of the sled rides above the table top. That wasn't an issue with the box joint jig because it mounts vertically on the front and could be lowered or raised to wherever it's wanted. Next I'm going to make a dual slot cutoff sled using these rollers. Probably two rows of three or four rollers spaced so the sled will remain stable if either sled edge runs past the TS edge. I'll see how that works. And Yes, the finger joint jig is using metal for the spacer finger. If anyone is interested I'll be happy to pass along my solution for the "ultimate box joint jig".
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Mike in Arkansas wrote:

Well there's one I haven't seen before. :-)
Sounds like it works great, but since those are metal casters on what is now effectively a cast iron "runway", I'd check every now and then to make certain they aren't peening the corners of the miter slots out of shape. I think it might deform the corner slightly, which would create a slight bump at the top of the table and inside the slot.
I don't know if this would be a problem or not. The more weight on the casters, and the more use, the more it would be a factor. Since you're pioneering you might want to keep an eye on it.
Dan
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Hi Dan, thanks for the suggestion. I'll watch for it. Before using the sled, I took a file and went down the corner top of each side of both slots. Just three or four passes at 45 degrees or so to slightly bevel and smooth out any dings. Bevels are barely visible but I think give a better and broader surface for the casters to ride on. Mike
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wrote:

that riding on the corner is a no-go for me. the miter slots have 2 machined index surfaces each- the sides of the slot, perpendicular to the top, parallel to the blade. they have enough area to provide accuracy for a reasonable lifetime of the machine. now you've gone and created another index surface, none to accurately, with a lot less area, and you're riding it with a curved follower to boot.
consider this: what happens when that surface gets a ding in it?
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Not exactly sure I follow your logic about creating an index surface. I only touched the slot corners with the file lightly. More just to make sure there were not any dings or blemishes to effect the caster movement than to create a bevel. I can't imagine a moderately used sled ever causing any noticable wear particularily since there is no friction. The caster rolls over the top of the slots, it doesn't slide. Seems counter-intuative to me they would cause more wear than a tightly fitting metal bar. Perhaps I just dont understand what your referring to. Mike
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I bet it rolls just perfectly. How much force will it take to knock the sled off sideways? Like in a jammed situation? Is it safe?
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It does rolls perfectly. As far as knocking the sled sideways, well I'm not sure. It does have the two handles to hold it with and as long as it were held firmly the worse that would happen would be to ruin your work piece. Having said that, surely it would be more likely to get knocked out of the slots more than miter bars would. Interesting. Maybe small blocks on front and back of each edge that would extend down into the slot but not touch it. That way if something happened to dislodge the bearings, then the amount of movement would be very limited. As far as general safety, I don't see it's any worse than the normal risk associated with working with power tools. If you use the handles, then certainly your hands are out of the way of the blade. When I was using it to cut box joints, I was holding the wood to the face with one hand and the other hand was pushing the sled forward centered on the sled. That put my hand directly in the path of the blade, but since the sled passes well over the blade I didn't see a problem. However, a high enough blade would cut into or through the sled base and you wouldn't want your hand or what then remained of it where I was placing it. Guess it's a matter of being careful and applying some common sense just like any potentially dangerous situation.
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Probably a lot less force than needed for something that uses the T bolt in the T slot technique that is gaining popularity.
.

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