I haven’t experimented yet, but my current design (which I believe is final and will be implemented) uses three wedge shaped pieces of HDPE that are separated by 1 inch channels. This saves material and allows a means for air to the vacuum, and, since the pieces are arranged such that there is a vertical channel below the bit to allow any residual dust or chips to fall out after the vacuum is turned off.
I am also planning to use a sled made from laser cut steel or aluminum, so there’s that, but the HDPE could certainly be screwed into plywood.
remember that you are cutting away the surface under the sled, so if you have
rings with gaps between them, there is a chance of getting hung up
if you try to float the sled (air hockey style) you run into the problem that
when you cross a section you have already cut, more air escapes and the sled
drops closer to the workpiece, throwing off your depth of cut.
I am counting on the 1 inch gaps being thin enough to ride over most of the surface, and since the gaps don’t run fully across the sled, then there should be no problem with them dropping in a previous cut.
Pictures being worth 1000 words, here’s the best I can do without my personal laptop:
With the corners being rounded and the edge rounded over.
Those sled slider sections might fit well on discount or dollar store cheap cutting boards. They can be cheaper and easier to find than sheet HDPE or UHMW
Definitely. I decided to go with an amazon purchase instead. More expensive, but virgin material with a super slick surface (whereas many cutting boards have a texture.)
It also pairs well with a nice chianti, Thin soft aluminum should be easy to cut and drill, and I have had success in the past using epoxy to bond it to wood.
I just picked up a 15x20.5x.5 High Density Polyethylene for $8. I was thinking of using it to make the sled. Would it be better to split, multi piece sled (like one posted by @Keith) or simply make a 15" one?
so, three things…
one, I haven’t actually made my final sled yet, so I don’t know how well, or even if (though I am pretty confident) it will work.
two, most people have regular sleds and they seem to work great. My reasoning for making the three part HDPE sliders is really two fold: first to reduce the amount and size of HDPE I needed, and second to provide air channels for the vacuum to pull air so that it doesn’t suck the sled onto the work piece (and having the bottom channel vertical also allows for dust to fall out rather than getting packed into the central circle)
three, I am planning to use the HDPE under steel or aluminum, but the 1/2" HDPE might be rigid enough to be it’s own sled, in which case you could also route out the vacuum channels to get the benefit I am hoping for without having to make a multi part sled.
That could work really well!
Thin soft aluminum should be easy to cut and drill, and I have had success in the past using epoxy to bond it to wood.