BuckeyeDennis wrote
Roy, I have a similiar idea for using nylon screws with the WoodAnchor sliding nuts. I plan to make a fixturing-slotted main table for a vintage DeWalt radial arm saw, so that I can easily mount special fixtures. For normal sawing purposes, I’ll mount a 1/2” MDF sacrificial top to the fixturing slots with the nylon screws and sliding nuts.
I’ve already bought a supply of 1/4”-20 flat-head nylon screws for that application, so I went down to my workshop to check the fit just now.
What I found was that the nylon screws start easily by hand, but begin to get tight after you get several threads engaged. I presume that’s because of imperfections at the screws’ mold-parting lines. They’re no problem to turn with a screwdriver, but the sharp edges of the flat screw head make it painful to do by hand. If they were socket-head screws, though, I suspect that hand-tightening them would be doable.
Dennis,
Thanks for checking, good information. In my experience with nylon bolts, I found that there were differences between two bolts out of the same bag. Some would thread nearly as easy as a steel bolt while most required a nut driver and a few needed a bit more effort. It didn't help that surfacing the bed created a very sharp starting edge to the inserts' threads, very easy to start cross threading the nylon. Like you, I suspect differences in the way they came out of their molds.
On my small bed, I used my CNC to machine the appropriate sized holes, used a tap chucked in a drill to tap the holes, and a put few drops of thin CA glue in each hole to strengthen the threads. This has worked well so far, with limited use.
I've now adopted the blue tape and CA glue hold down method for most of my work (blue painters tape strips on both the bed and material, thin lines of medium CA glue on the tape strips on one side, accelerator on the other, put the material in place and weight down for a bit and voila, amazing hold power; better than double-sided tape since the blue tape comes off both sides quite easily when you're done).
I suspect I'll mostly use your sliding nuts on my CNCs for holding positioning fixtures in place, maybe cam clamps, and occasional hold downs. Of course, I'll use them for non-CNC use as well with various jigs.
