help understanding these blade guard directions

[Ryan Brucks]

Hey guys,

I am making a version of this over-arm blade guard designed by Gordon Sampson. http://www.woodcentral.com/bparticles/overarm_guard3.shtml

I have the guard itself fully made and assembled. I changed dimensions radically. Mine is 20" long instead of 11", and the sides slope to only 1.5" wide at the bottom (to maintain surface area, since my guard is huge. gives a higher air velocity and thus higher escape velocity for chips and dust). Just working on the aluminum support system now.

The only thing I am confused about it how the T-knobs and bolts are working to keep the thing at the height you set. I don't understand how with this design you can tighten the T-knobs without the bolts just turning with the T-knob? I was thinking maybe they should be carriage bolts in square holes, but there's no mention of that in these directions, so maybe I am missing something? I hope using a wrench every time isn't part of the plan.

can anybody think of how to keep the bolt stationary while tightening the T-knob in that design?

Thanks
Ryan

[Ryan Wood]

I would use carriage bolts and just pound them in a little so the square part holds in the wood. Thats what i did when i made some cauls.

[michael osadchuk]

Hey guys,

I am making a version of this over-arm blade guard designed by Gordon Sampson. http://www.woodcentral.com/bparticles/overarm_guard3.shtml

I have the guard itself fully made and assembled. I changed dimensions radically. Mine is 20" long instead of 11", and the sides slope to only 1.5" wide at the bottom (to maintain surface area, since my guard is huge. gives a higher air velocity and thus higher escape velocity for chips and dust). Just working on the aluminum support system now.

The only thing I am confused about it how the T-knobs and bolts are working to keep the thing at the height you set. I don't understand how with this design you can tighten the T-knobs without the bolts just turning with the T-knob? I was thinking maybe they should be carriage bolts in square holes, but there's no mention of that in these directions, so maybe I am missing something? I hope using a wrench every time isn't part of the plan.

can anybody think of how to keep the bolt stationary while tightening the T-knob in that design?

Thanks
Ryan

I can't visualize the guard completely but my understanding is that two aluminum parts are connected with "bolt - washer - T knobs" with the T knob acting as a nut.

I would experiment with using a bit of adhesive (even a lock washer under the head), using the minimum necessary for the head of the bolt not to turn when you turn the T knob, just so that I could dismantle the parts later if required for fine-tuning, etc.

good luck

michael

[Greg Urwiller]

I built that exact overarm last winter for my General. I was worried about the same thing. But, I've found that tightening the T-knob till the bolt slips, even pushing on the bolt with my thumb, gives me just enough pressure that I can move the guard up or down to fit the thickness of the wood (without loosening the T-knob) but still holds the guard up in that position without it dropping down on it's own. That said, if you've increased the size of the guard that much, you're going to have a lot more weight in comparison to the original plan. Because of that I'd file out the tubing for a square hole and use a carriage bolt. Won't take long on the aluminum. Greg

[Ryan Brucks]

Thanks guys. Greg, you read my mind about the issue of weight and hand tightening. My guard is probably around 1.5x the weight of the "stock" one, since mine tapers and isn't as tall but is much longer. For me it needed to fit a large riving knife as well as cover a scoring blade, hence the 20" long figure.

Picked up some carriage bolts tonight and will be easy enough to make squarish holes in aluminum. Will post a pic later.