Raised panel bits on MK7

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BuckeyeDennis
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Re: Raised panel bits on MK7

Post by BuckeyeDennis »

JPG wrote: Wed Jan 27, 2021 12:30 pm
adrianpglover wrote: Wed Jan 27, 2021 8:43 am . . . I see that there's a bit of a tapered profile on the slot, but wondering what the advantage of it is.

Also, how do you adjust the outfeed fence separate from the infeed fence for full profile cutters?
#1 I anxiously await the answer from Dennis. I have my opinion on why. Contact area is a part of that. Tapers is another.

#2 Shims?
The reason for the tapered fixturing-slot profile is to maximize workholding strength without increasing the depth of the fixturing slot. It allows the "clamping wings" of the sliding nut to be considerably thicker at their roots, which greatly increases their strength and stiffness. It also helps equalize the stress profile across the wooden "ledges" at the top of the fixturing slot.

The "corners" of the fixturing slot are uniformly radiused, in order to minimize stress concentrations in the wood. It's no secret that cracks like to propagate from sharp corners, as you would get with a garden-variety T-slot bit. The overall effect on system strength amazed even me. If you technical types would like to see detailed strength-testing results, cruise over to the ToolQuest downloads page and check out the application note on WoodAnchor fixturing-slot strength.

The other key design feature of the sliding nut is simply that the clamping surfaces are much larger than those of ordinary fasteners, including T-bolts and the like. Ordinary fasteners are designed to be used with metal fixture components, and thus they can have relatively small heads. But if you use them with wooden components, and apply more than a small fraction of the fastener's design load, the pressure generated by those small heads will simply crush the wood. This effect is even more pronounced in T-slot applications, because the slot opening reduces the contact area even more.
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