QCW support blocks

A recent project required countersunk screws. When the countersink did its work, the table deflected so much that a small ‘low’ area remains. That can be repaired by repeating the spoilboard cutting step, but I’d like to prevent the problem. (Reducing plunge speed didn’t solve it).

My Journeyman rests on a very flat torsion box. I could put a few blocks with concave tops beneath the QCW. The hard way would be to make them from wood blocks. The easy way would be to contact one of the 3-D printing folks who make Onefinity support products. They should be able to add to their line, since this is likely to resonate with other users.

Does anyone (Onefinity Support??) know the diameter required to match the QCW tubes, and the minimum height (bottom of the arc) to properly support the middle of the QCW? Does anything like this already exist?

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Hey David,

sad to hear that the QCW frame (that I did not yet assemble) deflects.

What type of countersink did you use? Seems that it does not cut well downwards.

Do you drill the screw hole first, and then use the countersink?

Maybe countersinks made for wood that attach to a drill bit cut better, more room for chips evacuation than general purpose countersinks.

I find this intriguing… I have made the mistake of leaning on the front rail of my qcw causing it to deflect but I can’t see how a cutting bit would unless working on metals and smoking bits… I trust your experience as obviously I was not there… Just intrigued…

Is it possible to add a dwell at the bottom of the countersink? It could be that the plunge isn’t getting a a number of full revolutions at the bottom depth thus deflection or just incomplete cuts could occur.

Are you sure the bit isn’t slipping?

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Vectric has a cutting routine that does chamfers with a Vee bit, very little to no downward pressure.

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Just stick a flat piece of wood under the rail, no need for it to be concave and no need to 3D print anything. No need to over-complicate a shim.


Good question & advice.

The countersink is sharp, and was cutting acrylic. The deflection was most severe when beginning each pass, and the QCW visibly began to return as the cutter did its job. I used a “pecking” technique, with about 0.06” per pass. I didn’t pre-drill, because the countersink makes a hexagonal hole if you do that. You get a smooth round result if you drill second.

In fairness, the countersink is designed for either metal or wood.

I can shim with a board, thicknessed to fit. The only advantage to individual supports is the ease of cleaning up the debris that somehow gathers under the QCW. At present, I just blow it out with the outflow of the shop-vac. But maybe simple is better.

Oh, and as for remaining deflection: it’s very small. When I used a diamond drag to put registration lines on the acrylic piece, the portion over the center of the QCW was visibly lighter (less deep).

Hey David,

But the countersinks that attach to a drill bit would avoid that I believe. Drilling and countersinking in one step. Do you know these and these?

Also do you know countersinks that look like this:

Vibration-Resistant Through-Hole Countersinks

They are vibration-free, to use after drilling the screw hole.

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This tells me it is a spoil board surfacing issue or a material thickness issues. A diamond drag bit shouldn’t cause deflection and any permanent sag would be fixed by surfacing the spoil board.

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It didn’t. He just mentioned using the bit to “see” the deflection that had been previously caused during countersink operations mentioned above.

It’s easy to check anyway, toss a straight edge on the QCW.