Parf/Qwas dogs dimensions? (for use in CNC)

[fritter63]

Hey all, I'm designing a vacuum hold down table for my CNC machine (which will be cut by the machine itself)
and am wanting to bore some holes similar to the MFT so I can use dogs in them for workpiece or fixture alignment square
to the machine. See attached picture. The idea is to drill some 20 mill bores around the edges and maybe in the vacuum plenum "islands" so that I can square things up anywhere.

I'd like to keep the bores down to less than 19 mm deep, but could to to 38 if need be in some areas.

I've looked around and can't find mentions of the actual recessed lengths of the Parf and Qwas dogs. Does somebody have that?

thanks.

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[Jbmccombe]

I have the tall and short Parf dogs made by Lee Valley and they are both 17.2 mm deep. Not sure about the Qwas dogs

 

[Picktool]

That is a wicked idea. We have an LDF/Trupan spoilboard vacuum top on our Multicam 3000 and could use
a setup as such. Im gonna have to try it out and see how it goes. That might work out for the 'other side'
routing. Doesnt have to be just dogs setup. Well, like they say about learnin something new.
Thanks Frit

Hey all, I'm designing a vacuum hold down table for my CNC machine (which will be cut by the machine itself)
and am wanting to bore some holes similar to the MFT so I can use dogs in them for workpiece or fixture alignment square
to the machine.

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[bertv]

If your bores have no 'air escape' in the form of a through-hole, getting dogs in is very hard — they’ll bounce out because of the air pressure build up.

 

[fritter63]

If your bores have no 'air escape' in the form of a through-hole, getting dogs in is very hard — they’ll bounce out because of the air pressure build up.

Or would they just fart?  [eek]

Important safety note, Igon!

Might have drill a breather hole through the bottom, I think I can do that without hitting anything vital.

For that matter, why not just drill a passage through the middle of the parf dog?

 

[fritter63]

Got the parf dogs today. Turns out there is already a (threaded) hole in the center, so no air pressure problems.

The small diameter measures 19.87 mm, so I cut a series of test holes at 19.9, 19.95, and 20 mm in diameter.

I found that the smallest at 19.9 provides a good fit. Still a little room, but the 20 mm was just two sloppy, would have
to make sure they were pushed to one side to make it repeatable. So I'll go with the 19.9 x 17.5 mm holes.

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