# 20mm or 3/4" dog holes custom CNC worktop



## Jordan123 (Feb 13, 2018)

Im having a workbench top custom CNC'd for me at my local shop.

I'm having trouble with two things.

1. Determining what size dog holes I should use. I know festool uses the 20mm but more companies and products can be used with a 3/4" dog hole.

2. What material should I use? I know most people are using MDF for this. But I could use 3/4" ply also

Thanks


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## BubbaIBA (Nov 23, 2011)

Jordan123,

I'm trying to envision the need for a CNC'd workbench slab, please explain.

Unless there is a Festool appliance you can not live and work without go for the 3/4".

ken


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## Jordan123 (Feb 13, 2018)

Well I can CNC a 4×8' sheet of MDF/plywood for $150, rather than the cost of the MFT which is $700 and is much smaller.

See attached image for MFT home workbench


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## BubbaIBA (Nov 23, 2011)

Thanks Jordan123,

I was trying to envision a hand tool workbench with a MDF top and CNC dog holes, not that there are not some hand tool workbenches with MDF slabs. A table with 200 dog holes is a different story. Sounds like you want to use Festool accessories, if so I would go with the 20mm holes.

ken


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## therealSteveN (Oct 29, 2016)

> I know festool uses the 20mm but more companies and products can be used with a 3/4" dog hole.
> 
> 2. What material should I use? I know most people are using MDF for this. But I could use 3/4" ply also
> 
> ...


Kinda answered your own question there. So many more 3/4" items you can use in a dog hole, and the thing is 99% of them are cheaper than the cheapest green variant. Many offering more utility.

I think that really does depend on how much green Kool Aid you've drank before purchasing, some folks have green lips.

MDF is fine, it's biggest faults are cannot get wet, at least if it's not waterproofed hint, hint. It also really does need to be well supported. Snapping in half is possible if too much weight, and not enough support occur.

Playing with the Sagulator can help figure loads They show Birch, but only Fir in plywood, so you have to fudge a little. But know BB ply is the best in real use. Put in realistic figures, so if you plan on a 3/4" top, 48" x 36" plug that in. It will give you real figures, and it also will say acceptable, or NOT. Cool tool for figuring loads of shelves, worktops, etc etc.

MDF and fir ply are both way at the bottom, so scroll down.


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## OleGrump (Jun 16, 2017)

Go with the 3/4 holes. I wanted to add some additional holes to my Workmate 400. the existing holes were 20mm. What a pain in the ass. (Millimeters are for firearms, not he workshop!) Wound up having to bore the new holes with a 13/16 brace bit, which is slightly larger than the damned 20mm, but the B&D dogs worked fine in them.
Point being, unless you already own a 20mm bit, you're FAR better off with the 3/4 holes.


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