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Workbench Guide
20mm vs. 3/4" Dog Holes
3/4" is 19.05mm, so the two sizes are less than a millimeter apart. They still aren't interchangeable. 20mm is the standard for MFT-style tables and track saw work. 3/4" is common on traditional benches. Pick the size that matches the accessories you plan to use.
20mm = 0.787"3/4" = 19.05mmDifference: 0.95mm
Last updated
DRAWN TO SCALE
Close on Paper, Different in the Hole.
The gap is about 1/32". That's enough for a 20mm pin to not fit a 3/4" hole, and for a 3/4" pin to rattle in a 20mm one.
WHAT FITS WHAT
Mixing Sizes, Case by Case.
What happens when an accessory meets a hole it wasn't made for.
20mm accessory in a 20mm hole
Designed fit
The accessory registers the way it's meant to.
3/4" accessory in a 3/4" hole
Designed fit
The accessory registers the way it's meant to.
3/4" accessory in a 20mm hole
Fits with play
It drops in, but about 0.95mm of play means it can shift.
20mm accessory in a 3/4" hole
Won't fit
The pin is larger than the hole unless the hole is enlarged.
SIDE BY SIDE
20mm vs. 3/4" at a Glance.
| Factor | 20mm Dog Holes | 3/4" Dog Holes |
|---|---|---|
| Diameter | 20mm (0.787") | 3/4" (19.05mm) |
| Where it's common | MFT-style tables and track saw workflows | Traditional woodworking benches, especially in the US |
| Typical grid | 20mm holes on 96mm centers is the common MFT-style layout | Varies by bench |
| Typical accessories | Bench dogs, rail dogs, MFT-style clamps, fences, stops, and parallel guides | Bench dogs, holdfasts, and planing stops made for 3/4" holes |
| Guide rail work | Built around it. Rail dogs and stops register guide rails in 20mm holes. | Possible, with accessories made for 3/4" holes |
| Drilling | 20mm Forstner bit, drilling guide, or CNC | 3/4" Forstner or auger bit |
| Using the other size | 3/4" accessories fit with about 0.95mm of play | 20mm accessories won't fit without enlarging the hole |
WHAT WE USE
Our Benches Use 20mm Holes.
The Dash-Board and ShortCut tops use a 20mm dog-hole grid, so they work with our accessories and the wide range of 20mm accessories made for MFT-style tables.
- Bench Dogs in three heights
- SpiRail Dogs for guide rail registration
- Parallel Guides and fences with Fence Blocks
- Clamp tracks on both sides for brackets and stops
QUESTIONS
Dog Hole Size FAQs.
Not sure what fits your bench? Rob answers questions directly at (303) 376-5703.
Is 3/4" the same as 20mm?
No. 3/4" is 19.05mm, so a 20mm hole is 0.95mm larger, about 1/32". That's small on a ruler but big enough that accessories aren't interchangeable.
Can I use 3/4" bench dogs in 20mm holes?
They'll drop in, but with about 0.95mm of play. For rough holding that may be fine. For anything that sets a reference, like squaring a guide rail or a fence, the play can show up in your cut.
Can I use 20mm bench dogs in 3/4" holes?
No. A 20mm pin is larger than a 3/4" hole. You'd need to enlarge the holes to 20mm first.
Which dog hole size is better for a track saw table?
20mm. It's the standard for MFT-style tables, and most rail dogs, stops, and guide rail accessories are made for 20mm holes.
Can I convert 3/4" dog holes to 20mm?
Yes, by enlarging them with a 20mm bit. Use a drilling guide so each hole stays centered and square to the top, since off-center holes throw off anything that registers on them.
What spacing do 20mm dog holes use?
The common MFT-style layout is 20mm holes on 96mm centers. Matching it keeps your top compatible with the widest range of accessories.
Do holdfasts work in 20mm holes?
It depends on the holdfast. Holdfasts grip by wedging in the hole, so fit depends on the hole diameter and the thickness of the top. Check the maker's specs before you buy.
What size dog holes does the Dash-Board use?
20mm. Our Bench Dogs, SpiRail Dogs, Parallel Guides, and fences with Fence Blocks are all made for 20mm holes.
There's a Better Way to Work.
Built around 20mm, ready for your track saw. Talk to Rob, the inventor, directly.
Resources & Help
Questions?
Questions about our products? View our extensive resources and educational videos or reach out to us Monday-Friday.
Contact Us