20mm Bench dogs and 20mm hole sizes??

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Stevebod

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Hi all, recently put some holes in my workbench using a 20mm Forstener bit. I then ordered some 20mm bench dogs and clamps of Amazon. They are really good quality set with 4 dogs and 2 clamps for £22. However they arrived to day and are a little too tight to fit the holes. Now obviously a 20mm diameter bung will not fit into a 20mm hole, so I am just wondering which item should actually be 20mm the hole or the bung?
ie not sure whether to enlarge the holes or reduce the studs! (At some point in the future I want to buy an off the shelf MFT worktop, so I want the dogs to fit that at some point)...
 
Above my paygrade really, but I'd measure the dogs to see if they are 20mm Ø

Edit: ........as the MFT uses a 20mmØ hole, I believe, so benchdogs will probably be a tad smaller than that.
 
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I had assumed the holes should be 20mm, so the dogs need to be slightly smaller, but the dogs I got of Amazon measure 20mm....shame really as otherwise they are really good given the price......

..https://www.amazon.co.uk/dp/B0BM3YQXKD?ref=ppx_yo2ov_dt_b_product_details&th=1
 
I think I will try and find a way to "ream out" the holes first as it's only a gash bit of old kitchen worktop I am using.
Although I have also tried the dogs in my old, (very) Workmate and they wouldn't fit in those either!?
 
They'll loosen up very quickly with use. But better too tight than too loose.
I've got random holes in my bench but I put a bolt through them with a wing-nut on the bottom end, to hold down various bits n bobs. So size doesn't matter too much.
PS forgot to say the obvious - make some dogs with a few hardwood scraps, slightly tapered so they'll always be a firm fit?
 
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I bought the combined reamer/chamfer.

Most of the parf system dogs have a little collar that sits nicely into the chamfer but also having a sharp edge to the holes can get damaged so it protects them too.
https://www.axminstertools.com/ujk-...7868?queryID=71c9e8178414b615fcd2f62f097d05a0
It is twice the price of the standard reamer, but allows parf system dogs to be used.

" make some dogs with a few hardwood scraps, slightly tapered so they'll always be a firm fit "
Kind of defeats the purpose Jacob. Its all designed to be precise, and hand made tapered wooden plugs are never going to achieve that.
 
In my experience, Forstner bits all seem to cut slightly (~0.3mm) undersize. In this case, I’d take the advice to ream the holes either with one of the UJK reamers, or with a standard 20mm reamer.
 
I wonder if others have observed that (some) Forstner bits cut measurably undersize. I have 2 definite instances - a 14mm Axcaliber bit that cuts 13.6mm diam, and a newly-purchased Bosch 24mm bit (which I think is probably made by Fisch) that measures 23.6mm.

Neither bit has been re-sharpened.

I’m off to spend a happy afternoon measuring Forstner bits - you have to find your fun where you can :), but I’d be interested in others’ experience.

Thanks
Geoff

See this (very old) thread
 
I did some measuring for you…,
UJK dog = 20.0mm
Dog holes = 20.2mm
Dog hole cutter (from UJK PARF kit) = 20.0mm
 

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And for completeness….

Axminster 20mm forstner bit =20.0mm
 

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Hi all, recently put some holes in my workbench using a 20mm Forstener bit. I then ordered some 20mm bench dogs and clamps of Amazon. They are really good quality set with 4 dogs and 2 clamps for £22. However they arrived to day and are a little too tight to fit the holes. Now obviously a 20mm diameter bung will not fit into a 20mm hole, so I am just wondering which item should actually be 20mm the hole or the bung?
ie not sure whether to enlarge the holes or reduce the studs! (At some point in the future I want to buy an off the shelf MFT worktop, so I want the dogs to fit that at some point)...
Grab a few workmate stops, they are very cheap and work perfectly in correctly sized 20mm holes, personally I use a Festool router bit
 
Your holes should be bang on 20mm dia.
For a really good fit, the dog should be 19.97mm but you may be happy with 19.95mm.
You did ask ...
Exactly.

This information is also published on the benchdogs website and Festool use a 20mm hole too.

Not that I'm considering diving into such an expensive world, that is.

Although it does look nice and shiny and I can see the attraction of it all.
 
If you know any friendly woodworkers maybe ask them to make you some dogs out of wood?
I believe wood was the preferred material back in the dark ages.
Given a slight taper they will self adjust to fit varied hole sizes tightly and hence are inherently a precise fit.
Hope that helps.
 
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An option may be to get a couple of the veritas stainless steel bench dogs (pups?).
About the cheapest in their range I chose to return them because they measured 19.92mm and that is a waay sloppy fit in a 20mm hole.
 
An option may be to get a couple of the veritas stainless steel bench dogs (pups?).
About the cheapest in their range I chose to return them because they measured 19.92mm and that is a waay sloppy fit in a 20mm hole.
Why don't they make the metal ones with a slight taper?
 
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