My workbench top is 35 mm thick and I have always liked the concept of using those metal holdfasts that you can whack into holding something down. Does anyone know if there is a minimum thickness that these things need? I am contemplating adding a layer of particleboard to my top to make it a bit more robust in case the 35 mm is not sufficient.

From memory about 50mm is a minimum.

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Jim Carroll
One Good Turn Deserves Another. http://www.cws.au.com Vicmarc, Robert Sorby, Woodcut, Tormek
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I use the Law of Gravity. Bench is 8' long and 2" x 6" (nominal) thick. Not even attached to the frame and it has not floated away yet. Cracks sealed with bathtub silicone. Made entirely of SPF = spruce/pine/fir (we don't care what it is).

Tie-downs? I drill 12mm/1/2" holes where ever needed. Big eye bolt goes in there. Big strap with a stirrup for me to step into.

I'm carving as much as 1/2 logs, 90cm long x 45cm diameter. . . and a lot of smaller pieces. The pad is an old cotton blanket folded up with nonskid foam rubber sheet on top.
I can bash along with a 30oz mallet and a 9/15 Pfeil gouge and nothing jumps around.

I know this doesn't sound very elegant but my bench is a dream and as a means to an end (the carvings), ideal.

Try it as is
If the top is not thick enough, you could glue a collar to the underside where the hold fast is located.
The collar can be a square block that you drill out after the glue has set.

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regards from Sydney

ian

If Tiger is thinking the same way as me, he doesn't want to spend a pile of cash on holdfasts only to find they don't hold fast.

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Cheers, Richard

"... work to a standard rather than a deadline ..." Ticky, forum member.

Thanks guys, you're right Rhancock I already have enough tools that don't work as they should.

Tiger
Lee Valley imply that their holdfasts only need 1-1/2in of thickness to hold
Tools for working wood say the Gramercy hold fasts need a minimum of 1-3/4in

Also, while your bench might have numerous dog holes, you would typically only use a hold fast in two or three positions on the bench -- and those holes would typically not align with your dog holes.

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regards from Sydney

ian

Thanks Ian, my bench is about 1 1/4 inches so I now need to think about whether I glue up some particleboard or leave it as is, dilemma is though that at 1 1/4 it's just right for planing, to make it thicker I might have to make a new base which I don't really want to do.

I'd add the extra thickness to the underside -- but only where you want to use at holdfast
Benches I've seen with holdfasts, typically have one or two holdfast hole located well back from the front edge of the bench. Thickening two or three spots on the underside shouldn't be too difficult.
BUT if your bench top is made of particle board, it might be too brittle to support a holdfast.

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regards from Sydney

ian

I'm lucky enough to have a Lee Valley catalogue in front of me (for light reading)
Alternative bench dogs for benches around the thickness of yours are
Item 16F02.20 vise clamp
05G19.01 surface clamp
16F02.10 hold down clamp
03A02.73 hold-down -- designed for a 1" thick Sjoberg cabinetmakers workbench


The lee valley web site has a jump to item feature

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regards from Sydney

ian

I work with Particle Board on a daily basis and suggest that you look to real timber for hold fast anchors. Holdfasts work by generating side forces in the wall of the fixing hole. Particle Board will start to crush and expand the hole diameter within a few cycles of locking and unlocking the holdfast, and before long will not anchor in the hole.

I hope that the bench top is solid timber, as I doubt that a man made product will last long supporting holdfasts (or dogs). If it is solid timber, and you need more depth to lock the holdfasts, I would go the way of screwing and glueing blocks beneath the benchtop at the appropriate locations, then drilling them through from the top when the glue is cured, as suggested by Ian.

Thanks Ian and Malb for your thoughts. Fine Woodworking suggest using layers of MDF in one of their bench projects and they encourage using holdfasts in those so I thought particleboard might be ok. The bench is solid wood but I only made it 34 mm thick. I'll see how it goes with that thickness and assess down the track whether I need to make it thicker, I can live without a holdfast for a little while....