Holdfast not holding wood down

[worker]

I bought these holdfasts from eBay some time back and have only recently started using them. Once I hit holdfast with a mallet, I can't release it or get it to budge at all. Workbench is 40mm thick.

But the problem is the wood it's supposed to hold down can move around with a small amount of force, just pushing straight across is enough to make it move.

I tried the same on an offcut of the bench top and it also had the same problem. So it seems the holdfast is the problem and not the bench/workpiece.

Any idea how to make it grip more securely? I tried adding some scrap leather under the wood, under the holdfast head, etc, and it didn't help.

It took me a few months to finish the workbench and now it's done, I have this very annoying problem!

 

[tibi]

I bought these holdfasts from eBay some time back and have only recently started using them. Once I hit holdfast with a mallet, I can't release it or get it to budge at all. Workbench is 40mm thick.

But the problem is the wood it's supposed to hold down can move around with a small amount of force, just pushing straight across is enough to make it move.

I tried the same on an offcut of the bench top and it also had the same problem. So it seems the holdfast is the problem and not the bench/workpiece.

Any idea how to make it grip more securely? I tried adding some scrap leather under the wood, under the holdfast head, etc, and it didn't help.

It took me a few months to finish the workbench and now it's done, I have this very annoying problem!

Here is the quote from toolsforworkingwood.com

When you first receive the holdfasts take some coarse sandpaper (80-100 or so grit) and go round and round the stems. Round and round NOT up and down. This will remove any grease from manufacture but more importantly scratch a series of fine lines around the stems which really real help the holdfasts to grip.
The holes in the workbenches should always be 3/4" - which is just about the standard hole size for most workbench accessories.

 

[Droogs]

The holdfast will release pressure if the force against it is in line-ish with the direction of the tilt on the bar. I use a lump hammer on mine to ensure a good fit and then tap the holdfast from behind to release. Ususaly if it works loose while planing etc it is due to fine dust under the part or the angle at which I am attacking the work. I have the same grammecy type holders and yes as above give them a good going over with some 80g as if twisting a motorbike throttle. if it still persists then tap in a few nicks with a pointy cold chisel like on a rasp not too many just 1/2 doz or so

 

[worker]

I went around the shaft with 80 grit sandpaper before using them and once hit they stay solid. Bench holes are 19mm drilled with a brace and bit.

Even when the piece it's supposed to hold is moving around, the holdfast itself is not moving so it seems the holdfast head is the problem? Anything I can do to improve the grip there?

 

[Pedronicus]

Have you checked to see if the 'head' of the holdfast is in full contact with the workpiece when tapped down? Shine a light from the far side and sight along the joint between the head and piece. A friend had a similar problem and found that only the heel of the head was making contact so he filed the heel to give a better full area purchase. Problem solved.

 

[Phil Pascoe]

I wouldn't expect a holdfast to stop something moving sideways, only to hold it down. If the workpiece isn't long enough to fix at both ends, I put a stop somewhere on the bench to stop it moving - I have a removable strip down the middle of the bench for things like this. If you clamped the same piece down with a G cramp, the same thing would probably happen.

 

[Orraloon]

Like Phil says they hold stuff down but they are usually used with a stop and sometimes a birds mouth stick to keep things from sliding around.
The Holdfast and the Batten - Tail Vice Alternative For Hand Tool Woodworking - YouTube
Regards
John

 

[Droogs]

That is a good point @Phil Pascoe, i was assuming the OP was using a stop of some sort to prevent the reaction to his action. @worker if you are not then just get a bit of woo that fits in one of the dogholes and has a bit of hacksaw blade screwed on to act as a stop like below sort of thing

 

[worker]

Thanks for the insights all. I see in the Youtube video the bird's mouth moves quite freely under the holdfast so I think I need to reassess my way of working. In other videos they push/pull on the workpiece which is only held down with a holdfast and it doesn't budge in any direction. I'll check the contact area between holdfast and wood as well

 

[Phil Pascoe]

It does - but it doesn't matter, its range is limited. Your workpiece moves just as the bird's mouth does except in this case his workpiece is caught between two points, the stop and the bird's mouth.

 

[Orraloon]

This one shows holdfast use in a bit more depth plus some other work holding as well.
Mike Siemsen, Workholding on Viseless Bench - YouTube
Regards
John

 

[Adam W.]

As mentioned before, you need to combine the holdfast with pegs or stops to brace the work against the force from the tool that you are using.

 

[bazzason]

My experience is that a 40mm top could be a bit thin for a good grip. 3-4” is ideal, but you can get away with 2-2.5”. To get more depth on a thin top, you could add material under the bench where your holes are (although this doesn’t work so much if your top has lots of dog holes).

This clip illustrates the use of a batten with your holdfast to stop sideways movement, if you don’t want to modify your bench.

This clip shows how to modify holdfasts for increased grip.

HTH

 

[thetyreman]

I have the same holdfasts, they work best with thicker tops, mine is about 2 3/4" thick, a solution would be to glue on packer pieces under the holes and continue drilling down so that it's a bit thicker, I used a brace n bit with a 3/4" auger

 

[Orraloon]

A slick highly polished benchtop is also not going to help work holding or general hand tool work as the wood tends to slither around. I learned this many years ago using an old office desk to work on. A going over with 80 grit sandpaper helped things a lot.
Regards
John

 

[Droogs]

The traditional way to get a good holding surface on a bench for hand tool working is to go over the benchtop with a toothing plane.