Help with Gramercy holdfast technique - they are not holding

[Larry Cronin]

Hello,

I built my workbench with lots of advice and knowledge from here.

Came out really good and works great.

But

I cant get my holdfasts to work at all.

My bench is 3 inch thick maple

I drilled my dog holes using the Lee Valley 3/4 dog hole bushing kit.

I used 60 grit paper and sanded the shafts of my Gramercy holdfasts. (round and round not up and down)

I am hitting them with a 30oz Wood is Good mallet.

Most times they don't hold at all but every so often it is tight till I move the object side to side.

What am I doing wrong?

Thanks

Larry C

[Christopher Charles]

I've occasionally had similar issues with my 4" thick maple top. At least one of the times was related to wiping down the holdfast with oil to prevent rust. I re-sanded as you describe and no issues since, but that may not be relevant to your case.

Best,
Chris

[Steven Mikes]

I am hitting them with a 30oz Wood is Good mallet.

Maybe this.. try with a heavy wooden mallet without a coating, or a regular metal hammer like Frank Klausz.

[ken hatch]

Hello,

I built my workbench with lots of advice and knowledge from here.

Came out really good and works great.

But

I cant get my holdfasts to work at all.

My bench is 3 inch thick maple

I drilled my dog holes using the Lee Valley 3/4 dog hole bushing kit.

I used 60 grit paper and sanded the shafts of my Gramercy holdfasts. (round and round not up and down)

I am hitting them with a 30oz Wood is Good mallet.

Most times they don't hold at all but every so often it is tight till I move the object side to side.

What am I doing wrong?

Thanks

Larry C

Larry,

A 3" slab should work but it isn't. I try using a lump hammer first to set the holdfasts, the Wood is Good mallet can have some bounce. If that doesn't fix the problem counterbore the dog hole from the bottom maybe a 1/2' to 3/4" or so and that should fix your problem.

ken

[Hasin Haroon]

It should work just fine in a 3" thick bench. I second using a heavy metal hammer to set it - it takes more than a tap to hold well, hit it kind of hard. I pricked the surface of the post randomly with a punch, which seems to have helped it stay in place better.

I also use high friction tape on the pads of the holdfast to strengthen the grip even further. Might be overkill, but it works.

[Prashun Patel]

I suspect your holes are too perfect. I also suggest counterboring them at the bottom. My Gramercy holdfasts have worked better over time. I suspect it's built up patina, and micro-eccentricity of my dog holes over time.

[Warren Mickley]

I think your holdfast is too rigid. With a rigid holdfast all the wedging action has to happen in the bench wood. Roubo says that the arm of the holdfast should be very flexible and that it should gradually taper down to 1/6 or 1/8 inches (1 1/2 or 2 lignes). Roubo does not show any undercutting in the bench. The fact that the Gramercy is flattened at the very end does not give them much flexibility. Some have improved them by thinning down the arm by grinding for more spring.

Roubo valet.png

[Pete Taran]

Hello,

Most times they don't hold at all but every so often it is tight till I move the object side to side.

What am I doing wrong?

Thanks

Larry C

Larry, I don't think you are doing anything wrong except for falling prey to a fundamentally flawed design. The Gramercy holdfast:

gramercy.jpg

You will notice how the entire assembly is the same thickness of round bar stock.

A traditional holdfast, that well, actually holds:

holdfast.jpg

You will notice how the shank is much thicker than the arm. This is by design and what really makes the holdfast hold. By rapping it on the top, you wedge the shaft sideways in the bench and load the arm with tension which is what does the holding. Properly made, surprisingly little force is needed to load the arm with the proper amount of tension.

Gramercy, by constructing them the way they do, requires a ridiculous amount of force to load that arm with enough pressure to do any reasonable holding. It doesn't say what the diameter of the stock is, but, looks to be at least 1/2" to my eye. That's a pretty hard thickness to deform. Back in the old days, these were made of wrought iron which is even easier to deform than mild steel which is used today.

I'd take them up on their 6 month return guarantee and get a set that actually holds. The ones pictured are some dude selling them on etsy for $50/pr. Only $3 each more than the flawed design and infinitely better. No affiliation with either joint.

[Mike Brady]

My holdfasts from the source you mentioned did not hold either in a 3-1/2 ash bench top. I sold them to a guy who said they were fine in his bench. The Lie-Nielsen hold fasts are fine in the same bench and they are much lower profile than the Grammercys. They are ductile iron castings. Excellent.

[David Silverson]

I have the same problem with my Gramercy holdfasts. I’m going to try grinding the arm and see if it helps.

[Philip Glover]

I have Gramercy holdfasts and they have been working perfectly for 16yrs. In fact, when I need a light holding force all I do is hit it with the palm of my hand and it holds. When I need more clamping force a wooden mallet does the job.

My maple bench is 3.5 inch thick.
The dog holes are chamfered on both sides.

What I think may be happening is there is not enough clearance between the shaft and the hole. With more clearance it would allow the holdfast to cock and bend slightly in the hole and allow the shaft to act like a spring. After all, a holdfast is a type of spring clamp.
The holdfasts with a tapered shaft are much less sensitive to the dog hole diameter.

I will check the average I.D. of my dog holes with a bore gage and post the results tomorrow. Also, I'll measure the O.D. of the holdfast shafts as well.

Regards,
Phil

[Simon MacGowen]

Since my bench is thinner than yours and my wooden mallets (15 oz or so) are lighter than yours, I suspect your driving is the source of the problem. Try hitting the holdfast with a different section of your mallet head, and try hitting more than once, the subsequent hits less in force, to secure the hold-down. Also try using it on stock of different thicknesses to see if it makes a difference.

I have 5 of the Gamercy's (bought in different periods of time), and they all have worked well over the past decade. I have not sanded or done anything to them, other than adding a leather pad to their arms. The problem you reported CANNOT be a design issue if so many of them (hundreds or even thousands?) are sold and used with no hiccups.

Simon

[Rob Luter]

Mine slip sometimes too. Coarse sandpaper helps.

[Joe A Faulkner]

My bench is 3 1/4" thick hard maple. I had to sand the Gramercy hold fasts and that did it for me. I use a leather-faced, shop-made, jointer's mallet to set the hold fasts. Not ideal, but it works. I recall in a previous post, someone added a short series of dimples to their Gramercy hold fasts using an old nail set.

[William Fretwell]

I have Gramercy holdfasts and they have been working perfectly for 16yrs. In fact, when I need a light holding force all I do is hit it with the palm of my hand and it holds. When I need more clamping force a wooden mallet does the job.

My maple bench is 3.5 inch thick.
The dog holes are chamfered on both sides.

What I think may be happening is there is not enough clearance between the shaft and the hole. With more clearance it would allow the holdfast to cock and bend slightly in the hole and allow the shaft to act like a spring. After all, a holdfast is a type of spring clamp.
The holdfasts with a tapered shaft are much less sensitive to the dog hole diameter.

Regards,
Phil

Phil I believe you are correct. They need to move a little to wedge, the bend acts as a spring. My Grammercys did not work at 4” thick but I back bored under the bench 1/2” and at 3 & 1/2” they work very well. Shortening the hole increases the cocking angle.

I also varnished mine to discourage rust and oiled the holes with Tung oil on a small rag and string. The oil made the holes stickier. Just make your holes slightly larger.