Thinnest and thickest surface for holdfasts to work...

[Chris Hachet]

Thinking of building a new bench. Going to use Gramercy 3/4 inch holdfasts. I read somewhere they do not work well in tops over 3 inches thick, or in surfaces less than about an inch thick.

Wisdom please! Thanks...

Chris

[Frederick Skelly]

Chris,
The specs are on the Tools for Working Wood website. I tried to retrieve them for you but they are coming out garbled on this phone. Google grammercy holdfasts and read to the bottom of the description. I think thats what you need. See what you think?

I have them and love 'em. My bench is around 3" thick IIRC.

Fred

[Chris Hachet]

That's all I need to know, I plan on building a 3 inch thick bench. Thanks!

Chris

[Steve Baumgartner]

Don't omit the step of roughing up the surfaces of the shanks. That has a huge impact on their holding power. The tighter the fit into the holes, the more important this becomes.

Steve

[Chris Hachet]

Don't omit the step of roughing up the surfaces of the shanks. That has a huge impact on their holding power. The tighter the fit into the holes, the more important this becomes.

Steve

Thanks for reminding me! UPS tracking says that my holdfasts are on my front porch waiting for me to get off of work early. Christmas eve indeed!

[Richard Hutchings]

I just received a pair as well. Can't wait ti try them.

[Richard Hutchings]

I didn't have a lot of time to really test them but I did drill a 3/4" hole in my 3" spruce bench top. It seemed to hold pretty good and I haven't even sanded it yet. I like them.

[ian maybury]

I''m reasonably sure that the key variables are the diameter of the dog hole relative to the shank of the holdfast, and the thickness of the bench top. As in what matters is how far the locked holdfast is permitted to tilt out of vertical - this determines how well the shank is able to hook/lock under the top of the bench. (the action of the clamping pad/leg is to maintain this tilt) Friction plays some part (by making it harder for the holdfast to slip), but it's probably only a small part of the deal relative to the hooking/locking effect.

Use the same dog hole dia and holdfast with a much thicker benchtop and the angle is greatly reduced - and the holdfast may slip out.

The engineering/mechanics are described in post no. 20 here: http://www.sawmillcreek.org/showthre...ast-Help/page2

My guess is that if doing a thick bench top that (a) the shank of the holdfast has to be long enough to comfortably protrude out of the bottom of the hole (the Grammercy is farly short - so with a very thick top some counterboring from underneath may still be necessary to reduce the effective bench top thickness to something that is usable), and (b) that the dog hole diameter relative to that of the shank needs to be a bit bigger - sized so that the tilt of the locked holdfast is about the same as that which works best with a more typical thinner bench top/tighter clearance hole.

Easy enough to run a quick test….

ian

[Chris Griggs]

My bench is a hair over 4" and they did not hold well. I counter bored the underside of the wholes about an inch and now they hold fine (actually they started working with even less of a counter bore than that). They also held well in my previous bench which had a 1 1/2" top. Long story short I'd say they can at a minimum comfortably range from 1 1/2 to 3 1/2 (give or take) .

[Jim Koepke]

My pair of holdfasts came from Junior (Harry Strasil). My recollection is the shafts are 5/8". I have used them on a saw bench and my Sjoberg bench. I think the Sjoberg is a bit less than 1-1/2" thick.

The closer the shaft size to the hole size the less effective the holdfast will be. If my holdfasts were 3/4" my inclination would be to drill some 7/8" holes just for the holdfasts. A bit of trial on some scrap would be done first.

One thing I have learned it usually pressing them down with just body weight is effective at getting them to hold. My bench is open underneath so often just grabbing the shaft and pushing or pulling will release its hold.

Holdfasts work by a wedging action and pounding a wedge into a hole in wood can produce unwanted results. Some woods might split if overly wedged, DAMHIKT.

jtk

[ken hatch]

My bench is a hair over 4" and they did not hold well. I counter bored the underside of the wholes about an inch and now they hold fine (actually they started working with even less of a counter bore than that). They also held well in my previous bench which had a 1 1/2" top. Long story short I'd say they can at a minimum comfortably range from 1 1/2 to 3 1/2 (give or take) .

Chris,

I had posted earlier that slab thickness may not be the whole story but it was lost somewhere in the intertubes.

I have two benches both approximately 100mm (about 4") thick give or take a couple of silly mm's. Holdfasts have worked on the Beech topped bench from the get go. The SYP topped bench was not so easy, some would hold well, others wouldn't. Like you I ended up counter boring the bottom of all the dog holes by about 12-13mm. Whatever, the SYP one with the bottom relief holds as well as the Beech with out relief. One other factor keeps me from saying in my Flying Spaghetti Monster voice that 100mm in Beech is fine and with SYP the max is 85mm is; I used different drills to drill the 3/4" dog holes.

I drilled the dog holes on the Beech bench with a Fisch 3/4" brad point drill that I found at Woodcraft, the SYP bench was drilled with a 3/4" Irwin Speedbor. Is the difference the wood, the drill, or both.....I haven't a clue and bottom line it makes no never mind, the TFWW holdfasts work great on either bench and are fast, easy and best of all don't cost much.

ken

[Scott Rud]

My bench top is just over 4" of hard maple. I bought a tapering bit from LV and used it on all of my holes from the underside. I figure that I've tapered the bottom 1.5" on all of the holes. All I have to do is drop the holdfast into place and I can't move it. A solid rap with the mallet and it holds extremely well.