holdfast diameter?

[Augusto Orosco]

Just wondering, what would be the diameter range of a holdfast shaft to work well on 3/4" hole? My bench in progress is about 3.75" thick out of soft maple. I have a 5/8" holdfast that doesn't seem to be able to hold (even after some sand-paper roughing). I hit it with a mallet, and it just bounces up and down and doesn't catch. I am wondering that perhaps 5/8 is too thin, but before I go about buying new ones from Gramercy of LN, I want to make sure I am not doing something wrong.

Thanks!

[Jim Koepke]

My holdfasts, from Junior Strasil, are 5/8" and work fine in my 3/4" dog holes.

When a holdfast's shaft is roughed with sand paper, it should be around the shaft and not in the direction of the length in case that wasn't clear.

How thick is your bench?

A too thick of bench will make it difficult for the holdfast to catch. They need to be at an angle in the hole so there is "three point" contact, the bottom of the hold, top of the hole and the item being held.

Sometimes it helps to use a block of wood on the item being held to lift the holdfast a bit to get a better bite.

jtk

[Augusto Orosco]

My holdfasts, from Junior Strasil, are 5/8" and work fine in my 3/4" dog holes.

When a holdfast's shaft is roughed with sand paper, it should be around the shaft and not in the direction of the length in case that wasn't clear.

How thick is your bench?

A too thick of bench will make it difficult for the holdfast to catch. They need to be at an angle in the hole so there is "three point" contact, the bottom of the hold, top of the hole and the item being held.

Sometimes it helps to use a block of wood on the item being held to lift the holdfast a bit to get a better bite.

jtk

Thanks, Jim.

My bench is 3.75" thick, soft maple. I have only tried to make the holdfast catch without trying to hold anything yet (so, just catching the top's surface). Perhaps that's the issue, since it's not raised enough. I'll try with a block of wood and see if there is a difference.

[Jim Koepke]

Thanks, Jim.

My bench is 3.75" thick, soft maple. I have only tried to make the holdfast catch without trying to hold anything yet (so, just catching the top's surface). Perhaps that's the issue, since it's not raised enough. I'll try with a block of wood and see if there is a difference.

My guess is you will have better results with a block of wood. The holdfast "points" need to be in three distinct planes. Trying to hold the surface of the bench makes only two.

jtk

[Keith Mathewson]

How long is the shaft on the holdfast? My bench is the same thickness and short shaft holdfasts don't work but with the large ones from Peter Ross you could lift the entire table.

[Richard Hutchings]

You should make up some blocks of wood out of soft male at different thicknesses and hole sizes and find what's right for your holdfasts. You may need to plow a groove under you holes to make the thickness smaller. I use Gramercy holdfasts in 3/4" holes in a 3" top with no problem. Maybe you just got the wrong holdfasts for you existing bench.

[Augusto Orosco]

My guess is you will have better results with a block of wood. The holdfast "points" need to be in three distinct planes. Trying to hold the surface of the bench makes only two.

jtk

No dice. tried to hold a 2" thick board and the holdfast would not bite. Not even a little bit; it just bounces in the hole. I went again with 100 grit sandpaper around (not along) the shaft and still nothing.

How long is the shaft on the holdfast? My bench is the same thickness and short shaft holdfasts don't work but with the large ones from Peter Ross you could lift the entire table.

The shaft if 11.5" long.

You should make up some blocks of wood out of soft male at different thicknesses and hole sizes and find what's right for your holdfasts. You may need to plow a groove under you holes to make the thickness smaller. I use Gramercy holdfasts in 3/4" holes in a 3" top with no problem. Maybe you just got the wrong holdfasts for you existing bench.

That would be a way to test why things are not working; I might try it. But I rather buy a different set of holdfasts that work on 3/4" holes on a 3.75" top because 3/4" holes are also standard for other gadgets that I might to incorporate into my bench.

What surprises me is that it's not that there is at least a bit of an attempt to hold anything. The thing just bounces when you whack it; there is no bite at all. I even have seen videos online with holdfasts that get jammed just by dropping them into the hole.... not that I expect that with mine; but at least something!

[Jim Koepke]

That is odd. My holdfasts often hold tight enough for light work just by pushing them down with my upper body weight. Of course that might actually be more pressure than a light hit from a mallet.

Are the insides of the dog holes smooth?

Maybe pictures would help if you can post them.

jtk

[Augusto Orosco]

That is odd. My holdfasts often hold tight enough for light work just by pushing them down with my upper body weight. Of course that might actually be more pressure than a light hit from a mallet.

Are the insides of the dog holes smooth?

Maybe pictures would help if you can post them.

jtk

I'll see if I can snap some pictures tonight. The holes I am trying now are in the leg (the top is currently being worked on upside down, excavating mortises for the legs). The legs are actually 5" thick, but I counter-bored a 1.5" deep hole of 1" diameter to give it an effective 3.5" thickness. The 3/4" were bored using a drill press and a brad point bit from Lee Valley, so I would say they are reasonably smooth.

[Richard Line]

My Gramercyholdfasts have a diameter of 0.715", just as a checkpoint.

[Brian Holcombe]

Relieve the hole on the top and the bottom by tapering it lightly with a rasp or a tapered cutter. All of mine required tapering (either self inflicted or by my hand) to work, they are LN.

[Jim Koepke]

The legs are actually 5" thick, but I counter-bored a 1.5" deep hole of 1" diameter to give it an effective 3.5" thickness.

My focus at this point would be to see how the fit is on the back side of the bore to see if the counter-bore is wide enough to not interfere with the holdfast's shaft.

My saw bench is made with 2X construction lumber and a holdfast with a 5/8" shaft works well.

If all else fails trying a 3/4" hole in a scrap of 2X4 would tell if it is the holdfast or the bench leg.

While on the subject of holdfasts and un-bored bench dog holes, if my bench build round-tuit ever arrives, my thoughts are to drill a row of dog holes along the front of the bench for use with the tail vise. There will be a second row of holes further in from the edge to use specifically with a holdfast.

jtk

[Augusto Orosco]

My Gramercyholdfasts have a diameter of 0.715", just as a checkpoint.

Thanks, Richard!

Relieve the hole on the top and the bottom by tapering it lightly with a rasp or a tapered cutter. All of mine required tapering (either self inflicted or by my hand) to work, they are LN.

That's an interesting point particularly since I was contemplating the LN's if everything else failed I might try that on scrap first!

My focus at this point would be to see how the fit is on the back side of the bore to see if the counter-bore is wide enough to not interfere with the holdfast's shaft.

My saw bench is made with 2X construction lumber and a holdfast with a 5/8" shaft works well.

If all else fails trying a 3/4" hole in a scrap of 2X4 would tell if it is the holdfast or the bench leg.

While on the subject of holdfasts and un-bored bench dog holes, if my bench build round-tuit ever arrives, my thoughts are to drill a row of dog holes along the front of the bench for use with the tail vise. There will be a second row of holes further in from the edge to use specifically with a holdfast.

jtk

Making sure that the counter-bore was wide enough is the first thing I checked and it is fine; it doesn't interfere at all with the shaft. I have some 2x4 lying around. I'll drill a hole tonight or tomorrow and report back. Thanks!

[John Sanford]

There will be a second row of holes further in from the edge to use specifically with a holdfast.
jtk

You won't need a full row. Just measure the swing of your holdfasts, then subtract about an inch from the full diameter of their coverage. That will give you the spacing.

[Augusto Orosco]

Ok, sorry it took longer, but sometimes I need to work :-)

I am linking to two quick videos I took with my phone: The first one gives you a sense of the holes (3/4") vs. the holdfast shaft (5/8") and how it fits. I also shows the relief in the back so you see it's not interfering with the shaft. The effective length on the holes (length of the leg minus the counterbore depth) is about 4".

https://youtu.be/DOK2_irTFyg

The second video shows my attempt to make the holdfast bite (this was harder to film, because I needed two hands to make this work). You can see that there is not even the slightest attempt to bite.

https://www.youtube.com/watch?v=p20B...m-upload_owner

In this video I am not hitting it with the mallet too hard, and gravity is not on my side either as it would be on a top, but I have tried this before with much harder mallet whacks and with the holes perpendicular to the ground and the results are the same.

As I mentioned before, the shaft has already been roughed with 100 grit sandpaper going around the shaft and not along it, as it is recommended.

Next I will try to bore holes on a thinner piece (say a 2x4") and also try narrower holes and see if it makes any difference.