Help with Gramercy holdfast technique - they are not holding

[Derek Cohen]

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

Hi Larry

My bench is 3 1/2" European Oak. I use the Gramercy holdfasts. They are perfect. Never slip. They did not slip in my previous bench either, and that one was 1-1/2" MDF with a 3/4" layer of Karri. The common denominator was that the holes were drilled with a brace and bit ...



I repeat - the holdfasts never slip. I wack them with a 18oz UHMW-headed mallet ..



Look closely below, and you can see a slight gap around the shafts ...



They unseat with a rap. No drama.

The design of the Gramercy holdfasts is just fine, thank you. The issue is the hole in which yours are seated: the walls are too smooth or the hole is a little too tight.

Instead of sanding the holdfast, take a rasp to the holes and roughen them up. Them will widen them a smidgeon as well. That is probably all that is needed.

Regards from Perth

Derek

[Larry Cronin]

Thanks for all the suggestions.

I will try a bigger hammer and also I am going to try and rough up my holes and see if that helps.

I will report back in a day or so.

Larry C



Larry C

[Derek Cohen]

Larry, just to be clear ... I do not hit the holdfasts hard. In fact, I could secure them by pushing down hard. It is more that they require a wack to release than a wack to secure.

Regards from Perth

Derek

[Warren Mickley]

For those who have never seen the troubles that bar stock Holdfasts can give, here is a video. This one comes loose seven times in one minute of work.

[Derek Cohen]

Warren, is that the holdfast or the hole?

Regards from Perth

Derek

[Derek Cohen]

Here's a quick video I made ...



Good enough?

Regards from Perth

Derek

[Pete Taran]

Perhaps the OP can start using flex seal with his Gramercy holdfasts. Perhaps the only solution not yet offered. Don't see anyone complaining about slipping traditional holdfasts. I wonder if there is a correlation? hmmmm

[Steven Mikes]

Derek this is off topic but how did you do that lovely perfectly circular chamfering of your dog holes?

[Derek Cohen]

Steven, Lee Valley make a large countersink.

Regards from Perth

Derek

[Philip Glover]

Larry,

As promised, my stand-up morning report.
What I found is somewhat predictable.

First things:
- bench top has 36 holes
- holes have a semi-rough surface finish
- drill bit that I used for these holes is 0.742 dia.
- holdfasts are both 0.716 dia.
- holdfasts have a smooth surface finish; I sanded them only when they were new 16 years ago
- I used a B & S 0-1 inch mic and a Mitutoyo telescoping gage to measure the holes


I measured each hole in three locations - top, middle, and bottom.
- tops averaged 0.771 dia., range 0.015 inch
- mid points measured averaged 0.755 dia., range 0.005 inch
- bottoms averaged 0.770 dia., range 0.015 inch

- holdfast clearance at the midpoint is 0.039 inch.
- holdfast clearance at the top and bottom averages 0.055 inch.

So:
- the holes are hourglass shaped; which I strongly suspect is the result of the holdfasts cocking in the holes
- I definitely use some holes more than others

Your solution, if there is too little clearance, may be to slightly enlarge the dog holes using an electric drill with a 3/4" drill bit and wobble the drill around while drilling. This will create the hourglass shape.
As far as surface finish in the hole - the rougher the better.

I hope this helps,

Phil

[Simon MacGowen]

Echo that "no large hammer" advice by Derek.

Why do so many woodworkers think (brutal) force is the solution to their woodworking issues?

There also seems to be a movement encouraging people to use a sledge hammer to do chiselling work! (sarcasm, of course).

Simon

[Bob Glenn]

Steven, not neander, but a power router with 45 degree campher bit works also.

[Steven Mikes]

Steven, Lee Valley make a large countersink.

Regards from Perth

Derek

Haha of course they do! Guess I have no choice but to buy one. Thanks.

[JimA Thornton]

Steven, Lee Valley make a large countersink.

Regards from Perth

Derek

Oh sure..............this one just showed up yesterday: http://www.leevalley.com/en/hardware...,41328&p=54874 and now I need to order a bigger one to chamfer the dog holes in my newly built workbench. Oh well..........at least LV has free shipping for the next couple of weeks. Plus...... right hand Plough Planes are back in stock!

Jim

[Stewie Simpson]

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; I would recommend you view the following video. https://www.youtube.com/watch?v=S7lnfW4iT6o

Stewie;