Woodworking Talk banner

1 - 19 of 19 Posts

·
Registered
Joined
·
504 Posts
Discussion Starter #1
I have recently acquired a collection of nice brass 3/4" benchdogs and cast holdfasts. Problem is they don't seem to work all that well. Since both of these things have been uses for over 100 years now I'm sure its all my fault. In my mind at least I imagined the thicker the top the stronger the hold for my dogs. That in mind I screwed 3 inches of pine stock (because thats what I had) to the underside of my plywood bench. The dogs don't seem to mind but my quick release vise doesn't like the separation from my bench top and contorts into odd angles when tightened, and sometimes it releases involuntarily. The holdfasts are giving me trouble as well. To get any holding strength I have to pound them quite hard with a metal hammer... heavy wooden mallet does nothing. Even when they do hold it seems to do nothing for side to side motion. I imagine this could be because of the softwood, or I could be using them for the wrong application but I am not at all sure. Any suggestions?
 

·
Registered
Joined
·
909 Posts
To elaborate a little further, when I got my Gramercy holdfasts they worked better after I roughed the shaft (sandpaper in concentric circled and some nail set pings; may not be an issue with cast iron), glued leather to the pads, and got a feel for where to hit them with the mallet. I can get them to hold decently with a well placed blow with the heel of my hand now, whereas before I got better with the technique I had to hit them pretty hard to acheive any hold.

You'll have to experiment, but I hit mine where the arm starts to slop down rather than straight down on top of the shaft. Remember that you're basically wedging the rod into the hole crooked to get it to grab.
 

·
Registered
Joined
·
504 Posts
Discussion Starter #4 (Edited)
My bench is close to 3 3/4" thick in parts where I have bench dogs. This was my uninformed decision based on nothing more than that bench dogs being about that long. Since then I have seen that most prefab bench tops are about 1 1/2" thick. I'm wondering how thick mine should be.
 

·
In History is the Future
Joined
·
6,423 Posts
Two things -

The holdfast can be made to grip much better by texturing the shaft with a triangle file or hack saw - nothing sever just give it some lines to help it grab.

The other thing is that cast holdfast or very susceptible to cracking and can result in an eye injury. Probably not a problem for you working by yourself but I had the pad of one shoot off and wirl right past a young kid's face during a demonstration. That said the harder you are hitting these to make them hold the shorter the life will be - to not have to hit them as hard see first comment above.
 

·
recently retired
Joined
·
174 Posts
A holdfast needs to be sized, to some degree, to the bench in which it will be used. The longer the holdfast the thicker the top needs to be. Back when holdfasts were more popular than end-vices bench-tops were 5" to 6" thick and holdfasts were 16' to 18" long.

Cast iron holdfasts do not work as well as wrought iron ones. Wrought iron is softer and the pad has some spring to it so when driven which causes it to hold better.
 

·
Registered
Joined
·
504 Posts
Discussion Starter #7
I looked it up and have ductle iron holdfasts with a 3-1/2" throat, an overall length of 8-1/4". I had just assumed cast.
 

·
Registered
Joined
·
825 Posts
My workbench has a top made of 2x4’s on edge so it is 3 1/2" thick. The cast holdfasts that I use work fairly well, without an extreme hit to lock them down. I am, however, looking to find or make some wrought iron ones to replace them.
 

·
Registered
Joined
·
1,529 Posts

·
Registered
Joined
·
909 Posts
Maybe you should take a 2x4 and bore some 3/4" holes in it and relieve them to different depths so you can see what your holdfasts like.
 
1 - 19 of 19 Posts
Top