In this hypothetical situation, the stock and the holdfast are running along more-or-less the same axis. Is the holdfast stronger when work is forced towards the holdfast or away from it? It seems stronger when the force moves towards it, but I’ve seen a number of photos in work-holding articles where the setup seems just the opposite.
Thanks,
The Fledgling Woodworker
Replies
What are you calling a holdfast? I know a holdfast as an crook'd iron bar that is driven towards the bench with a mallet, wedging itself in a hole and pinning a workpiece to the bench. I don't see how your question applies to this device. Attaching a photo would help us to help you.
I am not willing to have a discussion about physics considering recent events.
FB=V(f-e)/G*M(m/s^2)
John, could you define your variables, I do not see the usual friction coefficient that I would expect to see in this discussion, friction of course between two surfaces...
Okay so here are a couple of photos to clarify my question. If I were establishing a shoulder line for cutting a tenon, and I needed to pare away material for my saw to register, which of these setups is preferred to avoid the having the stock slip beneath the holdfast.
I’m really just trying to gain a sense of the most effective way to use them. So far they’ve performed quite well, but stock sometimes pivots or slips when I’m doing chisel work. Thanks for your feedback, and apologies for the lack of clarity in my earlier post.
If work is pivoting with just a holdfast, have a benchdog, batten, or does foot behind the work to keep it in place.
This would be a tricky question at a statics and dynamics final exam but since there are fewer consequences here and that I am to busy to reach for my old books and to draw force diagrams, here are a few general comments as the possible behavior of the clamp.
My first taught is that since we are under static conditions, until the part starts to slide, and the holding force (resistance to sliding) is the product of the friction coefficient between the piece and the tabletop and the vertical force applied to it , any position of the holdfast will provide the same resistance to the part moving.
Now when the part starts moving, having the holdfast lined up with the direction of the force applied by the tool will remain in position while the one that is perpendicular to the work will likely rotate, and start releasing tension.
I would love to join this useful discussion, but sadly, my current study regarding the retention of navel lint verses temperature and humidity variables requires my full attention.
Naval fluff? Fluff?
It also just occurred to me that things slipping on a bench is the best reason to leave benches unfinished. I've never finished mine, and if it needs flattening or cleaning up, I do it with a toothing blade. It gives it a little extra "grab." Or increases the coefficient of friction. Or whatever.
Bragging here. Opened my finishing shop 2 days ago and already have more work than I can handle. Guess I never knew how many woodworkers hate the finishing process.
Mikaol
Robscaffe, how many sailors had to line up to fill each jar? I assume they were from different branches of service based on the uniform colors.
Interestingly, navel fluff has been the subject of proper scientific study - it turns out that if you shave off your abdominal hair, you don't get fluff. Itchy, but no fluff!
If your chisel is sharp, and you are taking only a registration cut then you barely need work holding. Although I suspect the holdfast is stronger when closer to the work due to leverage, if it matters, you are doing something wrong! I don't use hold fasts myself due to a thin plywood bench, but I find that for that sort of task, it is sufficient to brace the work against a bench dog.
"C2", LOL! There's a certain "A" word I won't use that, while unscientific, is quite descriptive of the retentive behavior displayed here.
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