Logarithmic Spiral Holdfast

[ken hatch]

Some time ago I read about using a logarithmic spiral to hold work on the bench top. I can't remember where so as to give credit but whatever this isn't new just new to me. Anyway when I read about it I kinda filed it away as one of those ideas that might work but would not be life changing.


Last night a pinched nerve in my right arm woke me in the middle of the night. When that happens about the only thing that relieves the pain is to get up and sometimes a little use of the arm helps. OK Bubba enough back story cut to the chase.


With nothing better to do I made one to try. It works. I don't think it would replace a holdfast with a doe's foot on my bench because the dog holes are placed to use a doe's foot but it works.


Here is a photo:

http://i257.photobucket.com/albums/hh222/VTXAZ/logarithmicSprialHoldfast_zpsnsybqhti.jpg



As you should be able to see, the arm from the pivot point gets progressive longer which pinches the work against a baton/stop as it is moved from right to left and releases as the work is moved left to right. Actually it is pretty slick and with correctly placed dog holes could work very well.

[Jim Koepke]

A great solution for viseless holding. Thanks for sharing.

It looks like it would be possible to have two of these opposed to each other to make it possible to hold a variety of sizes while working. Though there may be a problem of the work piece pivoting.

jtk

[bridger berdel]

Three point holding should prevent pivoting

[ken hatch]

Jim,

I had a longer post just disappear into the ozone, while I was looking for it Bridger posted a good answer.

ken

[Mark AJ Allen]

While cam-clamp is a really great idea (wish someone would make these and put to market) ... what gives with the weird hand thing on the bench?

[Kent A Bathurst]

Ken - nice work. Get up in the middle of the night more often, is my thinking.



While cam-clamp is a really great idea (wish someone would make these and put to market) ... what gives with the weird hand thing on the bench?

Mark - Thing from the Adams Family retired to AZ, along with a few jillion other people of that age group. He is helping Ken in his shop from time to time.

Which of us could not use an extra hand in the shop?


http://theredlist.com/media/database/films/tv-series/fantasy-and-sci-fi/1960/the-addams-family/013-the-addams-family-theredlist.jpg

[ken hatch]

While cam-clamp is a really great idea (wish someone would make these and put to market) ... what gives with the weird hand thing on the bench?

Mark,

I like Kent's answer better than mine :).

SWMBO is a ceramicist and she wants me to put some shellac on the hand to see how it would look. That's next on the todo list today.

ken

[Kent A Bathurst]

Mark,

I like Kent's answer better than mine :).

SWMBO is a ceramicist and she wants me to put some shellac on the hand to see how it would look. That's next on the todo list today.

ken

Can she make one with the correct finger extended? How much would that version cost?

[ken hatch]

Can she make one with the correct finger extended? How much would that version cost?

When I ran it by SWMBO a smile crossed her face.

When I first made the logarithmic spiral, let's call it a cam clamp, I thought it would just be a novelty and not of much practical use. After playing with it a bit, I found it to be a very robust and quick way to hold boards for face planing. While I do not expect it to replace my current methods I think with adding a dog hole just to the right of the face vise and maybe 25-30mm off the front edge of my bench combined with the current row of dog holes that are 330mm off the front edge it would give me a very useable and handy additional way to hold work for face planing. For it to work I will need several batons of different widths and it would be useful to make a couple or three cams of different sizes and thickness. Not a clue how much I would use it but drilling a dog hole and finding a few batons in the scrap pile isn't a lot of work for some additional functionality.

[Tom Vanzant]

Ken, Rockler has marketed blue anodized Cam Clamps for years, generally used with t-slots as hold-downs. The same cramming principle is used in wooden clamps. I use a much heavier cam in pairs to raise my cabinet-mounted tablesaw off its feet onto casters...that idea came from a WW magazine 25+ years ago.