Making a vise speed handle with math

speed handle 1Change one thing, break another thing.
Watching Tom Lipton’s video on mill vise tramming convinced me to ditch the angle base on my vise. Did that, trammed the vise, popped the handle on and went “opps” (or words to that effect). Notice the bright spots on the spokes, I’ve been here before, I had to chop the handle when I bought it. And I didn’t want to do it again, mainly because it is “universal” handle. What the description didn’t mention was “universal” meant a 5/8″ hex drive shaft. My vise has a 14mm shank so the handle was kinda sloppy although it worked fine. But it bugged me, so this time, all new handle.

speed handle 1How to make the hex hole? I don’t have a broach or an index table so I drilled a 14mm hole and eyeballed the six corners and ran an endmill down those. Then started filing the flats. File a bit, eyeball the shaft, repeat. When was tedious. I probably should have gone with one of my first ideas, which was go buy a socket and shove it in a hole. But it was late, stores where all closed, whatever. Ho hum fit but better than a Craftsman socket.

The next problems were the spokes. Notice that they are splayed, keeps you fingers from smacking the vise as you spin the handle. I measured between 10 and 15 degrees, I went with 15 and turned a small flat on the hub.speed handle math OK, now how to drill it? I pulled out a POS tiltable drill press vise and used that.
Which made problem #2 visible – where to put the three holes? Uh, uh, hmm. Pull out the note pad and trig, piddle for a while and calc the distance between holes‰¹. Set the calipers and scribe marks on the circumference. I could have easily done this with trial and error (lengthen or shorten until the third mark hits the first mark) but where’s the challenge in that?

speed handle 2
The spokes are attached with 1/4″x20 all thread, which might be a bit wimpy but I’m guessing the plastic handle will let go before the all thread does. If they do, there will be some lathe work on deck. Or, the spindle is longer than the hub so I could just use a wrench to reef if I need to.

¹Even easier (conceptually anyway) is using polar coordinates, but I didn’t think of that until later. Remember diameter is 1.75″ and radius is half that, 0.875″. The angles we are interested in are 0° and 360°/3 (spokes)=120°.
Using the law of cosines, we get
√(r² + r² – 2r²cos(120°)) ==  √(2r²(1 – cos(120°)) ==  √(2(0.875)²(1 + 0.5))
==  √(2(0.875)²(1.5)) ==  √((1.5313)(1.5)) == √2.2969 == 1.51
Using polar coordinates and then switching back to rectangular coordinates to calculate the distance:
The two points on the radius are (0.875,0°) and (0.875,120°)
Converting [back] to Cartesian coordinates ( (x,y) space): (0.875,0) and         (-0.4375,0.7577)The distance between two points points is √( (Δx)² + (Δy)²) :  √((0.875+0.4375)² + 0.757772²) ==√(1.7227+0.5741) == √2.2968 == 1.51

And finally, you can use the Bolt Circle pattern calculator web site to get the (x,y) for all three points on the radius and do the above math to get the span.

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One Response to Making a vise speed handle with math

  1. Pingback: Rod bender | ZK Project Notebook

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