[How do I?] Make a V grip cylinder

[Dan Krager]

I have a Tormek sharpening system and one of the very effective techniques they use to secure a fixture to a rod is to use a V grip cylinder as shown (in it's simplest form). A set screw forces the rod into the V and with very little torque prevents spinning on the rod.

Being relatively new to machining techniques, I've wondered how to recreate this in either mild steel or perhaps aluminum. I suspect broaching, but I've never seen a broach shaped like this and making one is beyond my pay grade and skill set. Other methods? Drill and square file works over time, I guess, but for a 2" long cylinder, well, I may not live that long. Making one off here and there as needed, as in hobby, not a production run.

Any hints?


DanK

 

[piper184]

Drill and file is my only guess. Drill small hole at point of V then drill/bore the large diameter hole. Layout straight lines tangent to the holes and use a saw if possible to remove the bulk of the material. Otherwise chain drill/mill and file to the line.
A good old shaper or at least a die filer would sure be handy...

 

[whitmore]

If it were a production item, an NC wire EDM can open up a thickwall tube to make this
profile. For a one-off, I'd be tempted to make a drift with the teardrop shank
shape, and drive it through a red-hot blank, then machine the exterior round after
it cools.
Plunge-cut EDM can make the hole, too, but that takes more than a few program
entries, you'd want to make form tooling.

Probably there's some extrude-over-mandrel options as well.

 

[Inferno]

If you had a shaper then it wouldn't be hard.
Without a shaper, you could simulate one with a boring bar and using your cross slide. It would take a lot of work though.
You could use a scroll saw. Won't look great but it would work.

 

[Eddyde]

I would hog out as much as I could with drills and a jig saw then file. You'd be surprised at how fast it can go with sharp files.

 

[brino]

more options;

1) drill thru with a clearance hole, thread a band-saw blade thru, silver solder the blade ends, set up in a bandsaw and cut the pointy bit, un-solder and remove the blade, finish with files.

2) make it a multi-piece assembly.
drill thru, cut in half lengthwise, mill the corner in one half, reassemble the two halves with screws buried in counter-bored pockets.
As stated above the outside diameter could be cut last to bring it back to round from the loss of the kerf.

Brian

 

[piper184]

I'm not sure if the finished product actually needs to be round on the outside but some inexpensive lathe dogs might be a good place to start. Just remove the parts you don't need on the outside.

 

[GeneT45]

welding would be another option for assembly / reassembly if making it in parts. My Tormek has a different geometry than that shown - which is not to say easier.

GsT

 

[homebrewed]

You might get some indications on how your Tormek V-grip device was made by examining its machining marks.

For yet another way to make something like it, you could make a mold and take it to your local foundry to make a casting. Finish the exterior and interior radius on your lathe. file the V to its final dimensions.

Or another: Bore the inside hole for an ID that matches the tip of the V, then make two inserts that fit inside the hole. Glue in place; or better yet attach them with screws. The inserts could be made from a tube with the right ID and OD, then saw the tube in half along its length. Mill the flats for the V. It wouldn't look like the Tormach but it would perform the same function.

For the latter approach, a 3D printed insert might work, too, depends on the accuracy requirements.

 

[Dan Krager]

As Gene pointed out with picture, Tormek flats do not come to a point as I had drawn from memory. Thinking about the difference, the Tormek spec is going to grip much better because the flats are closer to parallel than what I had drawn.

I may be able to accomplish homebrewed suggestion of inserted "flats", chord sections of a cylinder secured in place.

DanK