Need help with softjaw design

[delco]

Hi , I have a job to do holding multiples of 30mm x 40mm block of cast allow , they are not 100% square so I came up with this aluminium soft jaw design but they do not hold as firm as I would like - any ideas for a more secure hold .

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[burbingus]

There are several companies that make gripper jaws that might be good for this type of operation. I'm not sure you'd want to hold your final piece in there though, so you'd probably have to use a different vise for other ops. I know Mitee Bite and Glacern Machine Tools both make similar things.

[BRAIN-HURTS]

How about leaving a jaw slightly loose so it can move to suit your uneven blocks. If you judge it just so it should move to accommodate and tighten with the vice.

[deadlykitten]

check attached

[burbingus]

One more thing - I think a big issue is that you're clamping two pieces on one vise that are not the same size. One of them will always be a bit loose unless there's a secondary engagement.

[delco]

These are in a SMW mod vice so the movable jaw can swivel as it tightens on the cone of each holddown bolt , that was the reason i went with point loading on the movable jaw.

[delco]

The blocks are mostly square , maybe I should have machined a ball into the soft jaw rather than a cylinder to increase point loading and place it at the top of the vice so it forces the part down as its clamped.

[deadlykitten]

yes, or instead of a ball, you could simply cut a few threads, and use screws with kind of hemispherical heads

if you use a ball instead of a cilinder, then you will increase grip

if you tilt the cilinder 90*, then you will increase grip even more / kindly

ps : one more thing : placing the point in the upper half or lower half, actually is taken into consideration toghether with stock slope, and relative position between vice master screw and mobile jaw; the greater the distance, among z axis, between the contact point and the screw, the bigger the stress that will appear inside the vice, and the bigger the chance for a fly off during heavy cutting; take all these with a bit of salt, since if you try to clamp 30x40 inside a small vice and machine with a o30tool, you will have less worries compared to a part that is 300x70 inside a big vice, machined with a o150tool

[delco]

yes, or instead of a ball, you could simply cut a few threads, and use screws with kind of hemispherical heads

if you use a ball instead of a cilinder, then you will increase grip

if you tilt the cilinder 90*, then you will increase grip even more / kindly

ps : one more thing : placing the point in the upper half or lower half, actually is taken into consideration toghether with stock slope, and relative position between vice master screw and mobile jaw; the greater the distance, among z axis, between the contact point and the screw, the bigger the stress that will appear inside the vice, and the bigger the chance for a fly off during heavy cutting; take all these with a bit of salt, since if you try to clamp 30x40 inside a small vice and machine with a o30tool, you will have less worries compared to a part that is 300x70 inside a big vice, machined with a o150tool

These jaws screw down and out - different to a traditional vice.