Is renshape a reasonable material to make softjaws out of?

Not sure if softjaws is the right term - I just mean some custom shaped thing placed between the aluminum jaws of the vise and the work piece to more precisely place and safely hold the workpiece.

What I am currently doing is making fixturing pieces out of HDPE that I have sitting around. But I am getting some unwanted taper in my pieces, and I think it’s possibly because my fixturing is too soft. I was wondering what I should make this stuff out of instead of HDPE.

I was going to use some hardwood, but I don’t know if that stuff is stiff enough, or if it’ll warp or change over time. How would renshape hold up, both in terms of stiffness and resistance to changing shape when crushed in jaws?

Here’s an example of what I’m talking about. All the white pieces are HDPE.

Actually, this piece turned out great, but I have another example which I don’t have pictures of where I have some taper on a small piece that was hard to get a good grip on with my custom HDPE jaws, and I think the pieces are moving around as the endmill chips away at the wood.

In these pieces I was using HDPE jaws to hold the square end to mill the cylindrical pegs and ended up with some taper. Perhaps a harder, stiffer material would work better.


In my SpoilVice, I have gone to using exactly this. I have the wedge pieces cut from renshape. This stuff is very sturdy, but is generally softer than anything I cut, so if I do need to cut into the vice wedge it will go like butter compared to the obhect material.


I think your Renshape jaws might “Hold” the wood better than the slippery HDPE.
Renshape is available in multiple densities, we carry the mid range, 40-50 lb density.

If you do use the Renshape Jaws for this job, maybe just use it for Jaw #3 whcich would be in contact with the floating jaw, and set your part Zero on the Left side were your HDPE jaw is.
That way, as the renshape which is soft, starts to deform, your part Zero wont shift, because your HDPE will be on the Fixed Jaw side.

So the renshape is going to squash? My HDPE is squashing quite a bit - I was hoping the Renshape would be more un-compressible… Is there a better material to choose (easyish to machine - so not aluminum, but stiff)?

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Delrin would be harder than HDPE and machines very well.

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+10 Apollo Delrin/Acetal machines like a dream. One can make gears with it!

Delrin/Acetal is my preferred plastic for parts that will/may take a lot of wear.

Acetal is the generic name of the plastic. Delrin is DuPont’s brand name.

Downsides of Delrin/Acetal:

A) It can be a bit pricey.

B) There are many variants, each with interesting properties. This can make choosing difficult.

Homopolymer (Delrin) and Copolymer versions are both used.

Acetal Copolymer would be a good choice, as would Delrin 100 (a variant good at gripping; not too “slippery”). PVC - the hard kind - would be my second choice.



So my question when I am choosing new material is “how safe is to inhale chips?”:))
I want to try acetal but wonder do I need to be careful as with carbon or hardwoods? Thanks for answers!

Unless you machine plastics so that they smoke or burn there will be no issue with plastics; Acetal/Delrin is particularly nice to machine.

Smoking/burning plastics release cyanides and other nasty stuff. :frowning:

In general, plastics do not have nasty particle generation characteristics. It’s the woods, carbon fiber and fibre glass that one has to be careful about.

Beryllium, Plutonium and other nasty metals are not something we’re likely to machine on a Nomad. :wink: