Super Soft Jaws


We did a lot of thinking about workholding over the last half of 2010. Some of the steady readers here may have noticed some of the recent additions: the new 5″ CNC Vise, and new modular jaw plates, for example. We’ve still got a few other neat things that will be arriving shortly as well on the website.

One of the more creative ideas we came up with that made it to product is Supersoft Jaws. What is it?

Well, it’s a kit for our 5″ Vises that allows you to make custom jaws our of a moldable, formable plastic. The plastic’s official name is Polycaprolactone, and it has been a machinist’s secret for a little while. You may have seen it before – its a plastic compound that is moldable when heated up, but rigid at room temperature. Its machinable (actually looks and cuts a lot like Delrin), reheatable and remoldable, and dimensionally stable.

Here’s how it works: Heat the plastic up in hot water – not boiling, but kind of close. Then you can mold it around the workpiece and the studs on the Soft Jaw subplates. Tighten up the jaws slightly as it cools to room Temp and…Voila!… it holds firmly.

It’s perfect for holding difficult shapes in a vise. We especially like it for:
1. One-time and protoyping jobs where you don’t want to invest a lot of design time to make more permenant aluminum soft jaw plates
2. Engraving
3. Fixturing jobs that are nearly impossible

The Supersoft Jaw Kit is 31841. Click here to buy them


3 thoughts on “Super Soft Jaws

  • Avatar
    January 31, 2011 at 6:45 pm

    You must have just added this, I was looking for this the other day.

  • Avatar
    February 1, 2011 at 5:30 am

    Great video. I guess the “secret” is out. Its great stuff.

    I have used capa for 2+ years to hold non-standard geometries to my lathe faceplate. I push inverted T-slot nuts into the dough, then use short carriage bolts to hold the “fixture” to the plate. It does have holding limits – ask my tool chest!

    Polycaprolactone is a “green” product. It biodegrades in 6 to 9 months when exposed to CO2 or H2O (i.e. ambient room exposure). Store it in a sealed container to prolong shelf life. If warmed in water, keep that product separately stored. I have found McMaster-Carr (6225T11) to have one of the lower prices.

    The blog is a regular read for me. Keep up the good work.

  • Avatar
    February 1, 2011 at 5:50 am

    This is great. It will save from having so many machinable aluminum jaws laying around.

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