Polymer Nails for CNC Workholding





Introduction: Polymer Nails for CNC Workholding

As many of you running a CNC router probably already know - work holding can be a royal pain!  We have three differently-sized ShopBots at our TechShop location here in San Francisco, all three with their own unique limitations when it comes to work holding.  Brass screws inevitably strip out, clamps somehow end up in the way of the tool path, and spray adhesive just doesn't seem to hack it.  I just want to say one word to you. Just one word....Plastics.  Seems Mr. McGuire in The Graduate was right!  Modern polymer nails have most of what we need covered, though with a few notable exceptions worth exploring.

Step 1: Polymer Nails for CNC Workholding

Companies like Raptor Nails and Staples offer a variety of fasteners, all made from the same high-strength polymer and come in standard sized strips which fit most pneumatic nailers.  The tensile (pull) strength of these nails is, in some cases, double that of their steel counterparts which makes for great work holding on your CNC table - as long as you're using a soft spoil board, like MDF.

Step 2: Polymer Nails for CNC Workholding

Penetration of even the 1" 18gauge brad nails is excellent, but this is where the little niggly issues start to come to light.

Step 3: Polymer Nails for CNC Workholding

Our standard Porter Cable Finish Nailer had no problem driving the nails through soft pine, regardless of thickness.  Harder woods caused an increase in nail breakage and less overall penetration.  Part of the problem we noticed was that our standard shop air - 125psi - was absolutely killing the nails as they were driven in.  Running a regulator and lowering the pressure down to 75-90psi cured a bunch of the problems, but we still broke nails on those harder woods.

Step 4: Polymer Nails for CNC Workholding

So it sounds like these nails can be finicky, right?!  Well, their shining glory is revealed when you need to remove your part.  One quick tap with a soft mallet is all that's required to snap them off.  While they're strong in one direction, they're basically mush in the other.  Strong, but brittle, as it were.  Ever see Samuel Jackson in Unbreakable?  You get the idea.

Step 5: Polymer Nails for CNC Workholding

Flip the part over and you can see the results.  Both the part and the table show clean breaks, darned near flush.  Compare their impact to the screw holes nearby and you might find yourself jumping on their bandwagon too.  Any stragglers rising above the surface can be leveled with a quick scrape of a putty knife or a straight edge.  Don't bother with a chisel, you'll only damage your deck.  Additionally, they can be machined flat or, unlike that broken brass screw you're loudly cursing, sanded smooth.
The pros: Polymer nails are easy to use, hold very well, and break off cleanly.

The cons: They require some tweaking to get the air pressure right, they don't work well through harder materials, and they only come from limited suppliers.

The conclusion: If you've got flat sheet stock of fairly soft material and are looking for a fast way of securing it, then use some of these, you won't regret it  ;)

James Irmiger
Lead DC - Facilities Manager
TechShop SOMA



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    There's an old trick furniture makers use to hold down pieces of wood when carving. Stick a single sheet of newspaper to the spoil board with some PVA and the workpiece to the top of the newspaper. When you're all finished wedge a chisel in-between the two and the paper will split apart. Only needs a light sanding to get rid of the paper.

    Wow I've never heard of these composite nails. Are they insulative/non-conducting?
    That opens them to other uses... Thanks!

    What is the model number of the Porter Cable used with the plastic nails?

    2 replies

    We're using a Porter Cable BN138 18-gauge brad nailer. Even at full shop pressure of 110-120psi, I can get about 90% of them to get a full penetration hold. The rest of the time, the top 1/8" of the nail won't penetrate and will either stick up or break off. Even in those cases, the lower, part of the nail is still embedding itself into the spoil board, only, not as deeply.

    As near as I can see, the only real difference between nailer brands is the size of the driving pistons. It would make sense that a larger diameter piston can exert the same overall force at a slower rate of downward movement, resulting in less breakage. Though, I don't imagine it matters that much since you can just dial back the pressure to achieve similar results.

    Thank you for the quick reply. I will try to duplicate your results as I should have the B/18-100 by the end of the week.

    I've heard of these plastic nails some years ago, but was never able to find them to buy. I had pretty much the same idea of holding small pieces to a larger board for machining. Where are they available?

    4 replies

    The company that makes them is called Raptor and we bought them from Duckworks Boat Builder Supply (http://www.duckworksbbs.com/tools/raptor.htm). They also make larger 15 gauge nails for more serious work holding, but the 18 gauge I wrote about fit into the Porter Cable finishing nailers we already had :)

    Please tell us the model number of your Porter Cable. I need to duplicate what you did. I hit two screws I was using and ruined two $30 bits.


    the 18 guage brads are pretty much universal. every 18 guage gun I know of takes the same ones. only difference is some will drive longer nails than others, but this is clearly stated on the packaging of the gun.

    I agree with your comments but some 18 gauge brad equipment does a better job than others with the same nail. RAPTOR NAIL THE nail manufacturer says the only equipment they _know_ will work is the one they sell. Nice piece of equipment but I am trying to use what I have like irmiger did. It would be helpful to know _exactly_ the one he used. I was told by a seller of everything available the OMER would give consistent results. Anything else would be a gamble with only a 10% favorable outcome likely.

    Did you ever get around to trying the polymer nails?

    Printing a 1:1 picture of your cutting path and placing over the material to be cut. will allow you to see where to nail through waste wood.