Tapping threads in PLA

[Scott Goldthwaite]

Any advice for tapping threads in PLA?  I've tapped 4-40 and 1/4-20 holes, and they come out okay, but the plastic that's cut out is getting clogged up in the tap.  I'm just using regular High Speed Steel tapered taps.  I see that McMaster-Carr has some cobalt steel taps made for plastic.  They actually have a tap for hard plastic (P/N 2490A19) and soft plastic (P/N 2490A39).   They list hard plastics as: epoxy, melamine, EPDM, and phenolics; and soft plastics as: nylon, polyethylene, polypropylene, PVC, and polystyrene.  Would PLA be a soft or hard plastic based on these lists?  I'd be interested in any tips and advice.

[AKron]

I haven't had a problem with chip clogging tapping by hand, but I like
to print my threads if I can. The smallest I've printed though was a 6
mm threaded shaft.

[AdanA]

Hi Scott,

For a really bomber thread in the part, consider trying the melt-in inserts. I wrote an article about my experiments with hand-tapping vs. Helicoils vs. the melt-in options. There's a link there to a McMaster part number to consider:

http://www.makersite.com/blog/2012/8/24/threads-in-a-3d-printed-part

I just heated the brass insert in an oven, set to my extrusion temperature (ABS in my case, but same approach for PLA), then grabbed it out with pliers and jammed it into the printed part. Worked beautifully.

Adan

[Scott Goldthwaite]

The melt in threads look like a good solution.  I'll give them a try.

[Adan Akerman]

Best of luck! Observe the recommended hole diameters and lead-in tapers and all should go smoothly.

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