Is there a hot knife or hot wire cutter for plastics such as Kydex?
September 23, 2022 7:33 AM   Subscribe

I need to make precise cuts in Kydex. A wide kerf is ok as long as I can control its location. Scroll saws — the customary tool — are loud and violent. They fling particles everywhere. I'm trying to avoid collateral annoyance.

I searched online and found dozens of hot knives and hot wire cutters. However, they're all advertised as "foam cutters." So I don't know if they'd work on Kydex.

I sacrificed a couple soldering iron tips to test the idea. It seems like it could work, but the tool would need to be hotter.

Any info or advice would be greatly appreciated. Thanks ◉
posted by trevor_case to Sports, Hobbies, & Recreation (8 answers total)
How thick is the sheet you’re trying to cut?
posted by btfreek at 7:57 AM on September 23, 2022

I have never been able to cut Kydex -- even the thin sheets -- without a great deal of force. Using a knife with that much effort risks slipping and gashing the whole sheet. I've had to trace my cut lines many times, deeper on each pass. (That stuff is good and strong, but a real pain to work with!)

Thinking about your idea, it seems that the intense heat required to melt Kydex of any thickness quickly would probably also result in a fairly wide "kerf," with soft edges. Pretty ugly, unless the piece is a stiffener that will be hidden from sight.

If your hands are steady, maybe you could use a very fine grinding tip on a Dremel tool, dragged along your cut line? Still loud and messy, unfortunately.
posted by wenestvedt at 8:04 AM on September 23, 2022

Looks likely to produce hazardous fumes.
posted by jon1270 at 8:13 AM on September 23, 2022 [4 favorites]

Response by poster: How thick is the sheet you’re trying to cut?

0.080 inches
posted by trevor_case at 8:15 AM on September 23, 2022

You may want to check out using a bandsaw.
Advantage: the saw only pulls down on the work piece with a constant speed, where a scroll saw or a jigsaw will reverse twice on every stroke. It's the starting after reversing the stroke where the saw tends to catch on the work piece, causing the splintering. I've never had stuff splinter using a bandsaw where it definitely would have using a jigsaw or scrollsaw.
Downside: bandsaws obviously have their throat limiting the size of the work piece.

If it's straight cuts you need to make an angle grinder with a cutting disc (thin, not a thicker deburring disc) will do the job.
posted by Stoneshop at 8:52 AM on September 23, 2022 [3 favorites]

How big are the sheets? Are you cutting only in straight lines? Would an office paper slicer work?
posted by ZenMasterThis at 9:16 AM on September 23, 2022

Fret saw it you only do it occasionally.

It has halogens (chlorine) so do not burn or melt it.
posted by flimflam at 10:01 AM on September 23, 2022 [3 favorites]

If you have a pair of hardened steel shears they should work pretty well unless the pattern is really complicated.

If it IS complicated and you don't have a bandsaw, one thing I've done for similar problems cutting thin materials in the past has been to sandwich the material between two sheets of another sacrificial material (eg: thin plywood, or hardboard, etc). This helps stabilize things. I have not cut Kydex in this way, but it is probably worth a try and may let you continue to use the tool you've already got.

Also, just in case, when flimflam says don't burn it -- that applies DOUBLE if you were thinking of using a laser. Do not use a laser to cut Kydex, it will destroy the laser and possibly your lungs.
posted by aramaic at 11:51 AM on September 23, 2022 [2 favorites]

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