How Do I Retemper My Sewing Needles?

[ramrod]

well, the heading says it all. i recently curved a couple of my needles and realized that they're soft as butter. i know i read somewhere on here how to retemper them - and i did a search, but i can't find any info.

i'm not sure whether to heat and let cool....or heat and quench....what color to heat to.

HELP! beacuse i can't sew with them as they are now.

Edited October 22, 2011 by ramrod

[Art]

Well, if they are steel, pick one up with a magnet, heat with a torch until they drop off the magnet into light oil to quench. Keep a lid for the oil in case it ignites. After they are cool, pick up with pliers and heat till it turns gold or blue and let cool normally.

I'm driving blind here as I have no idea what steel they are made of. So you are on your own.

Art

well, the heading says it all. i recently curved a couple of my needles and realized that they're soft as butter. i know i read somewhere on here how to retemper them - and i did a search, but i can't find any info.

i'm not sure whether to heat and let cool....or heat and quench....what color to heat to.

HELP! beacuse i can't sew with them as they are now.

[TexasJack]

Flying blind, indeed! If you don't know what the steel is, you don't know what it will take to harden it. Heating to non-magnetic and quenching (followed by holding a more moderate temperature for a few hours) will work for simple steels. If the needles are stainless steel, a different method is needed.

Steels don't lose their temper over some period of time unless they are exposed to a lot of heat (like 500 deg. F.) If the needles are to malleable (soft), then they were always that way and may not be made of a steel that will sufficiently harden. The solution is simple: buy better needles.

Avoid packages with the term "Made In China". Chances are pretty good the steel isn't any good.

[TwinOaks]

Given the cost of needles vs. the time to heat, harden, temper, and resharpen..............just order another pack of needles.

[JDM]

As mentioned, heat to bright red (non-magnetic), then quench. Generally, with uknown steel, you should quench in oil first. Then check hardness (use a file). If it didn't harden, heat red hot again and quench in water. The reasoning behind this is oil hardening steel can crack if quenched in water, so try oil first. For cheap needles, maybe try water first. If it breaks, it breaks.

After hardening, the steel will be very hard and brittle. You'll need to draw (soften) the steel. Clean the steel with whatever is handy so you can see its color, then heat to the desired color. Temperature charts can be found online, which should put you in the ballpark. A toaster oven can work depending on how far you need to go. I don't know how hard needles generally are. If careful, you could slowly heat with a flame to soften the middle while keeping the tip harder. Quenching at this stage doesn't really matter. There isn't any need to, though it helps if you want to immediately stop the heat traveling to parts you don't want to get so hot. In other words, maybe heat mostly from the eye. Let that come up to brown/purple, while keeping the tip straw colored. Or whatever temp range needles need. They are cheap enough. Experiment. If you aren't happy with the tempering, heat red hot and quench to reharden, and start over. You can probably get away with doing that several times.

Of course, this assumes the needles will harden. If they don't after quenching in water, you're out of luck. Well, unless you want to get into case hardening. You don't.

Edited October 29, 2011 by JDM