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Discussion Starter · #1 ·
Well, I certainly know better and it actually crossed my mind in the process. But for some reason, I did not do what I know I should do and paid the price.

Been working with my centerstand on the '66 Bonnie. It was tweaked when I got the bike and actually close to rubbing on the chain. Managed to win a spare on ebay so I'd have a good example to check dimensions and angles. Got out the torch and started to bring the stand back into spec. Found a broken weld on one end of the crossbar and did not reweld it until I had the stand straight. I had let the metal cool naturally in air during the process. When I put it on the bike, it turned out to be pretty soft and the foot lever bent. So went thru the straightening process again. When I was done, I got out the rosebud and heated up the repaired leg and quenched it. I never thought there was enough carbon in that stand to make it too hard. I thought about tempering it, but decided it would be fine. Put it on the bike and tried to put the bike up on the stand. The repaired leg snapped off like it was made of glass. I could not believe it. But I have to admit I was not surprised and called myself a few special names, mostly because I know better than to do what I did.

So I thought I'd post this here for the next poor soul who needs to straighten his center stand. Make sure you temper it after you harden it or you'll end up snapping yours off just like I did. Actually, I'd suggest you try to cold straighten if you can, instead of putting the heat to it.
Embarrassing yours,
Rob
 

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Discussion Starter · #4 ·
doo doo happens to everyone. now why dont you tell the troops how to temper the metal.
Well, I'd have to look up the temps to be truly accurate. My old rule of thumb was to heat to cherry red and quench. Then reheat to straw color and quench. That was primarily for things made from drill rod. Using surface color requires you to clean the surface between treatments. Given the surface finish of these stands, it is probably easier to use either an infra-red thermometer or Thermomelt sticks. Sunshine Jim says go for purple spring temper, which could be a better choice than straw. I'm red-green colorblind so seeing purple requires assistance of the wife. It's been awile since I've done anything like this and doing something this size and shape with a torch is not as easy as a small part. If my memory serves me well, I remember the transistion from straw to blue coming very quickly.
regards,
Rob
 

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Tempering temps.

i was holding off on the technique, i did'nt want to hog the fun.

Basics:

Tool steel hardens when you take it to 1450-1500掳F (788-843掳C) basically cherry red, and non magnetic and then cool it quickly by quenching it in oil.

But fully 'Hard' also means brittle like glass with a lot of stress locked into the steel by the quenching.

Tempering changes the molecular structure and 'working' charecteristics of hardened steel.

So you can tell tempering colors by color or by using a pyrometer like I often do. But about 10% of us are color blind for one reason or another.

For a chunk like a centerstand I'd sand one of the legs full length about a half inch wide to "bare steel" and heat evenly with a tiger torch till it reaches the right color/temp and then tip it into a bucket or tub of water.

you don't have to heat it quickly, just go slow and even. I did a barrel catch spring for one of the oldest shotguns in BC and mirror polished it. It is a beauty dark purple.

heres some of the color range from cold to Blue temp.

0575掳F Blue 302掳C

0540掳F Dark Purple 282掳C

0520掳F Purple 271掳C

Purple to blue is "Spring temper". Blue would be fine for a centerstand

0500掳F Brown/Purple 260掳C

0480掳F Brown 249掳C

0465掳F Dark Straw 241掳C

Brown purple to Dark straw is tougher edged tools but a little bit brittle

0445掳F Light Straw 229掳C

0390掳F Faint Straw 199掳C

Light Straw to Faint Straw is the surgical cutting tool area still fairly brittle.
 

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Discussion Starter · #6 ·
Jim,
I'll bet you though we were gonna say sumpthin stoopid, didn'tcha?

Thanks for posting that info. Sure saves some research. The last time I did anything like this for the purposes of hardening/tempering was for small custom cutting tools I made a long time ago. And you are right, we would quench them in oil, not water. Normally I color pistol screws to flame blue when I need to replace a missing or buggered screw in an old gun.

I'm going to take the stand to my friend the welder. He's second generation owner of the shop and should be able to bring the stand back to life. He might even have a small over we could temper it in when he's done. I could weld it, but it just would not look as nice. Plus he'll have all the right rods.

What kills me is I had this stand absolutely perfect. Even welded up the stop so it stopped about 1/8" (that 0.125 inch Kadutz) from the muffler. Turns out there was not much meat to the stand where it broke. It fracture right at the crossbar socket so wall thickness was no more than 1/8" in almost all locations.

Did notice an axial crack had formed in the lever arm as well. I think I thermally beat the daylights out of that stand in the straighten process. It was pretty cockeyed when I started.
regards,
Rob
 

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It is very satisfying though when things work out. I recently had to straiten an operating lever that was permanently attached to a big chunk of cast iron. ( operating lever on old plough) I ended up hand forging it over a BBQ :)
 

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Discussion Starter · #8 ·
I agree, Panda. I was actually quite proud of how well that stand had come out... until I broke it. It was part lazy, part impatience and part over confidence. In hindsight, it is just stupid to not think that the stand was high grade of steel when you consider the duty it sees. I'm more upset over the error in judgement than the damage to the stand.
But adversity builds character, right?
regards,
Rob
 

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Stoopid? i thought i had the corner on the market!

Theres so many different attitudes in the old brit fan base that i just want to help without hurting. Sorta like the old Hippocratic Oath eh? But like that ancient code it's somewhat outdated, and occasionally inconsistent with today's riders.In the 60's we had a wonderful bunch of old fart, riding fools to get the tech from, nowadays we is the old fools. I live for the irony and the good company both.

I'd guess most of the probs with the stand were from it being in a hardened state when you put it back on and stressed it. Taking it to critical relieved all the stress, quenching it to hard is what put the stress back in, sorta reminds me of dating in the pre birth control era. no biggie. I remember a few knife blades and tools shattering like glass when they fell off the bench after hardening but before i was ready to temper. Good steel will do that.

welding will crack hardened stuff too. You could take it up to non magnetic and bury it in some sand to cool slow to annealed state, tweak, weld and grind and then harden and temper.

All this is for fun and the art of it mostly right? I like to think of my anachronistic self as being on the trailing edge of technology. That and I'm extremely fond of the noise a good ol twin makes on the putt home.
 
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