Straightening or bending metal

[bota7800]

Are there any guidelines about how to bend metal? What temperature do you preheat to?

Examples-
1. My new-to-me rock rake has a couple bent tines. Can I heat and bend them back to somewhat the original shape.

2. The blades on my manure spreader need to be straightened. I can lever these to bend them back but that work hardens them. Can I preheat the metal?

These are my current needs but I frequently come across this and I don't know what I am doing so I would like more information.

Thanks all.

 

[jmfox]

I do it with hammers and wood to avoid hammer marks. It's a Zen experience, unless of course you know what you're doing. Strange, yet the results always amaze my friends. If you have an eye for symmetry and level, try it.

jmf

 

[MJPetersen]

Rake tines should be made of spring steel. It is shaped and then tempered. So if you heat it you will destroy the temper. If you try to straighten them without heating they will probably fracture. The best thing to do with rake tines if you are not prepared to re-temper them is to replace them.

Sorry I do not know at what temp or the method that you should use to re-temper them either.

Mike

 

[bota7800]

Thanks. I have done OK using hammer and dolly when taking the dents out of a horse trailer but that is thinner metal. I thought with the blades I would need to heat them but I guess I will try carefully straightening them cold. I know that the trailer repair shop I used to weld some parts used heat when they straightened a bent step.

Mike, that is about what I thought about spring steel but wanted some input.

 

[ray66v]

The rule I was always taught was don't heat treated steel, and if you do heat it, use as little heat as possible, and let it cool on its own.
Try it on a tine or two, and see what happens. You can always replace them.

 

[bota7800]

The rule I was always taught was don't heat treated steel, and if you do heat it, use as little heat as possible, and let it cool on its own.
Try it on a tine or two, and see what happens. You can always replace them.

I will try it cold first. Makes me wish I had bought the Pequea- it has bolted on tines.

Is there a way to tell if steel has been heat-treated or do you just assume it has been in an application like this?

 

[MJPetersen]

Makes me wish I had bought the Pequea- it has bolted on tines.

Wait, are you saying that the tines on your rake are welded on? If they are then either they are not treated, or they have already been damaged by the welding.

Mike

 

[bota7800]

I would hit it with a rose bud tip on the oxy/acet rig and bend them how you want.

If they are heat treated then bending them back may break them without heat.

You can always quench them in oil after heating them, that'll put a little temper back in the heated part.

That's what I love about these forums- ask a question and get diametrically opposed recommendations .

I have been thinking about getting an O/A setup anyway so I may try it. It would be nice to know what temp range to heat to.

 

[ray66v]

The only way to know for sure, on your rake, short of finding someone whom has fixed one, is going to be to try it. Find out what works, and then you will know.

I would heat it only where it appears to have bent, and then, heat only enough to be able to bend it back. This is the safest approach. If it appears to soften up the area you heated, i.e. bends very easily there again, you could run a couple of beads of weld over it to stiffen it back up.

 

[bjcsc]

Rake tips are always getting out of line. I made a tool for lining mine back up (cold). It's just a 4' piece of 1 1/2 x 1 1/2 x 1/4 angle with a piece of 1 1/2 x 1/4 tube with one side cut off welded to it about 10" or so from one end. Slip it over the tine, bend it back.

Chances are it's spring steel, even if it's welded. If you heat it enough to bend it, you'll take the hardness and the temper out. If you quench it, you'll get the hardness back, but it will be brittle and will break in that spot next time instead of bend. You could try to re-temper it, but that is difficult as a pretty precise temp. has to be maintained for a period of time. Bend it cold...

 

[jgrieve]

in manufacturing most steel parts are bent cold. Heat makes it bend easier. Spring steel will break if bent cold generally.

 

[bota7800]

Wait, are you saying that the tines on your rake are welded on? If they are then either they are not treated, or they have already been damaged by the welding.

Mike

Yes, they are bolted to a piece of square tubing that acts as the shaft. I may try to weld on some triangular reinforcements like I saw on some larger spreaders.

 

[SPYDERLK]

The rule I was always taught was don't heat treated steel, and if you do heat it, use as little heat as possible, and let it cool on its own.
Try it on a tine or two, and see what happens. You can always replace them.

This is good advice as far as it goes.
In order the make hard springy stuff move harmlessly you will need heat absolutely! Springy steel, if high quality, is hard like grade 8 bolts or even harder. In the hardening process the steel is heated very hot and quenched. Then it is reheated to the 800-1000F range and allowed to cool. This softens it a little, but makes it much tuffer. If you were to reheat this steel very hot [bright red/yellow] and allow it to cool it would anneal it and make it soft. You dont want to use enuf heat to anneal it, but 600 to 800F will not spoil the original heat treatment. You can gauge this temperature by 1st lightly abraiding the surface to put a silver shine on the metal. Then heat the area you want to bend. When the shine turns straw brown you are at around 400F. At blue you are passing 600. At purple you are at 800 or so. Do not go further. A gradual [as opposed to sharp] bend can be done harmlessly in this range.
larry

 

[bota7800]

Yes, they are bolted to a piece of square tubing that acts as the shaft. I may try to weld on some triangular reinforcements like I saw on some larger spreaders.

D-0h!! What the blank was I thinking? Sorry

No the tines on the rake are not welded on - they are clamped like normal.


Thanks Spyderlk, that is what I was looking for.

 

[bjcsc]

Spring steel will break if bent cold generally.

I'll have to respectfully disagree with that line of thinking. If that were true, his rake tines wouldn't be bent in the first place - they'd be broken. If they are severely bent, they can't be fixed or bent cold, but if they're slightly out of line (which is my experience with landscape rakes) they can be tweaked cold. I've been tweaking mine like this for years. Catching those slight color changes in the steel is an art and is quite difficult for the average DIY guy (including me)...and what a considerable effort for a $4 tine...However, to each their own!

 

[AlanB]

Not sure if it is what you are looking for, but as for heating them (and I would not, I am in the bend cold if possible camp) And you are inexperienced (which, from the question, I gather you are in this discussion) then there are what is called Tempil markers that will be available from your local welding supply house.

Apparently Tempil is a brand, but if you ask at the welding house, they will know what you are referring too.

http://www.airgas.com/browse/product_list.aspx?catID=381&Keyword=tempil

That is the easiest, accurate way to tell temps on steel if that is where you are looking to go.

The problem with heat treating / spring steel and all the other discussions we are having here, is that none of us REALLY know, what steel you have, heck, depending on where your rake was from, and who replaced the tines along the way, the manufacturer may not know either.

I am off and wandering, but if you would like to learn more about heat treating in a practical, do it in your home shop kind of way, get the Foxfire book that talks about blacksmithing and rifle making. Excellent discussion in those volumes about seeing the colors etc. Next best thing to standing next too the crusty old timer in a dank dark shop up in the mountains.

That said, depending on how accurate you want to be, make a form out of plywood etc, and make a follower and curve them around it.

On ours (wife is a landscaper) I have a big hammer and when it starts looking gangly, I raise it up and beat the things basicly back into line, when one breaks, my local small time tractor store has a pile of them at a couple bucks each.

Good luck.