[67drake]

I have a forklift attachment that I use at work on the Bobcat and tractor. The previous guy had somehow bent one of the forks. This causes problems for obvious reasons.
I’d like to straighten out the bent one, but I’m afraid heating it with an oxy/acetylene torch might make it brittle and therefore dangerous.
Any ideas?
Thanks!

[sdbob]

Safety. Check Google for an answer

[Shiny]

With zero experience straightening forks, I'll jump in anyway.

I suggest you NOT heat it, as it is probably made of a heat-treated, tough alloy like 4140.

Heating enough to help bend it will weaken by annealing, or worse, could embrittle if the heat is high enough. To make it "tough" typically involves tempering back from a quenched, brittle state.... in other words, a controlled heat-treating process that will be difficult to reproduce with a torch, along with being "localized"

The fact that it bent without breaking shows the fork has significant ductility. Like a coat hanger, you should be able to just bend it back with low risk for it breaking and without decreasing its strength.

Net: I'd try and find a way to straighten it without heat. Will obviously involve some big forces or big levers, but you have a big machine behind the forks. Ask the guy that bent it how it happened and try to replicate the scenario in reverse...

Good luck!

Mike

[67drake]

Originally Posted by Shiny

With zero experience straightening forks, I'll jump in anyway.

I suggest you NOT heat it, as it is probably made of a heat-treated, tough alloy like 4140.

Heating enough to help bend it will weaken by annealing, or worse, could embrittle if the heat is high enough. To make it "tough" typically involves tempering back from a quenched, brittle state.... in other words, a controlled heat-treating process that will be difficult to reproduce with a torch, along with being "localized"

The fact that it bent without breaking shows the fork has significant ductility. Like a coat hanger, you should be able to just bend it back with low risk for it breaking and without decreasing its strength.

Net: I'd try and find a way to straighten it without heat. Will obviously involve some big forces or big levers, but you have a big machine behind the forks. Ask the guy that bent it how it happened and try to replicate the scenario in reverse...

Good luck!

Mike

Yeah, that guy doesn’t work here anymore!
Good info though. We have a full size Kubota “farm” tractor , which is what we usually use it on. I’m sure we could figure out some way to give it the beans to bend it back.

[FrankieT/A]

Straighten it in a Press.

[Jay S]

When we have bent forks it worked best to find something heavy to pry against to bend it back with it on the loader yet. Forks are generally heat treated, heating them again will weaken them.

That is a relatively light duty fork to bend like it did, probably made of 1050 or 1060 steel.

[Sirrotica]

Former fork lift tech here, DO NOT HEAT THEM, you will weaken them for sure because of the heat treat. You'll have to bend them cold such as on a press, but they will still not have the same strength as they did before they were bent.

Ideally if someone such as myself would inspect the truck the bent fork would be condemned until it was replaced. Straightening them isn't considered as a proper repair because the units safe lifting capacity would be compromised, thus compromising safety, leaving a liability.

In the real world things sometimes fall outside of the ideal circumstances, and people elect to save money and open themselves to a bit of increased liability after weighing out the probability of all factors. I can't say I haven't done this myself.

[b-man]

Maybe buy a new fork.

Or send it to a heavy equipment repair outfit and let them handle it.

Don’t hurt yourself trying to save your company a few dollars.

[455Grandville]

Buy a used pair; I see em occasionally at used construction site auctions for pretty cheap.

[Shiny]

Originally Posted by b-man

Maybe buy a new fork.

Or send it to a heavy equipment repair outfit and let them handle it.

Don’t hurt yourself trying to save your company a few dollars.

If you are making a decision for an employer, this is good advice.

Consequences of a bad decision are clearly different than if you are your own boss.

In theory, the risk for weakening the fork by straightening is low IF the bending was uniform along the fork AND the plastic deformation strain was low. If all the deformation happened in the tight root radius, risk for weakening by straightening is much higher. If the deformation strain is spread out along the fork, it will be much less likely to cause irreparable damage than if the strain was highly localized on the OD of that small root radius. But this is just theory and visual inspection might miss the truth. Not worth risking a failure if you are making a guess for your employer.

Sirrotica - are there shops that can "certify" a repair by "proof load" testing? Or is fatigue risk a big factor that makes it difficult to certify a repaired fork? Just curious.

Mike

[Bills Auto Works]

Watering Eyes Here! LMAO!!1

Had a really bad day today & then saw this.......

I use my fork lift with the extended forks I purchased for loading, unloading & removing from the chassis engines, transmissions etc.

If I bent one...I would back the dually inside the building & drive over it to make it back to straight, then would go onto the task at hand! Wouldn't post it on a forum or think twice about it! LMAO!

God Bless
Bill
https://www.jalopyjournal.com/forum/...closed.614419/

[Sirrotica]

Originally Posted by Shiny

If you are making a decision for an employer, this is good advice.

Consequences of a bad decision are clearly different than if you are your own boss.

In theory, the risk for weakening the fork by straightening is low IF the bending was uniform along the fork AND the plastic deformation strain was low. If all the deformation happened in the tight root radius, risk for weakening by straightening is much higher. If the deformation strain is spread out along the fork, it will be much less likely to cause irreparable damage than if the strain was highly localized on the OD of that small root radius. But this is just theory and visual inspection might miss the truth. Not worth risking a failure if you are making a guess for your employer.

Sirrotica - are there shops that can "certify" a repair by "proof load" testing? Or is fatigue risk a big factor that makes it difficult to certify a repaired fork? Just curious.

Mike

I've never seen or heard of any facility to test forks, if they were bent and noticed during a PM service the forks would be measured for wear and the bent one would be noted for replacement.

If they were worn more than 10% of the vertical portion on the carriage they would also be recommended for replacement. We had gauges to test for wear. You'd be surprised how many forks are worn along the bottoms more than 10%, especially if the unit was in a high production setting. BTW, 10% wear along the bottom reduces the load limit by 20%.

Proof testing would likely be similar in cost to replacement, plus the liability would be prohibitive.

[burd]

Have the other one bent the same.
One time a guy went under a bridge that was too low, he was hauling a FL, it snapped off both forks. If you could imagine.
There is an adjustment on the chain on ea side to even the forks out.

[nas t eh]

My experience at a large Chemical company with lots of forklifts is exactly the same as Sirroticas. Forks get replaced not repaired.

[JSchmitz]

Straightening shouldn't even be considered. Scrap metal now. I would also inspect the carriage for bends, broken welds, etc. It may just be the picture. But it looks like more than the fork is outta wack.

[67drake]

Thanks for the input everyone.

[justincampbell]

Honestly, I would've been in the "Just bend it back" camp. This was really interesting to read some of the more technical stuff regarding the forks.