Newbie bandsaw question on reusing a bent blade.

**DaveVman** · 9th July 2018, 06:11 PM

So I'm going to admit to a stupid newbie mistake.

Last month, the wife had a small log which she wanted cut crosswise to make 2 smaller logs. It was not nearly long enough to do it with the chainsaw. I don't have a proper vice so I couldn't do it with a handsaw - which is how I really wanted to approach it. The only saw with enough depth was the bandsaw. I had just changed the blade with a new cross cutting blade. I was not at all sure about doing it on the bandsaw but I wanted to please my wife. I didn't know for sure if this was a bad idea but my gut was telling me that something with no flat face into the bandsaw was too risky.

My only excuse is that, I've cut a lot of round plastic pipe with a bandsaw. A lot. I helped to create two entire industrial scale hydroponics hot houses of half round pipes. I have far more experience with round pipes in bandsaws than I have done any woodworking with bandsaws. So although part of me was thinking this must be wrong, my limited experience was sort of blinding me to the obvious difference with working with wood.

Whenever I get that bad gut feeling about a cut on any machine I stop and think about it and imagine or play act pushing the piece all the way through the cut. Then I hope whatever it was that was in the back of my mind will become apparent to me in my play acting before I turn the saw on. I stood there holding the log for a second and I thought well the log could try to spin a bit but it isn't going to come out of my hands. I'll go extra slow. For some reason it didn't occur to me that it could also twist suddenly. It did occur to me that I still had that bad feeling about this. If I had stopped right there and thought a bit more I might have realised, there was plenty that could go wrong. I might have at least thought of making a jig.

So I started the cut. No jig. The blade caught and the log twisted. The blade jammed.
It still took me a good two seconds to realise what had happened, release one hand and kill the machine. Felt like 3 minutes in my mind.
I instantly said to myself "what were you thinking?".

Ah well. I'm fine. My 10 fingers are fine. The machine is fine. The new blade is now bent. Could have had a different ending!

I replaced the blade and told the wife I can't cut her log at all unless she wants it split lengthwise with an axe, sorry.

I'm going to throw the blade away today. Even if I did twist it back flat I have lost confidence in that blade ever being safe again.

My question is not about the cut. That was wrong. Lesson learnt. Don't know why I tried it.
My question is an academic one for future reference. If I did hammer or bend the blade back to flat, would it still be OK or is it always going to be too risky to use such a blade? Ever worth straightening a bent bandsaw blade or just not worth the risk? I figure blades are cheap and new fingers are expensive but I was wondering.

**elanjacobs** · 9th July 2018, 06:23 PM

If the blade has been bent, throw it out. You'll never get it perfectly straight and, even if you did, there may be invisible stress fractures that could pop at any moment.

**woodPixel** · 9th July 2018, 06:52 PM

I've never recovered a bent blade successfully. They always have a tick or cut a thick messy kerf.

**Skew ChiDAMN!!** · 9th July 2018, 07:30 PM

I have a few blades that have been kinked and straightened.

As has been said, it's never 100% successful and I do not rely on them for any cuts I want to be clean, tidy or straight. That being said, they work perfectly fine for splitting or docking old logs (in a cradle, of course) and shortish boards. But I mostly use them for cutting up meat.

I'm not concerned about the blade failing dramatically; eventually they will fail and probably with a BANG from the upper wheel as the tension is released, making one wish they were wearing brown pants at the time. However, the blade itself usually either just stops dead or slithers off to one side.

Nowhere near as dangerous as a Table or Circ saw blade letting go, for example.

I wouldn't recommend you to do the same, but...

**simops** · 9th July 2018, 07:44 PM

You could have it professionally cut and resoldered but to be honest it’s more trouble than it’s worth........just ditch it and get another.......

**KeithP** · 9th July 2018, 10:57 PM

I doubt that you would get it flat enough so as not to foul the guide blocks on your bandsaw.

Regards
Keith

**arose62** · 10th July 2018, 10:16 AM

It's not just the physics-type issues (which you can address with jigs etc.) but there can also be hidden stresses inside the wood, which you can only find out about whilst cutting

I had one green branch, about 60mm diameter, snap shut on the bandsaw blade mid-cut, and vastly elevated my heart rate! I couldn't pull the cut open, or wedge it, so ended up handsawing and chiseling to free the blade.

**pkroeze** · 10th July 2018, 12:04 PM

You're not alone Dave

I have also done a similar thing on a bandsaw, I think mine was more dangerous, I had a small block 180x80x60 that I was cutting a PC mouse profile from, anyway the outer curves were fine to cut as the bottom was flat, the moment I threw it on its side to cut the top curve was when the stupidity began. Anyway, the moment the saw touched the block there was a big bang, the blocks face got pulled down and busted the plastic insert, the back swung up and jammed under the chassis. I was nervous about it to begin with, and had been holding it lightly so thankfully it just slipped out of my hand and I was fine, I'm glad I didn't decide to try and hold it tightly or put my hand on top of the block or that would have been the end of any woodwork for me. Anyway, I straightened the blade out in the x and y-axis but in the z-axis, there is a definite kink that I would never be able to fix so new blades for me. So yeah, only ever using jigs for stuff like this from now on

**Skew ChiDAMN!!** · 10th July 2018, 12:42 PM

Originally Posted by pedro66

I doubt that you would get it flat enough so as not to foul the guide blocks on your bandsaw.

It's usually fairly simple to flatten the blade enough to clear even the tightest guide blocks easily.

Where the problem lies is straightening it in the forward/back direction. This isn't really practical to even try and will result in the blade 'pulsing' in the cut which can cause it's own set off problems/perils while cutting.

I'm unsure whether this bent is caused by the stresses of impact or the process of flattening. (Most creases aren't 'even' and are tighter at either the front or back of the blade.) I suspect it's a combination of both. Bi-metal blades suffer the worst from this.

**China** · 10th July 2018, 05:21 PM

just cut the kink out and rejoin, i would have done so many times

**Toymaker Len** · 11th July 2018, 12:16 AM

Blades do get jammed and bent as you explore the limits of the machine. They are fine to straighten and then keep using but you will get a rough cut so only useful for firewood etc. As for danger, the damaged blade is going to fail in exactly the same way as an undamaged blade, that is it will go bang and at that moment you can be confident that the bandsaw is about the safest cutting machine available. As the blade snaps the bandsaw springs away from the wheels and stops almost instantly as it hits the outer covering. So I have always kept using them until metal fatigue makes them break.

**Just George** · 13th July 2018, 08:08 PM

Originally Posted by DaveVman

It still took me a good two seconds to realise what had happened, release one hand and kill the machine. Felt like 3 minutes in my mind.
I instantly said to myself "what were you thinking?".

Firstly, we have all done those things we shouldn't have, and asked ourselves "WHY" afterwards. When you do any cutting, routing etc, dry run it first. This will tell you if there will be any hang ups, etc.

Secondly, most bandsaw blades are cheap, buy yourself a couple of new ones. If it was the original blade on the machine, it was going to be of average quality anyway.

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