[JayWal]

I did a job last week for a car/truck wash, modifying a section of their floor grates. They used railway track flipped upside down (flat side up) spaced 1 1/2” apart running across the floor, the ends welded to 5x1/2 flat bar. They wanted a section made narrower so the job basically meant cutting 4 of the tracks off of the flat bar, shorting them by 1” and welding a new piece of flat bar onto those 4 pieces, making that one section removable from the floor giving access to the drain pit underneath.

Anyways I cut the 4 tracks out with oxy/acet, too the pieces to my band saw to trim them down to perfect length. I cut the first one and my saw seemed to really struggle to cut. I’ve cut track before, usually it slices like butter. It was an older blade so I slapped a new one on and finished the rest no problem.

Saturday I was cutting simple 2x2 box tubing and the cuts were horribly off square. The blade would twist in making a curved cut. I don’t use cheap blades so having 1 last just a week is a problem.

I wondering if tho if the oxy/fuel cut maybe hardened the steel? I was pretty much just shaving down along the oxy fuel cut with the bandsaw just to square it up. Anyone know if that could’ve been a hardened edge that maybe dulled my blade so fast?

[cj737]

Flame cutting it shuold not have hardened it. But saw cutting it is pretty hard work on a saw blade, especially if you don’t use a cutting fluid. Maybe you overheated the blade?

[JayWal]

Flame cutting it shuold not have hardened it. But saw cutting it is pretty hard work on a saw blade, especially if you don’t use a cutting fluid. Maybe you overheated the blade?

No I use lots of coolant the blade was never even warm. Maybe because I was just skimming off sometimes the teeth on one side wore a bit more than the other side so the blade pulls to one side? I don’t know 8 cuts shouldn’t be enough to to that to a blade I wouldn’t think.

What about breaking in a blade? The owners manual suggested that for a new blade, run it slowly with a ton of coolant through a solid 2” stock or something the like. Is there any point in doing that?

Edit
Old blade

C8C2E7A8-70BF-47EE-BEE7-EA28DB50F9A4.jpeg (22.29 KiB) Viewed 2363 times

New blade

112FFAB8-8A50-4450-B8C8-F6DBA0A35438.jpeg (21.02 KiB) Viewed 2363 times

Teeth on one side obviously rounded off compared to new

[cj737]

If you’re only trying to surface an edge with a bandsaw, yep, you’re going to waste that blade. It needs to be cutting through material, not “against” a surface.

I’ve never done a blade “break in”. WTF?

[noddybrian]

" Breaking in " a blade is a " best practice " thing which most folks don't do but can effect service life - most edged tools are similar in that mass production methods leaves them with significant burrs after grinding the cutting edges - if you apply gently pressure with plenty of coolant on a wide surface area of cut the blade will wear these off slowly & evenly & cut well - if you run it dry or little coolant on thin stock & / or with too much feed the burrs tend to hang up causing excessive cutting force or vibration & will " micro chip " the cutting edge leaving it much less sharp right from 1st use hence overall cutting life will be less the burrs are as hard as the blade & will get dragged through the cut giving high wear - wood guys are probably more aware of this type of situation which is why they hone a finished edge whether on a plane iron or axe - it's easier to see on this kind of blade than the size of a bandsaw blade tooth - it's also possible that you needed a different blade either in material type or tooth count - having too many in contact with the work results in too little feed pressure to make them cut & causes premature wear which is often a problem when occasional cutting large sections with your normal higher tooth count blade used on RHS etc
- track is also a crap shoot from what I've cut - it's rarely consistent & the top is usually harder than the base - any time I've cut it with a blade I've found a hard spot withing a low number of cuts & ruined a blade so now I only use abrasive - either a petrol cut off saw or a large electric chop saw .

[Mike Westbrook]

If anything heating and slowly cooling the track should have slightly tempered it and call me crazy but I always break in my blades maybe it's mental but I swear they stay sharp till there's nothing left the idea is a slow pass with zero vibration

[noddybrian]

@ Mike Westbrook
Sorry but I can't agree on the tempering thing - I often have to machine flame cut material & the cut edge / HAZ is almost always harder than the original material - a weld is even worse - I keep larger radius carbide tips for just this kind of job - I don't have any proof but I always assumed that on thicker material that the mass of material chills the cut edge & in effect hardens it slightly - the hotter & faster the localized heat the worse it hardens hence a weld becomes harder than a flame cut - but it's only a personal theory - maybe others have a more in depth opinion.

[cj737]

@noddy-

While I agree that flame cutting some materials will harden them, railroad track is not usually among the steels that will harden by heat. Its pretty mild carbon steel and if it wasn't quenched after cutting, at best the slag will be harder but the base doesn't get that way.

It sounds as though how he cut it (edged the blade) is more likely the culprit. I've cut heaps of antique rail track with flame and Zip wheels and bandsaws. I've never experienced a problem. That is not to say that somehow the material he cut that day isn't unique, but it should not be hardened after flame cut. I think the best evidence of that is his own statement that, "It was an older blade so I slapped a new one on and finished the rest no problem."

[Mike Westbrook]

In a sense flame hardened my thought was a large peice like that in the floor of a car wash wouldn't get to that kind of temperature I guess if he was just skimming the edge it would be slightly hardened

[Mike Westbrook]

CJ I think you nailed it if the drop came off of the track like a piece of bark then he definitely edged the blade essentially only using half of it to do all the work

[JayWal]

CJ I think you nailed it if the drop came off of the track like a piece of bark then he definitely edged the blade essentially only using half of it to do all the work

That’s exactly what I tried not to do I tried to cut enough off that the whole blade was cutting but my torch skills are terrible so it wasn’t a perfectly straight cut, and with the tracks so close together there wasn’t a lot of room to get the torch in and see. But yes don’t worry I’ll man up and admit I fudged up a new blade oh well, the fastest way to learn is to make an expensive mistake

[cj737]

LOL! The straightest cut by hand I've ever made would make Liberace look like a spaghetti noodle. I now use a bronze bar made form 1" thick flat stock, 2" wide. A clamp on either end, and guide the nozzle against it. I spent a fair bit of $ to buy it, but the time and discs its saved me in clean-up paid for itself 4x over within the 1st year.

[tungstendipper]

Or... build yourself one of these:
https://www.youtube.com/watch?v=JwExFph3e10

[Mike Westbrook]

a torch guide makes a huge difference I made one from a $6 Carpenter square with angle iron welded to the back I can put a pair of vice grips at a certain measurement and easily cut to depth with it

[cj737]

Those work well enough, but the bronze bar is not susceptible to the heat from the cut, doesn't slag up, and is strong and straight. I found using angle iron can introduce some twist after enough cutting.

I do like his idea of the guide "ring" for holding the torch perfectly in position

[Mike Westbrook]

At $6 it's definitely sacrificial I do like the idea of a chunk of bronze

[kwhit190211]

Back in the old days, when I was still working, now retired for almost 10 years. I learned early on not to use a bandsaw to cut something that has already been flame cut. All you do is ruin blades. Makes the metal harder & puts a real hurt to the blades. And, blades aren't cheap. Why don't you just put a smaller tip size in your torch and use the torch.