# puzzling questions about cutting and filing metal



## SE18 (Feb 21, 2008)

I've got a couple of really beginner questions here regarding metal working

1. My 59.5" band saw cuts soft metal but the metal cutting blade dulls QUICKLY if steel is cut. OTOH, my handy manual hacksaw cuts thru steel and doesn't dull nearly so quickly. Why is it that bandsaw blades can't cut steel. 


My guess: I'm guessing that my cheapy Harbor Freight bandsaw doesn't have blades made for cutting steel but other bandsaws do?

2. This really has me puzzled. I've been using a cross file to file hard steel for a couple years and the file has not noticeably dulled and keeps working well. How can a steel file file steel without itself getting filed down?


My guess: the steel file is made out of some super duper steel

Thanks in advance


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## SteveC (Jan 2, 2008)

Dave

As for the file, it depends on the actual alloy mixture and how it's treated with heat to make it harder, the same way that the bits used on a metal lathe cut steel but are also steel themselves.


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## Dwight Ennis (Jan 2, 2008)

Are you using a blade on the bandsaw that's designed to cut metal? Look at the number of teeth per inch on your hacksaw, which is designed to cut metal. Now look at the number of teeth on your bandsaw blade. Are they close? If not, that answers your question.


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## East Broad Top (Dec 29, 2007)

Also, the hack saw blade and the band saw blade are two completely different hardnesses of steel. The band saw blade has to be flexible so to go around the wheels, so the metal's softer and more prone to dulling. The hack saw blade is much more durable in that regard, but will snap like a twig if you try to bend it. 

Later, 

K


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## SE18 (Feb 21, 2008)

thanks; the teeth # are the same but now I see about the flexibility issue


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## Dwight Ennis (Jan 2, 2008)

You might look around for a higher quality 59.5" blade. While it's true the blade needs to be flexible, that has little to do with the teeth which actually do the cutting. In addition to their design and profile, the teeth can be made from carbide, hardened separately, etc. without necessarily affecting the flexibility of the blade itself. We have a bandsaw at work equipped with a "smooth style" blade used almost exclusively to cut fiberglass (which will dull a metal-cutting blade in a heartbeat). McMaster[/b][/b] and others have a whole range of blades to choose from tailored to specific applications.


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## Totalwrecker (Feb 26, 2009)

It's both alloy and the temper of the metal, files are tempered to a brittle hardness, rarely will you find a bent file (unless made that way) they break first. 

Dwight's right though about the teeth being harderned on the cutting edge. 

Try googling for quality xx" metal band sawblade... 

Then report back with the results...lol I'm being lazy! 

I have worked with hand engravers and have tempered them to glass hardness where they were unaffected by a file, then retempered slightly softer so they wouldn't chip. 

Steel is a generic starting point, there are many variables to quality.... like saw blades. 

John


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## Mik (Jan 2, 2008)

Without getting too technical, "steel" is a generic term for a whole bunch of 'ferrous' (iron based) metals. Industry has figured out how to manipulated the basic 'mild steel" which is mostly iron without a lot of other stuff, and has very little carbon (which is what makes cast iron brittle) from dead soft, like boiler plate, to various degrees of 'hardness' using 'heat treatment' (you literally heat it up until it glows a certain color, the control the speed it cools from very fast to days). They can also add other stuff (usually called 'alloys') to the basic 'steel' while it's being made, like nickle, chromium, tungsten, phosphorus, and good old carbon in small amounts to get whatever particular properties they are after. They can even make steel that a magnet won't stick to! 

Clear as mud?


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## Engineercub (Oct 18, 2008)

I personally use a dremel to cut my Stainless Steel track but I go through blades like CSX goes through employees. 

-Will


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## aceinspp (Jan 2, 2008)

Will buy some of the new Dremel EZ lock metal wheels for cutting and you wont't use them up as quickly At least you will be ahead of the CSX then. Later RJD


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## RimfireJim (Mar 25, 2009)

Posted By East Broad Top on 07/01/2009 8:11 AM
Also, the hack saw blade and the band saw blade are two completely different hardnesses of steel. The band saw blade has to be flexible so to go around the wheels, so the metal's softer and more prone to dulling. The hack saw blade is much more durable in that regard, but will snap like a twig if you try to bend it. 

Later, 

K

Have to disagree with you on this one, Kevin. Flexibility (deflection without permanent deformation) and hardness are unrelated. Strength (amount the material can be stressed without permanent deformation) are related. Often confused. There are plenty of metal-cutting band saw blades that are flexible enough to go around small wheels.

Stiffness - the technically-correct inverse of flexibility - depends only on cross-section and a material property called modulus of elasticity, or Young's modulus, which itself does not depend on hardness and varies very little with similar alloys. The modulus of elasticity for all carbon steels and most tool steels is virtually the same. 


I think you will find that a metal-cutting bandsaw blade is harder, and therefore less ductile, than a hack saw blade, and it will "snap like a twig" long before the hack saw blade, which will just take a permanent bend. It HAS to be harder to withstand the cutting speeds of the machine, and last long enough so that you don't have to keep replacing an expensive blade. A woodworking bandsaw blade isn't as hard simply because it doesn't have to be (expense).


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## Dwight Ennis (Jan 2, 2008)

Will - several 3rd parties make fiberglass reinforced cutoff wheels that fit the Dremel. Try those. They don't shatter or break like the cutoff wheels Dremel makes and they seem to last forever. Here's one[/b][/b] - there are probably others.


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## RimfireJim (Mar 25, 2009)

Posted By SE18 on 07/01/2009 6:01 AM
I've got a couple of really beginner questions here regarding metal working

2. This really has me puzzled. I've been using a cross file to file hard steel for a couple years and the file has not noticeably dulled and keeps working well. How can a steel file file steel without itself getting filed down?


My guess: the steel file is made out of some super duper steel

Thanks in advance



It's a matter of relative hardness, as Totalwrecker said. Files are made of high carbon steel and heat treated to somewhere around Rockwell C 62 (designated HRc 62) - extremely hard. Very few other steel items are that hard, one reason being that there is a decrease in ductility with an increase in hardness, so hard=brittle. Another reason is cost. The majority of steel items you are likely to encounter are made of "mild" steel, which is a lay term for low-carbon steel. It can't be heat treated to increase its hardness (not enough carbon). In between are medium-carbon steels and alloy steels that are used where a combination of strength, or hardness, and ductility are required.

A file WILL wear out - it will just last longer filing low hardness materials than filing harder materials. You can ruin one real quick trying to file something that is too hard. There is an imprecise yet fairly useful test called the "file test" to se whether an unknown material is machinable with high-speed steel tools, but don't do it with your best file, because it might come out on the losing end.


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## SteveC (Jan 2, 2008)

Dave

Another thing is you'll find that any one that does much file work will usually have at least two sets of files, especially if they work on other than ferrous based metals, one set will be used on only ferrous metals and the other set will be reserved for non-ferrous work.

The reason for the above is the differing properties of ferrous and non-ferrous metals. For example brass (a copper based alloy) is gummy/sticky and will dull a file much quicker than steel. Another example would be drill bits, most are sharpened with a profile that is most efficient for use on ferrous metal, but there are ones ground with a slightly different profile to match the properties of say brass.

Additionally, remember each alloy of any base metal (e.g. iron, copper, etc) has its very own specific properties, to which the tools made to work it must be matched, also the surface speed of the material being worked and feed-rate at which the material and the tool working it are engaged will have an effect on the tool's life (i.e. till it needs to be resharpened). The biggest enemy of any cutting tool is the exact same thing that made it capable of cutting in the first place, HEAT/TEMPERATURE.


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## SE18 (Feb 21, 2008)

Jim,

What is the file test? Something like Moh's scale?


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## Semper Vaporo (Jan 2, 2008)

The "File test" is simply to take your absolutely bestest ever file and rub it over some unknown piece of metal to see what happens. If the metal is easily machineable, the test metal will show file marks and the file will have shavings in its teeth. If the metal is not easily machinable your file will no longer be your absolutely bestest ever file and you will need to get a new one, as well as figure to use some more exotic machining tools to work the metal in question.


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## Tom Bray (Jan 20, 2009)

I think the real problem is that the Harbor Freight blades may be junk, regardless of what they claim on the package. The stainless steel may also be a bit hard on a band saw blade, regardless of who makes it. It depends on the quality of the stainless. 

I found that using a Dremel will cut through rail but the hacksaw with a decent blade does it a lot quicker. What I found was that if I turn the track upside down, stick it into the vice being careful not to deform it, it cuts pretty well. Make sure there is enough tension on the blade so that it doesn't wander around. After I cut the track, I dress it with the Dremel, and that seems to be much faster than using a file. 

I have been buying bandsaw blades for my 14" bandsaw that claim that they will cut wood and metal. I tested one and yes, it would cut through steel angle iron and I cut several pieces with it. Then I tried to cut some wood and it sort of burned its way through it. At $35 each, I decided the hack saw was just fine. 

Tom Bray


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## KYYADA (Mar 24, 2008)

A wood bandsaw runs about 1800+ feet per minute where a metal bandsaw can run as low as 50 but typically 200 or so for thinner stuff. You are quickly overheating the blade and taking the temper out. There are sites on the web to convert a wood bandsaw to cut metal but for all the trouble you may find one on ebay cheaper. 

Johnny


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