Questions on cutting steel

[bullsi1911]

(background info- in my past, I was once a metal fab guy building bumpers, trailers, etc...)

Would a cutting torch or plasma cutter work for rough cutting blades? Then using the grinders grind into final shape? or would the heat do something bad to the steel?

[Jamey Saunders]

Being a former metal fab guy, you'll realize that there will be some hardening around the edges where it has been cut. I believe you will find some folks on both sides. Some will say that the hardening that takes place is bad, bad, bad. Some will say it doesn't matter. I'll say it depends. I'd do an anneal on the steel after it's cut. Seems to me that doing an anneal would release any induced stress from the cutting process.

Also, think of this: Many production blades are cut with a laser. I'm sure that there's less heat leakage with a laser, but there's still going to be some edge hardening...

Now if you have access to a waterjet...that's another story.

[Ray Rogers]

To me, the hardening of the steel isn't the biggest issue. Most of the time annealing will fix any bad effects and, if you don't cut too close to the finished blade size much of the damaged area will be removed when you finish grind the final profile.

My big issue is how difficult it can be to clean up a rough cut, slaggy chunk of steel. If you use belts it can be very hard on them and they're not cheap. Of course, you can use an angle grinder or bench grinder if you and your neighbors can stand the noise (and again there's the issue of heat). I've never used a plasma cutter but I understand they make a very clean cut so most of what I said might not apply to plasma. There are makers who use plasma and others who use torches so it's probably just a matter of using what you have and what you are used to. For my part though, a simple metal cutting band saw is fast, quiet, reasonably clean, and doesn't heat the metal. The cut can be made so close to the outline that cleanup is fast and easy. But then, the band saw is what I have .....

[Jason Cutter]

I have access to a metal cutting bandsaw, that is a great time saver, but currently my favourite piece of machinery to cut steel before grinding to shape isa metal cut off saw.

I have a cut off saw "angle grinder" as they call it here that takes a 4inch metal cutting disc that is just 0.6mm thick = less than 1/32inch thickness. It MUSTbe mounted in a angle grinder holder than allows you to make accurate cuts like a chop saw. It is quite dangerous to use this set up to cut with the grinder hand held. The disc would shatter and grab the steel. It is very very fast, and a piece of steel can be profiled with minimal heat damage.

Hmmm. after trying to explain that, I think a picture would be best, if you can wait. Jason.

[tmiller5087]

of the two, a plasma whacker would be the best. i don't think it heats the metal as hot as a tourch. plus there is less slag to clean up. By the time you shape the blade the immeadiate area where you made the cut will be ground off anyways. Your gonna heat treat and anneal also. Unless your extremly skilled with a plasma cutter or tourch your gonna need a guide so unless your talking about cutting a wide piece of plate into straight strips to width and not cutting the actual profile i would use a bandsaw or as previously suggested a small cutoff wheel. By the time you made a guide piece the shape of the blade for the tourch or plasma to follow, you could of cut the profile. I use a cold chisel and files myself. My lady ( lil miss mangled hand ) holds the chisel for me while I whack it with a 20 lb sledge. Its a little slower proccess, mostly because i have to wait till she heals after the missed blows but it is speeding up. i think she doesn't have much feeling in her hand anymore and the cast asorbs some of the shock.

[bullsi1911]

The plasma will be in the distant future. I just picked up the Craftsman 2x42 belt sander for my budding shop. What belts should be used for cutting steel? Just the regular 60 grit that they have at Sears, or should I use a special kind?

[Paul Gibson]

hehehe...
...now THAT is true love.

[tmiller5087]

She'd take a 20lb sledge to my head if she read that :evil

[Ray Rogers]

bullsi1911,

Belts aren't normally used to cut steel in the sense that band saws and torches cut steel. But all belts will remove metal by grinding. To finish profiling a blade after roughing it out with a saw or torch most will use a worn 60 grit or coarser belt. Worn belts are generally chosen for this job because hitting a ragged, sharp edge on a piece of steel will most likely completely remove the grit from a brand new belt in a matter of seconds.

As for what kind of belt, you'll get a million answers from as many makers. Almost anything will work and only experience will help you decide what works best for you. Cheap belts fail so fast for me they are of almost no use at all so I like the Norton Hogger in 60 grit for profiling and also for doing the initial bevel grinding on the blade.....

[bullsi1911]

If I go get me a small bench-top bandsaw (my wife is gonna freak with all the new tools...), what kind of blade should I get for cutting bar stock into a knife? I'm guessing that you will need a better blade then the ones that they sell for cutting copper pipe to cut 440C stainless and O1 toolsteel

[oljoe]

Bullsi1911,

I don?t think that you want a bench top band saw for cutting metal. Most of the table top band saws are made for wood and run to fast for metal cutting. You may be able to get it cut but you will go through a lot of blades.

Harbor Freight has an inexpensive metal cutting band saw that works reasonably well. The same saw is sold by other companies with their name on them. Search around and you should be able to find one close to you.

You should consider buying a by-metal blade along with a couple of different toothed blades to saw wood and nonferrous metals.

Joe

[Ray Rogers]

Right, make sure whatever saw you get is designed to cut metal as wood saws run many times faster than metal saws. A bi-metal blade 14 - 18 teeth per inch is a good all around blade for knife work. The HF saw or one of its clones is a real bargain at less that $200. It is a small saw but if you think it's too large for your work area just do what I did. I hack sawed most of the table off of it and then mounted the stub to a wooden work bench. It has been in service that way for about 7 years and still works great. Other people have also made this modification so i think it is a fairly common thing to do with this saw.

The bi-metallic blades are expensive at around $25 each but they seem to last almost forever. Nothing else comes close to their performance ....

[bullsi1911]

Harbor Freight has an inexpensive metal cutting band saw that works reasonably well. The same saw is sold by other companies with their name on them. Search around and you should be able to find one close to you.

I could not find a listed metal cutting bandsaw on the HF website. Is it the 4 speed one?

[clw3]

Here's a link to the bandsaw page at HF.
http://www.harborfreight.com/cpi/cta...emnumber=37151

Good Luck!

[oljoe]

clw3 beat me to it. That is the one.

Joe Foster