Is metalworking in college a physically demanding task?

[zoobyshoe]

Metal cutting is typically an abrasion based process

No, metal cutting is a shearing process.

I'll accept it's doable if someone tells me they've actually done it.

It's certainly doable, it's just frickin' hard. Back in the day, people were good at it, and had all the tricks down. Certainly you have to hold the piece in a massive, rock solid vise. As you chisel along the chip curls up in front of the chisel. Depending on the depth of the cut, each hammer blow may only advance the chisel 1/8 inch or so. The chisels have to be resharpened constantly, and they wear out fast, but back then, they made all their own right there in the shop. There is, no doubt, a set of specific angles at which to grind the chisels for various kinds of cuts.

They were, for the most part, probably not working steel, but soft iron, probably softer than today's hot rolled steel, which is the softest common steel. In all cases, chiseling produced the rough cut. Finishing had to be done with scrapers and files.

I may hunt up a link if I get amitious. I researched all this machine shop history back when I was in school because it occurred to me that you're always copying the straight lines and flat planes built into the machine tool to the part you're making. That made me wonder how they arrived at the first straight line, or the first flat surface. It took me about three months to find out how it was done. (The web didn't exist back then.) (Edit: I mean back then when I was doing this research.)

 

[Gokul43201]

No, metal cutting is a shearing process.

Sheet-metal cutting is a shearing process, and so are milling, turning, facing, etc. But certainly not filing or sawing. I guess I just find it hard to imagine that shearing of this kind can be achieved with a hand tool.

I'd like to see what a metal-cutting chisel looks like.

 

[zoobyshoe]

Here's a few pictures of cold chisels:

http://images.google.com/images?hl=en&ie=ISO-8859-1&q=cold+chisel&btnG=Google+Search&sa=N&tab=wi

 

[Gokul43201]

I've used cold chisels on concrete. Are they what you'd use on metal too ?

Next time I'm in the machine shop I'm going have a go at a hunk of aluminum maybe.

 

[Moonbear]

I've used cold chisels on concrete. Are they what you'd use on metal too ?

Next time I'm in the machine shop I'm going have a go at a hunk of aluminum maybe.

Hmm...I've used cold chisels on concrete too, but they dulled awfully quickly, which fortunately didn't matter much for what I was doing since I didn't have any means of sharpening the chisel. I'm not so sure about how that would work on steel!

 

[FredGarvin]

Next time I'm in the machine shop I'm going have a go at a hunk of aluminum maybe.

Come on. At least get something to make it a bit sporting. Make you work a bit.

I worked with a machinist who came up through the ranks as a mold maker. He told me that as an apprentice (almost 40 years ago) he had an ongoing project which was to get a block as close to perfectly flat as he possibly could using nothing but files. He said it took him over a year to get it to the acceptable level that his boss would accept.

I have never heard of anyone using chisels, but really, what is the difference between an end mill and a chisel other than whose driving it.

 

[Gokul43201]

Come on. At least get something to make it a bit sporting. Make you work a bit.

Yeah, thanks for the encouragement !

I worked with a machinist who came up through the ranks as a mold maker. He told me that as an apprentice (almost 40 years ago) he had an ongoing project which was to get a block as close to perfectly flat as he possibly could using nothing but files. He said it took him over a year to get it to the acceptable level that his boss would accept.
I have never heard of anyone using chisels, but really, what is the difference between an end mill and a chisel other than whose driving it.

What's the difference between a Rembrandt and my doodling, other than whose drawing it ?

I know a machinist whose self-test was to turn down (in a lathe, not using an auto feed) a 6" long brass rod to the smallest possible diameter without breaking it. He'd start with a 0.25" dia rod and take it down to under 0.100" in a single cut ! I'd have never thought that possible.

 

[FredGarvin]

I meant in terms of the cutting action. Not tolerances, quality of cut, etc...it's at its most very basic level the same.

 

[Gokul43201]

And there's this welder who tests his control by grabbing a 3' long metal rod in one hand (actually, not with his bare hands ), a torch in the other and making a near-perfect circle out of the rod without letting go, switching hands, setting anything on any surface, using any other tools, etc.

 

[Gokul43201]

I meant in terms of the cutting action. Not tolerances, quality of cut, etc...it's at its most very basic level the same.

I don't disagree. In fact, I said much the same thing earlier :

Granted, cutting on a mill or a lathe is nothing but a microscopic version of chiseling, but with a far sharper cutting edge and much better control than you can dream of achieving with a hand chisel.

 

[Integral]

I bet that if you could learn to sharpen a chisel to cut steel when it came time to grind a lathe tool you would have a pretty good feel for it.

Grinding a good lathe tool is an art, now a-days it is to easy to just chuck up a carbide tip, does anyone still grind their own?

I think this chisel assignment is a bit over the edge, but if he can make it work, he will have a good feel for just how much work it takes to cut metal and how to make a tool that will do the job. There is some value it both of those lessons.

 

[Gokul43201]

I bet that if you could learn to sharpen a chisel to cut steel when it came time to grind a lathe tool you would have a pretty good feel for it.
Grinding a good lathe tool is an art, now a-days it is to easy to just chuck up a carbide tip, does anyone still grind their own?

I grind steel cutters now and then, but I wouldn't say I'm great at it. Mostly I don't have the need or patience to get a beautiful cutting edge.

 

[siddharth]

Siddharth : I had to sit with a giant block of steel, and essentially file it all away (under the despotic glare of a duo named Guptan and Goodman...they still around ?).

Goodman is still here. There is another person instead of Guptan.
When the instructor showed how it was done, he kept the rod in the vise, the chisel at an angle and hit really hard.
After two good hits, a layer of the metal came out. Of course, when I tried it, all that happened was that the surface just got dented. And a disadvantage of hitting it that hard is that when the chisel slips from the surface, my hand holding the chisel goes along and scratches the surface (Never happened to the instructor when he was demonstrating).

 

[FredGarvin]

Grinding a good lathe tool is an art, now a-days it is to easy to just chuck up a carbide tip, does anyone still grind their own?

We routinely make our own lathe cutters. There are too many weird and tough shapes to cut that a standard cutter just won't do. Admittedly, sometimes they look like they could have been dug up on an archeological dig, but they work.

 

[Moonbear]

And a disadvantage of hitting it that hard is that when the chisel slips from the surface, my hand holding the chisel goes along and scratches the surface (Never happened to the instructor when he was demonstrating).

I can't help you with the whole metal bit, but having used chisels for other applications, I can recommend some tips to not hurt yourself, at least not as badly . First, when you hold the chisel, if you're attempting downward cuts, keep your thumb tucked in front of your fingers, not up at the top (make a fist and put your thumb over the top of your fingers so the tip is trying to touch your little finger...hold the chisel the same way). Generally, this gets you a good grip on the chisel, and if you miss it with the hammer, you'll still have bruised fingers, but won't get the very sensitive tip of your thumb that would make it hard to do fine work later. Use your non-dominant hand to hold the chisel (if you are right-handed, hold it with your left hand)...you want to have the best control of your hammer. Position your chisel where you wish to make the cut, and then brace your forearm (from just ahead of your elbow, to about 1/3 to halfway up your forearm...basically the muscular part, not your wrist) against a stable surface...the work table, or your vice grip would be the best. You want to have a firm grip on the chisel, but you don't need to have a death grip on it...that will just tire out your hand needlessly. When you strike the chisel with the hammer, use short strokes...this isn't tennis, you don't need to "follow through." If you try to hammer "through" the chisel, you're more likely to just glance off the side of the chisel and either deflect the chisel in the wrong direction or whack your knuckles. Instead, sort of end the stroke as you hit the head of the chisel and let the hammer rebound back up. You can still do this with considerable force, and as you get the knack for it, you'll have a better idea of just how hard to strike and you'll have more control of your hammer. Some of the control really just relies on forearm muscles though. Focus on keeping the hand holding the chisel as steady as possible when striking it; resist the temptation to try to push it through the material to "help" it.

Intuition tells me you should try starting your cut from a corner (keep a flat surface facing up, hold the chisel at a slight angle at the corner, though not straight into the corner (i.e., not at a 45 degree angle to the flat surface, more like a 25 or 30 degree angle) and strike the chisel off-center (maybe 10 degrees to the surface). This might help give the chisel more of a slicing action than a blunt force action to get that first cut started instead of just denting the metal. But, I've never attempted using a chisel on any sort of metal, so my intuition may not be right, it's just a thought you might want to try if you haven't already and nothing else has worked yet.

Oh, keep the rest of your body away from the front of your work piece! Stand behind it (both of your arms should be somewhat in front of your body), and be absolutely certain if you are sitting that your legs are not under the work piece. You don't want to slip and sent that chisel through your thigh!

 

[Averagesupernova]

Some of you act as if using a chisel on steel is like using fire to fight fire. A good chisel will easily cut mild steel. Also, there are plenty of uses for a chisel in this century. Usually it involves disassembly or something. There are just some places you cannot get a grinder or saw into in order to remove metal. One thing I cannot stress enough is to have an anvil or something backing your work that is heavy enough to prevent ANY movement on the workpiece. A bench vise sometimes just won't cut it. A note on sharpening chisels though, don't let the chisel get too hot. Keep a container of water nearby to dip the tool in every few seconds to prevent overheating. Overheating will soften the chisel. Oh yeah, one last thing. If you're really worried about hitting your fingers hold the chisel with a pair of pliers or vise-grips locking pliers. At least until you become accurate with the hammer. Hmmm. I keep coming up with more suggestions. While on the subject of hammers, make sure it is sized for the type of work you are doing.

 

[siddharth]

I finished the exercise yesterday. The cube came out pretty well though my dimensions were off by 1 mm. I got 30 out of 40 marks for my work which is decent. I chiselled till it was somewhat flat and filed the rest of the uneven part.
Thanks for your suggestions and advice.