These are three of the scrapers I've made, well two at least. The one on the left is an old 18"+ planer blade from a sawmill. The local scrape metal place gets them now and then. It is very hard ferrous steel (high speed steel?). Whatever it is it can't be drilled, cut by a hacksaw, or filed, without being annealed. But it can be ground and cut with and abrasive metal cutting wheel, great stuff for making tools. The middle one is made like a draw knife. I use it and the full planer blade as draw knifes, for fast removal. The one on the right I made by cutting a piece from a planer blade, I made the handle too. This scraper is my workhorse. It works very well, and allows very fine control. When well honed, it will scrape for a long time without getting dull.
If you have never heard of scraping before, it use to be a skill that every machinest had to learn, and knew very well. It was the method of obtaining a very flat, true surface. Even today the finest machines made still use hand scraping on the sliding surfaces such as bed ways in order to get a very accurate surface. Even the most precise, modern machines can't match the level of accuracy of an old skilled machinist. Old and even new surface plates made of metal are hand scraped to a very near dead flat condition.
There is a true story about a machine shop that had a contract to fill. I required a large part to be dead flat to within a few one-hundred thousands of an inch. That is less than one hundreth of the thickness of a sheet of paper. They machined the part on their super accurate, ultra high precision, high tech, laser guided, computer controlled milling/surfacing machine. But the best it could do was a few ten thousands of an inch. So they needed to had scrape it. But in order to do that they needed a surface plate at least as accurate as the thing they where making. After check every high tech, modern surface plate thay had, nothing was accurate enough. Then one of the old-timers remembered an old surface plate sitting in the store-room covered in junk. It had not been used in decades and was made in the late 1800's out of seasoned cast-iron and was the size of a kitchen table. In desperation they gave it a try knowing something so large and so old made by hand more than a century ago could not possible work. To there utter astonishment it was over its entire surface accurate to within a millionth of an inch........ Made by hand, more than 100 years ago....... Scraping tips. I found that when I started scraping at a work piece I tended to scrape to lightly in the begining, and to heavily as I got near finishing. If you scrape and scrape and never seem to get anywhere you are probably scraping to hard. If you blue and test a piece and it shows you need to scrape the middle, scrape, blue, retest and it shows you scrape on the sides, and this pattern repeats you are very close to dead flat, take lighter cuts with the scraper.
Rule of three tips: If you are using the rule of three and working three pieces against each other to get them all true, work on (scrape) only one piece at a time, and be sure to rotate through all six combinations as you go. As you get closer and closer to being true lighten up on the pressure on the scraper and take lighter cut. I was able to get the top of the bed and the back way to somewhere in the ten-tousandths of and inch range. Not bad for the home shop. |
METAL CUTTING Metal Cutting - In the home shop there are only four viable options for cutting metal, in this case mild steel, Sawing, grinding, filing, and torch. Sawing is the old stand by method, usually with a hacksaw, but a metal cutting band saw is also possible but expensive. however a bandsaw, or power hacksaw can be made. Gingery has a book on making a power hacksaw. Filing, well that can take a long, long time. It is possible to file and Aircraft carrier into, however it would take a truckload of files, and a lifetime or more to do. Oxyacetylene torch, works great, is fast, but the set-up, torch, cylinders, etc, can all be expensive. A torch also leaves a ragged edge, especially for a novice. Grinding ultimatly is the best option, fast, fairly accurate, and can be fairly inexpensive. An angle grinder about 4 1/2" with a cutoff wheel works well, and can be had for around $20-$30. Metal cutting wheels are also available for 7-1/4" circular saws and work very well, the ultimate is a metal cutting cutoff (chopsaw) saw. These use 14" metal cutting wheel and cost around $150-$200 for a good one, well worth the money. It should be noted that to cut aluminum sawing and filling are the only viable options. Of course Steel and aluminum can be cut on a Lathe or mill. I'll post some pics when I get around to taking them..... 
This is one of the most usefull metal working tools in the shop. With it you can grind, cut, shape, etc mild steel and even tool steel. For example I cut the scraper out of tool steel, a large planer blade and a piece of a saw mills bandsaw. It is an 4-1/2" angle grinder, and uses abrasive grinding and cutoff wheels.
This is a common circular saw. This one is a very old Black & Decker. The saw's arbor got slightly bent, thus making it unusable for cleanly cutting wood. But it works great on metal. It has a 7" abrasive metal cutting blade on it. I used it to cut the lathe bed made of 1/2" by 4" cold rolled steel flats. It took two blades to make three cut in 1/2x4 plate cold rolled steel.
This is a metal cutting cutoff saw. It is specially designed to cut metal and uses a 14" metal cutting abrasive blade. This works great for cutting angle Iron, bars, flats. This is a 15 amp or 3hp saw. I tried a cheap less powerfull one but I had nothing but problems with it.
W A R N I N G . . . . . Got your attention?? Well there is one in every crowd. Some Moronic, stupid idiot who thinks you can cut metal (aluminum, mild steel and such) on a table saw or power "chop" miter saw or even a hand held circular saw using a carbide (wood) saw blade. This individual is either to young to fully realize the risk he/she (or it) is taking. Or is just plain stupid with an I.Q. not much more than the diameter of the blade of his saw. That said you should know it can be done. And it can work fairly well, but the risk you would be taking could very easily cost you your life. With thirty some odd years of wood working I can atest to the power with which an object (wood) can be thrown from one of these machines. They are dangerous enough just cutting wood. The problem is what is commonly called kick-back, when the saw blade grabs what is being cut and it is literaly thrown with tremendous force from the saw. I've seen pieces of wood hurled clear across the shop through a heavy cardboard box and imbed itself in the wall. People have been killed or seriously injured with just wood, just imagine a razor sharp piece of steel or aluminum hurtling through the air.
The only save way to use these saws is to cut mild steel with an abrasive blade like disk that is specially made to cut such metals, even then especialy on the table saw great care must be used. Aluminum can not be cut eaisily with abrasive blades, it tends to gum them up, use a hacksaw or band saw. Special Taps. 
These are two special taps I made using special steel rod called Drill Rod. This is the stuff that drill bits are made of, and comes annealed (soft). You then heat it to a red glow, and quench it in oil to harden it. One is 1/4" x 20 pitch, the other is 5/16 X 20 pitch.
Drills, Drill Press, Drilling, Tap-n-die Drilling should be done properly if you want good results. Drill bits will also last longer. 
This is a common bench type drill press. I've had this one for many years, but it has its limits. Many times I've wanted to drill the end of something to long or large to fit between the drill bit and drill's table. It is also a little to fast (RPM) to properly drill metal, I has however drilled many hold in metal, and burned many a drill bit. It will do a great job on wood.
This is a floor model drill press I bought from Homier. It is 16 speed two stage 3/4hp, and cost $110.00. On the drill presses table is what is called a Machinist's Cross slide Vise I got from Harbor Freight for $30.00 (on sale). The machinists cross slide vise is one of the best investments I've ever made, what a joy to use in drilling holes especially in metal as you can see. For you folks melting metal and looking for a project this would be a great one. Its like the carriage assembly a base to mount on drill table a cross slide, and a compound slide set perpendicular (90 degrees to cross slide) without the swivel, and a vise on top of the compound. It is and X / Y axis device. Jaws could be faced with cold rolled. A great project idea.
MORE TO COME....
DRILLING: The enemies of drilling in metal is speed, friction and the heat that the friction causes. Oil does several things while drilling in metal. It reduces friction, and helps cool the drill bit and will help prevent a bit from breaking off in the hole. Speed is another factor, you need a slower RPM than drilling in something like wood. A speed of around 150-350 rpm is best. RPM's 400 and over are a little to fast. At a slow RPM a drill bit will actually drill faster, last longer than at a faster RPM. NEVER DRILL A HOLE IN METAL WITHOUT OIL! A good grade of cutting or threading oil works best, or light machine oil, like 3n1.
TAPPING: A tap is what makes threads in a hole that has been drilled. Again you must use oil when tapping a hole, this reduces friction, helps prevent broken taps, and to wash away the chips produced. The biggest mistake you can make is to use the wrong size drill bit for the tap being used, especially one that is to small, this is one of the biggest causes of a broken tap. Drill bits come in Fractional (1/64ths,etc.), Numbered (#1-60) and lettered (A-Z) bits. A tap must be carefully aligned to the hole. It must not go in at an angle the hole. Also you must be carefull of chips produced by the process, back out the tap frequently and clean tap and hole of chips. Turn tap 1/8 to 1/2 turn at a time then back up tap by at least a 1/4 to 1/3 of a turn. In 1/4 turn, back 1/2 turn, etc., this is to break off the shaving/chip produced by the tapping so it doesn't jam the tap.
DIE: This is what makes threads on a round rod. The proper size rod must be used for the proper sized tap. Again use oil, and work the die back and forth as you do with a tap. You can however make a full turn or two then back up a half turn or so. Clean die of chips often. |
