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- Jul 26, 2011
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In the old days,when they had to make do with less,and a special dia. drill was needed,a skilled machinist would learn to grind a drill's lips slightly off center to make it's longer cutting edge swing wide and drill a somewhat larger hole than the nominal size of that drill.
Most of you probably know how to get a lathe cutting tool at the exact height needed: Use a thin steel ruler,or a thread gauge(the kind with "V's" in it for grinding threading tools. Place the ruler or gauge against the shaft you are turning. Bring the cutter right up to the rule,barely touching it. Adjust the height of the cutter till the rule or thread gauge stands vertical between the work and the cutter. Then,you are exactly half way up the height of the shaft where you should be. No fancy little levels needed,nor really wanted by those who use this quick,easy method.
If your lathe cutting tool is not exactly at the proper height as described above,you will not turn a correct,straight cut when turning a taper.
The lathe was the only machine,except perhaps a drill press,in very early machine shops. Lathes were often provided with T slots on the wings of their carriages. Odd pieces needing boring out could be clamped down on the cross slide without the compound in the way,shimmed to the right height,and bored out without having a milling machine to do it. Great use was made of the lathe faceplate for operations we rely on a milling machine for these days. Lincoln milling machines were a popular milling machine in 19th. C. shops. Their vertical adjustment was to laboriously adjust both ends of their arbors,like you do in a horizontal boring mill these days. They also sometimes had to block or shim up the parts to the needed height. Old timers had to be ingenious to deal with these primitive conditions. They determine the necessary height to bore a hole on center by simple means: A rod chucked in the lathe had a blob of clay or putty added to its end which faced the work. A straight pin,or other light pointer was stuck into the clay. The chuck was rotated,watching the pin as it went around the layout line scribed on the work piece. Shims and adjustments were added until the pin stayed exactly on the scribed line all the way around it. This got you within acceptable tolerance to bore the hole first by drilling,then by single point boring with a boring bar that reached,and was supported by the tailstock center. needless to say,these operations took skill. Brits called it a "sticky pin".
I measured the brass cylinder on an 18th. C. microscope in the museum. The cylinder provided adjustment just by sliding in a hole to focus the lens. The cylinder was turned freehand like wood,and the diameter was made constant just by feeling with calipers. This cylinder was not even .001" out of the same diameter along it's 6"+ length. The museum had bought a POS repro microscope made in England for the Apothecary shop. It constantly slipped out of focus. It must have been made from brass bed tubing,which was grossly out of round,with poor tolerances. It looked o.k.,but was in reality not well made at all. Do not think that those early machinists could not do accurate work. I was taught to "feel a thousandth" with calipers when I was young,and taking a machine shop course by an old,retired Navy machinist's mate. I've made use of this many times over the years.
Real early milling cutters were more like coarse files.The only way they could be sharpened was to anneal them to soft,and re chisel their teeth back on,then re harden and draw them. Must have been SLOW going!! Plus,everything was plain carbon steel without nearly the wear resistance of later tool steels like Mushet steel,and later HSS,etc.
Pressures for sintering carbide was first done in the breeches of large old Naval guns,buried vertically in concrete. Only they could stand the pressures needed at the time.
I knew an old,but inventive machinist who had to mill some trunnion grooves for large spot lights. They were circular arcs too large for the swing of any of his lathes to do. He strapped the head and ram of a Bridgeport down tightly on a good rotary table,got the swing he wanted adjusted by mallets,laid this assembly over the metal to be milled,and succeeded in milling the circular trunnion grooves needed. He also had invented the remote mechanical hands used when handling radioactive material,or dangerous biological samples.
I knew an old,retired,very intelligent machinist back in the 60's who made himself an extra $300.00 a week just putting long allen head bolts in his 10" South Bend lathe,and threading them all the way up. These longer bolts are only made threaded part of the way up,and some customer needed them threaded all the way. He first center drilled them,then threaded them. Then,he'd drill a 1/8" hole and put in a nylon locking plug. He made these by the 5 gallon bucket full. Today,that income would be nearly $3000.00 a week. He also got bronze submarine propeller nuts cast somewhere and threaded their holes on the 10" lathe. I guess those nuts were about 6" in diameter,but it's been many years ago to recall. He went to government auctions and bought all kinds of equipment and machines and sold them. I visited him often,picking up many tips of information. He died buffing large monel metal bolts. His hands were greasy enough to provide insulation from static,until he touched one of them wrong and got a shock that stopped his old heart. It was a big loss to those of us who knew him. Many machine shops would come to him to get solutions for knotty problem jobs. He always had an answer.
I prefer to only use single edge countersinks,or what some call "O" flute countersinks as they do not make the countersunk hole 6 sided. It is easy to make single edge countersinks,and I've made several,some with special angles. Turn your blank countersink and mill or grind one side flat to 1/2 the diameter. Then,file a relief angle behind the cutting edge. Harden and draw to a light brown color when using common W1 or 01 drill rod. 01 is better.
You can made a slightly undersize reamer cut a bit larger by drawing a HSS lathe tool fairly hard across the face of one of the flutes (not the top edge of the flute!!) This will raise a small burr that will enable the reamer to ream a few more holes,but slightly larger.
You only need to grind the angled front leading edges of a reamer to sharpen it. That is where the reamer cuts.
If you want to lacquer polished brass,you MUST,MUST thoroughly clean off the brass. Stoddard solvent(dry cleaner's solution) is the best thing to use. It is a refined paint thinner. It is very surprising how much black crud will ooze out of a polished brass surface. Keep rubbing the solvent on till the black stuff stops oozing out. Use a very soft cloth to keep from scratching the polished brass as you go. If you do not do this,lacquer will strip off the brass like Saran wrap when it is dry. When I made the surveyor's compass I have posted here,I had to keep applying Stoddard solvent to it for quite a while. Black stuff kept on oozing out of the surfaces for a long time. I had to be careful to use a soft cloth to not scratch the finely HAND polished surface that I spent days producing. Machine buffing would have smeared the engraving.
Packing a reamer with lard will make it cut a round hole,rather than a hole full of angles.
Most of you probably know how to get a lathe cutting tool at the exact height needed: Use a thin steel ruler,or a thread gauge(the kind with "V's" in it for grinding threading tools. Place the ruler or gauge against the shaft you are turning. Bring the cutter right up to the rule,barely touching it. Adjust the height of the cutter till the rule or thread gauge stands vertical between the work and the cutter. Then,you are exactly half way up the height of the shaft where you should be. No fancy little levels needed,nor really wanted by those who use this quick,easy method.
If your lathe cutting tool is not exactly at the proper height as described above,you will not turn a correct,straight cut when turning a taper.
The lathe was the only machine,except perhaps a drill press,in very early machine shops. Lathes were often provided with T slots on the wings of their carriages. Odd pieces needing boring out could be clamped down on the cross slide without the compound in the way,shimmed to the right height,and bored out without having a milling machine to do it. Great use was made of the lathe faceplate for operations we rely on a milling machine for these days. Lincoln milling machines were a popular milling machine in 19th. C. shops. Their vertical adjustment was to laboriously adjust both ends of their arbors,like you do in a horizontal boring mill these days. They also sometimes had to block or shim up the parts to the needed height. Old timers had to be ingenious to deal with these primitive conditions. They determine the necessary height to bore a hole on center by simple means: A rod chucked in the lathe had a blob of clay or putty added to its end which faced the work. A straight pin,or other light pointer was stuck into the clay. The chuck was rotated,watching the pin as it went around the layout line scribed on the work piece. Shims and adjustments were added until the pin stayed exactly on the scribed line all the way around it. This got you within acceptable tolerance to bore the hole first by drilling,then by single point boring with a boring bar that reached,and was supported by the tailstock center. needless to say,these operations took skill. Brits called it a "sticky pin".
I measured the brass cylinder on an 18th. C. microscope in the museum. The cylinder provided adjustment just by sliding in a hole to focus the lens. The cylinder was turned freehand like wood,and the diameter was made constant just by feeling with calipers. This cylinder was not even .001" out of the same diameter along it's 6"+ length. The museum had bought a POS repro microscope made in England for the Apothecary shop. It constantly slipped out of focus. It must have been made from brass bed tubing,which was grossly out of round,with poor tolerances. It looked o.k.,but was in reality not well made at all. Do not think that those early machinists could not do accurate work. I was taught to "feel a thousandth" with calipers when I was young,and taking a machine shop course by an old,retired Navy machinist's mate. I've made use of this many times over the years.
Real early milling cutters were more like coarse files.The only way they could be sharpened was to anneal them to soft,and re chisel their teeth back on,then re harden and draw them. Must have been SLOW going!! Plus,everything was plain carbon steel without nearly the wear resistance of later tool steels like Mushet steel,and later HSS,etc.
Pressures for sintering carbide was first done in the breeches of large old Naval guns,buried vertically in concrete. Only they could stand the pressures needed at the time.
I knew an old,but inventive machinist who had to mill some trunnion grooves for large spot lights. They were circular arcs too large for the swing of any of his lathes to do. He strapped the head and ram of a Bridgeport down tightly on a good rotary table,got the swing he wanted adjusted by mallets,laid this assembly over the metal to be milled,and succeeded in milling the circular trunnion grooves needed. He also had invented the remote mechanical hands used when handling radioactive material,or dangerous biological samples.
I knew an old,retired,very intelligent machinist back in the 60's who made himself an extra $300.00 a week just putting long allen head bolts in his 10" South Bend lathe,and threading them all the way up. These longer bolts are only made threaded part of the way up,and some customer needed them threaded all the way. He first center drilled them,then threaded them. Then,he'd drill a 1/8" hole and put in a nylon locking plug. He made these by the 5 gallon bucket full. Today,that income would be nearly $3000.00 a week. He also got bronze submarine propeller nuts cast somewhere and threaded their holes on the 10" lathe. I guess those nuts were about 6" in diameter,but it's been many years ago to recall. He went to government auctions and bought all kinds of equipment and machines and sold them. I visited him often,picking up many tips of information. He died buffing large monel metal bolts. His hands were greasy enough to provide insulation from static,until he touched one of them wrong and got a shock that stopped his old heart. It was a big loss to those of us who knew him. Many machine shops would come to him to get solutions for knotty problem jobs. He always had an answer.
I prefer to only use single edge countersinks,or what some call "O" flute countersinks as they do not make the countersunk hole 6 sided. It is easy to make single edge countersinks,and I've made several,some with special angles. Turn your blank countersink and mill or grind one side flat to 1/2 the diameter. Then,file a relief angle behind the cutting edge. Harden and draw to a light brown color when using common W1 or 01 drill rod. 01 is better.
You can made a slightly undersize reamer cut a bit larger by drawing a HSS lathe tool fairly hard across the face of one of the flutes (not the top edge of the flute!!) This will raise a small burr that will enable the reamer to ream a few more holes,but slightly larger.
You only need to grind the angled front leading edges of a reamer to sharpen it. That is where the reamer cuts.
If you want to lacquer polished brass,you MUST,MUST thoroughly clean off the brass. Stoddard solvent(dry cleaner's solution) is the best thing to use. It is a refined paint thinner. It is very surprising how much black crud will ooze out of a polished brass surface. Keep rubbing the solvent on till the black stuff stops oozing out. Use a very soft cloth to keep from scratching the polished brass as you go. If you do not do this,lacquer will strip off the brass like Saran wrap when it is dry. When I made the surveyor's compass I have posted here,I had to keep applying Stoddard solvent to it for quite a while. Black stuff kept on oozing out of the surfaces for a long time. I had to be careful to use a soft cloth to not scratch the finely HAND polished surface that I spent days producing. Machine buffing would have smeared the engraving.
Packing a reamer with lard will make it cut a round hole,rather than a hole full of angles.
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