Casting Good Type

[Music] Good type. But do you ever cast type that comes out porous like this or this with its frosted face? Does your caster suffer from spitting or squirting? Or does casting speed have to be kept below what's recommended for any given size in an effort to prevent this sort of thing with its bleeding foot being born? Then the odds are at least 20 to1 that the cause of the trouble lies in this group. The metal pot, the pump and nozzle. Take the pot first. What's in it? Tight metal, you say. Agreed. But is there anything else? The supplier of the metal takes far more care than you may think to ensure that the ingots he supplies are up to specification. Chemical analysis of metals is the traditional quantitative method practiced with all the painstaking care associated with laboratory work. The X-ray spectrometer, a modern tool of analysis, determines the proportions of the main constituent elements of an alloy and at the same time those of several impurities that may also be present. A sample is inserted for subjection to radiation from an X-ray tube. The consequent fluorescent secondary radiation from each element is characteristic for that element. It is detected and measured electronically. Press a button which asks for example how much tin and immediately a code number representing the percentage appears in the display window. A dozen buttons will give you the answers for other metals present according to how the machine has been programmed. To avoid mistakes, a punched card can be slipped into the overriding control to establish the correct program. And just in case you forget the answers, the machine obliges with a print out recording the displayed figures. Every batch of melt and remelt can be accurately assayed before the bulk of it is poured because the whole X-ray analysis is as simple as coining the slot and nearly as quick. By such means the specification of the metal can be even more accurately followed. For one thing, the human element has been eliminated. So you can be sure that unwanted ingredients are out when new metal from a reputable supplier arrives at the pot. But what then? Is it pre-warmed and fed in gradually? Or does it go in in cold dollops, dropping the temperature of what's already there? If it brings it down to the 500s Fahrenheit, even locally, you're getting into the danger zone because this is where the tin antimony compound starts to separate out from the alloy, forming a nasty looking scum. If this gets into the pump and the nozzle, there's going to be obstruction to the flow of the metal, and anyway, the quality of the product will be changed. Hold it. Don't throw that lot away. There's rather more baby than bath water in your ladle. Yes, that scum may contain a high proportion of tin and antimony, the more expensive parts of the alloy. They will have to be replaced to restore the quality of the melt. and nobody knows how much of each you're about to scrap so that the formula for the remaining metal may be all haywire. Allow the temperature to rise to normal, that is 650 to 700, and stir. All this trouble would be avoided by the use of an automatic ingot feeder. And talking of the metal pot, be careful not to let a heap of tangs from the mold pile up. Stir them in from time to time and guard against cold drafts of air, particularly in the winter. Now any scum left really is dross and it can be skimmed off. A nice bright silvery surface should result. Don't hold the metal very much above 700 because the hotter it is, the more readily it oxidizes, forming another unwanted top layer. But if a persistent lacy skin reforms behind the ladle as you skim, there's usually only one answer. It's a four-letter word, and like several others, it's a dirty one. At least to caster operatives. It's spelled z i n c. Zinc. Almost certainly, it came from shavings of brass rule or a zinc plate that got mixed up with used tight before remelting. Aluminium can have a similar effect, though it's not so common. Such contaminated metal can only be returned to your supplier for purification. Don't keep any of that batch hanging about the place as it will only give trouble. There will be clogging and certainly faulty type will result. If you see a pinkish blue tinge on the surface of the cast metal, ingot or type, there's too much copper. 0.05% of copper is not serious, but a larger percentage can lead to crystallization in the nozzle, hampering the flow of metal into the mold. Here again, there has almost certainly been contamination in remelting. Beyond continual cleaning of the whole metal passage, there's not much you can do about it except send it back to your suppliers. Nickel coming from a similar faulty mix will result in very much the same form of clogging and it won't give any indication in the pot. This is how many evildoers are traced. Do you know this man? Unfortunately, we do, but we're glad to say there aren't many like him about. He's a typical example of the caster operative who fails to drill his nozzle every day or drills it carelessly and then blames the machine for poor quality type. He's not likely to be lurking in the audience, but we'll show you in detail the evils of his ways. For one thing, if he leaves the machine with the pot down and the piston still up, or if he ever fails to put the ladle over the nozzle when replacing the piston, you see, and molten metal is very, very hot. Because the nozzle is bound to be a bit cooler than the tight metal from which it protrudes and because it loses heat through frequent contacts with the mold, it is the place where dross scum and metallic crystals are most liable to for gather. Obviously there is considerable obstruction to the flow and so there will be short supply to the casting cavity. You see that the bore of the nozzle has two diameters. The upper one requires a 1/16thin drill to restore it to its working diameter. On no account let the chuck touch the tip of the nozzle or it will start to mill it away as our acquaintance has done here. And look what he did when he was cleaning the larger diameter of this nozzle. He never measured the length from chuck to drill tip. He must have had 2 and 1/2 in or more of drill projecting. Consequently, he has pushed the larger diameter right through, ruining the hole at the tip. A correctly measured drill can never do this. Another time when he'd been neglecting his daily drilling, the deposit of dross built up into something real hard. So hard that it deflected the drill when he had to take action. And the result was something the designer had never thought of. The offcenter injection, which is excellent for casting really spongy type, if that's what's wanted, otherwise of course a dead loss. So is he broken drill? Another casualty due to carelessness. We strongly suspect that it is the same miscreant that fails to give regular attention to the piston and pump body. If you chance to meet him, tell him that once or preferably twice every day while the metal is still hot, he should withdraw the piston, clean the stem end with a brass wire brush, and polish with piston paste. Burnish it so as to leave no free paste. In addition, once a week, he should do as you do. Strip the pump and piston down for a thorough cleaning. No, you know that's not the way to knock out the metal. It would probably bur up a working face or bend the screw. The piston must simply be tapped with a wooden back of a brush. Then before it has time to cool, he too should slacken the lock nut above the stem end and then use the special key to undo the retaining screw. Each of the four end components must be cleaned with the brass wire brush. We can't afford scratches or any other sort of damage here. The slots in the washer must be clear. The inside of the stem end is just as important as the outside. And the tool that slacken the screw is also adapted for cleaning the washer seating. Unless the stem end makes contact with the conical nut, there will be no effective pumping. The parts are reassembled dry. Washer slots should be upwards and it is essential for the screw to be slackened back half a turn from tight to give the stem end a 132 movement before locking the nut. The stem end has got to have a showroom finish and be burnished with piston paste. As we said before handling of the pump body must be snappy. The nozzle must be unscrewed first. Then, as he removes the pump body from the molten metal, he should empty it out and immediately release the base plug before the remaining metal inside can solidify. It's as easy as that if it was properly handled last time. And he is advised to beware of stray metal when he removes the pump body from the plug. The hat valve has a small escape hole in the bottom. He must see that this is clear, but on no account enlarge it. No 0.59 drill. Then a wire probe will do. In any case, he should never apply any cutting tool such as a drill or a scraper until the part has cooled down. Otherwise, the edge will be softened and become useless. Both parts are cleaned with a brass wire brush. A special tool is provided for dealing with the valve seating on the base of the lower pump bushing. And the bores of both bushes are cleaned with another wire brush. A long shanked drill ensures that the passage up the well arm is clean, but it must travel right up into the space below the nozzle. This space too is cleaned out with a special tool and the half2in 13 tap will remove any deposits from the thread in the nozzle socket so that the nozzle can seat properly. Use the special tool to clean the space above the thread and the socket for the lifting lever. Check this for wear. Two precautions when reassembling. Remind him how you heat up the pump body to working temperature by putting it into the molten metal before doing up the base plug. Snug but not too tight. And of course, you do the same with the piston before tightening its lock nut. A trace of piston paste is permissible on the nozzle thread, but overtightening can cause damage. The recommended routines will save him lots of worry, but the obvious way to avoid interrupting production is to have a clean spare pump handy. The exact position of the pot wouldn't matter if it weren't for the fact that it is the support for the pump and the pump is the support for the nozzle and the exact position of that matters very much indeed. Preferably use a new nozzle when making the adjustments. The nozzle must come up directly into its appointed seating in the base of the mold and it is obvious that it must point vertically upwards. Nozzle out of position, wear and leakage. Nozzle out of square, same trouble. Damaged mold, damaged nozzle, imperfect filling of the casting cavity. And if the nozzle doesn't come up to the top of the nozzle plate, there will be a till spot in the tip. This will become worse if the gap grows due to tinning. Sluggish injection follows and then freezing. But raising the temperature of the metal is not the cure. To adjust, first reduce the level of the metal both to avoid spillage and to enable exposure of the pin of the nozzle end lifting lever. Dross accumulates in the inverted seating at the end of the pump arm. Clean this with a special tool as mentioned. Make sure too that the domed pin at the end of the lever is in good shape, curved, clean, and the right height, 7/16. Now, to check the nozzle itself for squareness when the pump is raised for injection with the machine in operating trim, this is impossible. So, lower the melting pot and swing it out. Remove the matrix case, the bridge, the mold, the piston, the pump, and piston levers complete with the link and the ingot. Now you can see what you're doing. A couple of checks at this point will make later adjustments easier. See that the distance from the top of the pump body operating rod to the bottom of this lock nut is 5 and 1/8 in. and that between this same nut and the one above it, there is a gap of about 13/16. Take the nozzle gauge and attach it firmly in place of the mold snug against the pin blocks. To avoid possible damage to the nozzle while lifting the pot into the casting position, press on the free end of the pump operating rod lever to depress the pump. Then allow the nozzle to rise, noting that it enters the cone hole in the gauge. If the nozzle binds on the side, the position of the melting pot, which carries the levers, pump and nozzle as a complete unit must be adjusted relatively to the swing frame table. Pod casing and table are held together underneath by two securing nuts which must first be slackened, but there is no need to touch the pivot screw below the casing at the swing post frame end. The three adjusting screws are at the other end. Manipulation of these will enable the nozzle to be moved freely about the center of its seating in the gauge. Now it's free to rise to casting position by inserting a wooden wedge or similar packing between the swing frame and the pump body lifting lever. Make sure that the pump body will retain this exact position relatively to the pot. Lower the pot again and remove both the nozzle and the nozzle gauge. When you once more raise the pot, check that the packing is still in place so that the pump body is back to exactly where it was before. Fit the nozzle squaring post. Don't press down or you'll lose the packing. It shoulder must seat firmly on the pump body. Does the post stand truly vertical? Use the nozzle gauge pin block faces as a set square to check its angle. If it leans backwards or forwards, this means that there is some bad wear. One lug of the pump body or its lifting lever or its bearings. And the only remedy for this is replacement. Now lay two 20M point measure gauges to bridge the gap in the main stand and rest the nozzle gauge on them as a sideways check. If you find the post leaning to right or left when seen from the front, one of the pump body lifting levers must be adjusted. Not the one that lifts the nozzle end because this isn't adjustable and its position is held by the packing. So it must be the lever to the other end of the pump. Ease off its lock nut and alter the adjusting nut as required. Then rettighten the lock nut and give a final check. Satisfied? Then you can dispense with the squaring post and the packing. Drop your melting pot and secure the gauge and the nozzle back in position once more. Raise the pot in the same careful way as previously to protect the nozzle and see whether its position is right relatively to the gauge for it will have been shifted by any change of angle. Under the lifting lever, put enough packing to hold the nozzle so that it's 132nd of an inch clear of its seating in the gauge. Check that the pump body can be moved to wiggle the nozzle freely and equally all around the hole without lifting the pump off its bearings. If not, reset the adjusting screws as previously described. Make sure that there is working clearance between the yolks of the lifting levers and the operating rod. If necessary, shifting the rear end of the pot slightly to one side with the securing nut slack. The pivot screw allows this movement. Be careful and you won't upset the nozzle position. But check it and then see that the securing nuts are tight before you call the job finished. Much of the mechanism operating the pump and piston is obscured, but its working appears far simpler when we can see all the main features at once. Here the pump mechanism is colored pink and the piston mechanism is shown in pale yellow to distinguish them more clearly. And when the working is understood, the effects of the adjustments can be more easily recognized. From the pump trip assembly, a connecting rod gives reciprocating motion to the bell crank, which raises a cross head, the lower cross head. Up simultaneously go the pump body spring, the pump body cross head, the piston operating rod, and the piston cross head. The rise of the piston cross head has raised the bottom piston spring abutment. The spring pressing against its top abutment which is adjustable lifts its rod and therefore the right hand end of the piston lever. This action releases the pump body operating rod lever so that the lifting spring can get to work on the pump lifting levers. Consequently, the pump, pump lever, piston lever, and cross heads rise as one man until the travel of the pump is stopped by the nozzle being seated in the mold. The stationary pump fixes the position of the left hand end of the pump lever. Now what happens? We have reached the point where injection is due. To bring the piston down, we must stabilize the top of the link by securing its lower end. To get our firm anchorage, we must prevent the right hand end of the pump lever rising anymore. Pump lever, cross head, rod. The stop knot at its foot is now in contact with the base of the swing frame post, so movement is halted. But the bell crank continues to raise its cross head. Motion on the pump lifting side is absorbed by compression of its spring and only the piston mechanism travels any further. Up go the upper cross head springs rod and right hand end of the piston lever. The link pin acts as a pivot, bringing down the left hand end of the lever and the piston, driving the tight metal through to the mold. Four adjustments enable these actions to be carried out with precision. to set the at rest position of the crosshads. With the cam shaft at 90°, verify that there is a clearance of about 164th between the collar stop and the pump crossh head immediately above it to prevent hammering when running. Press down the cross head to make sure it is not sticking. To correct any error, adjust the effective length of the connecting rod. Slacken its lock nuts, left hand thread at the right hand end, and turn as required. On early machines, the eye centers were set to 10 and 3/4 in. When you tighten the lock nuts again, make sure that the pins are free. After making the next adjustment, check the clearance again and if necessary, reset it. Now we are concerned with the link between the pump and piston levers. A clearance is provided between its upper pin and the piston lever. This can't be conveniently measured, but it can be regulated. As you will see, what we really have to do is to regulate the relative positions of the two upper cross heads when the cam shaft is at 220° on a complete machine with pump engaged. To make sure that the setting isn't being governed by the nuts at the bottom of the pump body spring rod, screw them well down out of the way. At the foot of the stop post, slacken the lock nut and turn the post itself with a screwdriver. First, take it down till its shoulder is free. Then up gently till the link pin just binds. Give the stop half a turn clockwise and retighten the lock nut. The third adjustment is a very simple one to get that link anchorage. Remember, pump lever yolk cross head rod. This is where we need the stop nut just touching the base of the swing frame post. Give it its lock nut. Lastly, there is the adjustment at the top of the pump operating rod. Set this so that there is approximately a 32nd of an inch clearance between the pump operating rod lever and the machine seating under the piston lever and the normal pressure of the piston spring or springs. With a new pump casting five or six point, have the lock nut nearly flush with the top of the rod, tightening to about four turns for 12 or 14 point. A little more pressure is permissible with partly worn components, but if any great increase seems to be needed, look for trouble in the pump itself and where the nozzle seats in the mold. We haven't yet mentioned one other item that the metal has to pass on its journey from the pot to the casting cavity, and that's the crosslock assembly. The gap between the fixed and the adjustable gates forms the passage into the foot of the cavity. Its base almost touches the tip of the nozzle. You can see how important it is that this should be in absolutely the right position at the moment of injection. Otherwise, the metal will be deflected and perhaps obstructed as it flows up. This will lead to a swirling round or turbulence in the cavity. and the porous casting or frosted face type is almost certain to result. You can easily avoid the deflection. Check the adjustment of the type carrier operation for this is directly linked to the cross block. First, set the machine at 220° and mark a convenient point on the type carrier adjacent to the trip plate. Turn the machine to 80° and check that the point has moved two and 53 seconds from the trip plate tongue. If not, raise or lower the cam lever extension as required to increase or reduce the travel. Remember that a new marking point will now be needed. To adjust the position of the cross block, slacken the nut at each end of the connecting rod. Left hand thread at the right hand end and turn the rod to position the type carrier so that at 220° the inside face of its head is exactly in line with the fixed type channel block. Push back the tight clamp and use a six-point point measure gauge to check the alignment, avoiding the rib on the channel block, but compressing the spring latch. The cross block will now be correctly placed, but bad wear of the hook, jet blade, or its cam track can also cause misalignment. So, check sample types from time to time for porocity, bleeding feet, and frosted face. But frosted face is more likely to be caused by too low mold temperature intended perhaps to give quicker cooling of the type. But this, as you may have found, isn't practicable. A good guide is the outflow from the mold should be a gentle trickle for the smaller type sizes and for the larger sizes a steady flow. Speaking of liquid, this is the sign of a Kentish pub that gives very adequate service. But there's no use for a type that shares this ducal distinction. Yet, it sometimes happens. The head of the type has been pulled off as a result of faulty bridge adjustment, which causes the matrix to hammer on the mold and become burred over. It grips the face, and something has to go. The next attempt to cast that character will be disastrous as the head of the type is still sticking in the matrix. In a less acute stage with too much heat, the rising matrix will gradually release the type like this lowerase I, but not before it has stretched it so that it prints heavy at the expense of adjoining characters. Look at these ends. If a proof shows a certain character to be consistently irregular, it clearly comes back to a defect in the matrix concerned. Possibly the tip of a serif has broken off and remained in its corner. Or some other matter out of place is preventing the face from being fully and cleanly cast. Oil will spoil the type. It produces a pitted face giving a broken impression. So floods of oil are very unwelcome hereabouts. Clean mattresses obviously prevent the trouble. But remember that they're made of bronze and so can be easily damaged by heavy-handedness in cleaning. There are three precautions to be taken. Examine all the mattresses at the end of a run. See that they are all clean, properly stored, and protected from accidental damage. When you want them again, check that they are still in perfect condition before slipping the matrix case into the sliding frame. See that there's no all steel matrix to damage constant height molds. The best way of cleaning mattresses is to use a soft brush and a bath of volatile oil solvent. No smoking and plenty of fresh air are essential safety precautions. This treatment will loosen and probably remove any deposit. The liquid evaporates quickly so that application of an air jet will dry off the matrix and drive away any dusty residue. You'll find it pays to run through this cleaning routine at least once a day. Have a good look at the cone holes. Any dirt and the centering pin will push the matrix slightly aside, giving faulty alignment. any sign of wear on one side and it's evidence that one of the draw rods and the centering pin are squabbbling as to where true alignment is to be found and the conflict is proving damaging both to the centering pin and to the mattresses. So check the adjustment of the draw rods and the bridge. You know the drill. And then space widths. Each of the spaces here is only a tenth of a hair's breadth out. But you can see the result. Make sure the screw in the space transfer wedge has been correctly set for equal-sized spaces from the type and space transfer wedges when the justification wedges are in the 38 positions. It's not every printer who sends his used type back to his metal supplier for remelting. And indeed the caster operative himself may be responsible for the job. So a word for his guidance. He should make sure that no zinc or brass goes into the remelting pot and he is advised to put aside anything that is not known to be a standard monotype metal as it may seriously affect the quality of his melt. On the other hand, he knows that the composition of his monotype casts can be closely controlled and an allowance made for routine loss of tin and antimony by oxidation. Standard reviving metals rich in these elements are available for this purpose to be added in the order of half a pound to every£100 or as recommended by the suppliers. Quantities of at least 300 lb of type should be melted at a time. So the pot of the caster isn't the right place to do it. Melt quickly. Temperatures of 700 to 750° F are suitable, but if higher temperatures are kept for more than a few minutes, the rate of oxidation will increase rapidly, though a properly designed furnace will restrict the supply of free air. Stir the metal thoroughly. Use a simple wax flux to separate the dross from the metal. Certain chemical fluxes may lead to corrosion and other troubles. Skim then add the revor. If this is well stirred into the melt, the result will not be very different from new metal. Allow the temperature to fall to about 650 before pouring into cool molds to prevent the formation of coarse grained metal in the ingots. If this coarse grain metal like the example on the left goes into the pot of the caster, it will form a heavy crust. And even if the temperature is raised far beyond the recommended casting range, this won't disperse. A similar condition will occur if type is thrown back into the pot, the bins the proper place. A section of an ingot or type selected from current production should be submitted regularly for analysis by the supplier. He will probably use a spectrograph. Here, a sample of metal heated to incandesence throws off light that is refracted into the spectrum, both visible and invisible. The spectrograph records the invisible ultraviolet light waves which appear on the photographic plate as lines. Each element has its own characteristic set of lines by means of which it can be identified. A large-scale projection of the plate gives an extremely sensitive means of detecting minute amounts of possibly harmful impurities and any appreciable deviation from the working specification of the metal. The record sheets should be kept with the dates in the caster department. For the production of good type, you needn't know a lot about metallergy, but you should know something of it. At the same time, you have got to be a mechanic capable of making your adjustments quickly and accurately. When a faulty product is being cast, you must be able to spot the reason, or at least the probable one. You want some knowledge of typography to recognize the characteristics and needs of various faces. And finally, you have got to be thorough and conscientious in keeping the vital parts clean and 100% serviceable. These are the qualifications of uncountable operatives all over the world. For the performance of his machine is reflected in a man's life. When the one is sweet running and productive, so is the other. When the machine is properly adjusted and unimpeded, life is free from anxiety and frustration. To help you achieve this state of affairs has been our object. So we hope that for your casting difficulties as for the film this will be the end.