Fig. 2555Fig. 2555.
Fig. 2555.
Instead of finding when the crank pin is on the dead centre by means of the process shown inFig. 2551, it may be found as inFig. 2555, which is for a vertical engine. On the face of the crank and from the centre of the crank shaft as a centre, draw a circlebequal in diameter to the diameter of the crank pin. Then take a spirit-levelcand apply it to the cylinder bore and note where its bubble stands. Then apply the spirit-level to the perimeter of the crank pinaand circleb, and move the crank until the spirit-level bubble stands in the same position as it occupies when applied to the cylinder bore. If the cylinder bore stands truly vertical the bubble will in both cases stand in the middle of the spirit tube; but in any event, the bubble must stand in the same position whenapplied to the crank as when applied to the cylinder bore, in which case the crank will be on its dead centre whether the cylinder bore be horizontal, vertical, or at an angle, the dotted lineepassing through the centre of the crank and the axis of the cylinder bore.
When an engine has two eccentrics, so as to enable the engine to run in either direction, as in the case of a locomotive, it is necessary to consider which eccentric is to be set for the forward, and which for the backward motion. In American locomotive practice it is usual to let the eccentric nearest to the wheel, and, therefore, the most difficult to get at, be for the backward motion, which is the least used, and therefore the least liable to get loose upon the axle.
The eccentric that connects to the top of the link is usually that for the forward motion, and hence that which connects with the eccentric farthest from the wheel.
In testing the lengths of the eccentric rods, work may be saved after the engine is first placed on its dead centre by putting the reverse-lever in the forward notch of the link, and adjusting the forward eccentric until the valve has the proper lead. Then set the reverse-lever in the back notch and move the backing eccentric (in both cases moving them in the direction in which they will run), until the proper amount of lead appears. The engine may then be placed on the other dead centre, and the lead both for forward and backward gear measured, so that if there are any errors both the rods may be corrected for length; but for the final trial the crank pin must be set on its dead centre for each direction of motion separately, so as to take up any lost motion in the connecting-rod brasses.
Fig. 2556Fig. 2556.
Fig. 2556.
In the case of large marine engines it is not practicable to move or rotate the engines to set the valves, and the eccentrics are therefore adjusted to their positions on the crank shaft by lines before the crank shaft is put into its place or bearings. First, the throw of the crank is set to stand horizontally true by the following method: From the centre of the crank shaft strike a circle of the diameter of the crank pin, as shown inFig. 2556, ata, and draw upon the face of the crank a line that shall just meet the two circles as denoted by the lineb, using a straight-edge, one end of which rests upon the crank pin, while the other end is coincident with the perimeter of the circlea.
Fig. 2557Fig. 2557.
Fig. 2557.
By means of the wedges shown atc dadjust the crank until the linebstands horizontally level, tested by a spirit-level. A straight-edge having straight and parallel edges is set horizontally level, beneath the eccentric, so that its edges will stand parallel with the throw line of the crank. On this straight-edge, and parallel to the edges, is marked the linea a,Fig. 2557. The first process is to mark ona athe centre of the crank shaftk, which is done as follows: Overkis placed the fine lineb b, suspending the weights or plumb bobs atb b; coincident with this line and acrossa a, are marked two linesc d; midway betweenc dis markede, which therefore stands directly beneath the shaft centre. Fromethe linefis drawn distant frometo the amount of lap added to the lead the valve is to have. Fromfas a centre two lines are drawn acrossa, their distance apart equalling the full diameter of the eccentric; the plumb line is then placed over the eccentric, and the latter is rotated on the shaft until the plumb lines come exactly fair with the linesg h.
Fig. 2558Fig. 2558.
Fig. 2558.
It is obvious that instead of using plumb lines a square may be employed to mark the linesc d, and to set the eccentric to the linesg h, the square being applied as atsands′, inFig. 2558.
Fig. 2559Fig. 2559.
Fig. 2559.
Fig. 2560Fig. 2560.
Fig. 2560.
In this example it has been assumed that the direction of crank rotation was to be as denoted by the arrow; but, suppose the crank rotation required to be in the opposite direction, then the marks on the straight-edge would require to be located precisely the same, but the position of the eccentric throw-line would require to be as inFig. 2559, the perimeter of the eccentric being set to the linesg has before. The eccentric rod being supposed to connect direct to the valve spindle, without the intervention of a rock shaft, for if there is no rock shaft the eccentric leads in the direction of rotation, while if the engine has a rock shaft the eccentric follows the crank-pin in the direction of rotation, andfmust be marked on the crank-pin side ofe, as inFig. 2560.
Fig. 2561Fig. 2561.
Fig. 2561.
If two eccentrics are used, as in a link motion, the lines for setting one eccentric are equally applicable to both; the lap and lead linefbeing located on the crank-pin side ofewhen there is a rock shaft, as is supposed to be the case inFig. 2561; and on the other side ofewhen there is no rock shaft; and in this case the eccentric that is to operate the valve to make the engine run forward must have its throw-line following the crank pin, as atj, inFig. 2561; the eccentrickoperating the valve for running backward. Conversely, in the absence of a rock shaft, the throw-line of the forward eccentric leads, while that of the backward eccentric follows the crank pin.
When the line of connection of the eccentric rod is not parallel to the axial line of the cylinder bore, the crank must be placed horizontally level (or if it be a vertical engine, on the dead centre), but instead of the straight-edge being placed parallel to the throw-line of the crank, it must be placed at a right angle to the line of connection of the eccentric rod.
Fig. 2562Fig. 2562.
Fig. 2562.
Thus inFig. 2562the engine is supposed to be a vertical one, and the crank is, therefore, placed on its dead centre, its throw-line being vertical instead of horizontal as in our previous examples (which were supposed to be for a horizontal engine). It is also supposed to have a rock shafta; hence the straight-edge is set at a right angle to the line of connection of the eccentric rod which is denoted byb.
It is obvious that to set the crank throw-line vertical the circlebinFig. 2509may be used, the spirit-level being resorted to to discover when the crank stands vertical.
Fig. 2563Fig. 2563.
Fig. 2563.
An example in the erection or setting of framed work is shown inFig. 2563, which represents a side elevation of a frame put together in four parts, two side and two end frames.aandbare journal bearings requiring to stand parallel and true one to the other,bbeing capable for adjustment in distance fromaby means of the adjusting screwsg,h. The bearingsc,d,e,f, are to be parallel one to the other and toa,b. Their proper relative distances apart, and the axes of all the shafts, are to stand at a right angle to the side frames.
Fig. 2564Fig. 2564.
Fig. 2564.
Fig. 2564represents an end view of the frame, the endstbeing bolted to the side framessands′ati,j,k, andl.
Now it is obvious that the ways for the bearingsa,b,c, &c., maybe trued out, ready to have the brasses fitted before the framework is put together, and that from their positions they would have to be planed out at separate chuckings; supposing, of course, the frame to be too large to be within the capacity of the machine table. It would be difficult to cut all the surfaces of the bearing ways to stand in the same plane, unless there were some true plane to which all might be made common for parallelism.
Furthermore, unless the surfaces wheretis fastened tosands′are properly bedded to fit each other, bolting them up would spring and bend the frames out of their normal planes. To meet these requirements, there are given to the side frames a slightly projecting surface where the feet oftmeet them, and furthermore, the feet oftthemselves project beyond the sides oftas shown. These projecting pieces may therefore be planed to a common plane without planing the sides of the respective frames; and this plane should be as nearly as can be parallel with the body of each frame surface. The surfaces of the bearing ways may then be planed parallel to those of the projections, and the jaw surfaces true to the side surfaces, and all the bearing ways will stand true if the frames be properly set—when put together with the bolts. But unless the bedding surfaces ati,j,k,l, be made to bed and fit properly, the whole truth of the bearing ways and their distances apart across the framework may be altered. Thus, supposing the feet oftatiandjto meetsas denoted by the dotted lineso r, and whether the fault lie with the feet oftor with the projections onsthe result will be that the pressure of the bolts holdingi jtoswill bendsso that its plane will be a curve as denoted by the dotted linep p, and the distances apart of the journal waysb bandd drespectively will be wrong, being too wide on account of the bend outward ofs.
But the feet may touch on the opposite corners, the surfaces ofs′or oftbeing out of true or out of full contact, as denoted by the dotted linesv wonk,l; in this case the frames′would be bent to the curveq q, and the journal ways would be too close together.
On the other hand, the want of fit between these surfaces may be in the direction of the length of the frame instead of the direction of its height, as has been supposed; or it may be in one direction on one foot and in another direction on another foot. But in whatever direction it does exist, it will inevitably bend and twist the frame.
It must not be taken for granted, that because these surfaces have been planed or milled, that therefore they are true; because frames of this class cannot, if large, be held without springing them to some extent from the pressure of the bolts or other devices necessary to hold them to be cut.
It is not uncommon to plane the surfaces as true as may be, and put the frames together, bolting them up tight, and then applying the straight-edge trammel and rule to test the truth, correcting any error that may be found by inserting pieces of paper, sheet tin or material of requisite thickness on one side of the surfaces, so as to offset the error in their fit and bring the framing true; but this is not the proper way, because it reduces the area of contact, and furthermore renders a new testing and adjustment necessary whenever the frames are taken apart. It is better therefore to apply a straight-edge to the surfaces and true them to it, testing them vertically as by placing the straight-edge acrossk l, and longitudinally acrosss′, atkand the corresponding projection at the other end of the frame, filing them until they appear true.
The holes through the frame may be drilled before filing these surfaces, so as to reduce the area to be filed. Since the end framestdo not in this example carry any journals or mechanism, the position oftis not so particular as it otherwise would be; hence, the holes in its feet may be marked off and drilled independently of the frame, the holes being drilled a little too small to allow for reaming with the holes in the frame. The framing will then be ready to put together (all machine work upon them being supposed to be done). The feet of all such frames should be planed true, so that the frame, when put together, may stand true and steady when placed upon a level floor or foundation, and in this case the distance and parallelism of the feet surfaces will be true with the ways or bearings, affording much assistance in holding the frame while putting it together. The height of the holes may be measured and marked from the feet surface, thus insuring truth as far as height is concerned. Lines may be drawn or marked on each side frame, at the proper distance from and parallel with the jaws of the waysa,b, thus completing on the side frames the marking of the location of the centres of the holes for bolting the end frames on.
If the frames were of a size to be sufficiently easily handled, the end frames might be put in their places, and the whole framework set true, so as to mark the holes in the end frames from those already drilled in the side frame. But if the use of a crane were necessary to lift them, it would be better to mark the holes on the end frames, and drill them before putting the framework together at all, leaving sufficient to ream out of the holes to bring them fair, notwithstanding any slight error in drilling them. In this case, a line denoted by the dotted linexinFig. 2564, should be drawn across the frame, and the holes atiandjbe made equidistant on each side of it, as well as the proper distance apart.xmust be at a right angle to the trued foot surfaces ati j, so as to cause the side frames to stand vertical while their feet are horizontal.
Supposing now the holes to be drilled and the frames are to be bolted together, the whole frame may be held temporarily together by bolts passing through the side frames at each end, or a bolt may be passed through the holesfto steady it. Indeed, if these holesfhave been accurately bored, a neatly fitting mandrel passed through them should hold the side frames true. The end framesthaving been set to stand at a right angle to the side frames, and with their holes ati j, &c., as near fair as may be with the holes in the side frames, two feet, asi j, may have their holes reamed fair with the holes in the side frames, and tightly fitting bolts be driven in and screwed firmly home. Before reaming the other holes (ask l) of each end frame, the jaws to receive the bearing boxes should be tested for alignment one with the other. Truth, in this respect, being of the utmost consequence for the following reasons:
Suppose the bearing ways on one side frame to stand higher than those on the other, then, the shafts will not stand level in the frame unless (except in the case of the brasses or boxes inb) the lower brasses are made of unequal thickness through the crown, to an amount equal to that of the error. In the case of the brasses ina,c,d,e, the joint faces of all the brasses of one side frame would require to be made thinner beneath the journal than above it on the high frame, and thicker beneath than above on the low frame, This would entail much extra work in planing, marking, and boring the bearing boxes or brasses, and be an inferior job when done.
Again, the bores of all the brasses would not be parallel to the crown or bedding faces, and this error would entail the following extra work: 1. Ascertaining the amount of the error, and allowing for it in marking the brasses; 2. The setting of the ways of the brasses out of true with the ways when clinking them for boring; and, finally, extra fitting or filing the brass bores when fitted with the shafts in place. This extra fitting would be necessary for the following reasons:
When the surfaces of work are to be parallel, they can be measured with calipers. Surfaces to be at a right angle can be tested with a square; those to be in line can be tried with a straight-edge, and in each case the truth or alignment of the surfaces is tested by contact of the testing tool. But in the cases where surfaces at an angle are tested or measured the tools must be set to a line or lines, and the work must be measured or cut to lines, thus: Suppose it were found that the bedding surface of the brassbwas a certain amount out of alignment with the corresponding bedding surface on the other side frame, and, by measurement, this amount determined to be1⁄64inch, then there is a liability to error in measuring this1⁄64. The brasses must be marked (for boring the same1⁄64out of square, inducing another liability of error in marking that amount); this marking being done by lines, there is a liability to error in setting the work to the lines. From these liabilities to error, it is generally found that work not true in alignment requires, when it comes to be put together, to have each piece fitted to its place and corrected for alignment.
But, suppose the ways are made true and in proper alignment, then the brass bores are simply made of equal thickness at the crown, and on the sides at a right angle to the inside faces of the ways; and truth, in these respects, may be measured by actual contact, with the square or calipers, eliminating the chance of error.
In repairing the machine, or putting in new bearings or brasses;the measurement and transferring of the error in the ways to the brasses has all to be gone through with again, and the parts fitted for alignment; whereas, if the ways are true, the brasses can be made true, and to go together, with but little, if any, adjustment when tried in their places.
Fig. 2565Fig. 2565.
Fig. 2565.
The most accurate method of testing the adjustment of the ways is as follows:Fig. 2565represents a plan view of the frame;nrepresents a straight-edge applied to the surfaces of the jawsa b. The method of applying this straight-edge is to place one end across a jaw, asa, while the other end is elevated aboveb; then, while pressing the end firmly againsta, lower the other end to the face ofb; if its edge at that end falls fair withb, so as just to touch it, the process may be reversed—one end being pressed tob, and the other lowered upona. By this means, it will not only be discovered whether the jawsaandbstand square across the frame, but also whether the frame on either side is sprung. A squarecmay also be rested againstn, and its bladedtested with the side face of the way, as shown. The same process of testing should be applied to the other jaw facese,f.
Suppose, however, that the width between the jawsa,fwas less than that betweene,b, then the straight-edge, when pressed toa, would show a space between its edge andb; and also a space between its edge ande, when its other end was pressed tof; and, when these spaces were equal in amount, the frames would be set true in one direction. To test the truth in the other direction, the straight-edge should be applied after the same manner to the bottom surfacesg,h.
It will not answer to rest the straight-edge against the two surfaces and observe their coincidence with its edge, because any error cannot be sufficiently, readily, or accurately tested by this means. Nor will it answer to test by the bearing marks of a straight-edge applied with marking, unless the coat of marking be very fine and the straight-edge be moved without any vertical pressure on it; because, under such pressure, the straight-edge will bend.
The ways for all the bearings should be tested in this manner; so that, if from any error in the machine work, some of them will not come fair, the frames may be set to align those that it is of most importance to align truly; or if there is no choice in this respect, then those carrying the largest bearing should be set true; because, if it be decided to correct the error on the other bearing or bearings, there will be less area to file or operate upon. The setting being complete the holes may be reamed and the remaining bolts put in, the testing being repeated after the frame is finally bolted together. If this final test shows that bolting the frame up has altered the alignment by springing the frame, the bolts in one foot, as sayi,Fig. 2564, may be slackened and the test repeated; and, if the frame is then found true, it is the bolting atithat causes the spring, on account of the bedding surfaces not fitting properly. Ifiis not found to be at fault, it may be bolted up again andjtested by loosening its bolts, and so on, until the location of the error is detected. Furthermore, when the frame is bolted up, the width of the bearings, as fromatob, should be tested; for in a job of this kind, it will pay to have the framework so true to the drawing that, if the other parts, as the shafts, bearing parts, &c., be also made to the drawings, the parts will go together, thus avoiding the necessity of varying all the other parts from the drawing to accommodate errors in the framework.
Fig. 2566Fig. 2566.
Fig. 2566.
Among the jobs that the erector is often called upon to perform is that of patching or repairing pieces that have cracked or broken.Fig. 2566represents a case of this kind, the fracture being atd. The principle to be observed in work of this kind is to cause the bolts to force the fractured pieces together, so that the irregularity or crookedness of the crack, as atdin the figure, may serve to lock the pieces together.
Fig. 2567Fig. 2567.
Fig. 2567.
Suppose, for example, we were to put on a patchp,Fig. 2567, and there would be but little to prevent the crack from opening under severe strain, and the patch would stretch, permitting the crack to open and finally causing the bolts to break or sheer off. A preferable plan, therefore, is to put two patches on the sides in the followingmanner:—
Fig. 2568Fig. 2568.
Fig. 2568.
The holes should be drilled through the beam and the plates held against the beam so that their holes may be marked by a scriber passed through the holes in the beam. The holes in the plates should be drilled closer together than those in the beam, so that when driven in they will serve as keys to close the two sides of the crack together, as shown inFig. 2568, where it is seen that one side of the bolt bears against the holes in the patch and the other against the holes in the beam. To facilitate getting the bolts in place the plates may be heated so as to expand them.
Fig. 2569Fig. 2569.
Fig. 2569.
In cases in which it would not be permissible to drill so many holes through the beam on account of weakening it, we may use patch bolts with countersunk heads, as inFig. 2569. Two only of the bolts pass entirely through, and it is best to let them be taper, as atain the figure, the head not meeting the patch. The hole in the beam, after being reamed taper, should be filed out on the sideb, and that in the patch plates on the other side, as atcandd, so that the bolts will serve as keys. After these two bolts are in placeand their nuts firmly screwed home, the holes for the patch bolts may be drilled through the plates and into the beam. When the countersunk head bolts are fitted they should be turned down behind the head, so as to leave a part weaker than the bolt, and then screwed in until the required end breaks off. The taper bolts should be of steel, but those with countersunk heads may be of iron.
Erecting an Iron Planer.—If an iron planer be properly fitted and erected, the table will be quite solid in theV-ways in the bed, and will not rock or move even though a heavy vertical cut be taken at the extreme sides of the table, but any error of truth of alignment or fit either in the bed-ways or the tableV’s will cause the table to lie improperly in theV’s and to be apt to rock as it traverses. The author has had planed upon a planer thirty years old, at the Freeland Tool Works, in New York City, a cast-iron surface 12 × 20 inches, the metal weighing about 60 lbs., and the surfaces were so truly planed that one would lift the other by reason of a partial vacuum between the two. These planed surfaces were exhibited by the author at the American Institute Exhibition in 1877, and were awarded a medal of superiority.
The manner in which this planer was fitted and erected, and the principles involved in such fitting and erecting, are as follows:
While it is essential that the foot or resting surface of a planer bed (whether it stands on legs or rests direct upon its foundation) be as true as it is practicable to plane it, still it is more essential that theV’s or ways be true, and as the casting will be apt to alter its form from having the surface metal removed, it is best to plane the side on which the ways are the last.
When the bed is placed upon the machine to have its resting surface planed, the casting being uneven, it will be necessary to place packing pieces of suitable thickness beneath the places where the clamping plates hold it, so that the pressure of those plates may not spring or bend the casting.
These packing pieces require to fill up solidly (without lifting the bed) the hollow places, and it is a good plan to place among them a piece of strong writing paper for reasons which will appear presently.
In planing the bed all the surfaces should be roughed out before any are finished. Before any finishing cuts are taken all the clamping bolts should be loosened and the pieces of paper tried by pulling them, so that if the casting has altered its form it will be made apparent by some one of the pieces of paper becoming loose.
In this case the packing must be readjusted, clamping both as lightly as will hold the work, and all as equally as possible, when the finishing cuts may be taken.
Fig. 2570Fig. 2570.
Fig. 2570.
The best form of template to plane the ways to is that shown inFig. 2570, in whichbis a side andaan end view. A corresponding female template being shown atdto be used in planing the tableV’s.
The lengthcof theVof the template must not be longer than from 4 to 6 inches, or it will be liable to spring or twist from its own weight. This template is not intended to be used in any sense as a straight-edge to test the truth of the length of the ways, but rather as one to test their width apart, and the correctness of the angles. The top surfacea bshould be quite true with theV’s, being equidistant from them, so that by testing that surface with a spirit-level it may be known whether the ways are level either crosswise or lengthwise.
TheV’s of the template require to have red marking on them so as to mark the ways when the template is moved, and show that the ways accurately fit to the template, which is highly important.
In planing the table or platen it is essential to bear in mind that the area to be planed on theVside is always small in comparison with that to be planed on the other or work-holding side of the table, and as the planing of this latter surface is sure to cause the casting to alter its form, it is necessary to plane it first, so that the alteration of form may occur before and not after theV’s have been planed.
In chucking the table to plane its work-holding surface, the packing pieces must be used as described for the bed, and the bolts placed as there described.
Both bed and table being planed they require to be fitted together (no matter how expertly the planing has been done) if a really first-class job is to be made of them. In doing this it is essential that the bed be supported at the same points as it will be when the machine is put to work, for in large or long casting the deflection or bending from its own weight is sufficient to have an important practical effect. The same fact will also apply to the table and even to the cross slide, even though the latter be heavily ribbed and but, say, 5 feet long.
If, therefore, the bed is to be supported by legs, its guideways orV’s should be fitted after the legs are attached. The bed must be carefully levelled so that the ways may stand horizontally true, which may be tested by placing the templatea binFig. 2570in place and applying a spirit-level first across and then lengthwise of the upper surface of the template.
If the bed rests upon a foundation at several points in its length it should be rested at those points while being fitted and carefully levelled as before, the template and spirit-level being tried at every two or three feet of the bed length.
To test the width of theV’s and their widths apart in the fitting, the templatea b,Fig. 2570, must be used in connection with red marking, but to true the lengths of the ways a surface plate about 4 feet long and slightly wider than the width of one side of the ways must be used, and if the template and the surface plate show the ways true they will be of the correct width, of correct angle and true planes. But this does not insure that the two ways are in line one with the other, and for this purpose separate test blocks are necessary, because the template is too narrow in width to give a good test, and cannot be made wider, because in that case its own weight would cause it to spring or deflect to suit any error in the work.
Fig. 2571Fig. 2571.
Fig. 2571.
These test blocks are simply two pieces of metal, such as shown inFig. 2571. The lengths of these blocks should be about 8 inches, and the best way to obtain them true and exactly alike is to make one block and then cut it into two. They possess an advantagenot possessed by a template that spans both ways, inasmuch as they may be turned end for end in each way and thus test the accuracy of the angles of each way.
Again, both may be placed in one way, and by various applications in connection with straight-edge, surface plate, and level they will test the truth of the ways, both individually and one with the other in a better manner than by any other method.
Fig. 2572represents the various positions of theVblocks for the testing,a,b,c,d,e,f,g,h, representing the blocks; straight-edges may be placed as ati, atj, and atk, and if the ways are true the straight-edge, lightly coated with marking, should have contact clear across the upper surface of bothV-blocks, and a spirit-level placed on the straight-edge (in each position of the same) should show them to be level.
The surfacep, on which uprights or standards on that side of the plane, rest, being planed with theV-ways will be true with them, and the uprights may be erected thereon, their base surfaces being fitted topuntil the standards stand truly vertical and parallel in their widths apart. In testing these uprights they should be bolted home as firmly as they will be when finally erected, as they will be liable to alter their set if bolted up more firmly than when tested. These front surfaces should be at a right angle to the length of the bedV-ways, and this may be tested by placing a straight-edge across their surfaces and testing it with a square rested against the edge of the planer table.
The method of erecting planers at the Pratt and Whitney Company’s shops is asfollows:—
To test theV’s, a platep,Fig. 2573, is applied as shown, its lugsa,a1fitting to corresponding sides of the twoVs; asb,b. InFig. 2573the test is made by inserting thin pieces of tissue paper betweena,a1and theV-sides, the friction with which the paper is held showing the nature of the fit. Thus, if the paper will move easily at one end and is tight at the other end of either of the lugsa,a1the fit is shown to be defective. When the fit on these sides is corrected, the platepis turned around, as inFig. 2574, and from a similar tissue-paper test, the other sides are corrected. Thus the outside angles of the twoVs are fitted to the same angle; inside angles are also fitted to the same angle. But it will be observed that it does not follow that the inside angles of theVs are of the same degree of angle as are the outside halves or angles, unless the two lugsa,a1of the platephave equal angles. It is on this account that the test is made by tissue paper, rather than by the bearing marks produced by rubbingpalong theVs, since that might in time wear the anglesa,a1out of true. The same platepmay be used to true the maleVs on the work-holding table of the machine, as is shown inFigs. 2575and2576, where the table is seen upside down, as is necessary in order to apply the plate. Here, again, the outside angles or halves of theVs are fitted from the sameV(a1) of the plate, so that the fit of the table will be true to the bed, even though the angle on one side of theV-ways were not precisely correct, and there is less liability to error than would be the case were a male and female plate used instead of a single plate. The alignment next in importance is that of the uprights, standards, or side frames of a planing machine, and to enable the correct erection of these, the devicea,Fig. 2577, is employed. It consists of a solid plate fitting into theV-ways of the planer-bed and having two steps,bandc, which receive the side frames to be erected. The widthdis the width apart of the side frames, and the side surfaces of the steps (asg) are vertical to the centre line of theV-ways of the bed, so that the side frames may be rested againstgon one side, and the corresponding surface on the other step. The surfacese,fare at a right angle to theV-ways of the bed, so that when the side frames are againste,fthey will be set square across the machine. The top face of the plateais planed parallel to theVs of the plate, so that in addition to resting each side frame against the surfaces (asf g) a square may be rested on plateaand applied to their trued surfaces, and thus may these side frames be set true and square, both one with the other, and with the ways in the bed, without the use of stretched lines and straight-edges, which secures greater accuracy and saves considerable labor.
Largeimage(213 kB).Fig. 2578Fig. 2578.
Largeimage(213 kB).
Fig. 2578.
All the smaller parts of the machine may then be erected true to the bed or the side frames, as may be required, and if it be a small planer, in which the bed rests upon feet, all that will be necessary in setting the machine in position to work is to set the surface of the work-table level. But in the case of a large heavy planer a solid foundation must be built for the bed, because it will spring, bend, and deflect from its own weight, and thus the side frames, as well as the bed, may be thrown out of true and alignment.Fig. 2578is a side and plan view of the foundations for a planer, showing the bed-plate in position upon the same.
The stone blocks forming the base of the foundation require themselves to rest upon a solid base, and not upon a soil or gravelthat is liable to sink beneath them. The brickwork above them is best laid in cement, which should be properly set before the planer bed is placed in position. Near the centre of the bed, and directly beneath the cross-slide, is shown a screw jack, to take up any sag of the bed, and cause theVs to have a good bearing directly beneath the cutting tool, which is essential to prevent the table from springing from the pressure of the tool cut.
Fitting up and Erecting a Lathe.—The first operation will be to true the bed or shears. If the lathe has raisedVs on the bed it will be sufficient to true them only, without truing the flat surfaces. The bed should during the fitting be supported at the same points as it will be when in use.