Modern Machine-Shop Practice Part 113

PLANER BEDS AND TABLES.--The general forms of the beds of small planers are such as in Figs. 1557 and 1558, and those of the larger sizes such as shown in Fig. 1563.

It is of the first importance that the [V]-guideways in these beds should be straight and true, and that the corresponding guides on the planer table should fit accurately to those in the bed; for which purpose it is necessary, if the greatest attainable accuracy is to be had, that the guideways in the bed first be made correct, and those on the table then fitted, using the bed to test them by.

The angle of these guides and guideways ranges from about 60 in the smallest sizes to about 110 in the largest sizes of planers. Whatever the angle may be, however, it is essential that all the angles be exactly equal, in order that the fit of the table may not be destroyed by the wear.

In addition to this, however, it is important that each side of the guides stand at an equal height, or otherwise the table will not fit, notwithstanding that all the angles may be equal.

[Ill.u.s.tration: Fig. 1600.]

Suppose, for example, that in Fig. 1600 all the sides are at an equal angle, but that side _e_ was planed down to the dotted line _e_, then all the weight of the table would fall on side _a_, and, moreover, the table would be liable to rock in the guideways, for whenever the combined weight of the table and the pressure of the cut was greatest on the right-hand of the middle _x_ of the table width and the feed was carried from right to left, then the table would move over, as shown exaggerated in Fig. 1601, because the weight would press guide _g_ down into its guideways, and guide _h_ would then rise up slightly and not fit on one side at all, while on the other side it would bear heaviest at point _p_. Great care is therefore necessary in planing and fitting these guides and ways, the processes for which are explained under the respective headings of "Examples in Planer Work," and "Erecting Planers."

In some designs the bed and table are provided with but one [V]-guideway, the other side of the table being supported on a flat side, and in yet another form the table is supported on two flat guideways.

Referring to the former the bearing surface of the [V] and of the flat guide must be so proportioned to that of the [V] that the wear will let the table down equally, or otherwise it would become out of parallel with the cross slide, and would plane the work of unequal thickness across its width.

[Ill.u.s.tration: Fig. 1601.]

[Ill.u.s.tration: Fig. 1602.]

Referring to the second, which is ill.u.s.trated in Fig. 1602, it possesses several disadvantages.

[Ill.u.s.tration: Fig. 1603.]

Thus, if there be four gibs as at A, B, and E, F, set up by their respective set-screws, the very means provided to take up the wear affords a means of setting the bed out of line, so that the slots in the table (and, therefore, the chucks fitting to these slots) will not be in the line of motion of the table, and the work depending upon these chucks will not be true. This may be avoided by taking up the wear on two edges only, as in Fig. 1603 at A, B, but in this case the bearing at E and F would eventually cease by reason of the wear.

Suppose, for example, that the pressure of the tool cut tends to throw the table in the direction of arrow J, and the surfaces at A and F resist the thrust and both will wear. But when the strain on the table is in the direction of arrow K, the surfaces B, E, will both wear; hence while the width apart of the table slides becomes greater, the width apart of the bed slideways wears less, and the fit cannot be maintained on the inner edges of the guideways. It is furthermore to be noted that with flat guideways the table will move sideways very easily, since there is nothing but the friction of the slides to prevent it, but in the case of [V]-guides the table must lift before it can move sideways; hence, it lies very firmly in its seat, its weight resisting any side motion.

[Ill.u.s.tration: Fig. 1604.]

It is found in practice that the wear of the guides and guideways in planer tables and beds is greatest at the ends, and the reason of this is as follows:--

In Fig. 1604 is a top view of a planer table, the cutting tool being a.s.sumed to be at T, and as the driving gear is at G forcing the table in the direction of the arrow A, and the resistance is at T, the tendency is to throw the table around in the direction of arrows B and C. When the tool is on the other side of the middle of the table width as at F, the tendency is to throw the table in the opposite direction as denoted by the arrows D and E, which obviously causes the most wear to be at the ends of the slides.

As the feed motions are placed on the right-hand side of the machines the operator stands on that side of the machine at X, and starts the cut from that side of the table; hence unless the work is placed in the middle of the table width, the wear will be most in the direction of arrows B and C.

The methods of fitting the guideways and guides of planer beds and tables is given in the examples of erecting.

[Ill.u.s.tration: Fig. 1605.]

A very good method of testing them, however, is as follows:--Suppose that we have in Fig. 1605 a plate that has been planed on both edges G, H, and that in consequence of a want of truth in the planer guideways edge G is rounding and edge H hollow, the plate being supposed to lie upon the planer table in the position in which it was planed.

[Ill.u.s.tration: Fig. 1606.]

Now, suppose that it be turned over on the planer, as in Fig. 1606, the rounding edge, instead of standing on the right-hand side of the planer table, will stand on the left-hand side, so that if that edge were planed again in its new position it would be made hollow instead of rounding in its length. It is obvious, therefore, that if a planed edge shows true when turned over on the planer table, the [V]s of the planer are true, inasmuch as the table moves in a straight line in one direction, which is that affecting the truth of all surfaces of the work that are not parallel to the cross feed of the tool, or, what is the same thing, parallel to the surface of the planer table.

PLANING MACHINE TABLES.--In order that the guides on the table of a planer may not unduly wear, it is essential that they be kept well lubricated, which is a difficult matter when the table takes short strokes and has work upon it that takes a long time to perform, in which case it is necessary to stop the planing operations and run the work back so as to expose the guideways in the bed, so that they may be cleaned and oiled.

[Ill.u.s.tration: Fig. 1607.]

It will often occur that the work will not pa.s.s beneath the cross slide, and in that case it should be raised out of the ways to enable proper oiling, because insufficient lubrication frequently causes the guides and guideways to tear one another, or cut as it is commonly termed.

[Ill.u.s.tration: Fig. 1608.]

The means commonly employed for oiling planer [V]s or guideways are as follows:--At the top of the guideways small grooves, _g_ _g_, Fig. 1609, are provided, and at the bottom a groove _x_. In the guides on the table there are provided pockets or slots in which are pivoted pendulums of the form shown in Fig. 1607 at A. Each pendulum pa.s.ses down to the bottom of groove _x_ in which the oil lies, and is provided on each side with recesses _e_, which are also seen in the edge view on the right of the figure.

The pendulums are provided with a long slot to enable them when the table motion reverses to swing over and drag in the opposite direction (as shown in Fig. 1607); as they drag on the bottom of groove _x_ of the bed they lift the oil it contains, which pa.s.ses up the sides of the pendulum as denoted by the arrow, and into grooves provided on the surface of the table guide, as at _h_ in Fig. 1608, in which V' is the table guide, V the guideway in the bed, _g_ oil grooves, (see sectional view, Fig. 1613), _x_ the oil groove at the bottom of the bed V, and _h_ _h_ the oil grooves which receive the oil the pendulum lifts.

The oil grooves _h_ on the table guide run into the grooves _g_ in the [V]-guideway in the bed, hence grooves _g_ _g_ become filled with oil.

But after the end of the table has pa.s.sed and left the bed V exposed, the oil flows out of grooves _g_ down the sides of the guideway, and constant lubrication is thus afforded at all times when the stroke of the table is sufficient to enable the pendulums to force the oil sufficiently far along oil way _h_. When the table reverses the pendulum will swing over and lift the oil up into grooves or oil ways _h'_.

[Ill.u.s.tration: Fig. 1609.]

[Ill.u.s.tration: Fig. 1610.]

Another and excellent method of oiling, also invented by Mr. Hugh Thomas, of New York, is shown in Figs. 1609 and 1610, in which P represents an oiling roll or wheel, [V]-shaped, to correspond to the shape of the [V]s. This roll is laced with cotton wick or braid, as shown by the dark zigzag lines, and is carried in a frame _f_, capable of sliding vertically in a box C, which is set in a pocket in the bed V, and contains oil. By means of a screw S, the roll P is set to touch the face of the table [V], and the friction between the roll and the [V], as the table traverses, rotates the roll, which carries up the oil and lubricates the table [V] over its whole surface. The dust, &c., that may get into the oil settles in the bottom of the box C, which can occasionally be cleaned out. In this case the oil is not only presented to the oil grooves (_h_, Fig. 1608), but spread out upon the [V]s; but it is nevertheless advisable to have the grooves _h_ so as to permit of an acc.u.mulation of oil that will aid in the distribution along the [V]s of the bed.

This method of oiling has been adopted in some large and heavy planers built by R. Hoe & Co., and has been found to operate admirably, keeping the guides and guideways clean, bright, and well lubricated.

Mr. Thomas has also patented a system of forced oil circulation for large planers. In this system a pump P, Fig. 1611, draws the oil from the cellars C (which are usually provided on the ends of planer beds) and delivers it through pipes pa.s.sing up to the sides of the [V]s, thus affording a constant flow of oil. A reservoir at the foot of the pump enables the dirt, &c., in the oil to settle before it enters the pump, which can be operated from any desirable part of the planer mechanism.

The pendulums are also used in connection with the forced circulation.

As the work is fastened to the upper face of a planing machine table either directly or through the intervention of chucking devices, the table must be pierced with holes and grooves to receive bolts or other appliances by means of which the work or chuck, as the case may be, may be secured.

For receiving the heads of bolts, [T]-shaped grooves running the full length of the table are provided, and in addition there are sometimes provided short [T]-grooves, to be shown presently.

For receiving stops and other similar chucking devices, the tables are provided with either round or square holes.

In Fig. 1612 is shown a section of a table provided with [T]-grooves and rows of round holes, _a_, _b_, _c_, _d_, _e_, which pa.s.s entirely through the table, and hence must not be placed so that they will let dirt fall through to the [V]-guides or the rack. Tables with this arrangement of holes and grooves are usually used upon small planers in the United States, and sometimes to large ones also.

[Ill.u.s.tration: Fig. 1611.]

[Ill.u.s.tration: Fig. 1612.]

[Ill.u.s.tration: Fig. 1613.]

It is obvious that the dirt, fine cuttings, &c., will pa.s.s through the holes and may find its way to the [V]-guideways. Especially will this be the case when water is used upon the tool to take smooth cuts upon wrought iron and steel. To obviate this the construction shown in Fig.

1613 is employed.

Fig. 1613 represents a section of one guideway of a table and bed. On each side of the table [V] there is cut a groove leaving projecting ribs _b_, _c_, and whatever water, oil, or dirt may pa.s.s through the holes (Fig. 1612), will fall off these points _b_, _c_, Fig. 1613, and thus escape the guideways, while falling dust will be excluded by the wings _b_, _c_, from the [V]s.

[Ill.u.s.tration: Fig. 1614.]

The capacity of a planer table may be increased by fitting thereto two supplementary short tables, as shown in Fig. 1614, several applications of its use being given with reference to examples in planer work. These supplementary tables are secured to the main table by set-screws at A, and have been found of great value for a large variety of work, especially upon planing machines in which the table width is considerably less than the width between the uprights or stanchions.

[Ill.u.s.tration: Fig. 1615.]

Fig. 1615 represents the arrangement of square holes and [T]-grooves employed upon large planers. The square holes are cast in the table, and are slightly tapered to receive taper plugs or stops against which the work may abut, or which may be used to wedge against, as will be hereafter described, one of these stops being shown at S in the figure.