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GRINDING SINGLE FLUTE GORTON CUTTERS

Trueing Grinding Wheel

Before grinding cutters, true up the grinding wheel using diamond tool 7566-A (Accessories Catalog) which is furnished with grinder. This tool has a taper shank and can be inserted in grinders having tool heads fitting Gorton taper shank tools only, or it can be held on its diameter in a 1/4″ collet in any of the collet type tool heads. After inserting the diamond, set tool head at approximately the same relation to wheel as shown in Fig. 1. Then swing across face of wheel by rocking the tool head in much the same manner as for grinding the cutter. Avoid taking too heavy a cut from the wheel with the diamond. One to two thousandths of an inch should be the very maximum. If the diamond fails to cut freely, loosen it, and turn slightly in the tool head, so as to present a new and unused portion of the diamond to the wheel.

Rough and Finish Grinding Conical Point

Set tool head of grinder to angle desired on cutting edge (see Fig. 2). This usually varies from 30 to 45 degrees, depending on the work desired. Recommended angles for relief characters on steel stamps for various work are given on page 41. For most sunk letter or design engraving on Bakelite panels, brass and metal plates, etc., a 30 degree angle is used (60 degrees included). Now place cutter in tool head and rough grind to approximate size by swinging across face of wheel as with the diamond dresser above. Do not rotate the cutter while in contact with face of wheel but swing straight across, turning cutter slightly after or before contact with wheel. This will produce a series of flats like Fig. 3, left. Now, grind off the flats and produce a smooth cone by feeding cutter into wheel and rotating at the same time. The finished cone should appear like Fig. 3, right. It should be very smooth and entirely free from wheel marks.

Grinding Flat to Center

Next operation is grinding the flat exactly to center. For average work this flat may be left a trifle full or oversize, up to half a thousandth. For very small delicate work however, it is absolutely essential to grind this flat exactly to center. If the flat is oversize it will be readily apparent after grinding the cone, and the point will appear as in Fig. 4. To correct this, grind the flat to center as in Fig. 5. For cutters used on very small accurate work, examine this point with a magnifying glass to see that flat and cone point coincide exactly. Be very careful not to grind the flat down too far. It is much better to leave it a trifle full.

Grinding Flat to Center with Tool Head 717-1

In grinding off flat, always keep it square with original surface—to do this it will be found necessary to lock the tool head spindle with the indexing plunger set in No. 4 hole. Now using the gauge 9684 furnished with all 717-1 Tool Heads, square up cutter and tighten collet nut. Then turning tool head spindle 90 degrees, plug in next No. 4 hole to square flat with wheel.

Grinding Chip Clearance

The cutter is now the correct angle, with a cutting edge, but it has no chip clearance. This must be provided to keep the back side of cutter from rubbing against the work and heating excessively, and to allow the hot chips to fly off readily. The amount of clearance varies with angle of cutter used. The following table will be found a very good guide in establishing sufficient clearance.

Conical Point Cutter Angles for Clearance

Angles in table are for one side of cutter. For instance a cutter having 45 degree angle will have a 90 degree included angle. Now set the tool head for clearance angle desired. If the conical point was ground as described above, to 45 degrees, then a 40 degree clearance angle will be used. Set the tool head back to 40 degrees.

GRINDING SINGLE FLUTE GORTON CUTTERS

Grinding Chip Clearance—First Operation

Now feed cutter into face of wheel very gently. Do not rotate, and hold the back (round side) of conical point against wheel. Gradually feed in toward wheel rocking the cutter continuously across face of wheel and without turning, until a flat is ground which runs out exactly at the point of cutter, as Fig. 6. Check this very carefully, with a glass if necessary, to be sure you have reached the point with this flat. Be extremely careful not to go beyond. Now you are ready for the final operation.

Grinding Chip Clearance—Second Operation

Now, without turning the feed handwheel any further, rough away stock as Fig. 3, then rotate cutter against face of wheel as Fig. 7, grinding away all stock on back of conical side, up to the cutting edge. Be extremely careful at this point not to turn the cutter too far, and thus grind away part of the cutting edge. All chatter marks must be cleaned up however and to effect this, it is general practice to remove an additional thousandth of an inch, or so, as necessary, on the cutting edge itself. Watch the point designated by small circle in diagrams. This is where the cutting is done. If this very point is not correctly ground, the cutter will not work, regardless of how perfect it may be farther out on the taper of cone. A section through the cutter should now be like Fig. 8, and an external view like Fig. 9. Here in Fig. 9 we have again called attention to the point that does all the work with the small circle. Watch this point!

Tipping Off the Cutter Point

For engraving hair-line letters up to half a thousandth in depth the cutter point is not flattened or “tipped off.” For all ordinary work however, it is best to flatten this point as much as the work will permit, as it is very difficult to retain a keen edge with such a fine point, and when the point breaks down, the cutter immediately fails to cut cleanly. Tipping off is usually done by holding the cutter in the hands at the proper inclination from face of grinding wheel, and touching it very lightly against the wheel, or by dressing with an oil stone as explained below. The angle “A” (Fig. 10) should be approximately 3 degrees. This causes the cutter to bite into the work like a drill, when fed down. The angle “B” (Fig. 10) varies depending on the material to be machined with the cutter. The following table will serve as a guide in maintaining this angle “B.”

Rake Angle Table for All Single Flute Cutters

Caution

In all finish grinding operations extreme care should be taken not to anneal (burn) the cutting edge. This can be done by (1) Feeding too fast into the wheel, (2) Removing too much stock at a pass, (3) Holding cutter continuously against the wheel, (4) Failure to keep the wheel true and clean as recommended on page 34. The tool head is arranged to rock back and forth across the wheel so as to provide interrupted grinding cuts, thus giving the cutter a chance to cool.

Stoning Small Cutters

The tipped off point of cutter (Fig. 10) can be dressed to size and proper angle, with an oilstone. This can also be done to advantage on the cutting edge and also the flat, but we do not recommend stoning these as it is very difficult to duplicate the angles obtained in the grinder, with the cutter held by hand on an oilstone. Our experience on cutters returned to us for regrinding has proven that cutters are very frequently spoiled by stoning. For this reason we recommend that the cutter be finished entirely on the grinder (except for dressing the tipped-off point as explained above) unless the stoning is done by an expert who is thoroughly familiar with the job. If stoning is attempted, be sure to keep the flat square. It is very easy to stone a cutter down below the point so it will not cut.

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GRINDING SINGLE FLUTE GORTON CUTTERS

Grinding Square Nose Single Flute Cutters

When square nose single flute cutters are ground they should always be tipped off as explained on opposite page, Fig. 10, unless all the cutting will be done with the side of cutter, in which case the end will not matter. All straight side (square nose) cutters have, of course, clearance ground on the cutting edge as explained above and illustrated in Figs. 7 and 8. After grinding the flat to center (which is very easily checked with this style cutter by using a micrometer) clearance is ground by feeding in the required amount toward wheel and turning the cutter until all stock has been removed from the back (round side) right up to the cutting edge, as Figs. 7 and 8. A table of recommended clearances for various diameter Square Nose cutters is given below.

Chip Clearance Table for Square Nose Cutters

Ball Nose Cutters

Gorton 375-2 Grinder with 717-1 Tool Head is designed especially for grinding ball nose cutters. To grind, proceed as follows:

Grinding Chip Clearance on Straight or Tapered Side

Set up in tool head and rough and finish grind for chip clearance and cutting edge as explained above for Square Nose cutters (if the ball nose cutter is to have straight sides like Fig. 12) or as explained above for Conical point cutters, if the cutter is to have a conical side as in Fig. 14.

Grinding Flat to Center

Before rough grinding the ball nose, be careful to see that the flat is ground exactly to center as explained previously for square nose cutters.

Rough Grinding Chip Clearance on Ball Nose

Tilt the collet tool head to the correct angle in degrees, setting to the Rake Angle Scale, (see “W,” page 31) and using the tables for clearance angle “B” Fig. 12 recommended for cutters to be used on materials listed there. We find that 10 degrees is suitable for nearly all kinds of work and all but the very softest materials.

Now insert cutter in collet, using the gauge No. 9839 which fits on flat surface of tool head and is beveled at proper angle for setting all size cutters. With the cutter set by gauge, lock from turning by means of the index pin.

When the cutter and tool head are adjusted for rake and clearance angles, it is necessary to set the collet spindle off center to obtain a perfect radius. This is accomplished by loosening stop screw “U” (Drwg. 9886, page 32) one-half turn and turning the knurled micrometer hand wheel to the left approximately .004″ for every 1/8″ of cutter diameter. To relocate spindle on center, turn stop screw back one-half turn to its original position with handwheel set at zero.

IMPORTANT

For grinding a corner radius on a cutter, proceed as follows: Subtract radius desired plus .004″ for every 1/8″ of cutter diameter from the diameter of the cutter and turn the knurled handwheel to the right by the amount of the difference. All settings are from zero line when spindle is on center.

With cutter locked, bring it parallel to and just clearing the grinding wheel, then feed into wheel using longitudinal feed handwheel on base of machine. Now swing head at right angles to wheel, feed cutter in until it touches wheel, using knurled micrometer handwheel X, page 31. Now swing head through an arc of 90 degrees until radius is formed on cutter blank, using stops to provide 90 degrees movement for blending ball into side of cutter. Now release index pin. Rotate collet spindle back and forth, about one-half turn, being careful to keep slightly away from cutting edge. While rotating spindle, swing the tool head through an arc each time spindle is turned. About ten swings of head should rough grind the surface.

GRINDING THREE and FOUR SIDED CUTTERS

FINISH GRINDING CHIP CLEARANCE ON BALL NOSE

Now feed cutter toward wheel with knurled micrometer handwheel X, page 31, exactly the amount of clearance in thousandths called for in table page 34. Swing the tool head back and forth, using stop Y, page 31 to limit travel on cutting edge side, until approximate center of ball is reached.

GRINDING THREE AND FOUR SIDED CUTTERS

Three or four sided cutters are sometimes used for cutting small steel stamps and other small engraving. They produce a very smooth finish. The index plate on collet spindle of grinder tool head has index holes numbered 3, 4 etc. for indexing to grind three and four sides. To do this two operations are necessary, as follows:

GRINDING ANGLES OF CUTTING EDGE

Set tool head to angle desired. Then plug pin in index hole for desired number of divisions, and grind flats.

GRINDING CLEARANCE ANGLE

Now without loosening the cutter in collet of tool head, reset the tool head to the proper clearance angle as table below. For example: you are grinding a 3 sided cutter to 45 degrees cutting edge. Referring to the table gives 26 1/2 degrees clearance. Set tool head to 26 1/2 degrees and grind each flat exactly to the point. Do not loosen cutter in collet or change index settings from those used when grinding the 45 degree edge.

Table of Clearance Angles for 3 and 4 Sided Cutters (in degrees)

(Angle of Cut = 2 Times Cutting Edge Angle)

7 WAYS TO INSURE PROPER CUTTER PERFORMANCE

• Keep your cutters sharp.

• A clean collet or spindle taper will help prevent cutters from running out of true.

• Check spindles worn in tapers, collet holes or bearings. Excessive wear at these points causes cutter trouble.

• Feed fine small cutters much slower than a larger cutter.

• Be careful to feed cutters in proportion to their strength of material to avoid breakage.

• Cutters may break or dull from defective steel or wrong temper, but all breakage troubles are not from that cause.

• Light Cutter Spindle Belts are recommended for extremely delicate work. These endless linen belts are lighter and operate the cutter spindle smoother and with less vibration. We can furnish these belts at slightly higher cost than standard belts.

GRINDING CUTTERS WITH ATTACHMENT 288-1 ON PANTOGRAPH MACHINES

Grinding Cutter with Attachment 288-1. First: Insert Pantograph style into hole in copy holder. This holds cutter head rigid. If cutter head is equipped with depth gauge, loosen foot nut and swing foot outward. Now insert grinding wheel and bolt cutter holder base in place, with cutter point at inside edge of wheel, all as photo at lower left. Remove cutter holder by lifting spring slightly and insert cutter tightly, using small wrench. Replace cutter holder and grind cutter point to the proper angle by revolving cutter and shifting table with cross slides. With cutter pointed as desired, it must be ground for clearance, as shown on Fig. 7, page 35, which means grinding away the metal back of cutting edge so that cutter will cut free and raise no burr on work. To grind this clearance, table must be shifted slightly so that wheel will grind above the cutter point. By rotating cutter (half turn) back and forth, clearance can be ground without actually grinding the point and cutting edge more than just enough to bring it to a sharp edge. Remove point slightly with a fine oilstone.