NOTE THE STATEMENT THAT EQUIPMENT IS COMPLETE FOR METRIC THREAD GAUGES; ALSO NOTE METRIC SCREWTHREAD SYSTEM, PRINTED IN DETAIL.

Pratt & Whitney Co. has for many years been an extensive maker of metric thread gauges, both regular and special sizes. In design they are similar to the standard type of thread gauge. The equipment for their manufacture is complete, the gauges being hardened and accurately finished in the angle of the thread.

NOTE THAT CHANGE GEARS "WILL CUT THE MOST PERFECT OF THREADS FROM 14 TO 200 PER INCH IN ENGLISH OR METRIC MEASURE."

ATTACHMENT.

THE SCREW-CUTTING ATTACHMENT

is a complete fixture in itself, and is fastened directly to the lathe bed. The change gears are cut with the greatest care, and will cut the most perfect of threads from 14 to 200 per inch in English or metric measure.

THE LEAD SCREW

runs in adjustable cone bearings fitted to a bracket which is attached to the T slot at the left front of the bed, has a 20 per inch thread inch (1.27 cm.) in diameter, 91 inches (23.49 cm.) long, and cuts threads about 4 inches (10.16 cm.) long. These lead screws are cut by the use of a special precision screw, used for no other purpose, and practically without errors. The gear change is very simple and quickly made, as will be seen by the gear change table.

METRIC THREADS.

The change from English to metric threads is made in the usual manner by the introduction of a 50-tooth and a 127-tooth gear screwed together into the gear train from the spindle to the screw which translates inches into centimeters.

TAPER SCREWS.

The cross slide which carries the tool post slide is a double dovetail, one part seated in the top of the lead screw driven slide, and the other top dovetail is fitted to the tool post slide. The screw cutting slide always moves in one plane, parallel to the plane of the lead screw axis. A movable guide, spring held at each end, can be shifted by means of a screw at each end so as to give the cross slide, which carries the tool post, a limited traverse movement crosswise of the lathe as the slide is drawn along, so that screws may be cut either truly cylindrical or taper in either direction, the extreme variation being about & inch to the foot.

LEFT-HAND THREADS.

are cut by the use of an extra intermediate pinion mounted on a block which slides on the change gear arm. The change gear arm has a split bearing and pinching screw support on the lead screw, which gives friction to hold the arm wherever it is placed.

21767°-S. Doc. 241, 64-1--4

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METRIC CHANGE GEARS.

[Note advertising that gear may be applied to this lathe, which will then be available for cutting metric screw threads.]

SCREW CUTTING ATTACHMENT is a complete fixture in itself, and is fastened directly to the lathe bed. A set of 25 change gears of extreme accuracy will cut the most perfect of threads from 14 to 200 per inch in English or metric measure. By obtaining extra gears threads as coarse as 10 per inch and as fine as 300 can be cut.

The lead screw runs in adjustable cone bearings fitted to a bracket which is attached to the T slot at the left front of the bed, has a 20 per inch thread inch (1.27 cm.) in diameter, 9 inches (23.49 cm.) long, and cuts threads up to 7 inches (17.87 cm.) in length. These lead screws are cut by the use of a special precision screw, used for no other purpose, and practically without errors. The gear change is very simple and quickly made, as will be seen by the gear change table.

The change from English to metric threads is made in the usual manner by the introduction of a 50-tooth and a 127-tooth gear, screwed together, into the gear train from the spindle to the screw, which translates inches into centimeters.

The cross slide which carries the tool post slide is a double dovetail, one part seated in the top of the lead screw driven slide, and the other top dovetail is fitted to the tool post slide. The screw cutting slide always moves in one plane, parallel to the plane of the lead screw axis. A movable guide, spring held at each end, can be shifted by means of a screw at each end, so as to give the cross slide, which carries the tool post, a limited traverse movement crosswise of the lathe as the slide is drawn along, so that screws may be cut either truly cylindrical or taper in either direction, the extreme variation being about 3 inch to the foot.

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SHOWING METHOD OF TABULATING CHANGE GEARS REQUIRED FOR METRIC SCREW CUTTING.

Left-hand threads are cut by the use of an extra intermediate pinion mounted on a block which slides on the change gear arm. The change gear arm has a split bearing and pinching screw support on the lead screw, which gives friction to hold the arm wherever it is placed.

The entire screw cutting scheme of this lathe is extremely simple, very easily understood, and very quickly handled, and permits the production of either straight or taper screws with the greatest degree of precision.

TABLE OF CHANGE GEARS FOR ENGLISH MEASURE.

METRIC LEAD SCREWS.

[Note that this lathe may be supplied to cut metric screw threads.]

9 AND 11 INCH "STAR" SCREW-CUTTING ENGINE LATHES.

Screw cutting. The range is extremely wide (see page 22), cutting all standard threads, right or left (including 11 and 27), from 3 to 64 without compounding the gears, and nearly all threads by compounding. When desired to cut both standard and metric threads, can furnish, for a slight advance in price, transposing gears and index for cutting international standard metric threads from 0.5 mm. to 8 mm.

Lead screw.-Cut from a master screw by a new process from 30 per cent carbon steel making an accurate, durable, and most desirable lead screw. When desired to cut metric threads only, can furnish metric lead screw and index in place of the regular lead screw and index at same price.

Spring nuts. Our patented spring nuts used in connection with split washers hold the change gears in place. They are easy and convenient to operate and allow quick shifts of the change gears.

Bed is broad, deep, thoroughly well braced, and is accurately proportioned throughout. The rack is in one piece accurately cut from cold-drawn steel.

Countershaft (see page 22) has patented friction clutch pulleys easy to operate, strong and durable, also has self-aligning and self-oiling shaft bearings. The pulleys and friction bands are provided with self-closing oil cups.

Electric motor drive. We can furnish these lathes arranged to be driven by directconnected electric motors, and will give further information on request.

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