US2401215A - Lap - Google Patents

Description

Patented May 28, 1946 UNITED STATE-S` PATENT OFFICE.v

LAP

AntonAnderson, Chicago,.1ll. Application January 9, 1945,4 Serial No., 572,063

' Claims.

cal barrel with longitudinal slits. arranged tan-` gentially or at an angle to the radius of the cylinder whereby the segments between the sl'itswill have a desired degree ofY resiliency; to provide a.

lap which will have a relatively fast abrading action when rotated in one direction and a smoothing or polishing action when rotated in the opposite direction; and to provide such other improvements in construction and advantages in operation as will appear from the following description.

In the accompanying drawing showing this invention,

Fie. 1 is a side View of the lap;

Fig. 2 is an enlarged longitudinal sectional view;

Fig. 3 is a cross section taken substantially on the line 3 3 ofFig. 2;

Fig. 4 is an enlarged cross section. showing the operation of the lap when turned in the direction to cause rapid abrasion; and

Fig. 5 is a View similar to Fig. 4 showing the lap rotating inrelatively opposite direction or in reversed position in the hole as for polishing purposes.

As shown in this drawing, the lap has a shank or stem portion I0 which is adapted to be held in a drill or other suitable machine tool for operating the same. AThis shank has a reduced threaded connection II which is engaged by a correspondingly threaded end I2 of the main cy` lindrical portion or barrel I3 of the lap. The ends of the barrel are provided with tapered or conical bores or recesses I4 and I5 which may conveniently be tapered at an 8 included angle. The inner ends oi these bores terminate at a cross wall I6 which is pierced with a hole Il leaving annular shoulders I3 extending inwardly at approximately the center of the barrel.

The barrel is provided with a plurality of substantially longitudinal cuts or slits I9 which extend to points adjacent to the threaded ends of the barrel. These slits may be milled, sawed, or

cut in any desired mannen, and the arrangement thereof forms one of the novel features of this inventionl Instead. of being radially arranged. as has been heretofore proposed, these slits, are at an angle tothe radiusV or as shown in. the present instance, are substantially tangential to the walls of the hole I7. These slits form expansibl'e` longitudinal segments 2Q., the outer surfaces of.A which provide the working areas of the lap The. positioning of the slits in this manner provides narrow lands 2l on each of the segments around the hole Il.

The segments or sidesv of the lap are adjusted by means of a tapered adjusting pin 22 which is adapted to enter the hole I'I and engage with the landsr 2l.. This pinhasf an enlarged threaded portion 23 that engages with a corresponding.- ly threaded end 24 of the barrel. This is" pref.- erably a left hand thread for reasons which will presently be described. The outer end 25 of the pin is flattened or otherwise shaped for engagement. by a wrench or adjusting tool. When this which pass outside of the working surface A26 of the corresponding lap, and consequently pressure exerted on the land by the pin is not` exerted directly or radially against the working surface of the segment. Likewisel pressure which is exerted on the working surface when thelap is in operation is not transmitted radially or directly against the pin, The land 2I may be considered as a fulcrum or bearing and when pressure is exerted against the outer or working surface of the segment, it will be resisted only by the twisting or torsional action of the segment, and therefore will have suflicient spring or resiliency to accomplish the desired results. The ends of the segments or longitudinal strips being relatively thin Will assist in permitting this torsional or resilient movement. The greater thickness of the segments or engaging elements at the center will provide for more wear as it is in such portions that the principal amount of work is done and the wear is greatest in this area.

When the lap is to be used, the shank is inserted in the drill or machine tool in the usual manner and the adjusting pin is screwed in to expand the segments to the desired diameter. The abrading material is applied in the usual manner and the lap is inserted in the hole as indicated at 21 in a work piece 28 which is to be lapped. If the lap is rotated in the direction indicated by the arrow in Fig. 4, the pressure on the segments will tend to swing the forward edges inwardly and thus permit more abrasive to enter the spaces between the segments and the walls of the hole. This operation serves for rapid abrasion or grinding. The adjusting pin 22, as above stated, is preferably provided with left hand thread 6 so that if the projecting tang 25 comes in Contact with the bed of the drill, it will tend to unscrew or loosen the same, rather than to increase the pressure. If the movement of the lap is reversed as shown in Fig. 5, as by reversing the position of the lap in the drill, the leading edges of the segments which Contact closely with the walls of .the hole will tend to wipe away the abrasive and provides means for giving a smooth-` ing action or smooth nish.

From this description, it will be seen that I provide a lap of simple construction having a single solid expanding pin acting against seats or bearings at substantially the middle of the lap whereby the abrading members may be uniformly expanded to provide a substantially barrel-shaped or curved working surface. Each segment has a cushion or resilient action which is inherent in the construction of the lap, and does not require-additional tension members, springs, or the like. This cushioning is created by a twisting or rotating-of the mid-portion of each lap segment with respect to the cylindrical uncut ends of the lap barrel.

My improved laps may be formed of any suitablematerial, but are preferably'made of soft or mild steel such as commonly used for this purpose.

While I have shown a preferred form ofr my invention, it is my intention that the same may be modified as for different sizes or classes of work without departing from the scope of the invention as set forth in the following claims in which I claim:

l. A lap having a cylindrical barrel kwith an inwardly extending annular projection with a central hole therethrough, the walls of the barrel and said projection having a plurality of longitudinal slits substantially tangential to said hole forming working segments and also forming lands terminating at the circumference of said hole and means coacting with said lands to expand the segments.

2. A substantially cylindrical lap barrel having longitudinal slits which terminate at a distance from the ends of the barrel, to provide working segments, inwardly extending lands on said segments the inner ends of which terminate at the circumference of a central hole and, which are positioned circumferentially substantially beyond the radii embracing the outer face of the respective segment, whereby they are oiset circumferentially with respect to the outer faces of the segments, said slits being arranged tangentially to said hole, and non-resilient adjusting means coacting with said lands for expanding the segments, the arrangement being such that the segments will have a torsionally resilient action when in use.

3. In a device of the character set forth, the combination of a stem, a lap barrel having Vthreaded engagement with said stem, the Walls of the barrel increasing in thickness towards the center thereof, an annular projection extending inwardly at the center and having a hole therethrough, slits arranged substantially tangentially to said hole and terminating short of the ends of thefbarrel and dividing the barrel into a plurality of working segments, a tapered adjusting pin having threaded engagement with the opposite end of the barrel and projecting through said hole and adapted to spread the working segments.

4. In combination, a stem, a lap barrel having threaded engagement with the stem and having conical bores extending inwardly from the ends thereof, an annular projection extending inwardly at substantially the center of the barrel and having a hole therethrough, said barrel having a plurality of longitudinal cuts through the walls thereof extending to points adjacent the ends of the barrel and extending through said projection, said cuts being arranged substantially tangentially to said hole, whereby lands are provided on each segment, a tapered adjusting pin having threaded engagement with the opposite endof the barrel and coacting with said lands for expanding the working segments, substan-

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