US2343275A - Honing machine - Google Patents

Description

, March 7, 1944. H. CALDWELL ETAL HONING MACHINE Filed Aug. l, 1941 3 Sheets-Sheet 2 .J L y wi w wav@ @Mem ,n w El! NU M T H W///Q/ N wm @QM M d FJ L Q//W/ w March 7; 1944. H. J. CALDWELL x-:TAL

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Patented Mar. 7, 1944 HONING MACHINE Harry J. Caldwell and Earnest Y. Seborg, Rockford, Ill., assignors to Barnes Drill Co., Rockford, Ill., a corporation of Illinois Application August 1, 1941, Serial No. 404,962

17 Claims.

The invention relates to honing machines generally and more particularly to improved power actuated means for expanding the honing tools used in such machines.

One object of the invention is to provide an improved tool expanding mechanism operative to eiTect a rapid initial expansion of a honing tool to operatively associate the abrasive element thereof with the Work and thereafter to effect a positive and progressive expansion of the tool in intermittent steps while the abrasive elements are operating on the work.

Another object is to provide novel means for electing expansion of a honing tool with either a uniform or a progressively increasing .pressure in accordance with the resistance offered to the shifting of the tool adjusting member.

Still another object is to provide improved means for effecting positive stepped expansion of the honing tool during the working cycle of the machine and rapid contraction of the tool at the end of the cycle or at any point in the cycle at which the machine may be stopped.

It is also an object of the invention to provide novel safety mechanism operative tov limit the expanding pressure on the hone and thereby prevent damage to the tool or work.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment illustrated in the accompanying drawings in which:

Figure 1 is a vertical sectional view of the tool spindle supporting head of a honing machine embodying the features of the invention.

Fig. 2 is a horizontal sectional view of the spindle head taken along the line 2-2 of Fig. l.

Fig. 3 is a horizontal sectional view of the spindle head taken along the line 3--3 of Fig. l.

Fig. 4 is a diagrammatic View showing the electrical and hydraulic circuits and their rela-- tionship to the operating and control elements of the machines.

For purposes of illustration the invention has been shown and will be described herein as embodied in a single spindle internal honing machine of the type in which the relative ro-tational and reciprocatory movements of the too-l and Work are eiected by rotating and simultaneously reciprocating the tool while the work is held stationary. It is to be understood, however, that the invention is not limited to honing machines of this particular type but is readily applicable to other types of honing machines as well as to other of machine tools. It is also to be understood that various modifications and adaptations may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention as expressed in the appended claims.

Referring now to Figs. 1 and 4 of the drawings, the machine selected to illustrate the invention comprises generally an upright frame or column IB (Fig. 1) on the face of which are mounted a pair of spaced cylindrical guide bars H forming a vertical guideway for a reciprocatory head constituting, in this instance, a support for a conventional honing tool I3 (Fig. 4). The tool is carried in the usual manner by a tubular tool spindle I4 suitably journaled on the head l2. The work to be operated on by the tool such as workpiece W is stationarily supported on a suitable work support or table l5.

In order to obtain the relative rotational and reciprocatory movements of the tool and work required for the performance of the honing operation, suitable power driven means is provided for rotatably driving the spindle and for simultaneously reciprocating the head l2 which carries the spindle. As herein shown, the spindle is driven by an electric motor M (Fig. 4) through the medium of a splined drive shaft 2li and gears 2l, and 23. These gears are rotatably supported on the head and are reciprocable therewith. The gear 2i has a splined driving connection with the shaft 2!) while the gear 23 is keyed or otherwise fixed to the spindle I4 Within the head l2.

The means for reciprocating the head I2 comprises, in this instance, a pressure iiuid actuator herein shown as a piston 25 (Fig. 4) Working in a vertical cylinder 26 suitably attached to the machine frame. A piston rod 2'! connects the piston with the head. Pressure fluid is supplied to the cylinder 2-5 by a pump P driven by an electric motor MI. A conventional pressure fluid actuated reversing valve RV operated under control of a pilot valve PV connects the respective ends of the cylinder lto the pump and to a drain 28 alternately to effect the reciprocation of the piston, The pilot valve is actuated in well known manner by ashiftable control rod 29 having spaced limit stops 3G and 3l and an intermediate stop 32 engageable by a dog or other suitable member 33 carried by the head l2 and reciprocable therewith. A pressure relief valve VI limits the pressure in the fluid supply circuit to a safe value.

The conventional honing tool employed for honing internal cylindrical surfaces, of which the tool I3 is an example, comprises a series of abrasive elements or honing stones 35 (Fig. 4) arranged around the periphery of a cylindrical carrier 3S for movement radially thereof. 'I'he abrasive elements are normally held in their inner or contracted position by suitable springs and are shifted outwardly or expanded by means of an adjusting rod 31 (Figs. 1 and 4) extending axially through the hollow shank of the tool and through the tubular spindle I4 on which the tool is carried.

In the operation of the machine the tool is inserted in the work with the abrasive elements contracted. It is then expanded, that is, the abrasive elements are shifted radially outwardly into operative engagement with the surface to be operated on. The expanding effort must be continued of course while the elements perform their metal removing functions. For some types of work it has been found that greater eiiiciency is attained if the expanding pressure is progressively increased in relatively small, graduated steps as the honing operation proceeds. The invention provides novel power actuated mecha nism for effecting such stepped expansion of the honing tool during the working portion of the cycle and for reducing the non-working portion of the cycle to a minimum by providing rapid initial expansion and rapid contraction of the tool to bring the abrasive elements into engagement with the surface of the work and to return them to their inner positions to condition the tool for withdrawal from the work. Moreover the stepped expansion of the honing tool is effected in a positive manner without interfering and V3 control the delivery of pressure iiuid to the respective actuators as will appear present ly. The pressure in the supply circuit is maintained at the desired level and the building up of excessive pressure in the system is prevented by a conventional relief valve V4. A pressure regulating valve V5 of any suitable type may be interposed in the branch line leading to the actuator 4I to permit independent regulation of the pressure of the iiuid supplied thereto.

`In the particular embodiment illustrated, the

actuators are arranged to operate through an elongated tubular actuating member 42 to impart endwise movements to the tool adjusting rod 31 both to effect rapid initial expansion and progressive stepped expansion of the honing tool.` The actuating member 42 as herein shown is arranged above and axially alined with the tool adjusting rod 31. At its lower end the memberis operatively connected to the adjusting rod 'so that endwise movements of the member are trans' ferred to the rod. y

The operative connection between the mem ber 42 and the rod 31 is provided in the present instance by a yieldable safety release mechanism which efectually prevents the application of excessive pressure to the abrasive elements of the tool and thus protects the elements and the work from damage under abnormal working con-- ditions. Asl shown in Fig. 1, the mechanism in its preferred form comprises a headed connecting element 43 having a cylindrical shank 44 of reduced diameter slidably fitted in a chamber 45 formed by a counter bore in the lower end of the tubular member 42. A pin 45 extending transversely through the shank of the element and engaging in oppositely disposed longitudinal slots 41 in the member acts to hold the parts in assembled relation and to permit limited relative movement therebetween longitudinally of the member. The connecting member is yieldably urged outwardly with respect to the tubular member by suitable resilient means such as a spring 48 interposed between the end of the shank 44 and the adjacent end of an adjusting bar 49 disposed within the tubular member with its lower end projecting into the chamber 45. A screw plug 50 threaded into the upper end of the member 42 provides for adjusting the position of the bar 49 and thus for regulating the tension of the spring 48. A second plug 5I may be screwed into the end of the member 42 to lock they first mentioned plug and bar in adjusted position.

The connecting element 43 serves to transmit the endwise movements of the member 42 to the tool adjusting rod 31 with which it is operatively connected. This connection as herein shown is provided by an antifriction thrust bearing 52 carried in a recess in the enlarged end portion of a sleeve member 53 iixed to the upper end of the tool adjusting rod. The bearing thus permits relative rotation of the parts for purposes to be described presently. To permit the required movement of the rod and sleeve member longitudinally of the tool spindle i4, the sleeve is slidably received in a counter bore 54 in the upper end of the spindle as shown in Fig. 1. A coiled compression spring 55 interposed between the bottom of the counter bore and the lower end of the sleeve urges the adjusting rod upwardly or toward the tool contracting position.

With the arrangement above described the tool adjusting rod is shifted toward the tool expanding position by an endwise movement of the actuating member 42 downwardly as viewedk in Fig. 1. However, due to the presence of the spring 48, the actuating member may continue its advance while the adjusting rod remains stationary in the event that the resistance offered to further expansion of the tool exceeds a predetermined value. This prevents the application of excessive pressure to the honing tool and efy fectually guards against damage to the tool or work when unexpected resistance to tool expansion is encountered.

Endwise tool expanding movements may be imparted to the actuating member 42 by either of the pressure iiuid actuators 40 or 4I'. The actuator 4I), in this instance, is arranged to effeet a continuous rapid advance of the member to initially expand the tool into operative engagement with the work. To this end, the member 42 is provided at its upper'end with a pistonmember working in a cylinder 6I rigidly supported in the upper end of the tool head I2 con centric with the spindle I4. Pressure :duid may be introduced into the cylinder above the piston through a pipe 62 thus forcing the piston and associated parts downwardly or toward the tool expanding position. The piston, in this instance, is loosely mounted on the member and is formed with a sleeve-like extension 63 having at its outer end an internal iiange 64 adapted to bear against the upper end of the member 42 and thus effect a one-Way driving connection with the member. This extension projects through acap 65 whichcloses the upper vend of the cylinder and is threaded for the .reciprocation of a nut 66 adapted to act as an adjustable stop to ylimit the vextent of movement of the pis# ton-toward the open end of the cylinder. A lock nut 66 threaded on lthe sleeve cooperates with the -nut .66 vto retain the latter iin adjusted position.

vThe actuator 4| is arranged to advance the actuating ember 4 2 in successive steps to .effect a positive stepped expansion of the honing tool. For this purpose, the actuator is operated intermittently under the control of any suitable means, .as for example a timer, as hereinafter set forth, and the actuating member 4 2 is rotated intermittently Aabout its longitudinal axis while a stationary nut 10 engages a lead screw 'il rigid with the member. As shown 'in Figs. 1 and 2 the actuator 41| in its preferred `form comprises a piston 12 working in a cylinder 13 mounted in a `horizontal position on one side of the tool head I2. The piston is provided :With a piston rodfM extending into the head and having racl; teeth 1.5 (Fig. k2) meshing with a Vpinion 16 rotatably supported'between spaced collars 11 xed to :the

actuating member 42. The teeth of the pinion are `sufficiently wide to retain their meshing engagement with the rack teeth as the pinion moves axially with the member between tool expanding and ,contracting positions. o f the pinion 1 6 `are transmitted to the actuating member through a one-way driving con.-

nection of -any suitable type interposed between the pinion `and the member. As herein shown, this `connection comprises a ball type clutch 18 arranged to drive ,the actuating member when the pinion 16 is rotated in a clockwise direction as-viewed 1in Fig. 2. When the pinion is rotated in the opposite direction, the driving connection is interrupted .thus ,allowing the actuator to return to its normal rest position while the actuating member is retained in the rposition to which it --was previously operated.

In the particular machine illustrated rotation ofthe pinion in the direction to drive the Aactuating member is effected by introducing pressure fluid into the outer end of the cylinder 13 through a pipe 19 thereby shifting the piston and its rod toward ythe right as Viewed in the drawings. An adjustable stop screw 8U positioned for engagement by the inner end of the piston'rod determines the length of the piston stroke and thus the angle through which the actuating member is rotated in each operating cycle of the actuator. When `the pressure on the piston 12 is relieved by the action of the control mechanism in shift- 111g theconnection of the pipe 19 from the pressure fluid source to the drain, a spring 8l returns the piston to its normal rest position at the outer .end of the cylinder. Ordinarily, no rotation ,is imparted to the actuating member in .this return lmovement due to the release of ,the clutch 18. j

The lead screw and nut mechanism b y which the rotating movements ci the vactuating member are `translated into intermittent vendwise steps is shown in Figs. l and 3 of the drawings. In the exemplary machine the lead screw 1I is formed by threading an enlarged section 82 of the actuating member. AThe nut 1 0 in its preferred form comprises a generally vrectangular block having an arcuate recess in one face threaded for engagement with the screw threads 1I. Thus the nut may be moved 4into .or out of engagement with the lead screw as required.

Relative movements til' With the nut -i-n the .engaged position, positivel longitudinal movement in .steps of 'predetermined length will be imparted .to the actuating member as the member is intermittently rotated by the actuator M. v4When the nut is disengaged, vthe actuating member may V.be shifted rapidly to tool expanding position by the actuator 40 or returned to tool contracting position under the influence of the spring 55.

While any suitable means may be employed for shifting the -nut 'l0 between engaged and disengaged positions, it is preferred to utilize pressure uid operated means for this purpose because of the ease with which the operation of the nut may be synchronized with the various operations of the machine. 'The pressure uid operated means as herein shown .comprise a piston 83 (Figs. 1 and 4) working in `a cylinder 84. The cylinder is rigidly supported on the frame work of the spindle 'head I2 as shown in Figs. 1 and 3 with its axis disposedin a horizontal position and substantially alincd with the axis of the actuating member 42. At its inner end the cylinder is formed `with recess 85 of generally rectangular cross-section dimensioned to receive the nut 10 with a vsliding fit. A piston rod 86 extends from the piston to the nut and is drivingly connected therewith as by a pin 81 which permits a limited vertical movement between the parts to eliminate any binding due Ito non-engagement of the lead screw and the nut. A spring 88 interposed between the piston and the inner end of the cylinder normally urges the piston to the right as viewed in Figs. 1 and 3 and thus tends to maintain the nut 10 in the disengaged position, Pressure uid introduced into the outer end of the cylinder 84 through a pipe 89 shifts the piston to the lef-t against the influence of the lspring 88 and thus moves the nut `into engaging relation with the lead rscrew thread 1I.

The operations of the hone expanding actuators 4Q and 4| are coordinated for most e'icient operation by timing the action of thenut actuating mechanism in ac cordance Vwith the operation of the actuator 40 to effect initial rapid vexpansion. More particularly the nut is maintained in its disengaged position to avoid interference with the operation of the actuator 40 until the piston Si! reaches the end of its operating stroke as determined by the setting of the stop nut 66. The nut 10 is then automatically shifted into engagement with the lead screw threads and the actuator 4I thus becomes effective to continue the advance of the actuator in intermittent steps and thereby expand the hone in successive positive steps.

Automatic control of the nut actuating mechanism is effected 4in the exemplary machine by connecting the cylinder 8 4 and the actuator cylinder 6l in parallel through a sequence or foot valve SV (Fig. 4). This valve may be of the conventional type arranged to open and allow pressure fluid to ypass into the pipe 89 only when the fluid in the pipe 5,2 reaches the pressure for which the valve is adjusted. Thus the delivery of pressure uid to the cylinder 84 is conditioned upon the building up of a predetermined pressure in the actuator cylinder and may be accurat-ely timed to take place `at the exact instant necessary for most eicient operation of the honing tool. The sequence valve, of course, is arranged to permit unrestricted fluid ow in the reverse direction when the pressure in the pipe .52 is relieved. The fluid may therefore be eX- hausted from the cylinder 84 by the action of the' spring 88 upon rthe piston 83. r The automatic control'of the hone expanding mechanism leliminates the need for close supervision of the machine lduring its operating cycle and'moreover insures'operation of the honing vtool in the most eilicient manner. Through the medium of these controls and others shown in Fig. 4, the machine attendant is relieved of substantially all duties except that 4of loading the workfon the workvsupport and removing the iinished work therefrom after the machine has been set up for a particular job.- Thus an operating cycle of the machine is started by momentarily closing a starting switch S'- (Fig. 4) to energize a-pair of motor control relays RI and R2. Relay RI closes switch RH toL start the spindle driving motor M. Relay R2 closes'switch R2I to start the pump motor' Mi. As the pump P begins to function, pressure iluid is supplied through the reversing valve" RV to the upper end of the -head reciprocating cylinder 26 thus moving the tool head down-'- wardly and entering the tool in the work. The attendant may release the starting switch Sas soon as the tool head leaves its normal rest' position which results in the closure of a limit switch LSI in well knownmanner. The limit switch completes a holding circuit for the relays RI and R2 which circuit includes a switch RIZ, closed by the relay RI when energized, and normally closed manually operable switches Sl and S2. Switch Sl is the inching switch commonly used in honing machines. Switch S2 is the fstop switch by which the operation of the machine may be yinterrupted at any point in its cycle.

When the tool head advances suiiiciently to enter the tool in the work, a suitable cam engaging member carried by the head engages a cam 9| on a vertical rock shaft 92 and through a linkage 93 closes a limit switch LS2. .Closure of this limit switch energizes a control relay R3 which, in turn, closes a switch R3! to energize a solenoid SOL. l. This solenoid is operatively associated with the valve V3 and is arranged when energized to set the valve in a position to connectV the discharge line from the pump PI to the actuator 1li] and to the nut actuating cylinder 84. In its alternate position the valve V2 connects the actuator and the cylinder to.

^ the drain 28. Upon connection of the pump Pl concurrentiywith the actuation of the's'tarting switch S to energize the motor relays RI and R2, a runningcircuit is completed for a motor driven timer TM and` for a motor driven Acurrent interrupter CI. The timer, in well known manner, determines the length of the opera-ting cycle of the machine and acts to-stcp the saine at the end of the cycle as will be explained presently. The interrupter intermittently closes and opens a, switch S3 to energize and deenergize a control relay R4. The relay through its switch RM controls the circuit for a Asolenoid SOL. 2 associated with the valve V2 whereby the valve alternately connects the actuator cylinder 13 to the pump PI and'to the drain 28. The piston.12 is accordingly reciprocatedfwithin the cylinder and, through the pinion 'I3 and the clutch 1B, imparts successive rotative steps to the tool actuating member 42- When the nut is shifted into engagement with the lead screw threads as above explained,` the actuating member and the 'tool `expanding rod 31 are advanced step by step to `progressively expand the honing tool. i

Reciprocation of the head l2 through a succession of strokes eiective to traverse the honing tool repeatedly from one end of the work piece to the other continues under control of the reversing valve RV and the associated pilot valve PV in the usual and well known manner. After a predetermined operating interval as determined by the timer TM, the latter closes its switch S4 to eiect the energization of a control relay R5. The relay by closing switch R51 energizes a pull-v out solenoid PS which, through a suitable me# chanical linkage, rocks the control rod. 29 to a position in which the intermediate stop 32 isY ineffective for control purposes. The tool head is thus free to move beyond an upper limit of the working stroke to the Withdrawn or normal rest position.

As the head passes the upper limit of the working stroke, the cam engaging member on the head engages a cam 94 on the control rod 9| and rocks the rod into a position to open the limit switch LS2. This interrupts the circuit for the control relay R3 which, in turn, interrupts the circuit for the solenoid SOL. l. Valve V3 is thereupon returned to open position in which it connects the actuator cylinder 6| and the nut actuating cylinder 84 with the drain 28. The pistons operating in these cylinders are immediately returned to their normal rest positions by their associated springs. Disengagement of the nut 'Hl from the lead screw threads as a result ofthe return of the piston 83 permits rapid return of the actuating member 4,2 and tool expanding rod 31 with corresponding rapid contraction ofthe hone tool. The tool may therefore be withdrawn from the work without danger of injury to either the tool or work.

The tool head l2 upon reaching its normal rest position acts through the member 33 and upper limit stop 3l to condition the pilot valve PV for the next operating cycle,that is, it sets the valve in the position shown in Fig. 4. At the sami. instant the limit switch LSI is opened to interrupt the holding circuit for the relays RI and R2. The relays and their associated solenoids accorde ingly become `deenergized and stop the machine. Operation of the interrupter CI and timer TM is also terminated, the latter being reset automatically in well known manner for the next operat ing cycle. Thus the head is stopped with the tool withdrawn from the work so that the attendant may remove the finished workpiece from the machine and replace it with the next workpiece to be operatedon. l y

It will be apparent from the foregoing that the invention provides novel power actuated means for expanding a honing tool in a manner effective to attain the most eiicient results. The iinproved mechanism operates to effect a rapid initial expansion of the honing tool to operatively associate the abrasive elements thereof with the work and thereafter to effecta positive and progressive stepped expansion of the tool while the abrasive elements are operating on the work.

Due to the rapid initial expansion of the tool, the non-working portion of the machine cycle is` reduced to a minimum. Moreover the improved tool actuating mechanism provides for rapid contraction of the tool at the end ofy the. working cycle thus further reducing non-productive time.

`The invention also provides a novel safety mechanism which effectually prevents the application of excessive pressure to the honing tool and thereby guardsv against. damage to the tool or work under abnormal operating conditions.

We claim as our invention:`

1. A honing machine having, in combination, a support fory an expansible and contractible honing tool, a support for work to be operated on by the tool, means for effecting relative rotation and simultaneous relative reciprocationl of the tool and work supports, a rst tool actuating means operable to effect a rapid initial expansion of the tool into operative engagement with the work, a second tool actuating means operable to effect positive expansion of the tool in intermittent stepsv while the tool is operating on thework, and control means operative to govern the operation of said tool actuating means selectively.

2. A honing machine having, in combination, a support for an expansible and contractible honing tool, a support for work to be operated on by the tool, means for eiecting relative rotation and simultaneous relativey reciprocation of the tool and work supports, power actuated means operable to eiiect a rapid initial expansion of the tool into operative engagement with the work, other power actuated means operable to effect expansion of the tool in intermittent steps, and control means operative automatically to initiate the. operation of said other power actuated means upon the completion of the operation cf said first mentioned power actuated means.

l3. A. honing machine having, in combination, a` supportv for an expansible and contractible honing tool, a support for work to be operated on by the. tool, means for effecting relative rotation and simultaneous relative reciprocation of theA tool and work supports, a pair of independently operable power actuated mechanisms each operative to expand the hone, control means operative to initiate ther operation of one of said mechanisms, and other control means actuated in response to a predetermined expansionV of the tool by said one mechanism to initiate the operation of the other of said mechanisms.

4. A honing machine having, in combination, a support for an expansible and contractible honing tool, a support for work to be operated on by the tool, means for effecting relative,` rotation and simultaneous relative; reciprocation of the tool and work supports, power actuated mechanism operable to eiect rapid continuous expansion of the tool, other power actuated mechanism operable to eiect positive expansion of the tool in intermittent steps, control means operative to initiate the operation of 'said other mechanism upon engagement of the work by the tool, and timing means operative to determine the rate of expansion of the tool by said other mechanism while the tool is operating on the work.

5. The combination with a honing tool, of an elongated actuating member shiftable longitudinally to expand and contract the tool, a first power driven actuator acting directly on said member to shift the member to tool expanding position, and a second power driven actuator arranged to rotate said member about its longitudinal axis,- said member having a threaded portion engageable with a stationary nut operative to impart longitudinal movement to the member in response to its rotation by said second actuator.

6. The combination with an expansible and contractible honing tool, of an elongated actuating member shiftable longitudinally to expand and contract the tool, screw threads formed on a section of said member, a power driven actuator directly coupled with said member and operable to shift the member in a direction to expand or contract the tool, a second power driven actuator operable to rotate said member in intermittent steps, and a threaded nut shiftable into engagement with the threaded section of. said member in timed relation to the operation of said rst mentioned actuator, said nut acting to` shift said member in a direction effective to expand the tool incident to the rotation of the member.

7. The combination with an expansible and contractible honing tool, of an elongated actuating member shiftable longitudinally to expand and contract the tool, screw threads formed on a section of said member, a power driven actuator directly coupled with said member and operable to shift the member in a direction to expand the tool, a second power driven actuator operable to rotate said member, a threaded nut supported for movement only transversely of said member into and out of engagement with the threaded section of the member, and power actuated means operating in timed relation to the operation of the first mentioned actuator for moving said nut into and out of engagement with the threaded sections of said member, said nut when engaged acting to shift said, member in a direction to expand the tool incident to the rotation of the member.

8. Thel combination with an expansible and contractible honing tool,l of an elongated actuator member shiftable longitudinally to expand and contract the tool, screw threads formed on said member, a pressure fluid actuator directly coupled with said member operable to shift the member in a direction to expand the. tool, power actuated means operable to rotate said member, a threaded nut supported for movement only transversely of said member into and out of engagement with the screw threads thereon and operative when engaged to shift the member longitudinally incident. to the rotation of the member, a pressure uid actuator operable to shift said nut between engaged and disengaged positions and a circuit arranged to supply pressure fluid to said actuators in predetermined sequence.

9. The combination with a honing tool, of an elongated actuating member shiftable longitudinally to expand and contract the tool, screw threads formed on said` member, a nut supported for movement only transversely of said member into or out of engagement with said screw threads, power driven means operable to rotate said member, said nut when engaged with the screw threads acting to impart longitudinal movement to the member in response to such rotation, and a power driven actuator coupled with said member operable to shift the member longitudinally when said nut is disengaged from the screw threads, said actuator having a one-way connection with the member to permit independent movement of the member in one direction.

l0. The combination with a honing tool having an axially movable adjusting rod associated therewith, an elongated tubular member supported substantially in axial alinement with the tool and to impart thereto the movements of the member, spring means interposed between said elements eiective to permit `limited relative movement between said other element and the member when the resistance of the adjusting rod to movement reaches a predetermined value, and means for adjusting the position of said one element with reference to said member to regulate Athe tension of said spring means.

11. The combination with a longitudinally shiftable tool adjusting member having a threaded section, `of a iirst pressure uid operated actuator coupled directly with the member andopervative to impart rapid longitudinal movement "thereto, means for imparting slower longitudinal -movement to the member in' successive positive steps including a second'pressure uid operated actuator operative to rotatethe member in intermittent steps, a nut supported for movement transversely of the threaded section of the member between disengaged and thread engaging positions, means normally eifective to hold said nut in the disengaged position, and means for shifting said nut to the engaged positionin timed relation to the operation of said rst actuator.

12. The combination with a longitudinally shiftable tool adjusting member having a threaded section, of a rst pressure fluid operated actuator coupled directly with the member and operative vto impart rapid longitudinal movement thereto, means for imparting slower longitudinal movement to the member in successive positive steps including a rsecond pressure fluid operated actuator operative to rotate the member in intermittent steps, a vnut supported for movement transversely of the threaded section of the meinb'er between disengaged and thread engaging positions, means normally eifective to hold said nut in the disengaged position, pressure iiuid operated means connected in parallel with said first actuator operative to shift said nut into the engaged position, and a control valve for timing the operation of said nut shifting means with respect tothe operation of said first actuator.

13. The combination with a longitudinally shiftable tool adjusting member having a, threaded section, ofa rst power actuated means operative to impart relatively rapid continuous longitudinal movement to the member, means for imparting slower longitudinal movement Ito the member'in progressive stepsincluding a second power actuated means operative to rotate the member about its longitudinal axis in intermittent steps, a nut movable transversely of the threaded section of the member into or out of engagement with the threads thereof, means normally effective to hold said nut in a disengaged position, and a third power actuated means operative to move said nut into engaged position to render said second power actuated means effective. e

14. The combination with a longitudinally shiftable tool adjusting member having a threaded section, of a first power actuated means operative to impart `relatively rapid continuous longitudinal movement to the member, means for imparting slower longitudinal-movement to the member in progressive steps including a second power actuated means operative to rotate the member about its longitudinal axis in intermittent steps, a nut movable transversely of the threaded section of the member into or out of engagement with the threads thereof, means normally effective to hold said nut in a disengaged position, means operable to shift said nut into engaged position and thereby render said second power actuated means effective to impart longitudinal movement to the member, and control means for initiating the operation of said nut shifting means in timed relation to the operation of said first power actuated means.

15. The combination with a rotatable honing tool having a plurality of radially movable abrasive elements, of an adjusting mechanism including a member shiftable axially of the tool to impart said radial movements to the abrasive elements, power actuated means operable to shift said member at arapid rate, other power actuated means operable to shift said member at a vslower rate, and control means eiective to initiate the operation of said otherpower actuated means in response to a predetermined increase in the resistance offered by said member to movement by said rst power actuated means.

16. A honing machine having, in combination, a support for an expansible and contractible honing tool, a support for work to be operated on by the tool, means for effecting relative rotation and simultaneous relative reciprocation of the tool and work supports, pressure fluid actuated means operable to eiect a rapid expansion of the tool into engagement with the work, other pressurefluid actuated means operable to expand the tool at a slower rate while operating on the work, and valve means operative to initiate the operation of said other pressure uid actuated means when expansion of the tool byv the first `mentioned pressure iiuid actuated means is interrupted by the initial engagement of the tool with the work.

17. A honingmachine having, in combination, a support for an expansible and contractible honing tool, a support for work to be operated von by the tool, means for effecting relative rota-

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