272,591. Williams, E. March 13, 1926. Milling-machines; milling helical surfaces; boring-bar machines; rifling.-A machine for boring facing, rifling, &c. comprises a cutter carrying body which is slidable and rotatable about a central support which may be secured to the work being operated upon, the central support being provided with a concentric detachable gear ring on which pinions rotatably mounted in the body roll, rotation of the pinions serving to impart rotary movement to the body. The body 2 is mounted on the central support 3 and carries any number of rotary cutters or grinding discs 28 or cutter teeth 28<A>. The support 3 has a platform 6 which may be attached to the work by one or more electromagnets or by pins 7 or by studs engaging tapped roles 8, 8<A> and the top of the support may be steadied by a stationary tripod 4, Fig. 15<A>, attached to the work by screws 75 or electromagnets "6. The body 2 may be supported on the inside or outside of hollow work by radially mvoable chuck jaws 54 carried by a member 12 attached to the body, and further support may be provided by plain gauge rings 62 or expanding jaws 50 carrying rollers 64A or by machined surfaces on the body itself. The shafts 29 on which the rotary cutters are mounted may be adjusted angularly as shown in Fig. 1 or may occupy any position with regard to the central ax:s of the machine. Rotary cutters may be mounted in removable pockets 73, Fig. 4, let into the periphery of the body 2 so that the projecting parts of the cutters may be adjusted about radial axes to act on the work in any angular direction. The body 2 may be held stationary by hand and the central support, provided at the end with a cutter, rotated therein :'or forming a central hole in the work for attachment of the machine or otherwise. Milling-cutters.-The toothed cutters 28 are adjustably mounted on their shafts 29 by means of nuts 32 and may produce the desired form of groove in the work in a single operation or by means of a series of differently shaped cuts. In the latter case a series of cutters have teeth of different sections and operate in sequence. Alternatively, a single cutter may have successively acting teeth of different shapes or a series of cutters having differently shaped interlocking teeth may be mounted on the same shaft, the teeth being located circumferentially by a keyway in the central hole of each cutter. Driving machine spindles.-The cutter shafts 29 are driven through spur and bevel gearing from a central gear 33<A> attached to the sleeve 33, the latter being rotated by one or more electric motors such as 10, 10<A>, or by hand or by a flexible shaft terminating in a bush surrounding the support 3 and having a coupling engaging the end 33<B> of the sleeve. A further bevel gear 14, slidably keyed at 13 to the support 3, is provided for imparting a rotation to the body 2 simultaneously with a rotation of the cutters on their own axes, or this gear may be dispensed with and the body 2 rotated by hand, in which case a ratchet hand grip is provided on the body to prevent reverse rotation when the cutters engage the work. The bevel gear 14 may be replaced by an internally toothed spur gear fixed to the lower end of the support 3, the teeth being elongated to allow axial movement of the pinions engaged therewith. When the cutters are inclined, skew gearing 75 is provided. The direction of rotation of all or some of the cutters may be reversed by the provision of additional gearing. The power for the motor may be supplied through brushes 57, Fig. 15<A>, on the stationary support 4. The bearings of the cutter-shafts and gearing are lubricated by passages such as 20 supplied by a pump 17<A> from a tank 15 mounted on the body 2 or supplied by a flexible connection attached to the centre of the support 3. Feed-motions.-When the machine is attached to the work an automatic feed is provided in which a gear 44 secured to the sleeve 33 engages pinions 45 freely rotatable on a frame 45<A> splined to the support 3, the pinions meshing with an internal gear 46 which transmits rotation, through a friction clutch 70 hand controlled at 69, to a nut 71 screwing on the support 3 and thus feeding the body 2 relatively to the support. In an alternative feed motion for rifling or cutting curved grooves of any shape, a nut 53 is attached by pins 53<E> and a locking ring 53<F> to the chuck body 12 and engages a sleeve 53A attached to the body 2, the nut and sleeve being provided with screw threads or interengaging cam grooves of the required shape. The cutters 28 may be fed radially by a worm 91<A>, hand controlled at 91, engaging a rack-bar 30<A> on which a cutter spindle is mounted. Gauging-devices. - The depth of cut may be limited by rollers mounted in spring-pressed holders on the body 2 or on the chucks 50, or by rings such as 62 mounted on the body and having the internal and external peripheries eccentric to each other so as to provide adjustment by rotation thereof on the body. Alternatively, interchangeable discs 40 may be attached to the faces of the cutters to contact with the surface of the work and limit the feed. Lubricating cutting-tools and work.-The cutters are provided with passages or grooves 37 communicating with hollow shafts on which they are mounted or with passages 20 in the body 2 for supplying cooling fluid during operation, the fluid being deflected from the peripheries of the rotary cutters by guards 42, 43. The hollow shafts communicate by passages 20 and a pump 17 with a tank 16 on the body, the tank being supplied if necessary through the support 3 by a flexible connection on the centre of the platform 6. An alternative form of lubrication is provided by blocks of solid lubricant such as soap which are mounted in holders on the body and are pressed into contact with the work by springs in the holders. Cuttings, catching and removing. - Rotary brushes 39 may be attached to the shafts 29 to sweep cuttings away from the path of the cutters and stationary brushes 39A may be attached to the body 2 or in holders interchangeable with the guide rollers 64<A>. The guards 42, 43 deflect the cuttings which may be collected by electromagnets 52. Reference has been directed by the Comptroller to Specification 263,580.