Boring. Contents. Boring

Transcription

1 ontents oring oring ackground... 3 oring operation types... 4 oring tools... 5 hoice of boring tool type... 6 Roughing... 6 inishing... 7 Inserts for boring... 8 uilding and setting boring tools... 9 Ways of countering vibrations in boring... 9 Success factors for boring Tool overhang and diameter utting data and chip control Insert nose and geometry utting fluid amped tools The tool coupling Specially for reaming ow to select boring tools oromant apto for boring oring tools for roughing oring tools for finishing oroore oroore 820 range uobore uobore range eavy duty boring tools oroore oroore 825 range Single edge fine boring tools ine boring head oring bars Start values for finish boring Setting values for high speed boring ine boring tools amped single edge fine boring tools Reamer T-Max U fine boring units Mounting dimensions fine boring units Setting the boring unit artridge replacement in fine boring unit utting speed recommendations for boring oromant flexible boring tool

2 oring 2

3 oring oring ackground oring operations involving rotating tools are applied to machine holes that have been made through methods such as pre-machining, casting, forging, extrusion, flame-cutting, etc. Roughing operations are performed to open up the exisiting hole to within large tolerances and usually to prepare for finishing, which makes the hole to within tolerance and surface finish limits. Typically, boring operations are performed in machining centres and vertical boring machines. The rotating tool is fed axially through the hole. Most holes are through-holes, often in prismatic or round components. xternal boring operations can be accomplished using specially adapted boring tools. The most common size holes being bored are 30 to 100 mm diameter. The range of Sandvik oromant boring tools covers 23 to 550 mm for roughing and 3 to 975 mm for finishing. s regards hole depths, four times the hole diameter is generally the maximum recommended depth. Various tools have individual maximum hole depths. or rough and fine boring of deeper holes - of six times the diameter - damped boring tools with tuned tool bodies should be employed. s regards hole quality, finish boring can typically achieve holes within tolerances of IT 9 with some achieving IT6. Surface finishes better than Ra 1 micron can be achieved. inish tools have adjustment possibilities to accurately pre-set cutting edges. In principal, however, a boring tool designed for roughing can also be used to achieve holes with a high surface finish and to within close tolerances as only one of the inserts generates the surface. 3

4 oring oring operation types oring operations are divided into: - single-edge cuts - multi-edge cuts - step-boring - reaming Single-edge boring is usually applied for finishing operations and for roughing and finishing in materials where chip control is demanding. single-edge boring tool may also be a solution when machine power is a limiting factor. a Multi-edge boring, involving two or three cutting edges, is employed for roughing operations where metal removal rate is the first priority. igh productivity levels can be maintained by allowing two or three inserts, set at the same axial height, each to machine at the recommended feed per tooth. This results in a high feed per revolution through the hole. a a Step-boring is performed in roughing by a boring tool having the inserts set at different axial heights and diameters. This also improves chip control in demanding materials with the different depths of cut of up to 1.0 or 1.5 times the cutting edge length. epths of cut of 0.5 times the cutting edge length can be divided into smaller cuts, providing smaller chips. a >a Reaming is a light finishing operation performed with a multiedge tool giving high-precision holes. Very good surface finish and close dimensional tolerance are achieved at high penetration rates. The pre-machined hole needs to be within close limits and the radial depth of cut is small. 4

5 oring oring tools boring tool is usually a modular tool, consisting of a basic holder, adaptor and a cutting unit in the form of a cartridge, slide or fine boring unit. fine boring head holds a boring bar which is radially adjustable and a reamer has a tool shank with a close pitch head with brazed blades. The tools are radially adjustable within a specific diameter range. The smallest diameter holes, from 3 mm upwards are bored with the fine boring heads while largest holes of up to 975 mm are finish-bored with a single-edge tool having an adjustable extension-slide mounted on an eccentric bar. dedicated boring tool is the best solution for operations on components in small to medium batches, with the key features being good productivity penetration rate -and high versatility one tool used for several hole diameters. to use a tool pre-setting facility, however, a modern design such as oroore 820 can also be set using Vernier calipers. oring tools for finishing with one cutting edge must be settable to within microns and, for this reason, the Sandvik oromant range of boring tools are settable to within 2 microns. Tools should be set in a tool pre-setter. With only one cutting edge, the finishing tool will experience some degree of radial deflection during machining. This means that a premeasuring cut is normally needed, followed by an adjustment of the tool. ifferent insert carriers are employed on boring tools and these are dedicated to the type of tool (slides, cartridges, boring bars and fine-boring units). The fine-boring unit is used in special tool solutions and can be mounted in blind holes without the need for locking after setting. does require access from the back of the shank and for the mechanism to be locked when set. The reamer provides through-holes with high surface finish and dimensional accuracy at high penetration rates. oring tools for roughing with more than one cutting edge have relatively simple adjustment possibilities and it is preferable The mechanism of oroore 825 can be used for special tool solutions. It is more rigid than the fine boring unit but Reaming Rough boring inish boring 5

6 oring hoice of boring tool type The choice of tool for single-edge, multiedge or step-boring operations is very much down to capability and requirement. Roughing tools are primarily multi-edge and finishing are single-edge tools. Roughing tools include oroore 820, uoore (R391) and heavy duty boring tools (R391. -R), all tools being capable of all the three operations. inishing tools include oroore 825, fine boring tools (R , fine boring head and the Reamer 830. Roughing oroore 820 is first choice providing high metal removal capability through boring with three inserts. Power requirement is higher with several cutting edges engaged. ll three inserts are set to the same diameter and height for high-producitivity boring while for step-boring, the inserts are set at different diameters and heights. This achieved by using different shims placed between the tool adaptor and slide, where the highest insert is set for the smallest diameter and the lowest for the largest. When single-edge boring with oroore particularily for finishing or when materials with demanding chip control is involved - only one insert-slide is used, with the other two slides replaced by covers to maintain the balance of the tool and to be protected. The maximum recommended depth of cut is half the cutting edge length. ach insert can be set accordingly making it possible to have depths of cut up to the full cutting edge length. The depth of cut of half the cutting edge length can be divided into two smaller cuts, giving smaller chips advantageous in demanding materials. When single-edge boring is employed, only one of the insert-slides is used, leaving the other seat to be protected by a cover that radially supports the slide. The heavy duty boring tools, primarily for larger diameters, are also capable of all three operations types. The tool design resembles the boring tools for the smaller diameter ranges but with mounting dimensions for standard milling arbour. pproximate settings are performed by moving sides across the adaptor or bar followed by fine setting on the cartridge. With two cartridges, each mounted on an extension slide, which is radially adjustable on an adapter and using shims, the cutting edges can be set in accordance with the operation type to be employed. The tool for the larger diameter range uses a wide bar mounted on the adaptor and on which two extension slides can be set. oroore 820 with tree cutting edges. uobore has two inserts and needs less power. or high-productive rough step boring, the two inserts are set to the same diameter and height in the tool providing a penetration rate giving double the recommended feed per tooth. or step-boring the tool setting principle is the same as for oroore 820. eavy duty boring tools for large diameters. oroore rough boring tools with two cutting edges. 6

7 inishing oring oroore 825 is the first choice for general finish boring within the diameter range of 23 to 250 mm. This boring tool has a single cartridge, with high stability and easily adjustable radially to within 2 microns, to achieve IT6 tolerances and surface finishes within Ra 1 micron. The oroore 825 finsihing tool complements the oroore 820 roughing tool for the same hole diameter and depth range to provide a modern solution for boring. ine boring heads hold dedicated boring bars fo diameters 12 to 25 mm and carbide bars of 16 mm to provide the capability to produce close tolerances (IT6) at high spindle speeds (7000 rpm). With a diameter range of 3 to 44 mm to depths of 13.5 to 128 respectively, these superfinishing boring tools machine at small depths of cut (0.05 to 0.5 mm) and small feeds (0.01 to 0.1 mm). enerally, the first choice for the boring bar is a positive knife-edge insert in a cermet grade machining at high cutting speeds. ine boring head with boring bar. oroore 825 The fine boring tools for larger diameters consists of two different designs : one for single or twin-edge boring of internal diameters 250 to 575 mm and external of 138 to 447 mm and one for internal boring of 250 to 975 mm. ommon for both are adapter, bar, slide and fine boring head. Rough setting is carried out by moving the slide along the bar and then adjusting the fine boring head. To avoid large holes becoming oval at high spindle speeds, recommendations for a counterweight can be supplied. Selecting the most suitable insert and entering angle and the ability to turn the unit provides a high-performance boring tool for high tolerance and surface finish demands. The Reamer 830 covers the diameter range 10 to mm with varying hole depths, hole tolerances of IT 7 are achieved along with high concentricity. asily exchangeable heads are secured by front clamping. The heads accommodate 4 to 8 cermet brazed blades depending upon diameter. ffective chip evacuation is secured by cutting fluid directed to each cutting edge. There is high concentricity and repeatability with a precision coupling. The combination of multiple cutting edges capable of high cutting speeds results in very high penetration rates. The heads are equipped with left-hand chip flutes which push the chips ahead of the reamer, thus necessitating throughholes for machining, but providing an advantage for machining with interrupted cuts as in crossing holes. This cutting action generates cutting forces directed axially into the spindle, increasing the rigidity and providing accurate control of the hole diameter accuracy. ine boring heads for large diameter. Reamer 830 high feed reamer. 7

8 oring amped boring tools (Silent Tools) should generally be considered for hole depths of more than four times the diameter. uoore damped tools are available for roughing operations in the diamter range 25 to 150 mm and with the ability to perform single-edge, multi-edge and step-boring. amped fine-boring tools are available from 25 to mm diameters. The tool coupling is a critical part of the total set-up and interface to the machine spindle. If the tool coupling is unsatisfactory as regards stability, strength, accuracy and handling, the chain of factors that ensure performance will be broken. good modular system oromant apto with a large range of tool types for roughing and finishing is an important amped tooling for long tool reach. part of the machining equipment for boring with rotating tools. The system provides the means for a tool and spindle interface with a self-centering coupling that provides the centre of rotation for minimizing the boring tool run-out and making it possible to adapt each tool assembly for the operation in question. Inserts for boring The selection of indexable insert for boring has a decisive influence on the outcome of the boring operation. Productivity, reliability and quality is directly related to the performance of the cutting edge. hip formation, tool-life and cutting data are determined by the combination of insert geometry and grade. s in all internal machining operations, chip control and evacuation are critical. Inserts for boring are essentially the same as for turning, where chipbreaking areas are defined for each geometry type. Short, thick chips can lead to excessive cutting forces with deflection and vibration as the result. hips that are too long, often in the form of stringy swarf, can accumulate in the hole and cause surface finish deterioration and then chip stocking, leading to breakdown.hips in the form of commas or determined spirals are the ideal. The depth of cut is determined by the recommended values for each insert geometry. The sharper a geometry is, and the smaller the nose radius, the smaller the depth of cut possible. It may very well be that an increase in depth of cut may lead to harder chipbreaking, while a reduction may lead to insufficient cutting edge engagement, with rubbing as a result.if chips are generated sporadically during machining, the depth of cut may be insufficient or excessive. oromant apto tool coupling. The right indexable insert provides the vitally correct cutting action. 8

9 uilding and setting boring tools uilding a tool for boring with modular holders, adaptors, extensions, reductions and cutting units provide a broad range of possibilities to perform operations and for optimization. Long reach tools with the best stability, the inclusion of damped tools and flexibility for use in other operations are some of the main advantages. This is especially important when building finishing tools as the cutting edge should be moved away from the machined surface in the bore to avoid retraction marks. It is then also vital that the recommended torque values are followed for assembly and that a suitable fixture is used and that a good tool pre-setter is used. oring influence not only surface finish but also the productivity of the operation. Surface finish is directly related to the same parameters as for rough boring but with the depth of cut also playing a role. enerally depths of cut are quite shallow but there is a lower limit to depth which relates to insert geometry and feed rate. Most boring tools for finishing have only one insert and are as such prone to deflection during cut. When the cutting depth is smaller than the lowest depth-limit, the insert will tend to ride on the pre- machined surface, only scratching and rubbing it, leading to unsatisfactory cutting action and and hence the final result. ach boring tool is delivered with setting instructions. or finishing cuts, it is often advisable that a measuring cut is made to see what adjustment is needed to compenstae for tool deflection. Special boring tools should be considered for optimization, especially when large batches or repetitive orders involving the same operation. oroore 820 can be combined with oroore 825 to accomplish roughing and finishing one hole diameter. Tool combinations for machining different diameters, chamfers and counterbores can be made. The factors for successful boring with tool assemblies are similar to those associated with internal turning. uilding tools with modular adaptors. With all parameters related to accuracy and surface finish generation under control, it is possible to achieve very good tolerance levels and surface finishes in boring. The surface finish in boring operations is influenced by various parameters component and fixturing stability, machine tool condition, tool holding stability, cutting data and the choice of indexable insert. The choice of Wiper inserts will Ways of countering vibrations in boring: - Uset the largest tool-diameter possible. - Use shortest tool over-hang possible. - Use tapered shanks/reductions whenever possible. - Use dedicated tools for longer overhangs - damped tools. - heck machine spindle, run out, wear, clamping force etc - heck that all units in the tool assembly are assembled correctly with the correct torque. - Reduce speed - Reduce feed/increase feed - increase depth of cut (finishing) - Use smaller nose radius (finishing) - Use insert with sharper cutting edge - Use 90 entering angle (roughing) - heck workpiece clamping 9

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