Reaming is a secondary finishing process that meets the more stringent machining requirements for hole size, shape accuracy, and surface finish. The reaming tools currently in use include traditional hand reamers that have been used for hundreds of years, as well as advanced reaming systems that can process high-precision holes quickly and efficiently. The following are three reaming systems that can meet the processing needs of different end users: the first reamer is designed for fast machining conversion on CNC machine tools; the second reamer is mainly suitable for cutting speed requirements. The processing occasion; the third is a composite reamer that integrates drilling and reaming functions.

MODCO BHR

1 Valenite's MODCO BHR Reamer

Auto parts manufacturers face pressure to control costs and “just-in-time-supply”, so they must reduce processing time to a minimum. One way to achieve this is to use advanced processing equipment that can quickly switch from machining a previous part to machining the next part, which results in the traditional production line being replaced by machining cells. In many cases, CNC machine tools in these machining units must be equipped with new tool systems.

In order to replace the servo-adjustable reamer commonly used in traditional production lines, Valenite (Valenite LLC, Madison Heights, Ga.) has developed a new type of high-efficiency, high-precision reaming for CNC machine tools and production lines. Reaming system. The Brad Head Reamer (BHR), called MODCO, features interchangeability, and the reamers with multiple carbide tips can be quickly replaced. This quick-change coupling mechanism has high rigidity and repeatability. It can be used to ream precision holes with ISO H7 accuracy without any adjustment after replacing the reaming head. In addition, the multi-cutting edge structure distributes the cutting force evenly, enabling the reamer to perform high-volume and high-efficiency machining with high cutting parameters. For example, in the case of carbon steel and high carbon steel workpieces in reaming, the cutting speed is generally 50-100 m/min, the feed rate is 0.40-0.50 mm/r, and the surface roughness can be up to 0.3-0.8 μm.

Recently, Valenite is providing custom-made manufacturing tools for the automotive industry's equipment manufacturers (OEMs) and their major suppliers. The MODCO BHR reamer is specially configured for specific machining materials, machine tools and production batches. The reaming system is designed with five different toolholder sizes, and the matching reamers can be used to ream blind holes or through holes with diameters from φ9.75 to 32.50 mm. Holes with a diameter of φ15.49 mm or less are machined by a four-tooth reamer, and holes of φ15.50 mm or more are machined with a six-tooth reamer. There are two grades of tooth material, one is uncoated ultrafine grained carbide grade VP-1R20, suitable for reaming aluminum and other non-ferrous metals and titanium alloys; the other is PVD TiN coating. Ultrafine grained carbide grade VP-5R15 for machining steel and stainless steel, cast iron and all nickel/cobalt/iron based superalloys.

Bob Coleman, product manager for Valenite's processing solutions, points out that the reamer is a finishing tool, not a primary machining tool for removing metal materials. “Typical hole machining operations are usually drilling → boring → reaming. If the quality of the drilled hole is high, it can be directly reamed, but the reaming is not possible to remove a large amount of workpiece material,” he said. A finishing process." When reaming with a BHR reamer, the maximum material removal allowance per side is 0.25 mm. Due to the self-guided function of the reamer, Valenite recommends using it with adjustable and floating tool holders. Coleman said, “Normally the reamer will feed along the finished bottom hole in the workpiece. All the operator has to do is move the reamer a little radially to determine the center of the hole.”

Kellerman also pointed out that when machining automotive parts with new materials, the use of processing unit production methods helps to increase production efficiency. When cutting high-strength, high-abrasive materials that are prone to rapid tool wear during production lines, the need to frequently stop and restart the entire line when changing tools can greatly reduce production efficiency. The processing unit production method allows the use of a quick-changeable spare tooling system for easy batch reaming of automotive parts for difficult-to-machine materials such as compacted graphite iron (CGI).

Bayo T-Ream

2 Iscar's Bayo T-Ream Reamer

The Bayo T-Ream reaming system from Iscar Corporation (Iscar Metals Inc., Arlington, TX) is an efficient, precision reamer developed for high speed reaming. The biggest feature of the tool is the interchangeable solid carbide multi-tooth reamer based on the quick-change bayonet principle. Bayo T-Ream reamers have a hole diameter range of φ9.5 to 32 mm and reaming accuracy up to ISO H7. Typical cutting parameters for low alloy steel and cast steel materials are: cutting speed 80-120 mm/m, The rate of return is 0.7 to 1.1 mm/r. The reaming system is designed for high volume machining applications where cutting speed is a primary consideration. According to Iscar, the Bayo T-Ream reamer allows a knife rate that is more than 30 times higher than a normal reamer.

The separation of the cutting function and the positioning function significantly improves the machining accuracy of the Bayo T-Ream reamer and enables high-speed reaming. Each groove of the reamer contains a cutting zone and a guiding zone. The cutting zone is located at the chamfer at the beginning of the grooved edge where the chips are formed during processing. The guide zone is a cylindrical band that supports and guides the reamer through the reamed hole during machining. The gap between the guiding portion and the reamed hole is small, and the surface of the workpiece can be squeezed. The function of the cylindrical guide also reduces the reverse taper of the reamer, and the diameter of the rear portion of the reamer is only 0.01 to 0.02 mm smaller than the diameter of the front portion.

The high machining accuracy and high cutting speed of the Bayo T-Ream reamer make it more rigid than the traditional reamer for the rigidity of the machining system. Craig Segling, Iscar's domestic product manager for hole machining and solid carbide round tools, said, "The Bayo T-Ream reamer has good rigidity when it is mounted in a SRKIN shrink chuck or ShortIN chuck. At this time, the overhang is only 1.25" (32 mm), so that no deflection occurs. If a floating collet is used, the entrance to the reamed hole must be pre-treated to exactly match the chamfer angle on the reamer. Most reamers always enter the reamed hole along the path of least resistance, but once the diameter portion of the reamer cylindrical guide enters the hole, the reamer feeds along the line. As with the boring of the boring tool, the Bayo T-Ream reamer can straighten it if it is eccentric or tapered. ”

Iscar recommends that when machining cast iron and steel parts with Bayo T-Ream reamer, the diameter of the pre-reaming should be 0.2 to 0.3 mm smaller than the hole diameter to be machined for optimum reaming; For workpiece materials (such as aluminum), the diameter of the pre-reaming should be 0.3 to 0.4 mm smaller than the diameter to be machined. In addition, the reaming should be performed under the same workpiece clamping state as the previous drilling process. If the workpiece clamping state of the reaming process changes with the drilling process, the reaming tolerance should be increased.

According to Iscar, the Bayo T-Ream reamer can increase the diameter of the reamed hole by up to 8 mm, so it can be used separately for finishing high-precision holes.

The T-Ream reamer for machining blind holes and through holes differs in the groove structure. The reamer for machining blind holes adopts a straight groove structure, because the straight groove can provide a smooth chip evacuation passage for the chips that are flushed out of the blind hole by the coolant; and when the through hole is machined, the reamer designed as the left-handed spiral groove can be used. Push the chips forward to prevent the chips from flowing along the sipe and protect the surface quality of the holes. In addition, the spiral groove is less likely to cause vibration than the straight groove, and thus is more suitable for processing the intermittent hole and the irregular hole. Another design feature of the T-Ream reamer that acts as a damping is the asymmetric distribution of the sipe. The use of unequal spacing distribution of the sipe of the outer circumference of the reaming head can effectively prevent the formation of resonance which reduces the accuracy of the reaming (roundness and cylindricity). However, in order to facilitate accurate measurement of the actual cutting diameter of the reamer, two of the sipe are 180° symmetrically distributed.

Iscar pointed out that in order to maintain good machining accuracy during high-speed reaming, the radial runout between the machine spindle, tool chuck, tool holder and reaming head needs to be controlled to a minimum. If the effect of controlling the runout is not guaranteed, a larger reaming tolerance is recommended. If the rigidity of the machine tool is not sufficient to meet the requirements of high-speed reaming, the traditional reaming process should be considered.

The Bayo T-Ream reamer is suitable for cutting speeds and feed rates much higher than conventional reamer. Segerlin, product manager at Iscar, cited an example of machining a reamed steel: he used the Bayo T-Ream reamer to process 12L44 steel with viscous material: spindle speed 1500 rpm, cutting speed 36 ipm (900 mm/min) The chip thickness per tooth is 0.004" (0.1 mm) and the reaming depth is 0.750" (19 mm). The diameter of the machined hole in the hole, the hole and the bottom of the hole is 0.6308" (16 mm), no taper error, the roundness error is less than 0.00020" (0.5 μm), and the surface roughness is Ra4μin. According to Segerlin, Bayo T-Ream reaming can achieve the same machining results as precision boring under certain processing conditions, and the processing speed is faster than boring.

Shefcut reamer series

3 Cofdill Tool Company's Shefcut Hinge-é•— Compound Tool

Developed and marketed by Cogsdill Tool Products (Camden, South Carolina, USA), the Shefcut Precision Hinge-Cutter System has the dual functions of precision reaming and precision boring. The structural features of this composite tool are in the tool. A plurality of guide knives are distributed on the outer circumference, and an adjustable single cutting edge insert is mounted on the knives.

Fred Ogburn, Cogsdill's public communications manager, said that the blade is mounted with a small reverse taper angle, making its cutting function "almost similar to a single-point cutting tool, although it uses blade cutting, but In fact, the cutting edge of the blade is used for cutting." The tool is designed for precision hole machining with high straightness and roundness (up to ISO H6). Hole tolerances (including straightness and roundness) can be controlled to within 0.0002" (5μm) when machining on typical shop floor machine equipment, with a surface roughness of up to Ra4μin (higher finish for certain materials) ).

Cutting inserts that are independent of the tool body can be fine-tuned to a limited extent and can be pre-adjusted to the specific aperture size being machined. Ogburn said, “The Shefcut tool is not an adjustable reamer. Although it does have fine-tuning, it is just a fine-tuning-type tool.” Adjustable range of the blade Only a few tenths of an inch, the role is to fine-tune the aperture size and compensate for blade wear.

The guide knives, which are independent of the cutting insert, are not adjustable and are ground to a size just a few tenths of an inch smaller than the size of a blade that is machined to a particular aperture. The shims can be customized to suit a variety of specific machining tasks (eg machining multi-diameter, short or extra long holes, interrupted cutting, guided machining, etc.).

The choice of the Shefcut tool clamping and cutting parameters depends on the type of machining selected (reaming or boring). When used for precision reaming, the tool can be positioned in the pre-machined bottom hole. The surface cutting speed used is usually low. The spindle chuck for clamping the tool is usually a floating chuck or a precision chuck. In order to increase the processing flexibility of the Shefcut tool, the size of the body behind the cutting head is immediately "reduced".

Ogburn said, "Therefore, the tool will be reamed until the guide pads are fully engaged with the hole walls. At this point, the reaming can be used to machine precise and straight holes, and the operator has little intervention in the tool. He cited an example of a precision reaming of an aluminum cylinder bore on a tilting bed lathe with a Shefcut reamer (clamped on a Cogsdill floating collet). The tool can eliminate the influence of the calibration error of the lathe itself on the reaming hole, and the reamed cylinder hole does not need to be further honed. The cutting speed used for machining is 150sfm, the feed rate is 0.007ipr, and the reaming accuracy achieved is: dimensional tolerance 0.0002′′ (5μm), surface roughness Ra5μin.

When rigid clamping is used, the Shefcut tool enables precise positioning of the hole size during machining, such as fine casting holes. When Shefcut tools are used for boring, the higher spindle speeds are usually used, so the rigidity of the machining system is high (including the precise coupling of the spindle and the tool). At this time, HSK chucks or adjustable chucks can be used. Ogburn said, “Floating chucks cannot be used for boring, because in fact the precise machining of the holes needs to meet specific hole size requirements.” He cited a fine sluice valve hole (gray cast iron) For the processing example, the hole has a diameter of 0.6245", a tool rotation speed of 1500 rpm, a feed rate of 0.005 ipr, and a machined surface roughness of Ra32 μin.

The positional relationship between the guide pad and the cutting insert is a major factor affecting the machining performance of the Shefcut tool. The key dimension is the difference in size between the diameter of the guide pad and the minimum cutting diameter. This difference is called the "safe area", because to avoid damage to the tool during machining, the dimensional difference must always be maintained.

Although it is also possible to measure and adjust the cutting diameter of the tool with a micrometer, Cogsdill recommends the use of a special knife setting (especially necessary for batch processing). When adjusting the tool with this clamp, place the tool between the adjustable tips and measure with two probes. The diameter of the guide pad is used as a reference point, one probe is used to measure the cutting diameter of the tool, and the other probe is used to measure the reverse taper of the blade.

The front adjustment screw is used to set the cutting diameter of the blade. The blade is moved by the adjustment screw until the difference in size of the blade above the guide pad is equal to the "safe area" value (ie, the blade diameter is about 0.008 to 0.013 mm larger than the blade diameter). The rear adjustment screw is used to set the reverse taper of the tool. The rear portion of the blade is moved by the adjusting screw so as to be flush with the blade (ie, less than about 0.013 to 0.020 mm in diameter of the blade).

Cogsdill can customize the size of the Shefcut tool to the specific machining needs of the user. The company also offers a range of tools for reaming common aperture sizes, although each of these tools can only be used to machine a specific aperture size. The so-called "standard" tools are stocked in the form of semi-finished products. The guide pads are ground according to the order requirements before delivery to the user, and the blades are installed and pre-adjusted according to the specific aperture size.

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