The most popular reverse scraping spot facer with

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A new type of reverse scraping spot facer is often used in the processing of bolt counterbore. It is usually machined by flat spot facer or sleeve type end face spot facer on the drilling machine or by scraping with a single-sided shaped blade clamped on the tool bar. However, due to the structure of some parts, it is difficult to carry out the front scraping processing with the above method. The processing method can only be used to clamp the single-sided forming blade on the tool bar for reverse scraping, that is, the blade cutting edge is clamped on the tool bar upward, and the drill machine spindle moves upward during processing. This is the case for certain parts in our products, and the partial view is shown in Figure 1. The M30 (its through-hole diameter is f33mm) bolt counterbore f60mm on it has a large number and a special location. Due to the structural requirements of the design, the outer circle of the counterbore intersects with the R30 arc, and the materials of this kind of parts are mostly steel castings. The surface of the parts is uneven, and there are often hard inclusions. When the general reverse scraping method is used, the cutting conditions of the tool are bad, and it is often in intermittent cutting state, which is very easy to cut; To process counterbore f60mm, the extended length of single-sided forming blade is too long, the cutting is unstable, easy to shake, and the tool life is short; Due to the limited part clamping space, the tool clamping is difficult and the auxiliary time is prolonged. Due to the above reasons, through continuous practice and improvement, our factory has designed a kind of reverse scraping spot facer with novel structure

I. structure of reverse scraping spot facer bar and cutter

reverse scraping spot facer bar is mainly composed of taper shank 4, cutter bar 1 and wedge 2, as shown in Figure 2. The Morse taper of the taper handle is matched with the spindle of the drilling machine. The wedge transmits torque. The inner hole of the taper handle is matched with the outer circle of the cutter bar with fg7/g6, and the wedge transmits torque. The outer circle of f33e9 on the tool bar matches with the drilled bolt through hole f33mm on the part, which plays the role of positioning and auxiliary support. It is worth noting that the mutual positions of the two 20 size cutting edges on the tool bar should take into account the rotation direction of the drilling machine during scraping. Otherwise, when the clamping of the processing sample is a very important link in the test process, the tool will fall off the tool bar and cause accidents. The cutter is as shown in Figure 3. The inner hole of the cutter and the outer circle of the cutter bar are positioned in accordance with f26h8/f8. The two end faces of the cutter bar with the cutting size of 20b11 and the 20+0 of the cutter bar. 12+0。 06 the two ends of the waist shaped counterbore are in contact to transmit torque

II. Operation process of countersink drilling with reverse scraping spot facer

after drilling each bolt through hole f33mm, adjust the spindle position of the drilling machine so that the tool bar passes through the bolt hole and the end face of the tool bar is flush with the lower end face of the part, then put the cutting edge of the end face of the tool upward and under a bolt hole, turn the tool, so that the waist countersink of the tool is aligned with the cut edge of the tool bar, so as to drive the nut to rotate flush, and the tool bar moves downward. After passing through the tool, Then turn the tool anticlockwise, so that the tool will be hung on the tool bar, start the drilling machine, lift the spindle upward, and then the counter scraping counterbore can be processed. After machining a counterbore, stop the drilling machine, turn the tool in reverse direction, and lift the spindle of the drilling machine to remove the elastic limit - the maximum stress applied to the material without permanent deformation For metals and other materials with obvious linear segments in the stress-strain curve, the elastic limit is roughly the same. Repeat the above operation process to reverse scrape another counterbore

III. characteristics of reverse scraping spot facer

it can be seen from the structural diagram of the reverse scraping spot facer tool bar and tool that its structure is simple, its accuracy requirements are low, and it is easy to manufacture

it can be seen from the tool diagram that there are multiple edges involved in cutting during machining, which makes the cutting stable and the tool wear small. Therefore, the cutting parameters can be increased and the production efficiency is high

tool bar is good. As the positioning excircle matched with the inner hole on the part is set on the tool bar, when the tool is under large force, the tool bar has strong support to avoid the bending deformation of the tool bar and affect the quality of the counterbore end face

tool clamping is simple, fast, safe and reliable

the disadvantage is that the design and manufacture of the cutting tool is complex

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