Article from: Modern Machine Shop
In business since 1968, Do-Rite Tool, Inc. (Garden City, Michigan), an eight-person job shop occupying 5,000 square feet, processes runs varying from one to 1,000 pieces. Its main source of work stems from the automotive industry, and the company cites milling and turning flat and round stock as its areas of expertise.
In March 2005, Do-Rite ran a part consisting of two flanges (six holes per flange) with a center section, and the diameter of each of the finished holes was 0.484 inches. To drill each hole, the drill had to penetrate a top flange, passed by a 0.407-inch wide groove, and continue through a bottom flange. (See photo below.) This essentially resulted in 12 holes that required deburring. The holes were extremely close in proximity to the wall of the hub, and some holes blended into the grooved portion between the flanges.
When drilling the six holes in the part, a burr was created on each of the two entries and two exits. Not only were the holes close to the wall, but also the burrs between the two walls needed to be removed.
To make the job profitable, it was imperative that the company remove the burrs in a timely and cost-efficient manner. Because of these time and monetary constraints, deburring these tools by hand was simply not an option, according to the company.
Dave McDonald, president of Do-Rite, first considered using a wire wheel mounted in the CNC and interpolating around the part within the undercut. However, this process would have been less than ideal for several reasons. When drilling a hole, the drill breaks through the steel, and the drill point or the chisel edge starts to push out a burr, or even a cap if speeds and feeds are too rapid. This pushed-out part represents the weakest part of the burr. Then when the full drill diameter breaks through the wall of the outer edge, the drill tends to extrude a burr around the hole. This extruded burr is firm. The process of interpolating a wire brush around the part within the undercut might remove the more firm part of the burr, but Mr. McDonald theorized that the weaker burrs would be pushed back into the hole, thus interfering with the ID of the hole.
This scenario would have called for a follow-up process using a 4-inch wire brush to clear the burrs from the ID of the hole. The machine operator might have to chase the burr from the slot into the hole, and from the hole back into the slot until the burr breaks loose.
Another possibility is that the firm burr may not be completely removed, and it might protrude. Such burrs, which would be too firm for the interpolating wire brush, would require manual filing or another means of removal. Ultimately, a 100 percent gage check for each hole would be required to prevent burr obstruction.
Mr. McDonald then came across an advertisement for a line of hole deburring and chamfering tools manufactured by E-Z Burr Tool Company (Plymouth, Michigan). After referring to the company’s Web site, Mr. McDonald determined that carbide deburring tools might help address the problem.
height adjustment feature
The close proximity of the holes to the wall of the hub made it challenging to reach between the flanges without distorting the tool. With its height adjustment feature, the carbide insert could be lowered, while maintaining enough pressure to remove the complete burr.
E-Z Burr recommended its standard Carbide Series tool, the CRB0484-B. Ground to a 0.477-inch diameter to ensure clearance in and out of the holes, the tool measures 5 inches in length, with a 3/8-inch shank diameter. Made of 1215 medium carbon steel, the product deburrs both the top and bottom of each hole in one pass at a recommended speed of 2,000 rpm and a recommended feed rate of 0.006 ipr.
As the revolving tool is fed into the workpiece, the carbide insert removes the top (front) burr. When the insert deburrs, it begins to collapse into the arbor. The polished crown of the insert is designed not to mar the ID of the hole. Once through the hole, the feed direction is reversed. Consequently, the insert will deburr the rear of the hole as the tool is retracted. The customized height adjustment feature enables the carbide insert to be lowered. Do-Rite used this feature to minimize interference between the wall of the hub and the hole location.
To complete the project, the part was drilled, reamed and then deburred on all four sides. The company drilled and chamfered a total of 8,800 holes; however, because of the configuration of the part, 8,800 holes equated to 35,200 chamfers.
Because each of the holes was so close to the wall of the hub, it was challenging to reach between the flanges without distorting the tool, says the company. With its height adjustment feature, the carbide insert could be lowered, while maintaining enough cutting pressure to remove the complete burr. Thereby, interference between the wall and the hole location could be minimized.
The same attribute can also be beneficial to the operator when the tool is first run, as the chamfer size can be fine-tuned within seconds while the tool is still in the spindle.
Other attributes of the tool (as noted by Do-Rite) are durability and ease of use and setup, all of which enabled the company to increase productivity while offering an end product that met its quality standards. The carbide tool required less time to complete the project than the alternative involving a wire wheel brush or hand deburring.
The company reports that this tool helped it streamline deburring and chamfering operation time by a total of 8 hours.