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techtalk:ref:tools147 [2019/05/09 21:36] hippysmack [Pre-Ream Hole Size Chart] |
techtalk:ref:tools147 [2019/05/09 21:57] hippysmack [Pre-Ream Hole Size Chart] |
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| - | ===== Pre-Ream Hole Size Chart ===== | + | ===== Calculating Pre-Ream Drill Hole Sizes ===== |
| + | The amount of material left in the hole prior to reaming (pre-ream hole size) plays an integral role in the quality of the reamed hole. ((http://blog.supertoolinc.com/2012/04/06/pre-ream-hole-size/)) \\ | ||
| + | The pre-ream hole size affects characteristics in the reamed hole including hole finish, hole straightness, tool life, and cycle time. \\ | ||
| + | There are several ways in which the pre-ream hole size may be obtained some examples include investment casting, boring, line boring, rough reaming, and stamping. \\ | ||
| + | The most common way to obtain the pre-ream hole size is through drilling. \\ | ||
| + | The appropriate amount of stock removal for carbide tipped and solid carbide reamers is generally 2% to 3% of the finished hole size. \\ | ||
| + | Carbide tipped and solid carbide reamers need to have adequate stock to remove or they will rub in the hole and generate excessive heat. \\ | ||
| + | This leads to premature tool wear and poor hole finishes. | ||
| + | A 0.7500” diameter reamer should remove between 0.0150”-0.0225” of stock. \\ | ||
| + | A 0.2500” diameter reamer should remove between 0.0050”-0.0075” of stock. \\ | ||
| + | A good way to calculate the drill bit size is to take the desired finished hole diameter and multiply it by 0.98 \\ | ||
| + | Then take the desired finished hole size and multiply it by 0.97 \\ | ||
| + | This gives you the range of stock removal best suited to the finish ream hole size. \\ | ||
| + | From that range refer to a standard drill chart to chose the appropriate standard drill size for your pre reamed hole size. \\ | ||
| + | Below are examples for calculating the pre-ream drill hole size for a 0.7500” finished hole diameter and a 0.2500” finished hole diameter. | ||
| + | |0.7500" x 0.98 = 0.7350"|0.7500" x 0.97 = 0.7275"| | ||
| + | |||
| + | Therefore, the appropriate range of the pre-ream drill hole size for a 0.7500” finished hole; \\ | ||
| + | 0.7275” – 0.7350” \\ | ||
| + | |||
| + | |0.2500" x 0.98 = 0.2450"|0.2500" x 0.97 = 0.2425"| | ||
| + | |||
| + | Therefore, the appropriate range of the pre-ream drill hole size for a 0.2500” finished hole; \\ | ||
| + | 0.2425” – 0.2450” \\ | ||
| + | |||
| + | If you are fine tuning your operation and are within the 2%-3% range; \\ | ||
| + | Try removing 2% of the reamer diameter for steels and tough alloys.. \\ | ||
| + | And 3% for non-ferrous and cast iron materials.. \\ | ||
| + | If you are rough reaming, stock removal can be up to 5% of the reamer diameter. \\ | ||
| + | |||
| + | The 2%-3% rule is great in theory. \\ | ||
| + | In the real world drill bits come in standard sizes. \\ | ||
| + | Most do not have time or money to wait for a special size drill bit to be made. \\ | ||
| + | You are usually forced to choose among standard drill bit sizes that are on the shelf. \\ | ||
| + | A Pre-Ream Drill Hole Size Chart below to help with this selection. Click here to download a printable PDF of the Pre-Ream-Drill-Hole-Size-Chart. This chart tells the appropriate standard drill bit size to choose when reaming fractional diameters from 1/8” to 1” in 1/64” increments. This chart allows for drill oversize based on research done by the United States Cutting Tool Institute. | ||
| + | |||
| + | ===== Pre-Ream Drill Hole Size Chart ===== | ||
| + | From Rock River Tool Inc. ((https://www.rockrivertool.com/documents/pre-ream-drill-size-chart.pdf)) | ||
| ^Reamer diameter \\ fraction - decimal (nominal)^Hole size \\ to leave 2%^Drill size \\ to leave 2%^Hole size \\ to leave 3%^Drill size \\ to leave 3%^ | ^Reamer diameter \\ fraction - decimal (nominal)^Hole size \\ to leave 2%^Drill size \\ to leave 2%^Hole size \\ to leave 3%^Drill size \\ to leave 3%^ | ||
| |1/8" - .1250"|.1225"|31|.1213"|3.0mm| | |1/8" - .1250"|.1225"|31|.1213"|3.0mm| | ||
