Обший каталог Yamawa 2016 - 2017 - страница 797

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13. How to set the tap's oversize to meet with the coating margin of internal threads 1) Relation between coating thickness and pitch diameter when applied with coating Description of products Dwg.1 shows the relation between coated internal thread and pitch diameter * Thickness of coating is measured at right angle to flank face. Pitch diameter is measured at right angle to axis (radially). Drawing 1 Coating thickness 3μm half of pitch diameter decrease (6μm) Where t (coating thickness) equals 3μm, by using following formula, oversize is roughly caluculated. Pitch diameter decrease 2t×2 (both side of threads) = 3μm×2×2 =12 μm (rough over size) 2) How to specify taps for coating 1. We suppose the accuracy of finished internal threads is 6H class, and inspection is done with GP-6H and NP-6H. 2. We suppose the disperse of coating thickness is controlled within the tolerance of 8~16μm. The disperse of coating thickness, when it is exchanged into pitch diameter, will become the disperse of 32~64μm. 3. Accuracy of internal threads before coating is the thread accuracy which GP-6H goes through (OK), even when max coating (64μm) is applied. And this accuracy is the thread accuray which NP-6H does not go through (OK), when min coating (32μm) is applied. 4. We propose followings for inspecting the accuracy of internal threads before coating : GO gauge before coating : GP-6H+64 5. Next, based on GO gauge before coating and NOT GO gauge before coating, we study to specify the suitable accuracy of the tap before coating. M6×1 How to specify the accuracy of tap before coating (Coating thickness 8~16μm) Pitch diameter of JIS 6H Pitch diameter of JIS 6H GP-6H NP-6H Internal threads before coating Internal threads before coating GP-6H+64 NP-6H+32 Suggested cutting taps Suggested roll taps Basic pitch diameter : 5.350mm (μm) M6×1 Basic pitch diameter : 5.350mm Internal thread tolerance 6H : 0~+150μm (Tolerance : 150μm) Information Technical Accuracy GP-6H : +7~+17μm Accuracy NP-6H : +150~+160μm Internal thread tolerance before coating : +64~+182μm (Tolerance : 118μm) Accuracy GP-6H+64 : +71~+81μm Accuracy NP-6H+32 : +182~+192μm Accuracy of suggested cutting taps (P5.5) : +90~+110μm Accuracy of suggested roll taps (G12) : +140~+152μm Technical-22 793