Обший каталог Yamawa 2016 - 2017 - страница 797

13. How to set the tap's oversize to meet with the coating
margin of internal threads


Description of products
1) Relation between coating thickness and pitch diameter when applied with coating
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

(μm)
Basic pitch diameter : 5.350mm
M6×1 Basic pitch diameter : 5.350mm
Information


Internal thread tolerance 6H : 0~+150μm (Tolerance : 150μm)
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
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