GB /T 3 - 1997 Run-outs, undercuts and chamfers for general purpose metric screw threads (ISO 3508:1976 / ISO 4755:1983)

外螺紋

1.1 外螺紋收尾和肩距的型式與尺寸按圖 1 和表 1 的規定。螺紋收尾的牙底圓弧半徑不應小于對完整螺紋規定的最小牙底圓弧半徑。

表 1 （mm）

螺距 P	收尾 x （max）		肩距 a (max)
螺距 P	一般	短的	一般	長的	短的
0.2	0.5	0.25	0.6	0.8	0.4
0.25	0.6	0.3	0.75	1	0.5
0.3	0.75	0.4	0.9	1.2	0.6
0.35	0.9	0.45	1.05	1.4	0.7
0.4	1	0.5	1.2	1.6	0.8
0.45	1.1	0.6	1.35	1.8	0.9
0.5	1.25	0.7	1.5	2	1
0.6	1.5	0.75	1.8	2.4	1.2
0.7	1.75	0.9	2.1	2.8	1.4
0.75	1.9	1	2.25	3	1.5
0.8	2	1	2.4	3.2	1.6
1	2.5	1.25	3	4	2
1.25	3.2	1.6	4	5	2.5
1.5	3.8	1.9	4.5	6	3
1.75	1.3	2.2	5.3	7	3.5
2	5	2.5	6	8	4
2.5	6.3	3.2	7.5	10	5
3	7.5	3.8	9	12	6
3.5	9	4.5	10.5	14	7
4	10	5	12	16	8
4.5	11	5.5	13.5	18	9
5	12.5	6.3	15	20	10
5.5	14	7	16.5	22	11
6	15	7.5	18	24	12
參考值	≈2.5 P	≈1.25 P	≈3 P	=4 P	=2 P

注：應優先選用“一般”長度的收尾和肩距；短”收尾和“短”肩距僅用于結構受限制的螺紋件上；產品等級為B 或C級的螺紋緊固件可采用“長”肩距。

1.2 外螺紋退刀槽的型式和尺寸按圖 2 和表 2 的規定。過度角（α）不應小于30°。

表 2 （mm）

螺距 P	g₂ （max）	g₁ （min）	d_g	r ≈
0.25	0.75	0.4	d-0.4	0.12
0.3	0.9	0.5	d-0.5	0.16
0.35	1.05	0.6	d-0.6	0.16
0.4	1.2	0.6	d-0.7	0.2
0.45	1.35	0.7	d-0.7	0.2
0.5	1.5	0.8	d-0.8	0.2
0.6	1.8	0.9	d-1	0.4
0.7	2.1	1.1	d-1.1	0.4
0.75	2.25	1.2	d-1.2	0.4
0.8	2.4	1.3	d-1.3	0.4
1	3	1.6	d-1.6	0.6
1.25	3.75	2	d-2	0.6
1.5	4.5	2.5	d-2.3	0.8
1.75	5.25	3	d-2.6	1
2	6	3.4	d-3	1
2.5	7.5	4.4	d-3.6	1.2
3	9	5.2	d-4.4	1.6
3.5	10.5	6.2	d-5	1.6
4	12	7	d-5.7	2
4.5	13.5	8	d-6.4	2.5
5	15	9	d-7	2.5
5.5	17.5	11	d-7.7	3.2
6	18	11	d-8.3	3.2
參考值	≈3 P	/	/	/

注： 1. d 為螺紋公稱直徑代号。

2. dg 公差為：h13 ( d > 3mm )；
h12 ( d ≤ 3mm )。

1.3 外螺紋始端端面的倒角一般為 45°，也可采用 60°或 30°倒角；倒角深度應大于或等于螺紋牙型高度。對搓（滾）絲加工的外螺紋，其始端不完整螺紋的軸向長度不能大于 2P。

内螺紋

3.1 内螺紋收尾和肩距的型式與尺寸按圖3 和表3 的規定。

表 3 （mm）

螺距 P	收尾 X max		肩距 A
螺距 P	一般	短的	一般	長的
0.2	0.8	0.4	1.2	1.6
0.25	1	0.5	1.5	2
0.3	1.2	0.6	1.8	2.4
0.35	1.4	0.7	2.2	2.8
0.4	1.6	0.8	2.5	3.2
0.45	1.8	0.9	2.8	3.6
0.5	2	1	3	4
0.6	2.4	1.2	3.2	4.8
0.7	2.8	1.4	3.5	5.6
0.75	3	1.5	3.8	6
0.8	3.2	1.6	4	6.4
1	4	2	5	8
1.25	5	2.5	6	10
1.5	6	3	7	12
1.75	7	3.5	9	14
2	8	4	10	16
2.5	10	5	12	18
3	12	6	14	22
3.5	14	7	16	24
4	16	8	18	26
4.5	18	9	21	29
5	20	10	23	32
5.5	22	11	25	35
6	24	12	28	38
參考值	= 4P	= 2P	≈ 6~5P	≈ 8~6.5P

注: 應優先選用“一般”長度的收尾和肩距；容屑需要較大空間時可選用“長”肩距，結構限制時可選用“短”收尾。

3.2 内螺紋退刀槽的型式與尺寸按圖4 和表4 的規定。

表 4 （mm）

螺距 P	G₁		D_g	R ≈
螺距 P	一般	短的	D_g	R ≈
0.5	2	1	D+0.3	0.2
0.6	2.4	1.2		0.3
0.7	2.8	1.4		0.4
0.75	3	1.5		0.4
0.8	3.2	1.6		0.4
1	4	2	D+0.5	0.5
1.25	5	2.5		0.6
1.5	6	3		0.8
1.75	7	3.5		0.9
2	8	4		1
2.5	10	5		1.2
3	12	6		1.5
3.5	14	7		1.8
4	16	8		2
4.5	18	9		2.2
5	20	10		2.5
5.5	22	11		2.8
6	24	12		3
參考值	= 4P	= 2P	/	≈0.5 P

注：
1. “短”退刀槽僅在結構受限制時采用。
2. Dg 公差為 H13。
3. D 為螺紋公稱直徑代号。

3.3 内螺紋入口端面的倒角一般為 120°，也可采用 90°倒角；端面倒角直徑為：（1.05～1)D。

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