M8 Dog Point Set Screw (Dog Point Grub Screw), ISO 4028

A headless M8 × 1.25 dog point set screw (ISO 4028), turned with a 4 mm hex key. Available as 9 lengths from 8 to 40 mm, each as simplified and threaded STEP.

How these parts are made, and what the levels mean: read the method

• Also searched as: M8 set screw, M8 x 8 to M8 x 40 set screws
• Model id: iso4028-m8
• Standard: ISO 4028:2003 · thread M8 × 1.25, ISO metric coarse, right hand

Lengths

Length (mm)	Part key	Simplified	Threaded
8	iso4028-m8x8	STEP	STEP
10	iso4028-m8x10	STEP	STEP
12	iso4028-m8x12	STEP	STEP
16	iso4028-m8x16	STEP	STEP
20	iso4028-m8x20	STEP	STEP
25	iso4028-m8x25	STEP	STEP
30	iso4028-m8x30	STEP	STEP
35	iso4028-m8x35	STEP	STEP
40	iso4028-m8x40	STEP	STEP

Dimensions

Symbol	Name	min	nom	max	Modeled	Rule	Level
P	Thread pitch		1.25		1.25	nominal	L1
s	Socket width across flats	4.02	4	4.095	4.0575	midpoint of min–max	L1
e	Socket width across corners	4.583			4.583	single limit (min), modeled at the limit	L1
t_short	Socket depth, short screws	3			3	single limit (min), modeled at the limit	L1
t_long	Socket depth, long screws	5			5	single limit (min), modeled at the limit	L1
dp	Point diameter, flat and dog point	5.2		5.5	5.35	midpoint of min–max	L1
dt	Truncation diameter, cone point			2	2	single limit (max), modeled at the limit	L1
dz	Cup diameter, cup point	4.7		5	4.85	midpoint of min–max	L1
z_short	Dog length, short dog point	2		2.25	2.125	midpoint of min–max	L1
z_long	Dog length, long dog point	4		4.3	4.15	midpoint of min–max	L1
fl_angle	Flat point chamfer angle			50	50	single limit (max), modeled at the limit	L2
cone_angle	Cone point included angle, long lengths		90		90	nominal	L2
cone_angle_short	Cone point included angle, short lengths		120		120	nominal	L1
dog_angle	Dog point chamfer angle			50	50	single limit (max), modeled at the limit	L2
cp_angle	Cup point outer chamfer angle			50	50	single limit (max), modeled at the limit	L2
cup_angle	Cup recess included angle		120 ref		120	reference value	L2
P	Coarse thread pitch		1.25		1.25	nominal	L1
tap_drill	Tap drill diameter		6.75		6.75	nominal	L1
d1	Basic minor diameter		6.646835		6.646835	nominal	L1
ch_angle	Chamfered end angle			50	50	single limit (max), modeled at the limit	L2
dh_fine	Clearance hole, fine series		8.4		8.4	nominal	L1
dh_medium	Clearance hole, medium series		9		9	nominal	L1
dh_coarse	Clearance hole, coarse series		10		10	nominal	L1

Thread and holes

• Tap drill: 6.75 mm (method: d − P), L1, sources amesweb-tap-drill, rule-tap-drill.
• Clearance hole (ISO 273): close 8.4, normal 9, loose 10 mm (L1: fine, medium and coarse series (albany-clearance, wikipedia-de-clearance)).

Drawing

As a PDF: CC-ISO4028-SZ-M8.pdf.

Goes with the M8 dog point set screw

• Hex key: 4 mm, the socket's nominal width across flats (s) in the table above.

The M8 dog point set screw beside the M6

The M8 is the largest of the 7 ISO 4028 dog point set screws published here, from M2 to M8.

• Thread pitch (P): 1.25 mm on the M8 dog point set screw, against 1 mm on the M6.
• Socket width across flats (s): 4 mm on the M8 dog point set screw, against 3 mm on the M6.
• Socket width across corners (e): at least 4.583 mm on the M8 dog point set screw, against at least 3.443 mm on the M6.
• Socket depth, short screws (t_short): at least 3 mm on the M8 dog point set screw, against at least 2 mm on the M6.
• Socket depth, long screws (t_long): at least 5 mm on the M8 dog point set screw, against at least 3.5 mm on the M6.
• Point diameter, flat and dog point (dp): 5.2 to 5.5 mm on the M8 dog point set screw, against 3.7 to 4 mm on the M6.
• Truncation diameter, cone point (dt): up to 2 mm on the M8 dog point set screw, against up to 1.5 mm on the M6.
• Cup diameter, cup point (dz): 4.7 to 5 mm on the M8 dog point set screw, against 2.75 to 3 mm on the M6.

Other sizes

• One size smaller: M6 Dog Point Set Screw (Dog Point Grub Screw), ISO 4028, 3 mm hex key.

Documents

• CC-ISO4028-DS-M8.pdf: M8 datasheet: values with levels, lengths, sources
• CC-ISO4028-SZ-M8.pdf: M8 drawing: this size's values on the views
• parts.json: the part record of every length (the platform contract)

Sources

accu-iso4027, albany-clearance, amesweb-iso4026-4029, amesweb-tap-drill, fasten-it-iso4026, fasten-it-iso4027, fasten-it-iso4028, fasten-it-iso4029, fuller-iso4026, fuller-iso4027, fuller-iso4028, fuller-iso4029, iso4753-2011-sample, iso4753-2011-sample-text, rule-basic-minor, rule-tap-drill, wikipedia-de-clearance, wikipedia-iso261. Full citations: the method page and this size's datasheet.

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