Standart MAS 403, JIS B 6339

Application of the standard MAS 403, JIS B 6339.

Shank tools are used in milling machines and CNC machining centers.
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Specification of the standard MAS 403, JIS B 6339.

Model	L1	L2	L3	L4	L5	L6	d1	d2	d3	d4	d5	D	a	b	T
BT30	484	22	24	7	136	16.3	31.75	12.5	56.144	46	38	8	2	16.1	M12
BT40	65.4	27	30	9	16.6	22.6	44.45	17	75.679	63	53	10	2	16.1	M16
BT50	101.8	38	45	13	23.2	35.4	69.85	25	119.02	100	85	15	3	25.7	M24

Standard MAS 403, JIS B 6339 additional information.

The BT "Bonsai Taper" standard was developed by the Japan Machine Tool Association to create a unified standard for milling machines.

History of the creation and application of the MAS 403 standard

The MAS 403 standard was developed in Japan for the machine tool industry, with the aim of standardizing spindle holders and tools used in metalworking on CNC machines. It was adopted in 1982 and is also known as the BT (bayonet mount) holder. Its main purpose is to increase the productivity and accuracy of machine tools, ensuring compatibility between different types of equipment.

BT holders are distinguished by a symmetrical flange and can be used for high-speed machining. They are used in metalworking, mechanical engineering and in the production of precision parts.

Standart JIS B 6339.

JIS B 6339 is a Japanese industrial standard that regulates taper shank toolholders for CNC machine tools. It is equivalent to the international standards ISO 7388-1 and DIN 69871, making it compatible with most modern spindle systems. The standard describes the dimensions and tolerances of BT-type (bayonet mount) taper shank toolholders used for high-precision metal machining.
The main objective of JIS B 6339 is to ensure the accuracy, reliability and interchangeability of tools between different manufacturers.

Machine tooling using MAS 403 standard.

BT30 accessories for milling machines
BT40 accessories for milling machines
BT50 accessories for milling machines