FS Series Vacuum Flange Sets

These versatile flange sets were among the first flanges developed for high vacuum service. FS Series is an excellent alternative to weld neck flanges when considering space-saving considerations. The socket weld design allows a smooth transition from the tube to the flange bore.

This comprehensive line of O-ring Socket Weld flanges is offered to accept tube OD’s as small as ¼” and as large as 6". FS Series flanges will operate in environments with pressures as low as 2 x 10-8 torr.

Available is Brass ASTM B 16 and 304 Stainless Steel

Set includes Viton® O-Ring, bolts, nuts, washers

Operating temperature 0 to 180°C

Available for ¼" OD to 6" OD tube

FS Series Vacuum Flange Sets Ordering Information

-BR = Brass, -SS = Stainless Steel

PART NUMBER	C'BORE DIA.	C'BORE DEPTH	BORE DIA.	FLANGE DIA.	BOLT CIRCLE	# OF HOLES / SIZE	FLANGE WIDTH
FS-25-BR	.258	1/16"	3/16"	1-1/8"	7/8"	3 holes 5/32"	3/16"
FS-25-SS	.258	1/16"	3/16"	1-1/8"	7/8"	3 holes 5/32"	3/16"
FS-37-BR	.388	1/16"	5/16"	1-1/8"	7/8"	3 holes 5/32"	1/4”
FS-37-SS	.388	1/16"	5/16"	1-1/8"	7/8"	3 holes 5/32"	1/4”
FS-50-BR	.508	3/32"	3/8"	1-3/8"	1-1/8"	3 holes 11/64"	1/4”
FS-50-SS	.508	3/32"	3/8"	1-3/8"	1-1/8"	3 holes 11/64"	1/4”
FS-62-BR	.633	3/32"	1/2”	1-3/8"	1-1/8"	3 holes 11/64"	1/4”
FS-62-SS	.633	3/32"	1/2”	1-3/8"	1-1/8"	3 holes 11/64"	1/4”
FS-75-BR	.765	3/32"	5/8"	1-3/4"	1-13/32"	3 holes 11/64"	1/4”
FS-75-SS	.765	3/32"	5/8"	1-3/4"	1-13/32"	3 holes 11/64"	1/4”
FS-100-BR	1.008	1/8"	7/8"	2-1/4"	1-3/4"	3 holes 7/32"	5/16"
FS-100-SS	1.008	1/8"	7/8"	2-1/4"	1-3/4"	3 holes 7/32"	5/16"
FS-112-BR	1.133	1/8"	1"	2-1/4"	1-3/4"	3 holes 7/32"	5/16"
FS-112-SS	1.133	1/8"	1"	2-1/4"	1-3/4"	3 holes 7/32"	5/16"
FS-150-BR	1.510	1/8"	1-1/4"	3"	2-9/16"	3 holes 7/32"	5/16"
FS-150-SS	1.510	1/8"	1-1/4"	3"	2-9/16"	4 holes 17/64"	5/16"
FS-162-BR	1.635	1/8"	1-3/8"	3"	2-9/16"	4 holes 17/64"	5/16"
FS-162-SS	1.635	1/8"	1-3/8"	3"	2-9/16"	4 holes 17/64"	5/16"
FS-200-BR	2.010	5/32"	1-3/4"	3-1/2"	3"	4 holes 17/64"	3/8"
FS-200-SS	2.010	5/32"	1-3/4"	3-1/2"	3"	4 holes 17/64"	3/8"
FS-212-BR	2.135	5/32"	1-7/8"	3-1/2"	3"	4 holes 17/64"	3/8"
FS-212-SS	2.135	5/32"	1-7/8"	3-1/2"	3"	4 holes 17/64"	3/8"
FS-250-BR	2.510	5/32"	2-1/4"	4"	3-1/2"	4 holes 17/64"	3/8"
FS-250-SS	2.510	5/32"	2-1/4"	4"	3-1/2"	4 holes 17/64"	3/8"
FS-300-BR	3.010	3/16"	2-3/4"	5"	4-1/4"	6 holes 17/64"	7/16"
FS-300-SS	3.010	3/16"	2-3/4"	5"	4-1/4"	6 holes 17/64"	7/16"
FS-312-BR	3.135	3/16"	2-7/8"	5"	4-1/4"	6 holes 17/64"	7/16"
FS-312-SS	3.135	3/16"	2-7/8"	5"	4-1/4"	6 holes 17/64"	7/16"
FS-400-BR	4.010	1/4"	3-3/4"	6"	5-1/4"	6 holes 21/64"	1/2”
FS-400-SS	4.010	1/4"	3-3/4"	6"	5-1/4"	6 holes 21/64"	1/2”
FS-412-BR	4.135	1/4"	3-7/8"	6"	5-1/4"	6 holes 21/64"	1/2”
FS-412-SS	4.135	1/4"	3/7/8"	6"	5-1/4"	6 holes 21/64"	1/2”
FS-500-BR	5.010	1/4"	4-3/4"	7"	6-1/4"	6 holes 21/64"	1/2”
FS-500-SS	5.010	1/4"	4-3/4"	7"	6-1/4"	6 holes 21/64"	1/2”
FS-600-BR	6.010	1/4"	5-3/4"	8"	7-1/8"	8 holes 21/64"	1/2”
FS-600-SS	6.010	1/4"	5-3/4"	8"	7-1/8"	8 holes 21/64"	1/2”

Product information is subject to change without notice. Product images may include options or accessories not included with the base model.

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For 50 years, Key High Vacuum Products, Inc. has been a trusted leader in precision-engineered stainless steel high vacuum weldments. With tens of thousands of unique weldments in use—from particle accelerators to industrial leak detectors—our expertise is proven across industries. Rooted in innovation, craftsmanship, and an unwavering commitment to customer satisfaction, we deliver high-quality, customized solutions that drive success. Every day, our team brings a unique blend of passion and precision, ensuring your goals are met with excellence—because your mission matters. Experience the Key High difference.

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