2-Bolt Flange
About 2-Bolt Flange
A two-bolt flange unit is a mounted ball bearing whose housing bolts flat against a wall, panel or frame member with two fasteners on a diagonal, so the shaft passes through the surface rather than sitting on top of it. The insert self-aligns in the housing to take up static misalignment between the two supports. The category is led by the Sealmaster SFT standard-duty and MSFT medium-duty cast iron units and the Browning VF2S, VF2E and VF2B series, with light-duty stamped steel SSF2S units, 316 stainless and composite CRES housings for washdown, and System Plast polymer units.
Also known as: 2-bolt flange bearings, two bolt flange bearing, two-bolt flanged units, diamond flange bearings, flange mount bearings
Series in this category
- Sealmaster SFT and MSFT — Standard-duty SFT in 1/2 through 2 3/16 inch and 20 through 55 mm bores, medium-duty MSFT, and the -T Skwezloc concentric-locking versions of both.
- Sealmaster CRFTS-PN and CRFTC-PN — Two-bolt flanges in 316 passivated stainless steel or high-strength composite, with PN Gold inserts and food-grade GoldPlex-FG grease.
- Browning VF2S, VF2E and VF2B — Intermediate-duty 100 series, standard-duty 200 series and medium-duty 300 series in setscrew, eccentric and BOA concentric locking, plus SSF2S stamped steel.
- Square flange units — The four-bolt SF and MSF alternative when the mounting surface allows a square pattern.
- 3-bolt flange bracket units — Sealmaster FB brackets for mounting against a wall where a flange bracket suits the frame better.
Related guides: Bearing selection guide, Bearing lubrication basics, ER bearings explained, Cross-reference help
How to choose 2-bolt flange
- Measure the bolt spacing and bolt size on the existing holes
- The two mounting holes fix the unit before the bearing does. Every listing states its bolt spacing and bolt size, which on the SFT series runs from 3/8 inch on the 1/2 inch bore to 5/8 inch at 2 inch bore. A unit that matches the bore but not the hole pattern means drilling the frame.
- Choose the duty from the load, not the bore
- Standard-duty SFT and medium-duty MSFT share bore sizes but differ in insert and housing section, and the Browning 100, 200 and 300 series are graded the same way from intermediate through medium duty. The basic dynamic rating listed for each part is what a load calculation is checked against.
- Pick the locking method for the shaft and the duty cycle
- Setscrew locking is the standard on SFT and VF2S. The -T suffix on a Sealmaster unit adds the Skwezloc concentric locking collar, VF2B uses the BOA concentric lock and VF2E an eccentric collar. Concentric locks clamp the shaft all round and are preferred where vibration has to be kept to a minimum.
- Match the housing material to the environment
- Cast iron is the standard housing. The CRFTS-PN unit is 316 passivated stainless steel and the CRFTC-PN a high-strength composite, both supplied with PN Gold inserts and NSF H1 food-grade grease for washdown lines, and the composite unit is rated for 0 to 150 degrees F. Stamped steel SSF2S units are light duty and are not relubricatable.
- Confirm the seal and the temperature range
- SFT units carry a felt seal with a contact seal optional and are rated -20 to 220 degrees F; Browning VF2 units carry a contact seal, with a flinger on the 200 and 300 series, rated -20 to 200 degrees F. Self-alignment is plus or minus 2 degrees on the Sealmaster units and 1.5 degrees on the Browning units.
Specifications explained
| Specification | What it means |
|---|---|
| Bore size | The shaft the insert fits. Sealmaster inch bores are coded in sixteenths, so SFT-20 is 1 1/4 inch, and metric standard-duty bores are coded 2## in 5 mm steps, so SFT-205 is 25 mm. |
| Bolt size and bolt spacing | The fastener diameter and the center distance between the two mounting holes, which must match the holes already in the frame. |
| Bearing type or duty | Standard, intermediate or medium duty, which sets the insert section and the dynamic load rating for a given bore. |
| Lock type | Setscrew, Skwezloc or BOA concentric collar, eccentric collar, or double setscrew, which is how the insert grips the shaft. |
| Housing material | Cast iron, ductile iron, 316 stainless steel, composite, polyamide or stamped steel. It decides corrosion resistance and the temperature rating. |
| Self-alignment | The static misalignment the insert can take up in the housing: plus or minus 2 degrees on Sealmaster units, 1.5 degrees on Browning units. |
| Seal type | Felt, contact, contact with flinger, or the HPS seal on the CRES lines. It sets how much contamination and washdown the unit tolerates. |
Common questions
What does the T mean in SFT-20T?
It is the Sealmaster Skwezloc locking collar option. The base SFT-20 locks with setscrews; the -T version uses a concentric collar that clamps around the shaft instead of biting into it, is designed for commercial-grade turned and polished shaft tolerances, and is preferred where vibration has to be kept low. The bore code 20 is 20/16, or 1 1/4 inch, in both cases.
When is a two-bolt flange the wrong choice against a four-bolt?
When the frame already carries a square pattern, or has room for one: the four-bolt SF and MSF units mount on four fasteners and are listed in the same duties and bore sizes. The two-bolt diagonal pattern suits narrow frame members and panels where a square flange would overhang. Both use the same insert families, so the bearing itself is the same choice either way.
Are stainless two-bolt flange bearings stocked?
Yes. The Sealmaster CRFTS-PN series is a two-bolt flange in 316 passivated stainless steel with a PN Gold insert, an HPS seal and GoldPlex-FG food-grade grease, rated -20 to 220 degrees F. The CRFTC-PN uses the same insert in a high-strength composite housing rated 0 to 150 degrees F.
Which bore sizes does the SFT series cover?
Inch bores from 1/2 through 2 3/16, in sixteenth steps across most of the range, with reduced-bore R versions at 1 1/4 and 2 inch, and metric bores from 20 through 55 mm numbered SFT-204 through SFT-211. The medium-duty MSFT series is listed alongside it, and the Browning VF2S 100 series also starts at a 1/2 inch bore.
