Taper, Sampson & Specialty Washer

What taper washers are for

A taper washer is a square washer that is thicker on one side than the other, with an 8 degree slope across its face. The flanges of tapered flange steel channels and I-beams slope, so a bolt through the flange would have its nut or head sitting on a slant. The taper washer fills that slope, so the nut or bolt head bears square and the bolt is not bent as it is tightened.

We carry two kinds, both 8 degree square: K0 taper washers to AS 1252:2016 (33 to 41 HRC), in hot dip galvanised or plain steel from M12 to M36, and AS 1252 taper washers (26 to 45 HRC galvanised, 35 to 45 HRC plain) in some sizes. Both sit in Hobson's structural range alongside its structural bolts, nuts and washers.

Taper washer sizes

How to fit a taper washer

1. Check the flange slope of the section you are bolting matches the washer's 8 degrees.
2. Turn the washer so its thick edge sits toward the outer edge of the flange, where the flange is thinnest, and its thin edge toward the web. The top face should then sit square to the bolt.
3. Use a taper washer on each tapered flange the bolt passes through, under the nut or the head on that side, and tighten the bolt to the specification for the job.

Sampson washers: large OD and thick

Sampson is the name on Hobson's range of hardened flat round washers. The two here are both hardened to 38 to 45 HRC:

• •Large OD Sampson washers (zinc yellow, 1/4 to 1 inch): a larger outside diameter than standard washers, to spread the load further. Hobson lists them for use with Grade 5 and Grade 8 bolts, on oversized or slotted holes, and where softer materials need the high clamp load only high-tensile bolts can give.
• •Thick Sampson washers (3/8 inch, 27 x 3.0mm, zinc yellow or zinc plated): extra thickness for better load spreading and to absorb shock and vibration. Hobson lists them for high-tensile bolting, industrial equipment and heavy vehicles.

Structural washers in this range

This range also includes hardened structural washers for structural bolt assemblies: EN 14399-5 K2 washers, hot dip galvanised (Hobson's structural guide lists them at 32 to 45 HRC), for K2 assemblies to EN 14399, and AS 1252 structural washers in plain steel and one galvanised size. Use the washer that matches the assembly class of your bolts and nuts, as the steelwork drawings specify. Our full structural washer range is on its own page.

TREP disc spring washers

TREP spring washers are anti-loosening washers made of three or four smooth tapered spring washers held together by a metal insert, so you handle one part instead of three or four. Clamped under a nut or bolt head they flatten and act as a compressed spring, keeping tension in the bolt even if the joint relaxes. The 4 layer plain steel TREP washer is made from carbon steel (over 0.75% carbon), core hardened, and Hobson lists it as compatible with bolt property classes 5.6 to 8.8. The 3 layer X8 stainless washer is listed for intense vibration, such as railways and heavy vehicles, electrical equipment and ships. For Belleville and other disc spring washers, see the disc spring washer page.

Which finish for where

• •Hot dip galvanised (taper, K2 and AS 1252 structural washers): high corrosion resistance; Hobson's finish comparison recommends it for long-term outdoor use, so it is the one for steelwork exposed to the weather, except in seaspray zones, where Hobson's corrosion guide for metal connectors calls for stainless.
• •Plain steel (taper, AS 1252 structural and TREP 4 layer): no coating, supplied lightly oiled to stop rust in the pack. For steelwork that is painted or kept dry inside.
• •Zinc yellow and zinc plated (Sampson washers): low corrosion resistance. Hobson recommends zinc yellow for low-corrosion environments or temporary fixing, and zinc plated for indoor, non-corrosive environments.
• •Match the washer's finish to the bolt and nut, so the whole joint lasts as long as its weakest part.

Taper and Sampson washers in Adelaide

Allmat supplies taper washers, Sampson washers, structural washers, nuts and bolts to steel fabricators, erectors and trade across Adelaide and South Australia. Add them to a quote with your bolts and nuts and we will price the lot.

Questions