Lock, Barrel & Specialty Nut

What is in this specialty nut range

This page gathers Hobson's specialty nuts that do not belong to one of the bigger nut ranges: three all-metal locking nuts, two 316 stainless internal hex barrel nuts that give a finished head on both sides of a joint and two class 8 flange nuts. The older AS 1252:1983 pattern structural nuts are now on the structural nut page. Hobson's anti-vibration paper defines prevailing torque as the torque needed to turn a fastener on its mating thread while there is no load in the joint; a nut with a built-in locking element builds that resistance in, so it does not spin loose freely.

• •Hobloch hex nuts (304 stainless): the metric coarse sizes are made to DIN 980 Type M. The M10 and M12 fine thread and 1/2 BSW Hobloch nuts are made to Hobson's own HEC specification in 304 (A2).
• •ERM dual slot self-lock nuts with free-spinning washer (Lanfranco): a dual slotted self-locking hexagon with a captive free-spinning disc spring, which Hobson says maintains tension in the joint under dynamic loads. Hobson lists consistent prevailing torque, locking slots that work independently of bolt tension, and an all-metal nut that is reusable; the 316 version also lists no galling. On reuse, Hobson's technical note (250225TD) adds that every use reduces their effectiveness, so check the prevailing torque before refitting one.
• •GSL cone lock hex nuts (Lanfranco, ISO 7042): Hobson calls them a reliable all-metal locknut that maintains prevailing torque in high temperature applications.
• •Barrel nuts with internal hex (316 stainless): an internally threaded barrel with a countersunk or pan head and a hex key socket, fitted from the opposite side to the screw so both faces show a finished head.
• •Hex flange nuts (JIS B1190, class 8): Hobson says the flange removes the need for a washer and spreads the load over a wider area than a regular hex nut. The galvanised M8 has no serrations, so the material can sit flush; the zinc yellow M8 and M10 fine nuts are serrated.

Every nut in this range

Select a row to open that type in the selector, then pick the size.

How the ERM, GSL and Hobloch nuts lock, and when a joint needs one

The ERM nut locks with its slotted hexagon and keeps the joint loaded with its captive disc spring washer; the GSL nuts and the Hobloch DIN 980 Type M nuts are all-metal locking nuts (no document we hold makes a locking claim for the Hobloch fine thread and BSW nuts). Hobson's ERM data sheets give a working temperature range: -50 to 300°C for the class 8 zinc and top coat nut and -200 to 400°C for the 316 A4-80 nut. The GSL sheet gives no range but says it maintains prevailing torque at high temperature. Hobson publishes no temperature range for the Hobloch nuts in the documents we hold, and its anti-vibration paper notes that nylon insert nuts are not suitable for joints exposed to high temperatures.

Hobson's anti-vibration paper finds that a preload above about 65% of the fastener's yield load is enough to stop loosening at the vibration levels commonly seen in the field. Where a joint is subject to vibration and the bolt cannot be pretensioned to at least 65% of its proof load, the paper says a locking device must be used, and under severe vibration one may be needed anyway. It also warns that two identical nuts locked against each other will hardly ever work, because both nuts rotate together under vibration.

Hobson lists the ERM and GSL nuts for mining and processing, railway and transportation, energy, military and industrial work. It publishes no tightening torques for the Hobloch, ERM or GSL nuts in the documents we hold, so tighten them to the equipment maker's or designer's specification.

ERM and GSL nut sizes

Internal hex barrel nuts: sizes and uses

Hobson lists the countersunk barrel nut for furniture, hidden connections, timber connections and double-ended countersunk connections, used with its 316 countersunk socket cap screws for a matching appearance on both sides, and as a replacement for the nut on Tygabolt anchors to give a countersunk finish. The pan head barrel nut is listed for furniture connections in steel, timber or heavy-duty plastic, as a decorative nut on a protruding male thread, and as a replacement nut on masonry fixings; its internal hex drive gives more leverage when tightening.

Hobson publishes no load or strength rating for these internal hex barrel nuts. When one replaces the nut on an anchor or masonry fixing, the anchor's capacity applies to its own nut, so check the anchor's data or the engineer before swapping it, and the anchor's own installation conditions still apply; and for anything structural, or that carries people or loads, the fixing comes from the engineer or designer's specification. For furniture connector nuts, Post Torx security barrel nuts and Phillips barrel nuts, see the barrel nut page.

Fitting internal hex barrel nuts and locking nuts

1. Barrel nuts: drill through so the screw passes from one side and the barrel shank (S in the table) fits from the other. Hobson publishes no hole sizes, so drill a test hole in an offcut first.
2. Check the screw reaches well into the barrel's thread (TL) without bottoming out, then tighten with the hex key in the table while holding the screw.
3. ERM, GSL and Hobloch nuts: Hobson's tightening torque sheets say a nut with a locking element must have full threads all the way through that element, with at least one full thread protruding from the nut.
4. Stainless screw into a stainless nut: Hobson's galling sheet suggests slowing the installation speed, lubricating the threads (with a lubricant high in molybdenum disulfide) and using different stainless grades for the bolt and the nut.

Finishes: stainless, zinc and top coat, galvanised and zinc yellow

• •304 and 316 stainless (Hobloch, ERM 316, GSL and internal hex barrel nuts): Hobson's corrosion guide for metal connectors gives stainless (304 or 316) or hot dip galvanising as the minimum where a fixing is exposed to the weather, stainless only in seaspray zones and 316 within 2m of a pool.
• •Zinc and top coat (ERM class 8): Hobson's finish comparison sheet does not rate this finish. For joints exposed to the weather, use the 316 ERM nut.
• •Hot dip galvanised (M8 flange nut): Hobson rates it high corrosion resistance and recommends it for long term outdoor use.
• •Zinc yellow passivate (serrated flange nuts): low corrosion resistance; Hobson recommends it for low corrosion environments or temporary fixing.

Specialty nuts in Adelaide

Allmat supplies ERM, GSL and Hobloch nuts, 316 internal hex barrel nuts, flange nuts and the bolts and screws to go with them to fabricators, maintenance crews, joiners and trade across Adelaide and South Australia. Add them to a quote with the rest of your list and we will price the lot.

Questions