ALuminum Set Screw FAQ

ALUMINUM SET SCREWS DISCLAIMER AND FAQ

IMPORTANT WARNING ON IMPROPER USE OF ALUMINUM SET SCREWS

Tin plated aluminum set screws (slotted and hex socket) are commonly used in OEM electrical aluminum bodied industrial wire connectors.

1) Screws sold separately are strictly NOT intended for repairing or replacing screws in ANY wire connector outside of the OEM (Original Equipment Manufacturer) factory environment which is field inspected by UL and CSA to assure compliance to the tested build procedures.

2) UL and CSA DO NOT PERMIT ANY unauthorized field repair or modification to any connector bearing the UL or CSA logos (see UL White Book).
It is entirely the responsibility of the purchaser to obtain all of the approvals from the AHJ (Authority(ies) Having Jurisdiction) covering the application.

3) Screws used in electrical connectors vary WIDELY in length, aluminum alloy, conductivity, plating, waxing, friction coefficient, nose geometry, drive size, hex socket specs, or slot geometry and torque capability, and many other factors. There is NO “standard replacement screw” for electrical connectors across the many brands and designs of wire connector.

4) Any and all use or misuse of aluminum set screw for electrical or mechanical or any other uses is entirely the responsibility of the purchaser to validate and duly indemnifies seller of all.

5) Tin plated aluminum screws on this site meet the standard alloy composition for 2024 (RoHS Lead Free) or in some cases 2011 (RoHS with lead exemption). In addition, electroplating with tin, over copper, over zincate will be present on the exterior. Numerous other metallic trace elements may be present.

6) Corrosion: due to the wide range of galvanic elements and alloys on the surface of these screws the presence of electrolytes including rain water will cause galvanic corrosion of the screw itself and or the mating component(s).

Consequently, only dry applications should be considered.
High or low pH environments are particularly corrosive to aluminum.

7) No representations for fitness for any use or any application are given or implied.

8) Possible applications for aluminum Set Screw are listed here.

9) See also information in the Aluminum Set Screw FAQ

2015-16 GUIDE INFORMATION FOR ELECTRICAL EQUIPMENT — THE WHITE BOOK

Field Modifications

What happens to the Listing if a UL-Listed product is modified in the field? An authorized use of the UL Mark is the manufacturer’s declaration that the product was originally manufactured in accordance with the applicable requirements when it was shipped from the factory. When a UL-Listed product is modified after it leaves the factory, UL has no way to determine if the product continues to comply with the safety requirements used to certify the product without investigating the modified product. UL can neither indicate that such modifications ‘‘void’’ the UL Mark, nor that the product continues to meet UL’s safety requirements, unless the field modifications have been specifically investigated by UL. It is the responsibility of the Authority Having Jurisdiction (AHJ) to determine the acceptability of the modification or if the modifications are significant enough to require one of UL’s Field Engineering Services staff members to evaluate the modified product. UL can assist the AHJ in making this determination. An exception for a field modification authorized by UL is when the product has specific replacement markings. For example, a switchboard may have specific grounding kits added in the field. The switchboard is marked with a list of specific kit numbers that have been investigated for use in that particular switchboard. Only grounding kits that are included on the marking on the product have been investigated for use in that product. If a party wishes UL to determine if the modifications made to a UL Listed product comply with UL requirements, the appropriate Field Engineering Service can be initiated to investigate the modifications. This investigation will only be conducted after UL consults with the AHJ to ensure that UL’s investigation addresses all areas of concern and meets all of the AHJ’s needs. If you have any questions or would like to inquire about a Field Evaluation, contact Field Services at +1-877-UL-HELPS, prompt #2 (+1-877-854-3577) or visit http://www.ul.com/field/.

POSSIBLE APPLICATIONS FOR ALUMINUM SET SCREWS

Aluminum set screws may be of interest to review and test for suitability in the following applications:

1) Mechanical devices where steel or brass or stainless steel is not appropriate.

2) Non-magnetic equipment where steel is not appropriate.

3) Non-ferrous equipment where steel is not appropriate.

4) High frequency devices where only non-magnetic alloy components are low enough in inductive properties.

5) Light weight devices where the high weight of steel or brass is not appropriate.

6) Where thermal or electrical conductivity properties superior to steel, stainless steel, bronze, or or common brasses is more appropriate

7) Spark free applications where steel alloy is not appropriate but aluminum/copper/tin is appropriate.

8) Thread filler. To fill a non-ferrous alloy component internal thread while sectioning with a saw to preserve thread and the sectioning saw from damage that might compromise inspection results or cutting equipment.

9)Mechanical fuse or shear pin. Where the screw is used for its ability to shear or slip before damage to a more expensive part.

10) Development of bona fide electrical wire connector devices which are tested to all relevant safety standards prior to use.

Feel free to contact us for assistance in designing electrical wire connectors using a wide range of existing tooled extruded shapes and UL486 rated wire connector formats to enable rapid ramping up to higher quantity production.

Aluminum set screws offered for sale on this web site are typically:

1. Inch “TPI” threads, USA Unified System (UNC / UNF).

2. “Oval points” meaning some form of radius nose or “cone points”, meaning conical in overall shape or a combination of “oval and cone”.

3. Hexagon socket drive (inch or metric across flats key size) or slotted flathead screwdriver drive.

4.Tin plated (tin over copper over zincate over aluminum base material).

5. Waxed to provide some “dry” thread lubrication to minimize thread galling under load.

6. Made from “aircraft” type aluminum known as “hard” alloy 2024 tempered to T4 hardness or other 2000 series grades like 2011.

HISTORY

Aluminum set screws have been widely used in aluminum electrical connectors in UL markets for about 50 years.

Aluminum connectors much more widely used than copper connectors for higher currents since it is more cost effective than copper per amp conducted.

Transmission lines and utility power panels are predominantly aluminum.

Only aluminum wire connectors are commonly able to accept both copper and aluminum wire (Dual Rated under UL486A-B).

ADVANTAGES OF ALUMINUM SCREWS

Aluminum alloy has over 50% more conductivity than common brass which is used to make many electrical screws. Aluminum alloy has about twice the conductivity of steel or silicon bronze.

Aluminum screws are about 1/3 the weight of brass or copper alloys screws.

Aluminum screws are non-ferrous and so is non-magnetic.

The thermal conductivity of aluminum alloy is also superior to that of brass, steel, or bronze.

Aluminum screws expand and contract along with an aluminum alloy mating part which assists reducing stresses from thermal cycling.

Tin plated aluminum screws have been used successfully in copper electrical bodied wire connectors designed specifically for copper conductors. Aluminum screw electrical and thermal conductivity being superior to steel or brass screws in this application.

GALVANIC

Aluminum screws used in electrical connectors are typically tin plated which allows them to be in gas tight or casual contact with copper or aluminum wire, with no long term galvanic activity in dry locations.

Aluminum screws are not suitable for wet (electrolytes such as rainwater) environments. Tin plated aluminum screws are not designed for outdoor use in wet conditions.

Some protection can be given using suitable oxidation proofing contact greases and total protection can be given if totally immersed in a water proof barrier grease made for the purpose. This typically would be a filled elastomeric boot designed for the total exclusion of water and other electrolytes.

MECHANICAL

Applications that could lead to fatigue cracking are not recommended. Aluminum alloys are prone to creep relaxation under load which should factored in.

Hexagon sockets are made deeper than standard in order to improve performance of hex key stripping.
Small hexagon sockets in aluminum require hex keys to be sharp cornered, not forged-rounded type bits in order to meet full available strip torque. Hex keys must always be inserted to full depth before applying torque.
Slotted drive screws require accurately fitted flat bits which fill the entire slot in terms of slot length and slot width. Bits should not have draft angles which invite bit cam-out and damage to slot walls.

Significant downward force to keep slotted bits fully engaged is required to avoid slot damage.

Marks and folds found in cold form screws