The LCN TB/MS4EA is the OEM Thru Bolt and Machine Screw Pack from LCN, containing four thru bolts and four machine screws - one complete set for a single LCN door closer installation. Finish must be specified at time of order to match the installed closer body. The "4EA" in the part number designates four of each fastener type: four thru bolts for the door side and four machine screws that thread into those bolts from the opposite side to complete the mechanical connection through the door.

This is not the standard fastener pack that ships with LCN closers. Standard LCN door closer series (1260, 1460, 4010, 4040, and related) ship with SRT (Self-Reaming and Tapping) screw packs as their default fastener. The TB/MS4EA thru bolt and machine screw configuration is specified separately, either at time of closer order or ordered as a field replacement when thru bolts are required for the specific door type and installation.

What LCN Thru Bolts Do and When You Need Them

Standard LCN door closer installations use self-reaming and tapping screws that drive directly into the door face and the door frame without pre-drilling. These work reliably on solid hollow metal doors with adequate steel gauge and on solid wood doors where the screw threads can bite and hold.

Thru bolts are needed when the door material can't reliably anchor self-tapping screws under the sustained load of repeated door closer operation. The situations where this comes up: aluminum storefront stile doors where the extrusion wall is too thin for screw threads to hold, hollow core wood doors where the internal structure won't support long-term screw retention, and any installation where local building codes or specifier requirements call for through-bolted closer attachment as a higher-security fastening method.

The thru bolt passes completely through the door from the closer-mounted face to the opposite face. The machine screw threads into the opposite end of the thru bolt from the back face of the door, pulling tight and clamping the closer body against the door through a positive mechanical connection rather than relying on thread engagement in the door material alone.

LCN Fastener Specifications: Thru Bolt Thread Size and Door Thickness

LCN thru bolts are manufactured from steel with zinc plating. They accept 1/4-20 machine screws - the standard thread size across LCN's commercial door closer fastener system. The standard thru bolt in this pack is sized for 1-3/4" (44 mm) thick doors, which covers the vast majority of commercial steel and wood door installations.

For doors thinner than the standard 1-3/4", different thru bolt lengths are required: optional sizes are available for 1-5/8" (41 mm) and 1-3/8" (35 mm) door thickness. Per the Allegion knowledge base, these non-standard sizes must be specified when ordering - the TB/MS4EA pack covers standard 1-3/4" doors. For a closer mounted thru bolts on a thicker door (for example 2-3/4"), longer 1/4-20 x 3-1/2" machine screws are required.

LCN Fasteners Set: TB/MS4EA Application Across LCN Series

The TB/MS4EA thru bolt and machine screw pack is compatible across LCN commercial door closer series. The four-count per fastener type matches the standard closer body footprint - LCN surface-mounted closers use four mounting positions, so four thru bolts and four machine screws cover one complete installation.

This pack is used as a field replacement when the original SRT screws on an installed closer fail to hold - a symptom that shows up as the closer pulling away from the door face over time - or when a new installation requires through-bolt mounting from the spec. It is also the replacement pack when existing thru bolts corrode or strip on a closure that was originally installed with this fastener type.