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LDT - Large Diameter Tapcon

Friday, June 28, 2013
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Purchase LDTs

Head Style

The head of the LDT is a hex washer with serrations under the head for anti-rotation to prevent back out.  A length identification code is stamped to allow for easy inspection.

Rust Resistance

The standard large diameter tapcon comes with a zinc coating for indoor dry applications.  The zinc plated LDT meets ASTM B695 & B633 specifications for zinc plating and is 5um + .0002 thickness. For outdoor applications where moisture may be present the EnvireX™ coated LDT should be considered.  Stainless steel LDT’s are manufactured for use in wet applications and are made from a 410 stainless steel.

Type of Bit

Hold tolerance is critical to ensure proper holding values.  The bit that must be used for drilling the hole in the concrete should meet ANSI Standards B212.15-1994.  The bit must have a carbide tip and be used in a hammer drill set in the hammer and rotation mode.

Hole Diameter

The diameter of the hole to be drilled must be slightly smaller than the designated diameter of the large diameter Tapcon being installed.

LDT DiameterBit Diameter
3/8” 5/16”
1/2” 7/16”
5/8” 1/2”
3/4” 5/8”

Hole Perpetration

After the correct diameter hole has been drilled in the concrete it must be cleaned of all dust and debris.  This can be done using a vacuum, wire brush or compressed air.

Hole Depth

The hole needs to be drilled a minimum of 1/4” deeper than the large diameter will penetrate the concrete.  This extra space at the bottom of the hole ensures that the LDT will not bottom out in the hole and allows space for the dust created during the tapping process to fall into and out of the way.

Minimum Embedment

Diameter of AnchorMinimum Embedment Depth
3/8” 1-1/2”
1/2” 2”
5/8” 2-3/4”
3/4” 3-1/4”

Installations Instructions for LDTs

WARNING – Failure to follow these instructions can result in serious personal injury. For any concerns or questions regarding proper installation, application or appropriate use of the large diameter tapcon, call the technical department of the manufacturer, ITW/Redhead, at 1-800-899-7890. Always wear safety glasses that meet ANSI standards. Using the wrong diameter drill bit will affect the holding values and may cause failure.

  1. Select the proper diameter, head style, and length of large diameter Tapcon screw.
  2. Choose proper diameter drill bit for the diameter of the anchor being installed.
  3. Drill hole ¼” deeper than the tapcon anchor is embedded into the base material.
  4. Drill hole. To ensure proper drill bit length and depth of the hole, refer to the selection chart.
  5. Drive anchor.

More Tapcons

Large Diameter Tapcon Zinc Plated - LDT

Large Diameter Tapcon Stainless - LDTS

Purchase LDTs


Always use personal protective equipmentAs with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.

Article Written By:
Mike Pistorino, Vice-President Operations





Concrete Fastening Systems, Inc. has over 40 years of experience selling concrete fasteners. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality... "your satisfaction is guaranteed". We ship all orders the same day the order is received.

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