3/8" Thick 4.125" OD Round Aluminum Tapped Pad | 5/16"-18 UNC Thread | Marine Grade 6061-T6
Part Number: 1009
4.125" OD Round Aluminum Tapped Pad — 5/16"-18 UNC Thread
Precision CNC-machined 6061-T6 aluminum round tapped pad with a single 5/16"-18 UNC threaded hole. Designed to receive a threaded fastener directly — no nut required on the back side. Commonly used where a threaded mounting point is needed on a fiberglass deck surface, radar arch, or T-top assembly in saltwater marine environments.
| Material | Marine Grade 6061-T6 Aluminum |
| Outside Diameter | 4.125" (105 mm) |
| Thickness | 3/8" (0.375") |
| Threaded Hole | 1 (5/16"-18 UNC tapped) |
| Shape | Round |
| Finish | Matte — tumbled, deburred, paint/powder coat ready |
| Weight | 0.56 lb |
Common Applications
T-tops, tuna towers, hard tops, radar arches, leaning posts, grab bars, bow rails, outrigger mounts, rod holders — anywhere a threaded mounting point is needed on a fiberglass or aluminum surface.
Frequently Asked Questions
What is a tapped pad?
A tapped pad has internal threads cut into its hole so a fastener screws directly into the pad — no nut or backing plate required on the opposite side. This makes it ideal for single-sided access installations.
What size fastener does this pad accept?
The tapped hole is 5/16"-18 UNC — use a 5/16"-18 stainless bolt or machine screw for a secure threaded fit.
Can I use this on a fiberglass deck?
Yes — the pad distributes fastener load across a wider surface area, preventing pull-through or deck damage. Thread the bolt into the pad from the exterior side; the pad threads hold it securely.
How is this different from a backing plate?
A backing plate has straight through-holes and requires a nut on the back side. A tapped pad has internal threads — the fastener screws into the pad itself, so no back-side nut is needed.
- Local pickup available
- One Business Day Shipping
- Call us Mon.-Fri. 9:00 a.m. to 4:00 p.m. if in any doubt.
Due to this item's size and weight we can only ship it in an economical way via Less Than Truckload (LTL) consolidated land shipping, and only to the contiguous 48 States.
For shipping inquiries to AK, HI, PR, US-VI, and international shipping, please contact us first at sales@weldingworldinc.com.
All of the destinations above we can only serve as a Free Carrier (or FCA) modality, that requires the customer to contract and pay for their carrier service of choice. We can still ship the item, but only to a warehouse/receiving office within the 48-contiguous States.
In plain terms what this means is that if you want to ship your product to any non-contiguous US territory or internationally, you, the customer, has to provide us with the warehouse address of the carrier that serves your locality with an address within the contiguous 48-US States, as we do not ship overseas on our own.
