1/4" Thick 5.25" OD Round Aluminum Backing Plate | 4 Through-Holes + Center Vent | Marine Grade 6061-T6
Part Number: 1019
5.25" OD Round Backing Plate with Center Weld Vent
Precision CNC-machined 6061-T6 aluminum round backing plate with four through-holes and a center vent. Designed as the backside of a sandwich assembly on fiberglass pedestal walls in saltwater marine environments. Four through-holes allow fasteners to pass through and accept nuts on the back side, while the center vent provides weld gas release during installation. Pairs with SKU 1020 Countersunk Pad for a matching hole pattern. Commonly used on top or through the side of a deck pedestal, as well as through the fiberglass skin of a hardtop or T-top.
| Material | Marine Grade 6061-T6 Aluminum |
| Outside Diameter | 5.25" (133 mm) |
| Thickness | 1/4" (0.250") |
| Through-Holes | 4 (25/64" dia. for 3/8" fasteners) |
| Center | 1 vent hole (weld gas release) |
| Pairs With | SKU 1020 (matching CS pad) |
| Shape | Round |
| Finish | Matte — tumbled, deburred, paint/powder coat ready |
| Weight | 0.46 lb |
Common Applications
T-tops, tuna towers, hard tops, radar arches, leaning posts, grab bars — commonly used on top or through the side of a deck pedestal, as well as through the fiberglass skin of a hardtop or T-top.
Frequently Asked Questions
What is a backing plate?
A backing plate reinforces the inside of a fiberglass pedestal wall. Fasteners pass through the exterior pad and the pedestal wall, and nuts thread onto the fastener behind the backing plate to lock the assembly in place.
What is the center vent hole for?
The center vent hole allows trapped air and gases to escape during welding, preventing blow-through and ensuring a clean, full-penetration weld.
Why four holes instead of three?
Four-hole patterns provide additional fastener points for heavier-duty mounting applications — radar mounts, outrigger bases, and multi-axis load points on T-tops and hard tops.
What size fasteners work with this plate?
The four through-holes are 25/64" diameter, sized for 3/8" fasteners. Use 3/8"-16 stainless hardware with matching nuts for best results.
- 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.
