Short answer: leave the box's blank in place if it ships one, drill it to 20.5 mm [0.81 in] for an M20 gland, and bed it on butyl tape. A side cutout sized for a 25-32 mm [1-1.25 in] conduit nipple cannot close around a 6.5 mm Ethernet cable on its own. A plate resting 5 mm [0.2 in] or more past the hole edge, screwed down over a butyl ring, brings the opening back to the gland's rating. On a typical stainless M20 that is IP66. When the RJ45 is already crimped, order the M20 variant with a split seal; the two seal halves close on the cable while the plug passes through the body during assembly. Count on an hour with a drill, a step bit and four screws.
Where the water gets past a big cutout
Compact camera boxes carry side openings meant for a rigid conduit nipple, so the maker expects a threaded pipe to fill the hole. A 6.5 mm [0.26 in] Ethernet cable centered in a 28 mm [1.1 in] cutout leaves more than 10 mm of open ring on every side. That ring faces up-slope under a soffit, where water runs down the cable and wind pushes spray at the gap. The lid gasket is doing its job; the hole is the leak, and it deserves the same treatment as any oversized enclosure cable opening. If the cable comes through the wall instead, sealing a camera junction box back entry without conduit covers that route.
The finished opening carries the lowest rating of its three parts: the box's own gasket, the plate joint you add, and the gland. All ratings named here are manufacturer ratings; our stainless enclosures are rated NEMA 4X / IP66 by the manufacturer and not UL listed. Your gland carries its own maker's marking. A plate screwed down over butyl tape is a gasketed joint, the same construction as a lid seal. For soffit and wall service, treat the finished joint as IP66: tight against driving rain and hose jets, with no immersion claim.
What you need
| Part | Spec for a soffit camera box | Why it matters |
|---|---|---|
| Plate | 304 stainless, 1.5 mm [0.06 in], for cutouts to 50 mm [2 in] | Stiff enough to clamp the butyl, no rust streaks on the wall |
| Plate, coastal | 316L at the same thickness | Holds near salt spray and pool chemicals |
| Gland | M20 for pre-terminated Ethernet, nickel-plated brass or stainless, rated IP66 or better by its maker | Passes the plug, closes on the jacket |
| Seal bed | Butyl tape, the non-curing rubber sealing kind | Stays pliable and sticky, squeezes into surface unevenness |
| Drills | 4 mm pilot bit, step bit to 20.5 mm [0.81 in], cutting fluid | Clean hole in stainless without work-hardening it |
| Fasteners | Four M4 stainless screws through 4.2 mm [0.17 in] holes | Even clamp that squeezes the butyl to a fillet |
Gland makers list nylon, nickel-plated brass and stainless bodies in metric and NPT threads, so match the thread to the hole you can drill cleanly. Under a dry soffit, nickel-plated brass is a sound choice; stainless matches a stainless plate and holds its finish near the coast. If the same box also lands an armored power cable, pick that gland for the armor first: M20 armored-cable gland selection follows the cable's construction, not just its diameter.
Sizing the plate: a 28 mm cutout with a pre-terminated Cat6
The inputs, each with its basis:
- Cutout: 28 mm [1.1 in], measured with calipers; compact camera boxes run 25-32 mm [1-1.25 in] across.
- Cable: outdoor Cat6, unshielded, at 6.5 mm [0.26 in] jacket OD, typical for 23 AWG conductors.
- Plug: RJ45 about 12 mm [0.47 in] across the moulded body.
- Gland: M20 with split seal; a standard M20 seal clamps 6-12 mm [0.24-0.47 in], per typical gland listings.
- Plate and fixings: 304 stainless at 1.5 mm [0.06 in], four M4 screws through 4.2 mm [0.17 in] holes.
Two rules size the plate. Bearing: the plate must rest on solid metal at least 5 mm [0.2 in] past the cutout edge on every side, so plate side = cutout + 2 x bearing. Gland hole: a metric gland clears at its thread nominal plus 0.5 mm, so M20 drills at 20.5 mm [0.81 in], the figure set out in the M20 cable gland hole size article.
The arithmetic, written out:
- Bearing: (60 - 28) / 2 = 16 mm [0.63 in] per side, more than three times the 5 mm minimum.
- Gland hole: 20 + 0.5 = 20.5 mm [0.81 in], centered.
- Seal fit: the 6.5 mm jacket sits inside the 6-12 mm clamp range; a heavier 7 mm outdoor jacket still fits.
- Screw land: screw centers 8 mm in from the plate edge with 4.2 mm holes, so a hole's inner edge sits 8 + 2.1 = 10.1 mm from the edge; the cutout edge lies 16 mm in, leaving 16 - 10.1 = 5.9 mm of metal around each screw.
The result: a 60 x 60 x 1.5 mm 304 plate, 20.5 mm center hole, four M4 screws set 8 mm in from the corners, all bedded on butyl tape.
The decision: cutouts up to 50 mm [2 in] take this build on 1.5 mm plate with four screws. Above 50 mm, go to 2 mm [0.08 in] plate with six screws, or have the factory cut the gland holes. With the plate on butyl and the split-seal M20 closed on the jacket, the opening carries the gland's rating: IP66 for rain and hose service.
Install it in six steps
Pull the run dead first: PoE delivers up to 57 V DC on the same pairs that carry the data.
- Mark the plate. Set the 60 x 60 mm plate square over the cutout and scribe its outline plus four screw points, each 8 mm in from a corner. Punch the centers.
- Drill the gland hole. Pilot at 4 mm, then open with a step bit to 20.5 mm [0.81 in] at low speed with cutting fluid on stainless. Deburr both faces so the gland's O-ring seats flat; cutting a hole in a stainless enclosure walks through speeds, bits and burrs.
- Dry-fit the gland. Run the body through from outside and the locknut inside. Confirm the flange covers the hole with margin on all sides before any tape goes down.
- Lay the butyl bed. Press one continuous strip of butyl tape around the cutout on the box face, ends overlapped about 10 mm [0.4 in]. Butyl stays tacky for years, so you can work at your own pace.
- Screw down evenly. Drive the four M4 screws in a diagonal pattern until butyl squeezes out around the whole plate; that squeeze-out is your gasket.
- Load the gland. Drop the nut and seal halves out, pass the RJ45 through the body from inside, then close the split seal on the jacket behind any moulded boot. Tighten the nut until a firm tug moves the box rather than the cable. Installing a gland without losing the rating covers locknut torque and O-ring seating, and gland sizing for an RJ45 connector covers split-seal ranges. Finish with a drip loop below the gland.
Checks that prove the seal
- Continuous squeeze-out. Butyl shows as an unbroken fillet around the whole plate; a dry stretch marks an open joint.
- Tug test. A firm pull moves the box before it moves the cable, and the seal grips the jacket rather than a sliding boot.
- Hose test. IEC 60529 proves the second digit 6 with a 12.5 mm nozzle delivering 100 L/min from about 3 m [10 ft] for at least 3 min. A hard garden-hose spray on the plate for 3 minutes is a fair field stand-in; open the cover, and dry passes.
- Re-check after the first storm, before the mount is buttoned up for good.
Where these installs lose the rating
- An oversize gland hole. A 24 mm hole leaves the M20 O-ring without its seat; hold the drill at 20.5 mm [0.81 in].
- Sealing on the boot. The moulded RJ45 boot is oversize and irregular, so slide it back and let the split seal close on the round jacket.
- A stretched butyl ring. Stretching thins the tape to nothing at the corners; run the strip flat with a 10 mm overlap at the ends.
- A weep hole added for luck. NEC 314.15 permits 3-6 mm [1/8-1/4 in] drainage openings in boxes and conduit bodies listed for damp or wet locations, and that hole drops this assembly below IP66. Under a dry soffit, seal the cutout instead of draining it.
- Silicone as the only seal. Keep cured silicone as a cosmetic fillet on top of the butyl if you like; the butyl bed carries the joint.
When to order the box with the holes already cut
Two big cutouts, or a new build, tip the balance toward a box that arrives with its gland holes cut at the factory. The cutout designer lays out gland holes, button holes and display openings on any face, checks spacing and sends the layout with the quote. The custom stainless enclosures page compares a catalog stainless body with new openings against a fully custom body in 304 and 316L, with a drawing checklist for the approval print. Everything is delivered in 10 business days anywhere in the world, counted from your order; for custom work, from your approval of the drawing. If the entry grows into a whole row of glands, read when to specify a stainless enclosure with a gland plate, and for the fundamentals of holes, seals and window openings, start with the cutouts and glands guide.
Enclosures for this job
Catalog sizes that suit the job this article answers, picked from its subject; open one for its full specifications.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 10 × 8 × 6 in | 304 stainless | 10 x 8 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 12 × 8 in | 304 stainless | 16 x 12 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 6 × 6 × 4 in | 304 stainless | 6 x 6 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Can I fill the oversized cutout with silicone instead of fitting a plate?
It holds for a while, but one-part silicone skins in about an hour, needs a full day to cure, and lets go of smooth metal after a few seasons of sun. It also blocks re-entry: adding a cable later means cutting it all out. A 60 x 60 mm plate on butyl tape keeps the opening at IP66 and comes off with four M4 screws in a minute.
Which gland size passes a cable that already has an RJ45 plug crimped on?
An M20 gland built for pre-terminated Ethernet: the body bore passes the 12 mm [0.47 in] plug, and a two-part seal closes on the 6.5 mm jacket. If you can only find one-piece seals, step up to M25, which typically clamps 13-18 mm and drills at 25.5 mm [1.0 in]; the plug passes through the open body before the seal goes on.
Should I drill a weep hole in the bottom instead of sealing the cutout?
Only when the box genuinely takes hose-down or washdown spray. A plain weep hole drops the assembly below IP66, and NEC 314.15 allows 3-6 mm [1/8-1/4 in] drains only in boxes listed for damp or wet locations. Under a dry soffit, seal the cutout fully. Where the box does get hosed, fit a breather drain rated IP66 at the lowest point and the assembly stays at 66.
Does the plate go inside the box or outside over the cutout?
Outside, over the cutout. Rain and spray pressure push an outside plate onto its butyl bed, which is the direction the joint seals best. An inside plate leaves the 28 mm hole facing the weather, and pooled water finds the tape edge; if the look forces the plate inside, press a butyl fillet through the cutout ring as well.
