Installing a strike plate on a metal door frame requires drilling and tapping holes into steel rather than simply driving screws into wood. The process is straightforward with the right tools, but the technique differs enough from wood-frame work that skipping steps can leave you with misaligned holes or a latch that won’t catch. Here’s how to do it correctly.
Tools and Materials You’ll Need
Metal frames use machine screws instead of wood screws, so you’ll need a few items beyond a basic screwdriver. Gather a power drill, the correct size drill bit for your screws, a matching tap and tap handle, a center punch, a hammer, masking tape or lipstick, a pencil, and the strike plate with its screws.
The most common strike plate screws for metal frames are 8-32 and 12-24 machine screws. For an 8-32 screw, you need a #29 drill bit (0.136 inches). For a 12-24 screw, use a #16 drill bit (0.177 inches). If your strike plate came with combination screws (half machine thread, half wood thread in sizes like 12-24 x 1 inch), those work in both metal and wood applications and are the standard for commercial frames.
Choosing the Right Strike Plate
Metal door frames typically come with a pre-cut rectangular cavity called a “prep” or “mortise” already formed during manufacturing. The standard commercial cavity measures 1-1/4 inches wide by 4-7/8 inches tall, following the ANSI/BHMA specification. The main difference between ANSI and the older ASA standard is the corner radius: ANSI uses a 1/8-inch radius while ASA uses a 1/4-inch radius. This matters when you’re buying a replacement plate, because even though the overall dimensions are identical, a plate with the wrong corner radius won’t sit flush.
If your frame already has a prep cut, match your new plate to that opening. Residential metal frames sometimes use a T-strike, which has an extended lip. Bring the old plate to the hardware store if you’re replacing one, or measure the cavity precisely if you’re starting fresh.
Marking the Exact Position
Getting the latch and strike plate to line up perfectly is the most important step. There are a few reliable methods.
The simplest trick, used by locksmiths and contractors alike, is the lipstick method. Coat the face of the latch bolt with lipstick, chapstick, or any thick colorant. Close the door so the latch presses against the frame. When you open the door, the colored mark on the frame shows you exactly where the latch contacts. That mark is your center point for the strike opening.
A more precise approach uses a short dowel with a headless nail pressed into one end. Slip the dowel into the latch bore hole, close the door, and press the dowel toward the jamb. The nail tip scores a precise center mark on the metal frame. This is essentially what professional locksmiths use for new installations.
You can also measure directly. Find the center height of the latch from the floor or from the top of the door, then transfer that measurement to the jamb. Next, measure from the face of the closed door to the flat portion of the latch bolt. On the jamb side, measure from the door stop to that same depth. Where these two measurements intersect is where the center of your strike opening goes.
Drilling and Tapping the Frame
Once you’ve marked the strike plate position, hold the plate against the frame and trace the screw holes with a pencil or scratch awl. Use a center punch and hammer to make a small dimple at each screw location. This prevents the drill bit from wandering on the hard steel surface.
Drill the holes using the correct bit size for your screw threads. Go slowly and use cutting oil or a drop of machine oil on the bit to reduce heat and friction. Metal frames are typically 16-gauge or 14-gauge steel, so you’re not drilling through much material, but rushing will dull the bit and produce sloppy holes.
After drilling, use the matching tap (8-32 or 12-24) to cut threads into each hole. Insert the tap into the hole by hand using a tap handle, turning it clockwise. Back the tap out a quarter turn for every full turn forward to clear metal shavings. Keep the tap perpendicular to the frame surface. Once threaded, blow out any metal chips and test-fit your screws.
If the frame already has a mortise pocket for the plate body, simply align the plate into the pocket and drive the machine screws. If there’s no existing pocket and the plate needs to sit flush, you’ll need to file or grind a shallow recess into the frame, though most commercial metal frames come pre-prepped for this.
Adjusting for a Tight or Loose Latch
A properly installed strike plate should let the latch bolt snap fully into the opening with no play. If the door rattles or feels loose when closed, the latch isn’t seating deeply enough into the strike.
One effective fix is adding frame silencers. These small rubber bumpers press into holes on the strike-side jamb (many metal frames have pre-drilled silencer holes for this purpose). Place three silencers on the strike jamb: one near the top, one near the bottom, and one close to the strike plate. They hold the door at a consistent distance from the stop, which forces the latch to engage more tightly in the strike opening.
If the door sits too far from the strike or too close, the issue is often hinge alignment rather than the strike plate itself. Shimming the hinges can shift the door’s position relative to the frame. A shim placed behind the hinge leaf on the door side pushes the latch edge closer to the strike jamb. A shim between the hinge leaf and the frame moves the door in the opposite direction. Adjusting the bottom and middle hinges has the most effect on how the latch meets the strike.
Fire-Rated Frames: What to Know
If your metal frame carries a fire rating, any modification has to maintain the integrity of that rating. Under NFPA 80, the fire safety standard for door assemblies, the strike plate is a listed component of the rated assembly. That means the frame, door, hardware, latch, hinges, and strike plate all work together as a tested unit.
Replacing a strike plate with an identical or equivalent listed product is generally fine. But if you’re drilling new holes in a different location, enlarging the existing prep, or swapping to a non-listed strike plate, the altered assembly may no longer comply with its fire rating. In commercial buildings, this can create code violations during inspections. For fire-rated frames, stick with same-size replacements from the original manufacturer or a plate specifically listed for that frame and door combination.
Common Mistakes to Avoid
- Skipping the center punch. Drilling into bare steel without a starter dimple almost guarantees the bit will skate across the surface, scratching the frame and landing off-target.
- Using wood screws. Wood screws won’t hold in hollow metal. They’ll strip out quickly. Always use machine screws with properly tapped holes, or combination screws designed for metal applications.
- Forcing a misaligned plate. If the latch doesn’t engage smoothly, resist the urge to just bend the strike lip. Re-mark, re-drill, and get the alignment right. A poorly aligned strike plate wears out the latch mechanism over time and compromises security.
- Over-tightening screws. Machine screws in thin-gauge steel can strip the threads you just cut if you crank them too hard. Snug is enough.