Kydex Spacing Calculator

How the Kydex Spacing Calculator Works

A thermoformed Kydex sheath lives or dies by its hole layout. The drilled eyelets have to line up perfectly with fixed-width hardware — a Tek-Lok, a Safariland mount, a DCC clip — and they have to sit far enough from the edge that the thermoplastic doesn't tear under the stress of the draw. This calculator turns a handful of inputs (hardware, thickness, length, build style) into an exact hole array, previews it live, and exports a true 1:1 drill template you can print, tape to the sheet, and centre-punch straight through. Every measurement runs internally in one base unit for precision and only converts to your chosen inches or millimetres at the end.

Kydex Thermoforming Temperatures and Thermal Shrinkage

Kydex is an extruded acrylic-PVC alloy: it takes the rigidity and formability of acrylic and the toughness and chemical resistance of PVC. To form it you heat the sheet into a pliable state — core forming temperatures generally sit between 325°F and 400°F (162–204°C) depending on grade and thickness — then press it around the item and let it cool. The formed part holds its shape below its Heat Deflection Temperature, which for standard grades like Kydex 100 or Kydex V is roughly 168–173°F (75–78°C).

Here is the catch that ruins beginners' sheaths: as the polymer cools from forming heat to room temperature, the chains contract, giving a predictable mold shrinkage of about 0.5% to 0.7%. Half a percent sounds trivial until you're mounting rigid hardware. If you drill from pre-heating measurements, the post-cooling shrink pulls the eyelets out of line with a fixed-width mount.

Eyelet Specifications, Material Thickness, and Drill Bits

The eyelets (makers often call them rivets) are what bind the sheets. The barrel length has to match the stack thickness or the eyelet splits, crushes, or fails to roll a clean flange when you flare it. That makes thickness the master input: pick it, and the correct eyelet and drill bit follow automatically.

Two shop-floor details worth internalising: use a brad-point bit rather than a standard twist bit, because the centre spur pierces cleanly and the flat spurs shear the hole instead of grabbing and tearing the thermoplastic; and set your flares with a proper die (such as a CKK Journeyman series die) under an arbor press to roll a blemish-free flange rather than a cracked, mushroomed mess.

Industry Standard Hardware Hole Spacing Measurements

The heart of the tool is its hardware database. Each mount has its own geometry, and a miss of even a millimetre makes the gear unusable, so the calculator toggles cleanly between imperial inches (the US tactical standard) and metric millimetres (common in Europe and Asia).

Blade-Tech Tek-Lok and the 9-hole grid

The Tek-Lok is the industry-standard polymer belt attachment, fitting belts up to 2.25 inches and using a fixed 9-hole grid. It gives you standard 0.5-inch (12.7 mm) vertical spacing plus 3/4-inch or 1-inch diagonal options so you can cant the mount for angled carry. The calculator loads this pitch and can rotate the array to your chosen carry angle.

Discreet Carry Concepts (DCC) slotted tolerances

The DCC Monoblock is a premium 10XX-steel clip that mounts through horizontal slotted holes measuring 0.220″ tall by 0.300″ wide, with a flexible centre-to-centre range of about 0.860″ to 1.15″. Because the mount is horizontal, the algorithm switches from a vertical column to a side-by-side pair and places the holes inside the slot tolerance rather than on fixed centres.

UltiClip and Safariland

UltiClip (Classic and 3+) rides on a single vertical alignment with variable sliding slots roughly 0.60″ to 1.00″ apart, while Safariland's QLS and Tek-Mount systems use a proprietary three-hole triangular pattern — an equilateral inverted triangle of fixed circular holes. The calculator handles each as its own layout rather than forcing one grid to fit all.

Holster Architectures: Taco versus Pancake Geometry

The build style decides how the holes are placed. A taco is a single sheet folded over the spine or slide, with binding eyelets down only one side; it trims up to half an inch off the profile and generates a single-column linear array. A pancake sandwiches the item between a molded front and a flat or molded back shell, running eyelets symmetrically down both sides for a wider, flatter profile that pulls tight to the body and supports dual belt loops. For a pancake the calculator takes the object's widest point, adds material clearance, and generates a mirrored bilateral array.

Edge Clearance and Adjustable Retention Spacing

Two more structural rules round out the layout. First, keep every eyelet centre at least 0.25 to 0.375 inch from the finished edge — closer than that and the Kydex can tear out during the draw. Second, modern holsters often use adjustable retention: instead of a permanent eyelet you place an EPDM rubber spacer (about 0.125″ thick) between the layers and compress it with a threaded Chicago screw. The calculator lets you flag one or more holes as retention points — typically just below a firearm's trigger guard or a fixed blade's choil — and marks them on the template so you know not to set a permanent rivet there.

Printing a True 1:1 Template — the Calibration Protocol

The single biggest failure in any print-to-drill workflow is the printer driver. Drivers love to default to “Scale to Fit Media,” “Shrink Oversized Pages,” or some arbitrary 97% scale to clear their hardware margins — and any of those silently compresses your hole spacing. That is why every template this tool generates prints a calibration line exactly 1 inch (or 100 mm) long with an explicit instruction to verify it with a ruler and set printer scaling to 100% or Actual Size. Measure the line first; only if it is exact are the hole positions trustworthy. This build draws the template with the browser's own physical print units rather than a pixel-based image library, so there is no rounding drift and no third-party dependency to slow the page down.

Scope and disclaimer. This tool provides layout planning estimates from published Kydex fabrication data, standard hardware spacings and typical shrinkage rates, for informational and educational use. Hardware tolerances and material batches vary, so always dry-fit against your actual mount and verify the printed calibration line before drilling. It is not professional engineering advice.