1/4-20 x 1-1/2 Pan Head T30 Torx Stainless Bolt (qty x10)

Blue Alpine part F00105-00 is a T30 Torx screw in inch sizes: 1/4-20 thread, 1-1/2 in long, pan head, stainless steel. Ten come in the pack for $10.49. Most of the screws we carry are metric, so it’s worth confirming that yours really is inch before you order.

Reading 1/4-20 x 1-1/2

Three numbers, all inch. The 1/4 is the nominal major diameter, about 6.35 mm. The 20 is threads per inch, the standard coarse pitch for that diameter in the Unified system, so the full name is 1/4-20 UNC. One thread every 1/20 in works out to 1.27 mm. The 1-1/2 is the length: 1.5 in, or 38.1 mm.

On a pan head, length runs from the underside of the head to the tip. The head itself isn’t counted, which is the opposite of how flat heads are measured. Wikipedia’s page on the Unified Thread Standard has the full table of inch sizes.

1/4-20, 1/4-28 or M6?

Three threads sit close enough together to cause trouble.

• 1/4-20 UNC: 6.35 mm, 20 threads per inch. This T30 Torx screw.
• 1/4-28 UNF: same diameter, finer thread, 28 per inch.
• M6 x 1.0: 6 mm diameter, 1 mm pitch, the nearest metric size.

None of them interchange. Try to mix them and the thread binds within a turn or so, and forcing it ruins both parts. A thread pitch gauge tells them apart in seconds. Without one, hold the old screw against a ruler and count the crests across one inch. Twenty means 1/4-20.

Picking the bit for a T30 Torx screw

T30 is the biggest Torx size among our fasteners. The small M3 flat heads take a T15, the M4 Torx screws and two of the M5s take a T20, and the M5 x 8 mm countersunk takes a T25. This T30 Torx screw needs its own bit.

Watch out for T27. It sits between T25 and T30 and looks nearly the same on the bench. In a T30 recess a T27 feels as if it fits, then cams out once there’s real torque on it and rounds the lobes. Read the marking on the bit before you start. Neither our T20 screwdriver nor the 5 mm hex key will drive it. You’ll want a T30 bit or driver. Wikipedia’s Torx article lists the sizes.

Running in an inch and a half of stainless

Thirty-eight millimeters of thread is a lot of friction, and when stainless meets stainless the threads can seize partway in. That’s galling. Start the T30 Torx screw by hand and keep it square to the hole. Then go slowly. A power driver at full speed is the quickest way to lock a screw halfway home. If resistance climbs suddenly, reverse a turn, clear the threads, and carry on.

The pan head has a flat underside, so it clamps squarely on a flat surface. On soft material, a flat washer of the right size spreads the load. A pan head also stands above the surface, so leave clearance for it if anything slides or closes over the spot.

Checking an old T30 Torx screw

• Diameter: about 6.35 mm (0.25 in) across the threads. A 6.0 mm reading points to M6.
• Pitch: 20 crests per inch, 1.27 mm apart.
• Length: about 38 mm from under the head to the tip.
• Head: domed pan head with a flat face underneath.
• Drive: six-lobe recess that takes a T30 bit with no play.

Quick answers

Can a T30 Torx screw replace an M6?

No. The diameter is close, but the threads don’t match. Replace like with like.

Is this T30 Torx screw fully threaded?

The listing doesn’t say, and we won’t guess. If thread length matters for your job, ask us before ordering.

Who can help me check?

We can. Call +1 (443) 514-5708, or write to us through the support page with your manual’s part number. Other hardware is in fasteners and tools.