JAPAN SKC HAND TAPES - No: 804 BSPT

More info

The SKC No. 804 series is the professional Japanese standard for Pipe Taps. While the No. 803 series you mentioned previously is for standard fastener threads (UNF/UNC/Metric), the 804BT specifically designates BSPT (British Standard Pipe Taper) threading.

Technical Specifications (804BT BSPT)

BSPT threads are tapered at a ratio of 1:16, designed to create a pressure-tight seal by mating the threads themselves (usually with the help of thread sealant or PTFE tape).

Nominal Size (Inches)	Threads Per Inch (TPI)	Pitch (mm)	Drill Size (mm)
1/16"	28	0.907	6.20
1/8"	28	0.907	8.20
1/4"	19	1.337	11.00
3/8"	19	1.337	14.50
1/2"	14	1.814	18.00
3/4"	14	1.814	23.50
1"	11	2.309	29.50

Key Characteristics

Material: Typically manufactured from SKS2 (Alloy Tool Steel) for standard hand use, though High-Speed Steel (HSS) variants exist for machine use.
Thread Angle: 55° (standard for British pipe threads).
Set Composition: Unlike the 3-piece sets for fastener threads (No. 803), the No. 804 pipe taps are often sold as single taps because the taper itself performs the starting and finishing work in one pass.
Identification: Look for the SKC logo and the "804" or "804BT" marking on the shank to ensure it is the Japanese-made Tapered Pipe version.

Difference Between 804BT and 805BS

It is easy to confuse these two in the SKC catalog:

No. 804 (BSPT/BT): Tapered thread (most common for plumbing/hydraulics to prevent leaks).
No. 805 (BSPS/BSPP): Parallel (straight) thread (used for mechanical joints where an O-ring or washer provides the seal).

[!IMPORTANT]

Because BSPT threads are tapered, do not tap too deep on your first attempt. If you run the tap all the way in, the hole may become too large for the fitting to seal properly. It is best to tap, test the fit with your pipe, and tap slightly further if needed.