Hand Tap set of 3 pieces ISO 529 HSS-G - BA 0 x 25.4

Specific applications

Typical tasks include threaded holes in components whose drawing explicitly calls for BA 0 to BS 93. The component drawing must specify the thread designation BA 0; check the material against the suitability information below.

Existing threads can be recut if their size, pitch and condition allow it. This does not restore missing material or severely damaged threads.

Suitable materials

HSS-G is intended for general use and readily machinable materials up to approximately 900 N/mm². These include unalloyed and low-alloy steels, structural steels, carbon steels, case-hardening steels, free-cutting steels, spheroidal graphite cast iron and malleable cast iron, as well as selected non-ferrous metals.

The following table shows example materials and represents only a selection of the suitable materials.

Close section

Cutting diameter D	6 mm
Shank diameter D2	6.3 mm
Overall length L1	66 mm
Thread length L2	19 mm
Square drive	5 mm

Close section

• Standard: ISO 529
• Tool material: HSS-G – ground high-speed steel
• Product type: Hand tap set
• Design: 3-piece set
• Thread type: British Association thread
• Thread standard: BS 93
• Thread size: BA 0
• Thread tolerance: medium
• Thread direction: Right-hand thread
• Flute form: N (straight flutes)

Chamfer of the three cutting stages

The chamfer is the front cutting section. Chamfer forms A, D, C differ in chamfer length; the tools each have the complete thread profile.

1. Secure the workpiece
   Clamp the workpiece securely so that it cannot rotate. The hole must be readily accessible so that the tap can be started squarely and guided in line with the hole axis throughout the operation.
2. Prepare the tapping drill hole
   Drill the tapping drill hole for BA 0 to the recommended diameter of 5.1 mm. You can find a clear overview of selection and calculation in the VÖLKEL article Calculating the tapping drill hole size for taps. Blind holes must also be drilled sufficiently deeper.
3. Deburr and clean the hole
   Remove the burr at the hole entrance and clear away loose drilling chips. A clean, lightly chamfered hole makes it easier to start the taper tap squarely and prevents damage to the first thread.
4. Start with chamfer form A
   Clamp the tool with the long chamfer in a suitable tool holder and align it precisely with the hole axis. Apply sufficient cutting lubricant for tapping to the tool and hole. Guide it with steady pressure and without sideways loading. The tools in this version differ in their chamfer forms, rather than having successively reduced versions of the complete profile.
5. Use chamfer form D
   Clear loose chips from the hole if necessary. Insert the tool with chamfer form D into the existing thread in line with the hole axis and again use cutting lubricant suitable for the material. Avoid sideways pressure and excessive force.
6. Finish with chamfer form C
   Finally, insert the tool with the short chamfer and apply sufficient suitable cutting lubricant again. Guide it steadily and allow sufficient space for the chamfer and chips in blind holes. The tool must not be pressed against the bottom of the hole.
7. Check the thread
   Remove chips and residual cutting lubricant from the finished thread. Then check the thread size and ease of engagement using a suitable inspection tool, such as a GO/NO-GO thread plug gauge if compliance with the required tolerance must be demonstrated.

Further guidance is available in the VÖLKEL blog article Cutting clean threads: how to produce internal and external threads .

• Hand Tap Taper ISO 529 Form A HSS-G - BA 0 x 25.4 (89400-1)
• Hand Tap Second ISO 529 Form D HSS-G - BA 0 x 25.4 (89400-2)
• Hand Tap Bottoming ISO 529 Form C HSS-G - BA 0 x 25.4 (89400-3)

Which dimensions does BA 0 represent?

BA 0 has a thread outside diameter of 6 mm and a pitch of 1 mm. The digit 0 is a size designation and does not mean a diameter of zero millimetres.

Which tapping drill do I need for BA 0?

For BA 0, the recommended tap drill diameter is 5.1 mm. Guidance on preparing the tapping drill hole. The simplified metric tapping drill hole formula is not applied indiscriminately to this thread designation.

Can I machine BA 0 with an M6 × 1 tool?

No. Similar diameters and the same pitch do not make the thread systems identical. BA 0 is designated to BS 93 and must not be replaced by a metric M6 tool.

What is the correct sequence for the 3-piece set?

Tool with chamfer form A, tool with chamfer form D and tool with chamfer form C. The tools differ in chamfer length; they each have the complete thread profile. Tapping step by step.

Why does the name for BA 0 also mention 25.4 threads per inch?

The pitch is 1 mm. Relative to an inch of 25.4 mm, this corresponds to 25.4 threads per inch. Both specifications describe the same pitch here.

Which materials is HSS-G intended for?

HSS-G is intended for general use in readily machinable materials up to 900 N/mm², particularly unalloyed and low-alloy steels. The material overview in the first section shows the assigned example materials. Comparing tool materials for hand taps.

Are the three BA tools classic profile stages?

The individual tools in this set are assigned to chamfer forms A, D and C. Each has the complete profile and differs in chamfer length. Select them according to the chamfer form and individual item number.

Which tap wrench fits this hand tap?

The holder must securely grip the 5 mm square drive. Compare this value with the specified clamping range of the tap wrench or tool holder. Choosing the right tap wrench.

Which individual tools can I reorder for item 89400?

The set includes a tool with chamfer form A 89400-1, a tool with chamfer form D 89400-2, a tool with chamfer form C 89400-3. When reordering, also compare the standard, thread and tool material.