Tap
Glossary · Threads & Fits
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- Threads & Fits
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- 2 terms
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- Written in the shop
A tap is a cutting tool that forms an internal thread in a drilled hole.
In practice
The hole is first drilled to a specific tap drill size that leaves the right amount of material for the thread form. Taps come as taper, plug and bottoming, differing in how far the cutting action extends to the tip.
Why it matters
Tap drill size is not the thread size. Drilling a tapped hole to nominal diameter leaves nothing for the thread to be cut in, and a broken tap in a nearly finished part is one of the more expensive small mistakes in a shop.
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