Stainless steel tapping!

[bosstaki]

Hi there! Just a quick one for you! I’m going to have to re-tap a new thread in a stainless steel bracelet! The thread at the moment is 1.2mm & I’m going to tap a bit larger to 1.4mm! Do i need to pilot first to 1.1mm or will it just be ok to tap the 1.2mm thread straight away!

 

 

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[rogart63]

Never done it . But feels like a big step from 1,2 mm to 1,4 mm tap . I think you need to drill the hole first with the right size drill . Maybe 1,3 mm . But there must be a tap size chart somewhere . Be careful as i imagine it's easy to snap a tap that small? 

[rogart63]

https://www.custompartnet.com/quick-tool/tap-size-chart

[manodeoro]

Hi there! Just a quick one for you! I’m going to have to re-tap a new thread in a stainless steel bracelet! The thread at the moment is 1.2mm & I’m going to tap a bit larger to 1.4mm! Do i need to pilot first to 1.1mm or will it just be ok to tap the 1.2mm thread straight away!
 
 
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It depends of your tap size ... 1.4/0.3 or 1.4/0.2 ?
If I had to do that I would first redrill then tap, the difficulty being to drill perfectly centered.

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[vinn3]

  look up the "pilot drill diameter" (also known as "tap drill" )  in the "machinests handbook",   use lots of oil while cuting most types of  stainless steel.  vin

[nickelsilver]

Definitely drill, if standard 1.4mm tap then 1.2mm drill. If you have special tapping fluid on hand use it, if not beeswax is surprisingly good. Go slowly and reverse often. Stainless is a pain to tap but even different sources for the same alloy can be night and day difference in machinability.