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Tap Lead Grinding

Lead grinding / Chamfer Grinding

Lead grinding, also referred to as chamfer grinding, and is the most important feature of the tap that effects the cutting action.  The lead length is most commonly referred to as “bottom” or “plug” and also less often “semi-bottom” and “taper”.

Chamfer Name

Chamfer Length

Application

Bottom

1.5 – 2 thd’s

Blind Hole

Semi-Bottom

2.5 – 3 thd’s

Blind Hole

Plug

4 – 5 thd’s

Thru Hole

Taper

7 – 8 thd’s

Thru Hole

The lead is the only part of the tap that “cuts” threads.  The longer the lead, the more tapped holes the tap can produce.  For this reason it’s important to apply the proper length tap lead to the part being tapped.

Resharpening the Lead

Resharpening the lead of a tap requires regrinding the lead 2-3 threads up the tap to remove the worn, dull, and chipped threads, then cutting off the tap shortening it 2-3 threads.

Resharpening the Lead on Taps

Because the lead is the only part of the tap that cuts, this feature gives the tap its “sharpness” so it is very important for the lead to be ground properly, concentric,  with equal relief,  properly timed to each flute.

Lead Grinding Taps

 

Another feature of the lead may be spiral point or gun point style.  This is mostly included on plug style taps for tapping thru holes.  The spiral point design is an additional grind that adds a shearing angle to reduce the torque required to cut threads while pushing the chips ahead of the tap.

Lead Grinding Taps

 

TapSaver has specially designed, unique fixtures on dedicated grinders to control the lead grinding process on any type of thread cutting tap.

Lead Grinding Large Tools
Lead Grinding Large Tap Tools