Mastering Multi-Lead Taps: Basics and Benefits

Watching a machinist smoothly cut clean threads into metal with seeming ease, ever wonder how it is done? The secret lies in utilizing the appropriate cutting taps – multi-lead taps in particular. They are special tools that allow for faster and more productive thread-cutting relative to traditional single-lead taps.

In this post, we will go through what multi-lead taps are, their workings, advantages as well as some tips for becoming proficient in their use. So, are you ready to level up your threading experience?

What are multi-lead taps?

A multi-lead tap is a threading tool used for making threads that have several starting points or leads. Commonly found configurations include the 2-lead,  3-lead, and 4-lead taps.

On the contrary, a normal single-lead tap only features one spiral cutting thread wrapped around the body of the tap. With one full rotation of such a single lead tap, it moves forward axially by only one thread pitch.

However, given that you have a multi-lead tap, each time you turn it on, rotation varies depending on the number of leads by these multiple pitches of threads. As an example:

  • A 2-lead tap progresses by two thread pitches per revolution
  • A 3-lead tape advances by three thread pitches per revolution.

That means you would need much less number of turns to make up a thread while using a multi-lead instead of a single–lead type of tap. 

How do they function?

It is important to note that multi-lead taps have different starting points for each lead.  On a 2-lead tap, the leads are 180° opposite from each other.  On a 4-lead tap, the leads are 90° from each other.

When the tap is rotated, each lead cuts a section of the thread shapes one after the other in a progressive manner, thereby providing multiple turns to create an entire threaded profile.

The idea behind it is similar to single-lead taps but still, multiple threads are done away with by the smart design of multi-lead products.

Advantages of multi-lead taps

Having learned all these, let’s now go through some major reasons why we should use multi-lead taps:

1. Faster linear movement per rotation

This is the biggest benefit. By advancing multiple thread pitches per revolution, you can move the component part (the nut) over the distance much faster.

2. More Contact Surface

In multi-start threads there is more contact surface in a single thread rotation.  A common application is the cap of a plastic water bottle.  If you look at the threads there are multiple starts and when the cap is fully closed, the multiple threads will securely hold the cap in place.

3. Quick connect / disconnect

Multi-lead threads are often used in components that require quick connect/disconnect abilities due to their shallow radial depth requirements..

4. Longer service life

The lower surface pressure resulting from the increased contact area results in longer service life compared to single-lead threads..

Tips for mastering multi-lead taps

However beneficial multi-lead taps are, they still require certain specific methods:

Think of using a forming tap

Forming taps, or Jarflos, are excellent options when tapping multi-lead threads with standard thread forms (60° threads).  Because of the fast radial movement, chip management is a larger challenge.  The forming taps eliminate the concerns around chip management and result in a high quality thread.

Start with a spot drill or pilot hole

Since the threads start at multiple points, you need to guide the tap accurately into the initial hole. To begin with, always have a spot drill or pilot hole whose size is appropriate.

Apply cutting fluid correctly

It is important to take into account that multi-lead taps require proper cooling and lubrication because of higher chip loads. You should opt for good quality cutting fluid made specifically for this material.

Ensure you have enough tapping depth

Staggered threads on multi-lead taps mean that slightly more hole depth is required than the thread length for all leads to be completely formed.

Check concentricity

This is due to multiple thread starts which makes them more susceptible to getting misaligned. It is necessary for your set up to be concentric properly.

Final thoughts

Whether one is a production machinist or just a weekend warrior, mastery over multi-lead taps will elevate threaded designs. Save time, extend tool life, and achieve precision threads more easily than ever before.

So what are you waiting for? Purchase yourself an excellent multi-lead tap set and begin tapping into better productivity!