If you’re cutting extremely abrasive material, we’re confident that you’ve already investigated the benefits of carbide taps. Whether you’re tapping cast aluminum, nonferrous materials, polymers, cast iron, or any number of other materials, carbide taps offer better edge wear resistance and, more importantly, help to reduce downtime and increase profitability.

As an ISO 9001:2008 registered manufacturer, Allen Benjamin is absolutely committed to offering the best taps on the market. In today’s post, we’re going to look at a few of the benefits of using our carbide and high-performance taps.

Stronger
Ideal for very abrasive metals, carbide taps have a much higher tensile strength than standard taps. Because of this, they offer a longer tool life and work to reduce production costs.

Better performance
Due to their ability to increase tool life, carbide taps have a positive effect on your operation’s performance. Helping you to reduce maintenance and – by extension – downtime, they allow your staff to focus on more productive, more profitable tasks.

Cost-effective
While the initial cost may be higher than standard taps, carbide taps are far more cost-efficient in the long run. Their extended tool life results in fewer replacements which, of course, leads to less reorders and money saved over time.

At Allen Benjamin, we are steadfastly dedicated to our customers’ productivity. Always aiming to offer products that are capable of reducing maintenance, increasing uptime, and improving profitability, we strive to act as a convenient, responsive supplier of high-quality carbide taps. Whether you’re a small, local manufacturer in need of a handful of taps or a large, multi-national operation looking to place a large order, you can be confident that we can help. If you have any questions about our products, we encourage you to reach out to us today to discuss your needs!

Allen Benjamin’s carbide taps provide a substantial increase in performance and tool life over HSS – or high speed steel – taps. As a result, our customers experience longer tool life and, due to this, reduced production costs that help to contribute to higher profits and a more efficient line.

Getting a good understanding of the definitions of the parts of a tap will help you to better understand the functions of  tap designs.  Special thanks to North American Tool for letting us share their short and simple explanations!

Have you ever had a tapping job that was so troublesome that it caused heartburn or acid indigestion due to broken taps, bad finish, short tap life, over or undersized threads, etc.?

One way of avoiding or alleviating such a condition is accomplished with the use of a tap feature called “relief”. The definition of “relief” according to Marian Webster, is removal or lightening of something oppressive, painful, or distressing. For a tap, “relief” is the reducing of surface contact between the tap/tap feature and the part being tapped. Surface contact generates unwanted heat causing the issues mentioned above. Depending on the tap feature, relief is applied in a direction that is, radially, around the tap, or axially, along the axis of the tap.

All taps require a minimum number of features to have relief for it to cut, other reliefs are applied when the tapping application requires it. There are always tradeoffs when designing a tap, if a relief is applied or it’s amount is greater than necessary, it can cause the tap to run free or loose to a point it will cause heartburn or acid indigestion by producing issues mentioned above.

Relieved features that are always necessary on a tap are:
               
Chamfer, the tapered threads at the front of the tap. The crests or major diameter of the chamfered threads are radially relieved from the cutting edge to the heel of the land. Without this relief it would be like cutting a tomato with the non-sharp side of a knife, you can imagine the results of that. When looking at a taps chamfer, relief results in the crest width being wider at the cutting edge and narrowing towards the heel;

Back Taper, a slight gradual reduction of the taps thread form including it’s major, pitch and minor diameters. It starts at the chamfered end of the tap and continues axially for the length of thread towards the shank end.

Additional features that can be relieved

Thread Relief, a radial reduction of the taps major and pitch diameters from the cutting edge to the heel. Relieving of the pitch diameter results in the minor diameter being relieved as well due to the manufacturing process whereas the major diameter is relieved separately. The application of the major or pitch diameter relief is normally applied separately but both can be done in combination. Relief of pitch diameter is the most common followed by the major diameter. Thread relief is applied when Back Taper alone is not enough to prevent surface contact when tapping materials that close in and squeezes the tap like stainless steel. The rate of reduction from the cutting edge to the heel is based on the material being tapped and, in some cases, the tapping application.

There are two common types of Thread Reliefs:

• Eccentric, a radial relief in the thread form starting at the cutting edge and continuing to the heel.
  
• Con-Eccentric, Radial relief in the thread form starting back of a concentric margin.

The reliefs we have discussed so far are applied during the tap manufacturing and other than the chamfer relief cannot be added or changed. If you are in a bind and must ship parts but can’t wait for us to design, manufacture and ship the appropriate tap, there are additional types of relief that can be applied that may work in a pinch. Sometimes referred to as a poor man’s relief, something you may be capable of doing in your shop without too much trouble to get you through a quick job, or until properly designed tools arrive.

The application of relief types and amounts are dependent on many factors such as material properties being tapped, style and size of tap, how the tap is being used (hand, machine, etc.) and application requirements, etc. By providing us with as much information about your tapping application, it will enable our engineers to design a tap with the proper relief. This will help alleviate troublesome heartburn or acid indigestion.

First things first, what is the root of a tap?

The root of a tap is the surface at the bottom of the thread-form that connects adjacent thread flanks and is expressed as a width or as a diameter. The term root diameter is also called minor diameter, it’s one of those things, you say rain and I say precipitation, meaning the same thing...

Recently we had an application question at North American Tool.   A customer had opened up the drilled hole to 55 percent of thread in hopes of reducing wear and increasing tool life.  Instead, it lead to the cut tap breaking at the first full thread of engagement.  That prompted a engineering discussion and is the basis of this technical article to address this very common misperception.

If a tap doesn’t create the hole, why is the hole size so important?

This leaves the good machinist to select a drill that is more or less than 75%.  If 75% is good, then a higher number is better, right?  WRONG (in many cases).  On page 115 of the current North American Tool catalog a range for percentage of threads from 50% to 85%, with the recommended range between 65% and 75%.  This guideline range to use is a reflection of several factors:

1. The higher the percentage of thread, the greater the stress factors on the tap and the greater the likelihood of failure.  Excessive torque can lead to catastrophic failure, with broken pieces of tap or galling in the thread form.
2. A lower percentage of thread still provides the same pitch diameter, which is the only point the flanks of a fastener contact with the threads that have been tapped. They still provide the same pull out torque.
3. Too low of a percentage of thread can lead to cross threading when engaged with the fastener.

In higher tensile steels, larger hole sizes (less percentage of thread) may work better to reduce torque in tapping. When using oversize hole diameters, the tap should also have an oversize chamfer point diameter so all threads in chamfer are cutting and not just dropping in a hole.

Such was the case with the application porblem. As was stated above the operator thought that by increasing the drill diameter size would lead to better tool life. Instead, because the diameter was of the hole was so large the cut tap did not engage the threads along the chamfer length and instead engaged at the first full thread at the end of the chamfer.  The caused premature wear and stress on the that thread in the flutes and eventually to catastrophic failure.  The solution was a modified tap from North American Tool.

At the end of the day, taps are made to very strict tolerances, often much more so than the piece parts they are called on to machine, and the first place one might want to find blame is with the tap. 

Why?
Because;

1. the tap is easily replaced with another one and 
2. it is the least expensive component of possible issues with an application.

What if one manufacturer makes a tap that works and another one made by a different company doesn’t work at all? 

In all likelihood, the “general purpose” of one is closer to the correct geometry for the application.  One might get a completely different result if another material were being machined. Therefore it is always best to order a tap for the specific application.

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​​“Pulley” taps
“Pulley” taps were originally designed to tap threads in a pulley assembly. Length was extended, but shank diameter was approximately the same as the thread major diameter.

The shank was used as an alignment guide to reach through the pulley hub. Thread depth could not exceed the thread length of the tap. Today, the term is rarely recognized by recent generations.

“Extension” taps
“Extension” taps provide additional length for reach just as pulley taps do. However, the shank diameter is reduced to allow tapping beyond the ground thread length of the tap. The shank diameter “clears” the drilled hole.

All this seems pretty straightforward, but somewhere the industry decided to add a twist. In thread diameters 3/8” and smaller,

Pulley and Extension taps use the same Industry-Standard blank. If additional reach is needed, with the desire to tap beyond the thread length of the blank, the terminology changes to Extension/Small Shank.

Above 3/8” in diameter, the standard Extension blank has a smaller shank diameter, and is defined only as “Extension”. When in doubt, specify “small-shank” when tap use is intended to exceed standard thread length.
 
As with any tool, these extended-reach taps can be made to custom lengths. Most manufacturers have standardized on 6, 8, 10, and 12 inches in blank length (varies by diameter) for stock tools. Maintaining Industry-Standard shank and square dimensions allows the use of standard tool holders.

Allen Benjamin color codes HSSE taps to simplify the selection of the right tap for specific materials. Each of the six color-ring taps are manufactured with application-specific design criteria based on characteristics and hardness range of various part materials.

The table below illustrates which color ring tap is best suited to the material being threaded.

*NOTE: For material or material group not shown (such as No Lead Brass), please consult Customer Service here.
** BHN hardness range may vary depending on steel/workpiece condition.