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Hand Taps vs Machine Taps - What's the difference?

Hand Taps vs Machine Taps – Differences?

A brief knowledge drop from our friends over at North America Tool

Hand Tap and Machine Tap are terms that don’t always mean what you think! These are stale industry legacy terms. Originally meant to define a purpose, they can be misleading. They should not define a tap’s modern method of use.

According to some handbooks, the term Hand Tap has traditionally been applied to fractional-size taps having a standard general-purpose length. Most manufacturers don’t limit the description to fractional sizes. Assumed to be straight-flute, these are taps whose flutes are provided as a space to accommodate chips created as the tap cuts. Some research suggests the terminology originated in the early 1800s, when most threading applications were literally done by hand. Yet, when the Machine Age hit its stride after the 1880s, the term Hand Tap was still used for taps that were unchanged in design, and now used on machines, as well as by hand.

As machine tapping is a much faster operation than turning a tap by hand, chip evacuation became more difficult to control. Machine taps would become defined as those with flutes designed with geometry to direct the flow of chips out of the hole. Spiral-point and Spiral-fluted taps fit this category. These alterations in flute geometry improved tap efficiency. Today, with the increasing use of coolant-holes in taps, and external directional coolant-flow, a straight-flute hand tap can offer a similar assist with chip evacuation, and yet it is still perceived by some as different than the machine tap.

Don’t get hung up on a name. Both hand and machine taps sold today are manufactured from the same base materials, and can be used by either method. The decision of which design to use should be influenced by the needs of the job.

P.S. Check out the cool apps North American Tool has to help with tapping and tap design!

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Acme vs Trapezoidal Threads

A brief knowledge drop from our friends over at North America Tool

Acme threads appeared sometime in the late 1800s as an improvement on the square thread form. Square threads were the first choice for motion transfer and heavy loads. But square threads were difficult to produce with available cutter technology. Although the square form was relatively efficient for the purposes required, it was inherently weak at the base of the thread due to the sharp 90-degree angle of the flank. Modifying the included-angle to 29-degrees widened the base of the thread making it stronger. Over time, standards in Acme diameters and pitches were established, all with Imperial Inches in diameter and Threads-per-Inch units of description.

In Europe, similar standards followed using metric units of measure, and the slightly different included flank angle of 30 degrees. Metric standard trapezoidal threads are covered under DIN103. Diameter and pitch descriptions are in metric units of measure.

                            Acme Threads

Acme Threads

                              Trapezoidal Threads

Trapezoidal Threads

Both thread forms serve the purpose of producing linear motion when rotated, usually under heavy load. Some common uses include lead screws for linear actuation on CNC machinery, table lifts, clamps and vises, valve stems, medical diagnostic device drives, trailer jacks and jack-stands. The American Acme form has an included flank angle of 29 degrees. The metric Trapezoidal thread is at 30 degrees. The uses for these thread forms are essentially the same. In fact, taking manufacturing tolerances allowed into consideration, they may be interchangeable when TPI (threads-per-inch) is the same.

The demands placed on the tools that produce these threads are higher due to the amount of material being removed, per tooth, in the process. Controlling chip-load is critical. To design a tap for these threads, North American Tool requires specific detail on the application. Information on the material being tapped, tapping depth, condition of the hole (through or blind), and Class of Fit, is essential to engineer the proper tap. General-purpose taps are available, but are definitely not suitable for every application.

So, what’s the difference between Acme and Trapezoidal? Not much physically. Although the American Acme thread-form is used and accepted throughout the world, the choice of which to use is usually dictated by the origin and user destination of the finished part. To that manufacturer, the difference is everything!

North American Tool is a tier 1 manufacturer of special taps and dies with many taps having a 24-hour lead time. Call us today for a quote.

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