Easily Overlooked Threaded Hole Chamfer Dimensions

What is injection molding? What is vacuum casting? What is 3D printing?

Help Center

My Orders

My Account

Balance & Coupons

Delivery

Service & Refunds

Payments

Technical Support

FAQ's

Help Center / Basic Machinery

Easily Overlooked Threaded Hole Chamfer Dimensions

Last updated on Dec 31, 2025

Today, we're going to talk about a small topic regarding threaded hole chamfers. It's very inconspicuous, but neglecting it may lead to some unexpected problems—especially for designers who haven't observed physical products or engaged in machining.

Typically, we add a chamfer at the mouth of a threaded hole, which is a common practice as shown in Img. This serves multiple purposes: protecting the thread, assisting in alignment and assembly, and facilitating drill bit entry.

But what size should this chamfer be? Many designers mark it arbitrarily, such as 1×45° or 2×45°, without considering the reasons, assuming that any chamfer will suffice and size doesn't matter. In reality, there are certain considerations to keep in mind.

Since a nut is equivalent to a hole relative to a bolt, let's first look at the requirements in nut standards, as shown in Img:

- When specifying the washer face type, it should be indicated in the order;

- β = 15° ~ 30°;

- θ = 90° ~ 120°.

It can be seen that the chamfer angle θ on the nut ranges from 90° to 120°, and the value of the chamfer dimension da should be larger than the nominal diameter D of the thread. A maximum value is also specified to ensure a sufficient contact surface area.

The above data provides a useful reference for machining chamfers at threaded holes. The main purpose of determining the chamfer size is to avoid machining burrs. As shown in Img: an excessively small chamfer is prone to producing burrs, which not only hinder the fixation between the fitting and the flat workpiece surface but may also cause internal thread deformation and increase the risk of cross-threading.

(Too small a chamfer / Appropriately sized chamfer)

Generally speaking, 45° chamfers are most commonly used for threaded holes. After considering the influence of tolerances, the diameter of the chamfer should ensure that it exceeds the major diameter of the internal thread. If calculation is inconvenient, using a chamfer equal to one pitch (P) can basically meet the requirements.

Have you encountered any problems or accumulated relevant experience in this regard? Welcome to leave a comment in the comment section!

CNC Machining

Sheet Metal Fabrication

3D Printing

Injection Molding

Vacuum Casting

Help Center

Easily Overlooked Threaded Hole Chamfer Dimensions