Shoulder Screws — Discover 3 Ways to use Shoulder Screws in Weld Fixture Design

Posted by rentapenblog on Oct 22, 2012 in clamping, Fasteners, Locating Pins, Machine Design Tips, Tolerancing, Weld Fixture Design 101 |

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How do you use shoulder screws in designing jigs and fixtures for the welding and assembly processes?

I have thought of 3 ways. Orient, Pivot and Slide. Maybe you can think of others. Please feel free to add your ideas to the comment section below. We are here to learn from each other.

First, let’s start with the basics and take a look at the shoulder screw.

What is great about the shoulder screw is that the shaft is a nice toleranced shaft like a dowel.

The thread is usually course. When you order a shoulder screw, remember that a 3/8″ shoulder screw is referring to the SHAFT size, not the thread size. A 3/8″ shoulder screw has a 5/16″ threaded part.

The shoulder of the shoulder screw will have a minimum relief so it sits nice and flat. This is the weakest part of the screw. So keep that in mind as you design.

The shaft part of the shoulder screw fits into a bored hole that has the same kind of tolerance as for a slip fit dowel of the same size.

Notice in the cross-section, that the hole bored for the shaft is slightly less than the length of the shaft on the shoulder screw. This allows the shoulder to snuggly screw down to the bottom of the bore before the head of the screw bottoms out.

Check out McMaster-Carr's website for information on the types and sizes of shoulder screws available.

3 – Ways — Orient, Pivot & Slide

Orient

Shoulder screws can be used to orient a diamond pin (as shown in the cross-section and the top view at left).

The shaft has a diamond shape on the end that enters a hole in the production part. To keep the diamond facing the right direction, a flat is cut into the side of the shaft and a shoulder pin is placed close to that cut so that the shaft cannot rotate.

Pivot

This green clamp finger is attached to the clamp arm with a shoulder screw. A set screw helps set the exact amount of pressure placed on the production part.

A little room is allowed (in this case .015″) between the clamp arm and the finger for freedom of movement. Two jam nuts are placed on the threaded part of the shoulder screw.

Shoulders screws can be the pivot point for a manual clamping arm.

Pivot and Slide

This picture shows shoulder screws being used for pivots and slides.

Orient, Pivot and Slide.

I am sure you have some fun ways you have used shoulderscrews in machine design. Add your ideas below in the comment section so we can learn from each other.

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