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Guide to Shoulder Screws

Use shoulder screws to hold your machinery together or keep it moving smoothly

By W. Aiman Mueller

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Part of the shank of a shoulder screw has no threads. From under the head of a shoulder screw to some point toward the tip, the shank surface is smooth; threads only cover a portion of the shank toward the tip. Additionally, the smooth portion of the shank may have a greater diameter than the threaded portion.

Shoulder screws hold machine or other assemblies together, where the bare portion of the shank passes through one component and the threaded portion secures into a second component. They commonly secure rollers, levers, pressure pads and countless other components. The bare portion of the shank can also act like a bearing allowing movement of one part relative to the other.

There are many variations of the shoulder screw and the terminology used to describe it, but here are a few of the common types:

1. Locating screws, to locate cylinders on fixture plates

2. Socket head shoulder screws, for secure holds

3. Stripper bolts

4. Swing bolts

5. Latch bolts

Action Steps
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Buy precision shoulder screws that match your application

As you shop, you'll have to find shoulder screws that match the size and thread type of your application, but there are other parameters to consider as well. The common head types are hex and slotted. Also, while black oxide is common, the finish can vary. Finally, there are various compositions, like a brass shoulder screw as opposed to stainless steel shoulder screws.

I recommend: Rino Mechanical Components, Inc. is the one-stop shop for shoulder screws. They carry a wide range of both English and metric sizes. Their prices are low, and they even produce custom screws. Accurate Screw Machine Corporation is an alternate source. They carry a range of products, including male-female and low profile screws.

Buy metric and custom shoulder screws

If you're application involves metric measurements, you'll want to find a shoulder screw source or manufacturer that carries a full range of metric shoulder screws. Additionally, some applications require custom parts.

I recommend: Rino Mechanical Components, Inc., listed above, is a place to start; but do comparisons at other companies as well. National Cap & Set Screw Co. is an option for custom hardware. They take your samples or drawings and produce just what you need, including, but not limited to, shoulder screws. Also, if you would like to keep a paper catalog on hand for your shop or factory, Mil-Spec Fasteners Corporation offers a fully illustrated 160 page catalog.

Find specialty shoulder screws or ultra-miniature shoulder screws

Machine parts require a very wide range of fasteners. Some websites do a better job than others at guiding you to the right product.

I recommend: Grainger breaks the categories down to get you to the right parts. Besides the most common categories, they also offer knurled, self-locking and tamper-proof shoulder screws. On a whole other level, If you need shoulder screws that are smaller than small, you may want to check out MicroGroup, Inc.. For ordinary small shoulder screws, the other companies listed in this guide will do.

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