![]() Assembly jigs-tools for holding parts in correct alignment during assembly operations-are one of the biggest areas that can benefit from slip fit dowels. While this is rare in consumer products, it’s common in the tools used for assembling them. Dowel pins are perfect for this type of fit: they hold the two parts in correct alignment, allowing relaxed tolerances around bolt location and hole diameter.Īnother handy application for dowel pins is when parts need to be disassembled and reassembled numerous times while retaining alignment. ![]() Sometimes, especially in machinery design, you can’t have the loose tolerances which would be ideal because, for example, a head bolting onto an engine block needs to be exactly positioned. If slip fits are only for aligning tight geometry, should we redesign the parts for looser tolerances? Ideal Use of Slip Fit GeometryĪ rule of design for assembly (DFA) is to avoid tight tolerances, where possible. ![]() How much clearance is excessive? More on that in a moment, but first, the ideal uses of slip fits. The goal of a slip fit is easy alignment, requiring enough space around the dowel that alignment is easier: no excessively tight fits – this concept is commonly known as slip fit clearance. To make a slip fit work, the parts must be able to slip into place, meaning there must be minimal assembly friction. Want to know more about slip fit geometry and slip fit tolerances? Read on! Slip Fit Basics While interference fits create tight assembly tolerances, slip fits are just the opposite-they can easily give you a self-locating assembly, making manufacturing easier when needing close alignment. Using the example of dowel pins, there is another important application: slip fits (aka push fits or clearance fits). We’ve previously explored interference fits (press fits), using a dowel pin as an example, to explore interference fit design limitations. ![]() Pro-tip: If you are looking for a bit of comedic relief to add to your workday, head over to this video where you can see lots and lots of dowel pin slip and interference fits in action with an Ikea furniture assembly that is sure to bring tears of laughter to your eyes! The good news is that you did gain something from the experience (other than a piece of Swedish furniture that you may or may not be able to ever move) – you gained excellent experience with slip fit geometry and even interference fit geometry (depending on the machined size of the hole diameter for each dowel pin fit – ha)! Yay! I send my condolences for the frustration you experienced when the holes did not line up with the pins you put in other holes or when you realized you were missing a fastener. Have you recently assembled Ikea furniture? If so, I apologize. ![]()
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