Last month’s newsletter discussed bilateral vs unilateral tolerances. This month we are going to cover a fairly simple topic – countersinks, chamfers and the tolerances of these types of features. Any machined part that has holes in it probably also has countersinks. Countersinks are used as a lead-in for threads, for flathead screws, and just…
Last month’s newsletter discussed Surface Profile tolerances. This month we are going to stay on the topic of dimensional tolerance but focus on unilateral vs. bilateral tolerances. Bilateral tolerancing (also known as symmetric tolerancing) is a method of tolerancing a dimension using equal plus and minus deviations from the nominal dimension. Unilateral tolerances (also known…
Last month’s newsletter discussed undercuts. This month we are going to talk about surface profile requirements and minimally dimensioned drawings. The use of GD&T has increased significantly over the last several years. Engineers are being trained to use it and becoming more familiar with it. It can be a great way to specify what tolerances…
Last month’s newsletter discussed chemical conversion coating and anodizing. This month we are going back to geometry to talk about undercuts in machined parts. Sometimes it is impossible to avoid creating a feature that can’t be made with a standard endmill; often this means using an undercut feature. See Fig. A for an example. These…
Last month’s newsletterdiscussed some cost drivers and details with threaded holes and threaded inserts. This month we are going to talk about two different types of plating and some strategies to make those finishes more successful and cost effective. Chemical Conversion Coating In reference to coating aluminum, this process is known by many common names…
Last month’s newsletter discussed some of the factors related to tolerances that drive machined part cost. This month we are going to talk about threaded holes and threaded inserts. We will go into greater depth in future newsletters about other types of holes and threads. Threaded holes can vary widely in cost. One thing to…
Last month’s newsletter discussed some of the issues with specifying material sizes and specs. This month we are going to discuss the topic of geometric tolerances and how they drive cost. Nothing can drive up costs on a part more quickly than tight tolerances that are difficult to machine or measure. Some tight tolerances are…
Last month’s newsletter discussed some of the issues specifying floor and wall radii. This month we are going to leave the topic of geometry and instead talk about material specs, sizes, and other material cost drivers. The ideal scenario for selecting a material for your parts – is to choose one that is the cheapest…
Last month's newsletter discussed the length to diameter ratio of inside corner radii. We are going to explore this general topic a little further in depth this month. It isn’t uncommon for engineers to put a radius both on the floor and wall intersection as well as the vertical walls (see fig A). With the…
One of the single biggest cost drivers for machined parts is the length of time it takes to machine it. The rigidity and strength of the actual cutting tools often determines how much time it takes. Very simply, the shorter a tool is, the faster it can feed, and the less the part will cost…
