Tolerancestack-up calculator

While it's fairly easy to drill most holes in metal using nothing more than a handheld drill, you'll almost always get greater accuracy and better results using a drill press. Most drill presses are actually built with metalworking in mind. Pulling down on the handle causes the bit to plunge straight down into a workpiece and make a very precise hole.

Tolerance analysispdf

After drilling a hole in metal, it's a good idea to remove any sharp edges or burrs left behind. You can buy fancy deburring tools to smooth sharp edges, but before spending money on one, try this trick: Take a twist bit slightly larger in diameter than the hole you just drilled, and gently hand-twist it over the top of the hole. This will smooth out the edge of the hole and grind away any burrs.

The report can be formatted to return the worst-case or statistical tolerance variation. Worse-case determines the absolute maximum variation possible for a selected distance gap. Statistical determine the probable or likely maximum variation possible for a selected dimension. A simple rule of thump to determine which format to use is that as the number of tolerances in the stack increases, the benefits and validity of using a statistical analysis increases.

Tolerance Analysis is the only way to determine the allowable variation between the features of a part or between part sizes in an assembly and whether parts will satisfy their dimensional objectives. The analysis is iterative in nature and it could be done from the Top-Down (letting the assembly requirements determine the part tolerances) or the Bottom-Up (part tolerance determine assembly goal). The information gained leads to better understanding of the machine or device in consideration.

Tolerance stack analysisexample

In order to perform the stack-up analysis shown here all tolerance styles must be converted to equal-bilateral form. The figure below shows how this is done.

For drilling holes in steel that's 1/8 in. or thicker, use cutting fluid or a multipurpose oil like 3-IN-ONE. Lubricating the bit reduces friction and heat buildup, which makes drilling easier and your bits last longer. For easier-to-drill metals like aluminum, brass or cast iron, lubrication isn't usually necessary.

Tolerance stack analysispdf

For large holes, a hole saw gets the job done cleanly and quickly. Like twist bits, hole saws chuck right into your drill and will cut through thin-gauge sheet metals like aluminum and steel. Use a scrap of plywood as a backer for the hole saw's pilot bit and to protect your work surface.

Tolerance stackup example PDF

A sample of a Statistical report and sketch is shown below. Note that the Root-sum-square (RSS) of the tolerance is used to determine the max. and min. size of the gap. The Worse-case calculation was also included as a way of comparison. As you can see, it shows a possible 3.7mm interference upon assembly.

For most do-it-yourselfers, there will likely come a time when you'll have to drill a hole through a piece of metal. The tools and methods used to do it are almost as varied as the different types of metals out there. Here are 12 tips to make the task fast, easy and safe.

Tolerance stackupanalysisExcel

A sample of a Worse-case report and sketch is shown below. Note how assembly shift due to floating fastener variation is calculated (two entries) and the importance of how the dimension-chain direction affect the summation of the stack. Fixed fastener variation would only require one entry line in the spreadsheet.

Drill presses also come with beefy cast-iron tables with tilt and height adjustments, and allow a variety of clamping options. Speed changes are as easy as opening the lid and moving a rubber belt from one pulley to another. The most expensive drill presses are floor-standing models, but you can buy a decent benchtop unit for about $100.

In Case One the perpendicularity tolerance applied to datum feature B allows portions of the Datum Feature to tilt and/or have form error relative to datum B, which is perfectly perpendicular to Datum A. Therefore the tolerance analyst may choose to include the perpendicularity tolerance in the tolerance stack-up. The Perpendicularity tolerance only allows the distance between datum feature B and the groove to decrease, so it must be accompanied by a negative zone shift. The perpendicularity tolerance is added as an equal-bilateral tolerance of ±0.25, with a Zone Shift of 0.25, which is half the perpendicularity tolerance value. The zone shift is indicated by placing the 0.25 value in the -Dir column on the same line as ±Tol. column. Case two is very self explanatory.

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It is important to note that these calculations apply only to parts and assemblies functioning at 25° C. Thermal expansion or shrinkage must be considered when the device is expected to endure extreme temperatures.

The location of features is typically the most important characteristic of features in linear tolerance stackups (TS), which is why position and profile tolerance are more commonly included in TS than form tolerances. This is because TS are done to find a minimum or maximum distance and in the majority of cases the form or shape of a feature has little to no effect on the distance being studied.