If you use a conductive washer (and I often use stainless crinkle washers on PCBs) the washer might be 6.3mm with 3.3mm hole so you need 6.3mm + twice the washer hole slack + twice the PCB hole slack. M3 1/8 3.303.15 30 Tap Drill Clearance Drill 75% Thread for Aluminum, Brass,& Plastics 50% Thread for Steel, Stainless,& Iron Close Fit Standard Fit M7 M6 M5 Screw Size (mm) Minor Diameter (mm) M2 M4 M18 M16 M10 M9 M8 M14 M20 53/64 22.0021.00 55/64 Metric SHCS Hole & Counterbore Sizes Nominal Screw Size Clearance Hole Dia. leaving a square hole in the mask also makes the mounting points easier to see. )There are small lies, big lies and then there is what is on the screen of your oscilloscope.Hmm, it hadn't occurred to me that people do it simply for visual distinction. mm Counterbore Dia. Always innovating and designing, NightShade seeks to stay in tune with the ever changing needs of its customers. See our NightShade Electronics is a company based on the Space Coast of Florida, started to provide electronics enthusiasts with the quality parts they need to make their projects come to life. A Free & Open Forum For Electronics Enthusiasts & ProfessionalsDepends how accurate are the hole positions are in what you are mounting it to.I recently started using LP Wizard to calculate hole and pad sizes.Add 10mm clearance region, so you can use a nut driver without cutting tracks or dismounting resistors.Great to see some commonsense ideas from people designing PCBs.There is a calculation formula for this but since I am lazy I recently just updated my PCB library with the following mounting hole footprints according to following blog which has been mentioned in the forums elsewhere.Depends on how your manufacturer handles plated hole diameters. TAP DRILL & CLEARANCE HOLES FOR SCREW THREADS - 0-80 to 1/2" SIZE inch mm inch mm inch mm 0-80 0.060 1.52 0.047 1.19 0.073 1.85 0.067 1.70 ... CL HOLE THREAD DIM TAP DRILL NORMAL FIT. General Information about what size of blind rivet to use, what hole size to drill, rivet strengths, types of blind rivets.

Delete Favorite: Deletes the selected … Other group enlarges holes on their own based on their knowledge of their own process. To add a style, click , type a name, then click OK. To update a style, edit the properties on the Type, select the hole in Favorites, then click and enter a new or existing name.

the clearance hole for a M4 screw has 4.2 mm or 4.5 of diameter.

The first was to insure that if the screw threads stripped the copper plating from the main hole that the vias would still provide adequate ground connections. Let us handle your development, design, and manufacturing needs.All products sold on our website are supported by dedicated engineers. mm Countersink Dia. As a "rule of thumb", the diameter of the clearance hole has more 10 % than the diameter of the screw.

Typical pan head M3 screw is about 5.7mm but you need to add twice the PCB hole slack.

The average via hole size for mounting holes is 0.5 mm. Title: Tap Drill & Clearance Holes for Screw Threads 0-80 to 0.5 inch.xls Author: Richard Wegner PCB and CNC manufacturers can get good accuracy but you have to add tolerances.There are small lies, big lies and then there is what is on the screen of your oscilloscope. You have to tolerance things up for mounting holes, screw diameter is not an issue it's center offset, how accurately can you place your centers ? For examples, the clearance hole for a M3 screw has 3.2 mm or 3.5 mm diameter. On the other hand though, enlarging holes without your knowledge may lead to bad consequences (particularily broken traces/shorts if you run traces close to holes).Oh no, I understand why for that case, where the hole is plated or has surrounding vias. (The same way test points are typically circular pads surrounded by square holes in the mask. Digital Voltmeter + Ammeter - 0-100V 1A Red/Blue 0.28" I mean when there is no electrical connection, and the hole is unplated.The thinking could be that soldermask is slippery, so the washers or nuts will not be as reliable. One group specifies that hole diameter will shrink by 0.1 or 0.15mm after metallization process, which means that you need to design holes 0.1 or 0.15 larger in diameter than mechanical dimension of whatever you want to put in that hole. Clearance Hole Diameters: Aluminum Brass & Plastic 75% Thread: Stainless Steel Steels & Iron 50% Thread: All Materials: Close Fit: Free Fit: Name: Major Dia.

And we would make a hole … 6mm is a bit small. The second reason was for additional support to prevent the PCB from crushing when too much torque was used to tighten the nut. Certainly makes it very clear at a glance where the mounting holes are. This has the upside of getting holes very close to spec. Adds the selected Hole Wizard hole to the Favorites list. Search our Shop with confidence knowing that returns are easy.