"b" Dimension in Mounting Hole
Printed From: PCB Libraries Forum
Category: PCB Footprint Expert
Forum Name: Questions & Answers
Forum Description: issues and technical support
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=2765
Printed Date: 25 Nov 2024 at 3:42am
Topic: "b" Dimension in Mounting Hole
Posted By: Batiskaff
Subject: "b" Dimension in Mounting Hole
Date Posted: 30 Dec 2020 at 6:05am
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What does mean "b" dimension? This is hole dimension that I want to get in MTG or this is diameter of screw that will be insert in MTG?  |
Replies:
Posted By: Tom H
Date Posted: 30 Dec 2020 at 10:35am
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For Plated Through-hole the "b" dimension is equal to the hole size. For Non-Plated Through-hole the "b" dimension should be larger than the hole size. Probably the hole tolerance +/- 0.05 annular ring. If the hole is non-plated, you want the drill bit to go through FR4 material and not touch any copper to avoid copper slivers in the hole. ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |
Posted By: Batiskaff
Date Posted: 30 Dec 2020 at 2:02pm
| So, if i need the Plated Mounting Hole with loose fit of M3 screw i should add a bit to 3 mm. For example: b=3+0,5=3,5mm. After that i should enter 3,5mm in "b" field, will it be correct? |
Posted By: Tom H
Date Posted: 30 Dec 2020 at 2:16pm
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A Plated Through Mounting Hole the b = Hole Size. b > than Hole size for Non-plated holes. There is a Hole Size Calculator in the main toolbar "Tool Box". ------------- Stay connected - follow us! https://twitter.com/PCBLibraries" rel="nofollow - X - http://www.linkedin.com/company/pcb-libraries-inc-/" rel="nofollow - LinkedIn |