Tapped Hole Info: M6 Size & Bolt Diameter Clarified

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SUMMARY

A tapped hole is a hole that has been threaded to accommodate a bolt. For an M6 bolt, the major diameter of the thread is 6mm; however, the hole drilled for tapping must be smaller than this nominal size. The specific tap drill size depends on the number of threads on the bolt and requires reference to a tap drill size chart. Additionally, when measuring the hole, one must consider both the minor diameter for threading and the major diameter for the unthreaded portion of the bolt.

PREREQUISITES
  • Understanding of tapped holes and threading
  • Familiarity with bolt sizes and specifications
  • Knowledge of measuring tools such as calipers and micrometers
  • Access to tap drill size charts
NEXT STEPS
  • Research tap drill sizes for various bolt specifications
  • Learn about the differences between major and minor diameters in threading
  • Explore the use of calipers and micrometers for precise measurements
  • Investigate the impact of thread count on tap drill size selection
USEFUL FOR

Manufacturing engineers, machinists, and anyone involved in mechanical assembly or design requiring precise hole specifications for bolts.

engineer1969
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I just want to clarify. A tapped hole is basically a hole that has been threaded for a bolt. Is this correct?

So would a tapped M6 hole be 6mm in diameter for a 6mm diameter bolt?

Cheers
 
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yes :smile:
 
Wait, are you asking what size hole to drill that will then be tapped for an M6 bolt? Then that's not 6 mm, and it also depends on the number of threads on your bolt. You need a chart of tap drill sizes like this
http://www.csgnetwork.com/screwmetmachtable.html"
which also gives you clearance hole sizes.
 
Last edited by a moderator:
You're right that a tap drill is smaller than the nominal call out diameter on any tapped hole, but that's not what the OP is asking. In an M6 the major diameter of the thread is 6mm. I would just be certain that the OP realizes that if they take a set of calipers or mics to the hole, they will be measuring the minor diameter and thus gtting the tap drill size.
 
depends if the unthreaded part of the bolt also needs to be in the hole
then you need two drills a smaller one for the part the threads are cut in
and a true 6mm for a redrill of the unthreaded upper part
 

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