1. Screw Threads Manufacturing Technology Bayside Secondary School HPEDSB

2. Basic Thread Profile

3. Thread Designation Imperial MD – Pitch UNF or UNC Ex. ¼-20 UNC ¼-28 UNF Metric M(MD) x Pitch Ex. M10 x 1.5 M10 x 1.0

4. Threaded Holes Created in a 3-Step Process: –Center Drill in desired location –Drill to correct Tap Drill Size –Create threads using a Tap

5. Finding TDS on a chart

6. Calculating Tap Drill Size TDS = D – 1 N Where D = Major Diameter N = # of threads per inch

7. TDS Calculation Example Find the TDS for a 3/8-16 UNC bolt TDS = D-1 N TDS =.375” – 1 16 16 TDS =.375” – 0.0625” TDS = 0.3125” or 5/16” It is important to know that drills come in fractional, numbered and lettered drill bits and you must cross reference your answer to the appropriate size and type

8. Threaded Hole Tips Countersink the hole slightly to give yourself a lead-in for your tapCountersink the hole slightly to give yourself a lead-in for your tap Use Rapid Tap or other cutting fluid to help the tapping processUse Rapid Tap or other cutting fluid to help the tapping process Always start with a taper tapAlways start with a taper tap

9. Taps

10. External Threads Most commonly created using a Die and Die HandleMost commonly created using a Die and Die Handle Material Diameter = Major Diameter of the ThreadMaterial Diameter = Major Diameter of the Thread

11. Example If the material on the left is ½” diameter, you can thread it with a ½”-13 UNC dieIf the material on the left is ½” diameter, you can thread it with a ½”-13 UNC die

12. Questions?