Myford lathe/drill and thread charts

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Handy drill and thread charts for use with the lathe.
Remember for all drilling operations to use a suitable RPM and drill fluid.

Drill RPM calculations

Steel
Aluminium
Brass

Center Drills

For any drilling operation on the lathe the Center drill is used first to make the small accurate pilot that the next drill will follow.
They are also use for drilling the required hole when using the live or dead centres.
Use the Highest RPM setting on the lathe!
General rule of thumb is to drill no more than 2/3 up the 60 degree angle
We have 4 Center drill sizes to chose form, BS1 to BS4
For general piloting work the BS3 or BS4 are recommended as the smaller ones are easy to snap.

When supporting work with a live or dead centre lookup the work diameter in the following table to determine the correct drill size and size of the hole needed.

Gauge Size (Inches) Size (mm)
BS1 1⁄8 in 3.175 mm
BS2 3⁄16 in 4.763 mm
BS3 1⁄4 in 6.350 mm
BS4 5⁄16 in 7.938 mm
BS5 7⁄16 in 11.113 mm
BS5A 1⁄2 in 12.700 mm
BS6 5⁄8 in 15.875 mm
BS7 3⁄4 in 19.050 mm

Threading Charts

Metric

The Hackspace has a tap and die set with the following metric coarse sizes
M3 M4 M5 M6 M8 M10 M12
For tapping internal threads use the chart bellow to select the correct drill size and if needed clearance size for the tap.
For the external threads turn down the work piece to the major diameter.
It is advisable to add a slight chamfer to the right end of the work, to just under the thread minor diameter using the left edge of the cutting tool.


British Standard Whitworth (BSW)

Reference Sites

http://www.tribology-abc.com/calculators/metric-iso.htm