Post by Ianb on Feb 28, 2006 20:40:28 GMT
Hi,
I have a couple of wonderful whizbangs I inherited from my father, who liked to accumulate such things. The best is a small circular disc of white plastic with a sweep-arm loosely pivoted to the centre. Printed on the arm are the thread types: gas, whit, BSF and metric that correspond to concentric scales on the disc. You swing the arm around to say 7 on the BA scale then go to the outer edge where there are scales for decimal inches, letter, number, fractional and mm drill sizes and read off the tapping or clearance drill sizes in whatever type of drill you want.
This one is marked SHETACK and dated 1958 and is about 5" diameter. I have another about 8" diameter that does similar as well as including UNC, UNF and whatever else you can think of. This one works backwards so that you measure the diameter, set the arm to threads per inch then look down the arm to see what thread it is.
I use the smaller one all the time for selecting drill for screws and bolts - its quick and simple.
Ian
I have a couple of wonderful whizbangs I inherited from my father, who liked to accumulate such things. The best is a small circular disc of white plastic with a sweep-arm loosely pivoted to the centre. Printed on the arm are the thread types: gas, whit, BSF and metric that correspond to concentric scales on the disc. You swing the arm around to say 7 on the BA scale then go to the outer edge where there are scales for decimal inches, letter, number, fractional and mm drill sizes and read off the tapping or clearance drill sizes in whatever type of drill you want.
This one is marked SHETACK and dated 1958 and is about 5" diameter. I have another about 8" diameter that does similar as well as including UNC, UNF and whatever else you can think of. This one works backwards so that you measure the diameter, set the arm to threads per inch then look down the arm to see what thread it is.
I use the smaller one all the time for selecting drill for screws and bolts - its quick and simple.
Ian
