I read that tang sight screws for old Winchester levers are 10-36 thread and Savage are 8-40. Both same length .25. Have box full of these screws mixed. Any way I can tell which is which w/o gun? I have it in mind this Win is the one with smaller diameter. Is that what the 36 indicates? Thanks
36 is the thread pitch or number of threads per inch. #10 indicates the size (diameter) to convert to a decimal take the number and multiply times 13 and add .060. This gives you the diameter of a number designated screw expressed as a decimal .xxx" that you can measure with a micrometer or caliper. Here's another handy formula for you, if you need to determine the size of the tap drill. Take the size of the screw expressed as a decimal and subtract the pitch of one thread. Example say you want to know the correct size tap drill for a 1/4-20 screw, take .250 which is the decimal equiv. of 1/4 and subtract .050" which is the pitch of one thread. To determine the pitch divide the number of threads per inch into 1" 1.000 divided by 20 equals .050" which when subtracted from .250 is .200". The correct tap drill for a 1/4-20 thread is a #7 (.201"), you've found the answer without using a chart or handbook. So now you have you "mental tap drill chart", a handy little timesaver.
We were taught these things a kids,apprentices, no one teaches these things now most High school grads can'read a tape measure correctly. Makes you wonder...
I started serving my apprenticeship in the early 70's, somewhere along the way I picked-up the "mental tap drill chart". It served me well over the years along with a lot of other knowledge I picked-up form the old timers. Sadly a lot of what was once common knowledge amoungst craftsmen is becoming lost as the years pass. Computers having become so dominant in the workplace most workers today lack any practical knowledge or skills.