....i just acquired 4 old brush handles, and i am going to try my hand in removing the old knots and putting in new ones.....
..... but one question, how do you know what size knot to put in??
......how do you measure the inside of the handle to determine this?
...i am guessing that when the old knot is removed, that it is in such a bad state that you can't use it to measure for the new knot......
Remove the old knot first...90% of the time it will not come out intact, but will have to removed in pieces. Once the knot is removed, measure the inside diameter of the hole. A cheap pair of calipers is useful for this, but you can just use a ruler and eyeball the diameter. Generally, the knot you purchase should be a millimeter or two smaller than the hole. Any excess space will be filled by the epoxy, or by the hair as it expands.