Hi, I am new to this forum so please go easy on me :-) I am making modifications to a hi-fi tonearm and I am making a new component for it and require help with a particular part of it. I have written to another engineering forum, but the replies are simply out of my depth to understand as the pointed me to sites that are simply gobbledygook to me !! Anyway, I have a aluminium ring about 35mm in diameter and 15mm high and 5mm thick. I have drilled a hole through the edge of it (from od to id) with a 12mm drill. This made a hole of 12.03mm. To this I want to connect an aluminium bar that is 14mm thick and want to turn the end of the bar to a depth of 5mm so that it is a tight press fit (or I believe this is called an interference or force fit). What I mean is that it need to be tight enough that it is pressed in with a machine vice (very carefully !) but cannot easily be removed if at all. The reason fir this is that the size of the ring has to be fixed as it is for a commercial tonearm so the dimensions can't be changed to allow fixing with screws. Can anyone tell me what size diameter to make the shoulder of the bar to be such a fit in the hole. The web sites I have been pointed to talk about H7 and s6 fits and such like and I am totally confused about it all. If you can, could you point me to a web site where this can be calculated by inputting the dimensions, or if not, just help me with this particular size I need. Thank you in advance for any help you can give. Sincerely, Soundssupreme.