<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Machine Threads in Pinblock, was WD-40</title></head><body> <div>Hello Terry and Will,</div> <div><br></div> <div>Nice to see you posting Will.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial">Hi Ron!  I also use coarse thread as you do. However, I have tried tapping the maple and found that it made the hole too big - I used the proper tap for the given machine screw. I figured that the maple must have enough give in it (compared to metal), that caused the poor fit.</font></blockquote> <div><br></div> <div>I suspect there are two factors here which may be contributing to the outcome you've experienced. Firstly, we prefer to use older taps which have lost their very sharp edge when cutting a thread in maple. The duller cutting edge will cut a slightly undersize threaded hole which will help to produce a slight interference fit. The other factor is that lower grade nuts, bolts and machine screws will tend to be more undersized when compared to their higher grade brethren. This may lead to a looser fit when lower grade fittings are used. When we machine the threaded bolt for the plate to belly rail brace, because we make them in house, we can deliberately turn them a little larger in nominal diameter to ensure an interference fit. When cutting the threads for the plate perimeter bolts we actually use a bolt with an off-hand-ground cutting slot, ground longitudinally into the bolt. This also gives us the interference fit we are looking for.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial"> I've gone to simply drilling a hole a little smaller than the thread and simply running a buttered (wax) machine screw into the hole (just like one does with a wood screw). I seem to get the nice tight fit that way.</font></blockquote> <div><br></div> <div>That will certainly work, but I do like to have a reasonably large area of thread contact with the wood (this is more important for the plate to belly brace, since the axial loads are very high). The slightly blunt tap is probably the ideal solution for maximising contact area. If you only have a sharp tap on hand, the application of a little Titebond in the threaded hole, spread around evenly with a bottle cleaning brush also provides for a nice interference fit.</div> <div><br></div> <div>Ron O.</div> <div><br></div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>