<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Bandsaw maintenance</title></head><body> <div>Hi all,</div> <div><br></div> <div>Yesterday I lost almost the entire day servicing my only-just-big-enough resaw bandsaw.</div> <div><br></div> <div>The saw has a 2hp motor with 45 mm (1.75") wide 500 mm (20") diameter pressed steel wheels and a cast iron tilt table and adjustable fence. I run a 2" wide Simons Red Streak blade, which has a 0.89 mm (35 thou) thick back with 20 thou of tooth set per side with tooth pitch of 1". Theoretically the blade cuts a 75 thou curf, but after all the vibration and blade flex is taken in account, the reality curf width is around 100 thou (2.5 mm).</div> <div><br></div> <div>When I first bought the saw, being the commercial quality (read cheap and nasty) item that it was, performance was less than startling. After much fiddling getting everything shimmed up and straight, and after building a custom roller bearing guide system for the upper guide post and under the table, and speeding the blade up to 5,000 feet per minute, the saw remained an ordinary performer. After some further reading I realised that the wheels, which were rubber tyred, probably were not crowned properly and had axial run out. So I set to work and ground the wheels with a 1 degree crown angle which peaked at 1/3 width back from the font edge of the wheels. Bandsaw wheels are usually crowned slightly closer to the front of the wheel to allow them to properly track a thinner blade, should this be required.</div> <div><br></div> <div>It's been many years since I first crowned the bandsaw wheels. However, over recent months the saw has been acting up and refusing to track well. When a blade is cutting well it should never come in contact with the back guide. But this started happening regularly and over the weekend we lost an expensive piece of wood when a blade stepped right forward off the wheels and had a chew at the cast iron table.</div> <div><br></div> <div align="center"><img src="cid:a06110404bec11cdb6518@[192.168.1.101].1.0"></div> <div align="center"><br></div> <blockquote align="center"><i>A view of the saw showing the roller guide system. These are now available as an accessory item. The roller guides shown were custom made over fifteen years ago.</i></blockquote> <blockquote align="center"><br></blockquote> <div>Should anyone wish to receive a higher resolution close image of the guide rollers, email me privately. The images shown are re-sampled lo-res to get them onto the pianotech list.</div> <div><br></div> <div>An examination of the wheels revealed that there was little wear of the rubber tyres. But, while the original crowning machine marks remained just visible, the crown was almost flat in the middle of the wheel.</div> <div><br></div> <div>The industry standard for crowing steel band saw wheels is 1 degree of crown.  After reading a few articles on crowning wheels I found that some recommend a crown angle of up to 7 degrees.</div> <div><br></div> <div>Four useful articles on band saw maintenance can be found at;</div> <div><br></div> <div><font face="Lucida Grande" size="-3" color="#000000">http://www.owwm.com/FAQ/Default.asp</font></div> <div><br></div> <div>I decided to re-crown the wheels to 1.5 degrees. A higher crown would probably increase the stress on the blade back, and the original 1 degree of crown seemed to track reasonably well. I am very pleased to report that the saw is now performing better than ever. We did a test cut on an 8" (205 mm) deep board after re-assembly. The cut was straight and the blade didn't budge from its free-running track position during the cut.</div> <div><br></div> <div align="center"><img src="cid:a06110404bec11cdb6518@[192.168.1.101].1.1"></div> <div align="center"><br></div> <blockquote align="center"><i>A view of the wheel surface, shown against a square, clamped to the housing, to show the crown of the freshly crowned tyre</i></blockquote> <blockquote><br></blockquote> <div>While I often feel cheated of time when I lose a day doing something like yesterday's bandsaw maintenance day, it was a different case yesterday. Its most pleasing  to have the saw performing better than I could have imagined.</div> <div><br></div> <div>Now its back to work to finish the resawing I started over the weekend.</div> <div><br></div> <div>Ron O.</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>