BANDSAW BLADE REPAIRS

  Talking to members during my demo in January gave me a few new ideas and certainly increased my knowledge, one of the best reasons for belonging to our group! Dave Smith suggested I put pen to paper and share a few ideas with you in relation to bandsaw repair.
 I have in the past used silver solder and flux powder, but on this occasion I was trying out the solder sticks pre-coated with the flux. Dave Connelly, whose engineering knowledge is vast, advised that when silver soldering, adequate fluxing of the joint is essential. This can be achieved most effectively if the flux powder is mixed with water into a thick paste and the two ends of the blade coated. Even when using the flux coated solder it does improve the process.
 Heating the blade ends thoroughly to cherry red is important and best achieved by using PROPANE gas rather than Butane since silver solder melts at a much higher temperature than the ordinary soft solder used for copper pipes etc.
 Once the blade is joined it is advisable to remove all traces of flux using water and a brush or scotchbright pads. This prevents oxidation or corrosion setting in, caused because the flux is producing Hydrochloric acid to etch the surface of the steel blade and provide a key for the solder. Set out below is the procedure that I used during the demonstration. The sketch shows a simple angle-iron jig that I have made up for this purpose, and the positions of each end of the broken blade ready for repair.

1. Each broken end of the blade should be ground to an angle of about 45 degrees to provide a scarf joint. This process also cleans the damaged ends. Quickly running it across the bench grinder is enough to do this.

2. The blade ends should be clamped onto the jig using toolmakers clamps, or something that will not overheat and bum or melt. Allow daylight to 'just' show through between the ends so that they are not quite touching.

3. Coat each end of the blade with flux paste and heat the whole of the joint to bright cherry red before applying the solder.

4. Apply the fluxed solder and allow it to run across and into the joint.

5. Remove excess flux as described above.

6. File the blob of solder off flush with the surface of the blade and flat off the blade edges to allow smooth running of the blade through the saw guides.
(Courtesy of Roger Holley, Wessex Woodturners)