MadModder
Gallery, Projects and General => How to's => Topic started by: one_rod on November 21, 2009, 07:46:23 PM
-
Don't know if anyone else bothers doing this, or is interested, but here's how it works for me.
Good quality made-to-size blades for my saw cost about £10 to £12. If I make my own from bulk blade stock that falls to about £4 to £5 per blade.
Even better are the Ebay bargains. I regularly get brand new blades for £1 or even less. Of course they are always the wrong size for my saw, but if they are longer than the 85in my saw needs then it's no problem to cut them down to length.
Even if they are too short, it's worth buying two and joining them together. So, how's it done?
1. Cut your stock to length. Try to get the cut ends fairly square, but don't be fanatical about it. (http://farm4.static.flickr.com/3261/2428398843_d9d4040c67_o.jpg)
2. Grind a bevel onto the ends of the blade stock. Strictly speaking it's known as a scarf. Remember the scarf on the other end has to be on the opposite side of the blade, so the two pieces fit together. Don't worry too much about the actual angle, just try to get the scarf nice and flat and both ends to the same angle. Bench grinder, belt grinder, angle grinder, even hand filing are all good.
(http://farm3.static.flickr.com/2144/2428398769_1df693284f_o.jpg)
3. This is my super sophisticated hi-tech blade brazing jig. OK, it's an old piece of angle iron with a big notch sawn out of it. (http://farm4.static.flickr.com/3279/2429211298_7316efedab_o.jpg)
4. Clamp one end of the blade in place with a bulldog clip, scarf upwards. Mix some brazing flux with a little water to form a thick paste. Apply a little to the scarf.
(http://farm4.static.flickr.com/3238/2428398579_e7bcc25006_o.jpg)
5. Line up the other end of the blade carefully so the two scarfed ends form a nice close-fitting joint. Try to get the back edges accurately in line otherwise the blade will bump every time passes through the blade guide. Apply a little more flux to the joint if necessary. I put this offcut of fire brick under the joint area to help reflect the heat back onto the joint and make heating a little faster.
(http://farm4.static.flickr.com/3081/2429211092_562bcfda6f_o.jpg)
6.Heat with a gas torch. Once a good temperature is reached touch the joint with the brazing rod. I use low temperature silicon bronze rods. The idea is to get the blade hot enough for the braze to flow nicely into the joint, but without getting it so hot that it softens and begins to sag under it's own weight. As soon as the braze has flowed into the joint remove the heat and allow to cool. Don't move anything until the joint is solid. (http://farm4.static.flickr.com/3178/2428398377_c6acfb93a1_o.jpg)
7. I would normally like the finished joint to look a bit tidier than this, but I was trying to braze and take photos at the same time. That's my excuse, anyway.
(http://farm3.static.flickr.com/2085/2429210928_f02068aa8a_o.jpg)
8. Remove the surplus braze from the joint area. I usually use an angle grinder and finish off with coarse emery cloth. (http://farm3.static.flickr.com/2098/2428398151_e2db8141ed_o.jpg)
Job done. Should take about 20 minutes.
one_rod
-
Nicely done, And timely. I'm getting tired of buying blades. :thumbup: :thumbup:
Ron
-
thanks for the pictures and the write up, now i will have to get some blades and give it a try. :dremel:
chuck :wave:
-
Nicely done and shown, that ones filed away for the future :thumbup:
Cheers
Stew
-
Nicely and neatly done Rod. :thumbup:
Not sure...... It was a very long time ago...... Did I work on a bandsaw with a built in electric butt weld device, to do that? :scratch:
I`m getting old/ forgetful...... ::)
David D
-
Excellent sequence of pictures, the page has been download to my Engineering Tips folder.
Many thanks.
Trev
-
one_rod, would silver soldering work or has it got to be brazed?
:thumbup:
Rob
-
Rob,
I used to silver solder my own, and it works just fine.
John
-
Not sure...... It was a very long time ago...... Did I work on a bandsaw with a built in electric butt weld device, to do that? :scratch:
David D
Yep. Those electric resistance welders are a great piece of kit. Do the whole job in about two minutes. Some even have a little grinder to clean up the weld afterwards.
Some big industrial saws had them built in, but portable units can be had. Trouble is that even tatty, second units tend to be eye-wateringly expensive.
one_rod, would silver soldering work or has it got to be brazed?
:thumbup:
Rob
I can't see any reason why silver solder shouldn't work, although I have never tried it myself.
If you have a worn out blade to play with then the easiest thing would be to cut it, solder it back up and run it on the saw for a while.
As you probably know, even if the joint fails nothing bad will happen. the blade simply loses contact with the drive wheel and stops.
Got to be worth a punt, if you have some silver solder laying around.
If you do try it, let us know how you get on.
one_rod.
EDIT:
Thanks John.
So now we know.
:thumbup:
-
Yep. Those electric resistance welders are a great piece of kit. Do the whole job in about two minutes. Some even have a little grinder to clean up the weld afterwards.
Some big industrial saws had them built in, but portable units can be had. Trouble is that even tatty, second units tend to be eye-wateringly expensive.
A major advantage of having the built in butt welder is the ability to break the blade, place it inside a work piece, weld it back and carry on with the project. Once finished , break the blade again to free up the work piece. This was handy for cutting openings in SS plate.
Joe
-
one_rod, would silver soldering work or has it got to be brazed?
:thumbup:
Rob
I have a similiar rig that I use to silver solder the blades. It works well. I just use a regular propane torch. I had a problem getting the blade up to proper temperature. I found out the slot was too small and the metal on the sides was drawing a lot of the heat away. I opened the slot and everything works.
-
Can this method be used on the bimetal M42 type blades as well as the standard ones ?
Cheers
Jim
-
Yep,