snipped-for-privacy@prolynx.com fired this volley in news:45566318-1852-4a1d-8b86- snipped-for-privacy@y11g2000yqm.googlegroups.com:
"Smoking out" the part with an un-oxygenated acetylene flame, avoiding or cleaning only the work zone is a quick way to mask your work, and it works fine.
LLoyd
Perhaps he cut it deliberately in order to make an inside cut-this is commonplace in metalworking and many band saws intended for that purpose have a blade welder attached.
When you say "brittle", what do you mean? Does the joint break along the braze line, or does the band saw blade material itself break? If it's the braze, then wrong material or poor adhesion (poor wetting). My concern would be the 45 degree angle. I usually scarf the joint for at least a quarter inch, maybe more. The 45 degree angle gives you about 35 thou contact, whereas 1/4" overlap would give you almost 3/8" contact. Overheating the joint just once during the process can easily oxidize the joint. Once the braze material has flowed properly into the joint, slowly pull the torch back, away from the joint, taking, maybe, 15 or 20 seconds to get 6 or 8 inches away. This will anneal the joint and redice the brittleness of the band saw blade metal on either side of the joint. You can test this part of the process with a used-up blade. If you heat it to cherry red or thereabouts, and pull the torch away, you are probably hardening the blade. Then it will be very brittle. Try snapping a piece off with pliers, both before and after this treatment. (Safety glasses required, here!). Then heat another piece to cherry red, but instead of just pulling the torch away, SLOWLY pull back, taking several seconds to get the red to go away, as I said above. Now try to snap off a piece with the pliers. The end should bend some before breaking. The reason the I generalize about some of this is that band saw blades can be made of many different materials, that act in different ways as far as hardening and tempering go. With some materials, you may have to take a longer time than I specified above to cool the part below any redness at all.
Pete Stanaitis
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Use a TIG welder
Yup. That makes sense. Thanks!
--Winston
what's wrong with drilling a hole in each end and running a rivet through it?
;~)
"Leon" fired this volley in news:G4Odncn74PZ3FI_RnZ2dnUVZ snipped-for-privacy@giganews.com:
MY bandsaws have guide rollers. mebby yours don't...
LLoyd
Thump! Thump!.. Oh Sh&t!! It just tore a great big hole in my metal piece when the rivet went by again.
That would be like putting a volt through the middle of a handsaw blade.
;~)
And a big, woooosh over both of you.
Shit disturber.
Didn't know you had it in you.
Flying rivets are too small to woooosh. ;-)
I've just read the manual for that welder...
You chaps are allowed to play with guns, why don't you do something useful with them and reduce the number of lawyers infesting your country :-|
Mark Rand RTFM
Excellent idea. Where on the lawyers should we drill? I'm guessing heart area, plenty of room where the heart should be.
techomaNge
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I just realized my own error on the width of the joints with various scarfs. What was I thinking? 45 degrees will give just over .025 contact (.025 X 1.414) and 1/4" will give just over 1/4" contact (0.2503122, I think).
Pete Stanaitis
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spaco wrote:
They breed.
The number of women in law school greatly exceeds the number of men.
It's terrible.
No, they are not. Are they being serious? That little torch is a joke. I have a couple and they will not heat anything unless it is very small. I would not be surprised if the solder joint as demonstrated were rather poor. The saw blade is going to conduct the heat away from the joint faster than that torch will heat it even if you *can* keep it lit :-) Note that the picture of the final result in the video was not seen well, if at all.
OTOH I wonder if using one of these pastes would be an option. I like the concept of precise application to the joint:
As usual you guys are right on target. The miserable scarf joint I had was the biggest problem. I hand ground a new one about
1/4"(a sloppy job) and (using the same Oatey solder) soldered up a real blob, but it held. Next I built a jig to hold both ends at the same time, and after fiddling with adjusting it, I got some real nice matching 5/16" scarfs. Pounding the solder wire to a thin sheet, careful application of the flux to just the scarf faces and the propane torch got me a reasonably nice looking splice. It held my weight without failing and bent at a 1/2" radius with no failure. The cross section area of the blade is .025 x .125 and I weigh 180 lbs so I calculate that's 57,600 PSI tension - well over the 15,000 PSI in actual use.The blade is too short to go back on the saw but it gives me plenty of material to practice my technique on. They always seem break at the factory weld so I don't think I need to worry about a tired blade as someone pointed out. I'll keep the 50% Ag stuff in mind should I have problems with the wider blades. Thanks to all who responded. Art
I have silver brazed ( often called silver soldering ) numerous things using small propane torches. Propane is hot enough. It is no problem to silver braze bandsaw blades using silver braze. I have done it. Silver brazing larger objects takes some thought. Insulating fire bricks ( IFB ) are useful. You can take some IFB's and build a little corner that keeps the heat from being conducted away. Silver braze flows at dull red heat.
=20 Dan
One tip on grinding the scarf joint. Take the bandsaw blade and twist it so that the sides that need to be ground are both on the same side and next to eachother. Then grind both ends simultaneously. Helps to get the same angle on both ends.
Dan
Please keep us posted.
There is a lot of tribal knowledge advising against use of 'soft solder' for band saw blade welding. I am interested to know your experiences with longevity of the joint.
Thanks!
--Winston
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