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View Full Version : Blade Welders: Carbon VS Bi-Metal



EddyCurr
02-24-2010, 02:21 PM
How is a blade welder rated for bi-metal service different than one
rated for carbon?

What are the consequences of attempting to weld a bi-metal blade
with a welder rated for carbon service?

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bborr01
02-24-2010, 07:25 PM
Hi Eddy,

I just responded to Joe Lees post about blade welding and addressed the different types of metal I have welded on a blade welder.

Simple answer is that in my experience welding blades with a blade welder is that carbon and bi-metal blades weld the same.

I didn't even know there was a seperate welder for each.

I tried welding high speed steel blades though and they were a no go.

If anyone reading this knows how to weld high speed steel blades I would be interested in hearing about it.

Also, if you don't try cutting hard steel with a bi-metal blade they will outlast carbon blades my many times. Probably 5 or 10 times.

What kind of blade welder are you using?

Brian

EddyCurr
02-25-2010, 10:36 AM
I just responded to Joe Lees post about blade welding (Band Saw
Blade Welder Help ! (http://bbs.homeshopmachinist.net/showthread.php?p=525046#post525046)) and addressed the different types of metal
I have welded on a blade welder.

Simple answer is that in my experience welding blades with a blade
welder is that carbon and bi-metal blades weld the same.

I didn't even know there was a separate welder for each.Thanks for the reply. In the same thread, Michael Hall expressed similar sentiments


JoeLee

I know I've read several times that these old welders will not weld bi-metal
blades. Having looked at both the DBW-1 and DBW-15 schematics I found
no fundamental difference other than the size of the transformer. I believe
the DBW-1 is 4.5kw where as the DBW-15 is 7.5 IIRC. So I called DoAll and
they said they see no reason why the DBW-1 would not weld bi-metal
blades. However they said one should follow the annealing instructions in
the DBW-15 manual. If anyone here can explain a difference in welders I
am all ears.

Michael

What kind of blade welder are you using?I am considering purchasing a bench style 220V/1Ph blade welder
capable of joining 3/4" blade stock. I have been using carbon material
but am interested in the longer life offered by bi-metal.

In looking at specs, I noticed that Grob and Enco welders indicate
differences based on blade material. Enco has machines for 1" blade (http://www.use-enco.com/CGI/INPDFF?PMPAGE=588&PMITEM=293-8025)
that are both rated at 7.2 KVA (220V/1Ph), but the bi-metal unit
is 62 lbs heavier and 80% more expensive - I suppose there is an
explanation.

An alternative may be to silver braze blades together. Here are a
couple of tutorials.


Silver Brazing Your Own Band Saw Blades (http://www.shakerovalbox.com/finished/BandSawBlades.pdf)

BANDSAW BLADE REPAIRS (http://www.merseyturners.co.uk/learn_stuff2.htm)


If anyone reading this knows how to weld high speed steel blades
I would be interested in hearing about it.
I do not know whether silver braze would work successfully for HSS blades,
but I suspect it is worth a try.

An electron beam welder might be the ideal tool for difficult materials,
but I haven't come across a suitable home shop unit, yet.

.

DougA
02-25-2010, 06:49 PM
Carbon and bi-metal weld differently because they are different. A carbon blade is made entirely from carbon steel from the tip of the tooth to the back of the blade. Bi-metal blades are just that. The tooth edge is made from either a m-30 or m-42 material and is welded to a backing steel of spring steel. Different brands of blades weld differently as well since there is a couple different companies that supply the backing steel to the blade companies. The production welder we use does both carbon and bi-metal. In general though I find that a bi-metal blade needs a little more heat then a carbon blade. So with that said I assume a welder that does bi-metal will also do carbon but a carbon blade welder won't weld the bi-metal blade properly.

Dr Stan
02-25-2010, 07:04 PM
The weld on factory welded blades are far superior to those made in a shop. They use much more sophisticated equipment than the ones even sold along with big name saws such as DoAll. So as a rule I do not even bother trying to weld 3/4" or larger blades.

I have successfully welded 1/2" and smaller blades over the years, but for the average home shop it would be very difficult to justify the cost of a butt welder. The only possible exception would be if one was using a band saw to cut the inside feature of a part made of plate material.

You could also experiment with a TIG welder to see if you could get an acceptable weld on a band saw blade.

wierdscience
02-25-2010, 08:10 PM
The big Doall welder at work will but-weld up to a 2" wide carbon blade.

It' will not weld bi-metal anything,all it does is,spit,sputter and blow holes in it.

I have been meaning to try using an Argon purge during welding.but haven't had time yet.

There has to be some major difference in the machine judging by the major difference in price/weight etc.

EddyCurr
02-25-2010, 09:46 PM
The only possible exception would be if one was using a band saw
to cut the inside feature of a part made of plate material.Bingo. I do not use up blades frequently enough through conventional
sawing to justify building replacements, but having the means to rejoin
my blades would offer a new way of making inside cuts.


You could also experiment with a TIG welder to see if you could get
an acceptable weld on a band saw blade.I believe I have suitable equipment for this: an inverter machine
with collets & electrodes down to 0.040, along with gas lenses.

However, I also have a Smith's Little Torch on oxy/acetylene. I am
inclined to believe that the wetting action of silver solder will contribute
to easier joining of the parent metals than tig work will. Tensile strength
of silver braze alloys is said to be 40,000 - 70,000 psi (and more than 70k
in some cases.)

I'll have to give both methods a try.

.