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Bandsaw Blades

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Stub Mandrel30/10/2010 17:28:55
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4318 forum posts
291 photos
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Dang! I just broke my bandsaw blade - I think I upped the tension a bit too much, it cracked across at the joint, while the joint was passing round the wheel.
 
In the past I have silver-soldered broken blades with limited success.
 
I now have an arc welder. Is it worth running a bead across the blade and grinding it down?
 
Any hints or tips beyond making sure the two halves are properly aligned?
 
Neil
john swift 130/10/2010 18:36:59
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318 forum posts
183 photos
Hi Neil
 
in the past when i've repaired damaged door panels with a mig welder
 
 I placed a bit of brass behind the place I was welding
this prevented me blowing a hole through the thin metal using the minimum setting
 
you may need to heat treat the joint
 
        John
 
 
Speedy Builder530/10/2010 19:46:10
2878 forum posts
248 photos
Stick to silver solder.  Make the joint feathered, ie file a taper about 8mm in length on each end of the blade.  Make a brazing jig up to hold the two ends together and silver solder the joint.
KWIL30/10/2010 23:16:04
3681 forum posts
70 photos
I used to join by silver solder but with limited success over time, using a jig with edge aligning details and clamps.
 
I now use a proper Resistance Welder which aligns and brings together the ends causing an upstand on both side which I then file/grind away. I can also anneal the joint after the weld. The alignment is held over about 5" by means of a thin plate on the face of each of two electrode clamps which aligns the teeth edge, the clamp is cut away so as to not contact the teeth from the sides, it handles 6mm- 30mm wide blades.
 
So Neil, a bead across the blade on both sides is equal to what I achieve with the upstand, yes it is essential to anneal the end result or else it will crack quite quickly. Tension is a matter of practice, not so tight that it has a sharp twang when  struck lightly, I can usually tell by the cutting noise as it runs. I can give better sizing details if anyone is really interested.
 
www.ideal-werk.com   might show you more.

Edited By KWIL on 30/10/2010 23:17:50

Ramon Wilson30/10/2010 23:18:13
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1655 forum posts
617 photos
Hi Neil,
I'd certainly agree with the silver soldering - I've been doing that for years on my small Burgess. I bought some Starret bandsaw blade material -100ft reel - and cut a length off as required then taper the ends as Robert says but shorter, only about a 3mm overlap and done on the off hand grinder. You do need to ensure theres no 'thick bit' at the join which will stick in the kerf. I use one of those small pencil torches filled with lighter gas and easyflo - so far never had a break of the actual join but sometimes within half an inch of it. They last quite well and I've regularly cut inch thick cast iron (I have some slabs which once cut gets turned into round bar for pistons etc)
 
Regards - Ramon
Terryd31/10/2010 08:30:32
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1946 forum posts
179 photos
Some ideas, hints and experiences discussed here.
 
We used to butt weld using a specialised welding machine but it is important to get the thickness right by grinding.  If using a mig welder and jig, it is important to anneal twice,  once after welding and again after dressing (grinding) the blade.  Just heat to blue with a softish flame and allow to cool slowly.

Terry
Terryd31/10/2010 08:43:05
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1946 forum posts
179 photos
Hi Stub,
 
Just read your post again, if using a stick welder, clamp blade with a piece of copper or brass sheet backing it as John suggests and then use a series of quick tacks.  These should be staggered and then filled between with more tacks.  If done properly you will not need to weld both sides but if you do need to, then dress the first side and repeat on the other side.
 
Terry
Stub Mandrel31/10/2010 09:34:35
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4318 forum posts
291 photos
1 articles
Plenty of advice there!
 
I've been booked in to put flooring down in the loo today Of course that means shorten door. Door was probably the 1930's outside loo door and has huge gate hinges under many layers of paint - so i'm typing this in between applications of paint stripper.
 
When I eventually earn my free time it seems that whatever method I use the  main message is anneal it. On my earlier attempts I assumed that heating for silver soldering would be sufficient anneal, obviously not!
 
Also thanks for the back with brass idea - I'm really good at blowing holes.
 
Neil
Weldsol31/10/2010 10:07:43
74 forum posts
Hi Neil I would not recommend the use of brass as a backing as you could pull some zinc into the weld pool which will give rise to cracking.
The most common material for backing on steel is copper.
 
Paul
Stub Mandrel31/10/2010 18:46:36
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4318 forum posts
291 photos
1 articles
Oh woe is me!
 
Set up for welding, got the rod nice and hot on a bit of black bar... then blew a 1/4" wide gap in the blade. It will be easier if I borrow my SIL's auto darkening helmet. Must see if I can find my old carbon steel blade and I'll practice on it.
 
Swapped over to silver solder it instead. on the first anneal the joint sprung apart?!
 
Realised I hadn't overlapped it enough and tried again.
 
It now works but it was a hell of a job to get it on again as its a bit short!
 
I wonder if it will last?
 
Neil
John Olsen31/10/2010 21:11:48
1294 forum posts
108 photos
1 articles
I've silver soldered a few over the years, my experience is that if it broke because it was old and fatigued it will not last long, but will not necessarily break anywhere near the repair. If it was a newer blade and broke as the result of a mishap, it may last better, provided of course it is not too kinked around the break.The usual "standard far eastern" bandsaw has wheels that are a bit smaller than ideal, which does not help.
 
I do have one blade, never been repaired,  that lasted really well, to the point that I finally wore the teeth off. It is hung on the wall as a shining example for its succesors to emulate. I wish they were all that good.
 
regards
John
Terryd31/10/2010 21:18:53
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1946 forum posts
179 photos
Posted by Stub Mandrel on 31/10/2010 18:46:36:
Oh woe is me!
 
Set up for welding, got the rod nice and hot on a bit of black bar... then blew a 1/4" wide gap in the blade......
 
Neil
 Hi Stubs,
 
That's why you should use copper as a backing.  It conducts much of the heat away, much better than steel.  You can use black bar for rigidity with a good layer or two of thick copper sheet backing the blade.
 
Terry
Peter Tucker01/11/2010 06:52:02
185 forum posts

Hi John O.,

 

Take your worn blade to the saw doctor and have it sharpened.  I took my broken blade to the local saw doctor to weld and he threw in a sharpening.

 

Peter.

Ian S C01/11/2010 11:16:47
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7468 forum posts
230 photos
With the little horizontal/vertical bandsaw you can lengthen the slot where the loose wheel is adjusted. With the saw upright, and the cover open, on the left, lower side of the top wheel you may find a web of castiron that needs cutting away (about 1/2" x 1/4" x 1/8"), I did my one today, cut it with a thin wheel on the Dremel. I'v had to put a longer bolt for tentioning. Ian S C
Stub Mandrel01/11/2010 19:52:23
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4318 forum posts
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Thanks Ian, I could do that! - I only need about 1/8" to 6.25mm extra travel
 
This blade is fairly young (it's done about 20 cuts, although up to 2 1/4" FCMS). It was a fatigue break at the weld. The blade itself is a HSS teeth on spring backing one from Dragonsaws, and it has variable pitch teeth. I want to fix it, not least because it knocks the spots off the crummy carbon steel blades from other sources. If I need to replace I'll go back to Dragonsaws although a link on the web suggests they've gone into receivership (too cheap and blades lasted too long???)
 
Neil
 
Ian S C02/11/2010 03:46:41
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7468 forum posts
230 photos
Hi Neil, I use similar blades,they are second hand(the bloke I do some work for does'nt like rejoined blades, recons that when  worn they don't cut straight). Just looking at the machine last night, and the adjustable wheel shows about 1/4" of the rim out in the open, but while I can get the bi-metal blades welded free I,ll use them until they wont fit, or they fall to bits.  Ian S C
keithmart02/11/2010 07:48:09
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165 forum posts

Hi


QUOTE: I'll go back to Dragonsaws although a link on the web suggests they've gone into receivership


Yes they have gone into receivership, but Ian has started on his own. I did get an email from him some time ago, (February)


Try [email protected]

I have had good service from [email protected] as well


Regards


Keith

Leeds UK



Stub Mandrel02/11/2010 21:32:52
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4318 forum posts
291 photos
1 articles
Thanks Keith,
 
I bookmark that and try it if the repair doesn't last.
 
Neil

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