tensile strength solder for repairing small band saw blade - Page 1
Forum section: electronics / repair

author: pcmad
author_rank: Regular Contributor
timestamp: January 18, 2021, 03:46:55 am
content: how strong is solder in tensile strength i.e. pulling apart I've got two bits of steel bandsaw blade that I want to glue together using solder and then tension it would it survive or will it need something strongerwould 60/40 eletric solder work bestor lead plumpers solder work best

author: rfclown
author_rank: Frequent Contributor
timestamp: January 18, 2021, 04:09:44 am
content: Google "tensile strength steel" and "tensile strength lead". Even if the tensile strength wasn't off by an order of magnitude, soldering to steel can be a pain.

author: beanflying
author_rank: Super Contributor
timestamp: January 18, 2021, 04:50:21 am
content: Quote from: pcmad on January 18, 2021, 03:46:55 amA far better option that can be done with a fairly simple Butane torch would be high content Silver Brazing rods and suitable flux.

author: IanB
author_rank: Super Contributor
timestamp: January 18, 2021, 04:51:01 am
content: The internet says to use silver solder (hard solder)--needs a MAPP torch to melt it. Grind the ends to be joined at a taper and use a jig to keep the blade aligned and straight when soldering. Use the appropriate flux. Grind smooth after the joint cools.Electrical solder is far too soft and weak for high strength joints. Don't even consider it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 18, 2021, 04:52:38 am
content: Even in a carefully tapered lap joint: not even no, hell no (it would at least handle the tension, but would just peel apart after a few trips round). "An order of magnitude" is not at all an exaggeration!Metallic fillers are perfectly acceptable, you just have to use the right kind: silver solder. Which is actually braze, it's just called solder historically I guess. Do not confuse with "silver bearing" solder, which is a soft (Sn or Sn-Pb) solder with a few percent silver mixed in. Braze has a higher melting point, needs a torch and a different kind of flux. Brass filler works too. Joints still won't be as strong as the base metal (it would if the blade were mere mild steel, but it's spring steel), but it'll be pretty close actually. (Mind, the join will be weaker than the base material, for brazing or welding, because of the temperature applied. But that's fine, there's still plenty left.)Tim

author: Berni
author_rank: Super Contributor
timestamp: January 18, 2021, 06:43:05 am
content: Firstly 40/60 lead solder would not stick to regular steel like it does to copper, and if you could get it to stick it wouldn't be even close to strong enough.Try taking a spool of solder wire, grab the wire with both hands and just pull. It snapped didn't it? Now imagine how much force it would take to snap a steel wire of the same diameter, pretty sure you would need quite a bit more than just your hands to pull it apart like that.You might be able to braze it together with silver, but as others said that still is not quite as strong as the blade itself. Ideally you would weld it together with something like a TIG welder, then grind the joint flat and smooth.

author: james_s
author_rank: Super Contributor
timestamp: January 18, 2021, 06:46:14 am
content: Solder a band saw blade? No way, there is not a snowball's chance in hell that will work. Even brazing is unlikely to be strong enough. The big band saw at my friend's shop has a blade welder built into it. It works a lot like a spot welder, it presses the ends of the blade together and then passes a large current through the joint to fuse the metal.

author: IanB
author_rank: Super Contributor
timestamp: January 18, 2021, 06:51:27 am
content: Quote from: Berni on January 18, 2021, 06:43:05 amAccording to many people describing their experience online, silver brazed bandsaw blades last longer than welded blades, even though this seems to go against expectation. It may be that the higher temperatures from welding change the properties of the blade and make it more prone to failure?Since silver brazing or soldering is easier to do than welding and requires less in the way of special tools, it can't hurt to try it first.

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: January 18, 2021, 12:53:29 pm
content: I'm certain that when I first started work, the R&D dept used to have the bandsaw blade in a big roll in a flat cardboard box. When a new blade was needed the old chap there used to use a spot welder to butt join it. Maybe my memory is not what it was.A friend of mine has just acquired a lovely vintage tool that aligns and clamps the ends of the blade, and has a little pocket to add a snippet of silver solder (and borax presumably for flux). There is an electric element that heats the whole shebang, and the operator uses skill and experience to judge the 'on' time of the heater. He has not tried it yet.BT

author: aqibi2000
author_rank: Regular Contributor
timestamp: January 18, 2021, 01:24:20 pm
content: 🤣

author: torch
author_rank: Frequent Contributor
timestamp: January 24, 2021, 09:09:19 pm
content: I have a small home machine shop with 2 bandsaws. I silver braze bandsaw blades without any problems at all. I use this kit (but I bought it from R&D Bandsaws, where I get my blades):https://www.ebay.com/itm/313256898933Preparation is key.

author: PaulAm
author_rank: Frequent Contributor
timestamp: January 25, 2021, 04:37:13 pm
content: Some bandsaws have blade welders on them but it takes a good technique to get a properly annealed weld that will stand up.The welders typically force the 2 ends of the blade together while a large current flows so you get a thickened weld area which then has to be ground down. It will also be very brittle so needs to be annealed using the welder to heat it up again and cool it gradually. If you don't do it right it will break almost immediately.It;s probably easier to silver solder them

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2021, 07:56:30 pm
content: I'm a bit shocked to learn that brazing is strong enough for this sort of thing, I'll have to give it a try sometime as an alternative to welding.

author: m3vuv
author_rank: Super Contributor
timestamp: January 25, 2021, 08:07:19 pm
content: ive always but welded them using a mig,doesent normaly last long due to the haz,can sometimes get you out of the brown stuff tho.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 26, 2021, 12:03:44 am
content: Blades for small band saws are allways prone to fatigue. For the really small ones (e.g. < 2 m lenght) it hardly worth to sharpen them. So if they break it is rarely worth a repair as chances are they will not last long.Barzing can work and needs less special tools. With the right machine electric welding is faster. So commercially sold blades are usually welded.

author: Dubbie
author_rank: Unknown
timestamp: January 26, 2021, 12:27:45 am
content: I use this stuff:https://www.muggyweld.com/product/ssf-6-silver-solder/it claims 70,000psi strength and I would believe it. I have never had it fail. I bought a packet about 10 years ago and still have over half left, you only use such small amounts.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2021, 01:51:21 am
content: I was thinking beyond the original question, there are all sorts of things that are too small and precise to weld easily where brazing might be a good choice, I've never done it before.

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 01:58:11 am
content: the only problem with brazing is over heating. I suggest an air acetylene torch for most things, it made a difference. You can get the whole area glowing like a dull coal with silver braze that melts nicely and flows aroundyou need the black flux and 40% or greater silver rod for steel to steel

author: beanflying
author_rank: Super Contributor
timestamp: January 26, 2021, 02:02:54 am
content: Butane based brazing has plenty of use cases and a wide range of materials it can be used on.This job was done with a disposable can and a $12 Chinese torch after a so called evilbay packaging jobJigging, preheating, filling then post heat treating to even it out in this case were all important steps. Basic Aluminum filler rods used.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2021, 02:07:07 am
content: That's amazing, I must try that. Didn't know you could braze cast aluminum like that.

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 02:43:52 am
content: Trust me, that takes skill. What often happens is you get it molten but bad adhesion or you melt the parent metal or other BS. Its especially marketed for casting, at least from muggyweld.IMO Actually putting aluminum down with a torch is often EASIER then brazing the stuff.I figured out how to mig weld steel, stick weld steel, gas weld stainless and steel, gas weld aluminum structures that are like balanced (this is tricky, it has to do with thermal mass, but its still welds I don't like with too many random hard to prevent holes) but aluminum brazing has a special place inhell. Personally I just.. lean towards using stainless steel now rather then aluminum when I need to weld up a structure.. for me the money spent on the steel is less then the time spent trying to fix fucked up brazes. I had modest success making frames for window screen material with Al-braze and aluminum strip (you braze up a frame and glue a window strip over it, so you have a framed removable vent cover you can screw on). It is very weak (the joint is tiny).. but I don't care since its holding up a plastic dust screen, and usually bolted right to a metal perforated plate. Stronger then epoxy in an application where epoxy is just too weak.Now i only ever tried 2 rod types, used about 20 rods, and I had more success with a benzomatic hardware store rod then the big box of rods I bought from the welding store. But I found this interesting informationThere is 2 main industry types of aluminum braze1) patching holes in leaked aluminum hydraulics (radiator)2) more joining typeI think my dislike may be for the type 1 aluminum braze, and using it in a incorrect application, I believe the primary application for this stuff is to fill a divet made in an aluminum radiator tube (literary a crater filler). I also got the real flux from harris for brazing aluminum (not using welding aluminum flux).That joint almost makes me want to buy muggyweld and try it for the nth time. At this point I feel like I would rather remake that entire handle with a file then try more fucking Al brazing.Anyway if you try it, its cheap.. if it comes to you, I am impressed, but if you can't do it, don't kill yourself over it.. its a bad process compared to like everything else metal.Now the low temperature aluminum solders sold with liquid flux are actually.. some what decent. Its the products marketed as BRAZES that I have such trouble with.Every once in a while I watch a new youtube video and decide to give it another try and it ends bad.I am serious when I say the mindset I have now when it comes to approaching an aluminum braze job is similar to putting my hand into a fire.I also noticed that every successful youtube video on this stuff uses a different type of blow torch, I am thinking that the normal benzomatic north american torch is not what you want for this application. It seems the successful people use one with a very wide broad flame.The flow characteristic is chunky peanut butter. Silver is beautiful, this crap is like smearing tar.To be honest if I did it I would be paranoid it will break my toe when I am carrying it. Haha as cheap as I am I would have to mail it out to get welded with a tig by someone that had the patience to figure it out and could pay for my medical bill !

author: beanflying
author_rank: Super Contributor
timestamp: January 26, 2021, 03:02:33 am
content: Regardless of process be it MIG, TIG or Gas they all take skill. Picking the right process for the job for a start is key. Preparation then plays a major part from cleaning in the above case and preheating even before you go near it with a filler rod. That job was done with Bernzomatic rods btw.As to material choice for other construction Aluminum due to it's lower melting point is more prone to blowing holes in it with MIG or TIG processes. Gas process is actually easier to avoid this. Another thing that is often overlooked with Aluminum is what is the actual material you are working with and with cheap hardware sections this is generally a complete unknown.

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 03:05:58 am
content: Yes, when I got legitimate aluminum plate, the weld I made was nice, and the problem was more distortion and learning the exact spacing distances and stuff. Still hard to get a nice pattern though, but I would figure its not going to fall apart. Finally looked like some melted mozzerella.But on more complicated stuff like inner corners, T-joints and dissimilar size joints.. its still very hard I think.Also another problem with aluminum is when you fucking use power tools to sand it and stuff, it hides problems easily. I had stuff that looks great but when I start probing it with a pick I find nasty defects.The best success I had was with alumiprep cleaning solution and the british welding flux on real aluminum sheet maybe 2mm thick. I have made alot of fixtures and accessories last year and I hope to try to get some hard joints done when it starts getting warm. Rod holder, flux tray, torch holder and got some cleico clamps.Still not going to approach it before I get/make a few more hand -vise type things and or clamps that i have in mind specifically for holding it nice.I also invested in a full set of alumicut burrs and the aluminum-flap disks and such and made an aluminum only kit. But now its like too coldI swear like once, when I first got my torches and stuff in early 2016, I made the best freaking aluminum braze job with a benzomatic rod. It looked like those videos, never repeated it. Stick with the benzomatic rods. I kept thinking the hardware store had some kind of conspiracy going on. I bought more and tried it again and.. it was fail. It felt like one of the crazy ass sports stories. Like a hockey champion thing. I was like perfectly tuned there was no cleanup, poor fixture, little prep, the joint was complex, weird angle, etc. A freaking homer. It like penetrated too. the braze ran across the weird dissimilar metal right angle complex geometry joint like a baseball field.

author: langwadt
author_rank: Super Contributor
timestamp: January 26, 2021, 03:12:14 am
content: https://youtu.be/mzKSk_Zs0Ew

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 03:22:28 am
content: also, what meter is that from HP that you fixed? I can't read the label.

author: coppercone2
author_rank: Super Contributor
timestamp: January 26, 2021, 04:01:55 am
content: I watched the saw video, if you make that aluminum sanding fixture, make sure to screw that metal into a big wooden block that is long if you feed it into the bandsaw when making it. I am sure most people that have bandsaws know this but its an easy way to loose a finger or break a hand to cut something shorter then it is tall. Or use a hack saw or horizontal saw of some kind. I would recommend screwing it to the end of a 4x4 to make the cut with the saw you are fixing with the same blade.

author: beanflying
author_rank: Super Contributor
timestamp: January 26, 2021, 04:38:09 am
content: Quote from: coppercone2 on January 26, 2021, 03:22:28 amStill a work in progress but a little more detail here on the 740Bhttps://www.eevblog.com/forum/testgear/hewlett-packard-740b-dc-standard-digital-voltmeter-(and-740a)/msg1419955/#msg1419955

author: geggi1
author_rank: Frequent Contributor
timestamp: January 26, 2021, 09:02:28 pm
content: Her eis how its done.http://www.steves-workshop.co.uk/tips/bandsawblade/fixingbandsawblade.htmI think it would also be able to jon a band saw blade with a spotwelder.

author: notsob
author_rank: Frequent Contributor
timestamp: January 26, 2021, 09:12:47 pm
content: This may be of use to you, Tom shows how he makes up his own blades and the jig he made to do it

author: Dubbie
author_rank: Unknown
timestamp: January 26, 2021, 09:42:41 pm
content: Quote from: geggi1 on January 26, 2021, 09:02:28 pmI would never join a blade with a spot welder.Sport welds aren't strong enough for this application.

author: Gregg
author_rank: Super Contributor
timestamp: January 26, 2021, 10:40:02 pm
content: Quote from: Dubbie on January 26, 2021, 09:42:41 pmCommercial bandsaw welders are basically spot welders and when properly utilized will make as strong of a weld as possible; that is how almost all of the factory made blades are joined. See the process at 7:15 in this video:Unfortunately good commercial blade welders are quite expensive and it takes practice to properly anneal the blade after welding.

author: IanB
author_rank: Super Contributor
timestamp: January 26, 2021, 11:11:44 pm
content: There is a difference between "spot welding" and "resistance welding" as a process, even though they both rely on resistance heating.Spot welding is literally what it says, creating little spot welds joining two overlapping pieces of metal. Spot welding may be used, for example, for attaching metal tabs to batteries.Bandsaw blades are joined by resistance welding, where the two ends of the blade are butted up together and the whole blade is heated to melting point by passing a current through it. The weld is not confined to a small spot, but covers the whole length of the join.

author: David Hess
author_rank: Super Contributor
timestamp: January 27, 2021, 12:53:41 am
content: 2% silver low temperature solder is the strongest of the tin/lead solders but that is not saying much. It would be entirely too weak for a bandsaw blade.Quote from: IanB on January 18, 2021, 04:51:01 amSilver brazing solders with about 50% silver work just fine with a common propane (or butane) torch, and apparently are strong enough for this application. I have done plenty of silver brazing but never on a bandsaw blade.

author: coppercone2
author_rank: Super Contributor
timestamp: January 29, 2021, 09:06:02 am
content: a mad man decided to deal with aluminum braze in a large scale testso I was right about benzomatic being more fluid. defiantly looks like you can get a bad brand to mess you up hard core.