Thread: Beginner metal-working question re. bending

Hi, and welcome to the mob

I would be asking about a simple leverage bender . To most of the metalworkers here the term brake is one associated with bending or folding of sheet metal stock.

If you require brass, I would opt for 5/16" (8mm ) brass rod, a material which is readily available at most engineering supply places.

In the u shaped configuration shown it would handle the 80-90kg strain.
I take it you are seeking a cheap and effective method of bending.

To bend it, I would make a bender from a piece of steel plate ( say 50x 10 x 100 L) with steel "pegs" of say the same diameter as the brass rod. The steel pegs fit into drilled holes in the steel plate and the brass rod is bent around the diameter of the steel peg to form the angles required.

Some heat, say from a LP torch could be used to coax the bend smoothly around the peg.

The plate would fit into a bench vice and sufficient leverage could be had to bend the brass rod by slipping a longer tube or pipe over it.

The brake, if used would not be suitable as it would indent the soft brass leaving a potential failure point right at the bend radius.

That's my 2C worth on it.

Grahame

Will, You don't need anything elaborate to bend the rod and 3/16" brass rod would have the needed tensile strength to cope with the load from tightening the strings. If you're doing a one off then bending in a vice will be sufficient. Get some rod longer than needed, work out where the bends need to come. You can use a piece of wire to practice on and get the shape right. Looking at the picture I suspect that the trapeze is a continuous piece of rod brazed into the bridge. The anchor plate could be 18g brass sheet, shaped and bent up. It would be folded over the trapeze then silver brazed or riveted (or both ) to together. It could even simply hook over the trapeze without having to fix it on.

The bridge itself could be made from a solid rectangular section of brass bar, drilled for strings and filed to shape and the fixings would probably be 1/4" or 6mm studs through the bottom with a clamp plate under the sound board. It may even be glued on. Depending on acoustics you'd need to decide how to fix it on.

Soften the brass by heating to red and let it cool or quench before bending. The anchor plate looks to be the most complicated part. You won't need to heat treat after but repeated annealing would be needed while shaping it up.

Originally Posted by wsal

Hey guys, I have no experience or knowledge when it comes to metalworking so bear with me here: I want to fabricate a guitar tailpiece of this style: http://www.worlandguitars.com/Models...0end1%20sm.jpg (it's the trapeze shaped bit in the foreground of the photo).
As you can see, this will require bending a piece of rod to say an 80 degree angle. What I want to know is how to do this and ensure that it ends up with enough strength to hold the tension of the strings (can be as much as 80-90kg). Mechanically speaking I imagine what's required will be what I believe is called a 'brake'? What I'm more interested in knowing what heat treatment might be required (if any) to achieve this? Heating the place to be bent til it's red hot? Doing some kind of heat treatment (annealing?) to make it more malleable for cold working? (remember I'm a beginner here, I'm just throwing up words I've seen around ). Heat treating it after bending?
My preferred material is brass or bronze - ie something yellow coloured, not silver/grey like steel, aluminium etc.
Thanks in advance
Will

Thanks for the quick replies guys!
So what are the advantages/disadvantages of working the bend hot, blacksmith style, vs. annealing then working it cold? My plan for attaching the block that holds the strings is to drill some holes through it, tap a thread onto the ends of the trapeze part and bolt it through said holes. Will any of this heat treatment affect the ability of the ends of the brass to hold a thread?
Cheers
Will

very difficult to anneal brass, not like copper, air cooling brass will only make it brittle and it will crumble like chalk, if you can cast it fron brass then post heat at a very gradual cooling rate you will be ok, other wise you can work it with a small peen hammer into shape

Originally Posted by kraits

very difficult to anneal brass, not like copper, air cooling brass will only make it brittle and it will crumble like chalk,

I've never had that experience, I've annealed lots of brass and never seen it go brittle. It work hardens like copper and is annealed in the same way. Quenching is not needed for copper alloys but is helpful if you want to work on it strait after heating.

Originally Posted by Swarfmaker1

I've never had that experience, I've annealed lots of brass and never seen it go brittle. It work hardens like copper and is annealed in the same way. Quenching is not needed for copper alloys but is helpful if you want to work on it strait after heating.

perhaps ive been doing something wrong for the past 14 years but, as i recall the last bit of brass i heated and hammered crumbled like the west coast eagles at a semi final.

You may have cooked the zinc out of it. I've done a lot of work flanging brass sheet, annealing and bending brass wire and rod with not the slightest hint of trouble. Brass tends to require more frequent annealling than copper but it's worked in the same way. Pitty those poor brass workers in India cold working brass to make all those jugs dishes and urns, they anneal over a pit fire. Likewise spinning brass on the lathe is a cold working process and requires the worker to anneal the brass regulary. If you don't anneal often enough that's when things fall to bits. To make a simple bend in brass rod of 5mm dia you would only have to anneal it onces. If you need to adjust it then anneal it again before reshaping to be in the safe side. It's also best to work with a wooden mallet so you don't bruise the material.

Originally Posted by kraits

perhaps ive been doing something wrong for the past 14 years but, as i recall the last bit of brass i heated and hammered crumbled like the west coast eagles at a semi final.

Originally Posted by kraits

perhaps ive been doing something wrong for the past 14 years but, as i recall the last bit of brass i heated and hammered crumbled like the west coast eagles at a semi final.

Hi Kraits,

No mystery (about the Eagles*** that is...) Brass is another story... with brass it all depends on the alloy, Alloy 260 is good for cold working, peening and bending. There is a zillion brass alloys, some are brittle, some soft.. I'm not up with the current code numbers, but I'm sure someone here can recommend which one of these C35200 / C35300 / C36000 / C38500 / C68600 would be best for cold bending. Whichever of those is the closest to alloy 260 is what I would recommend..

That list of brass alloys' was copied from here.. George White | Australia's leading stockist & distributor of non-ferrous metals - Product List

It's been a while since I was last at George White's, but they sell over the counter, and don't mind cutting to length.

Regards
Ray

PS..*** Here's hoping the Pies can do what the Eagles failed to do...

you see Ray the thing is that the brass i get i generally old bush's, things ive hammered out off shafts, scrap i scrounge and bring home to cast/hammer into what ever it is i may need from a latch to an attempted hinge, more failures then success's but what i have found is that no matter what or where the brass has come from it does tend to conform to a small peen.

my logic behind it needs a slow post heat cooling process is that it does become brittle when heated (what i have found)

PS, it's a Vic grand final and i support the origional maggies (Port Adelaide) so it's neither here nor ther for me but, a good reason to have a good old Sth Ausie brew (Coopers pale) cheers and good luck Saturday fellas.

Hi wsal,

Like already mentioned there are numerous copper alloys. Suggest that you first determine the ideal diameter and colour that you need. Then look at stockists to see what alloys are available in that size and shape.

My experience is that suppliers of copper and brass such as (austral wright (brisbane), George weston and sons (brisbane)) only stock 1-2 specific alloys in rod. Then determine how you can bend and if you need to anneal these.

Bending brass and its behaviour is affected by things like material thickness, grain size, alloy composition, bend radius and prior working of the material.

I have found that cold bending some brass flat bar resulted in fracture a bit like crazing in plastics, and a quick "anneal" with the oxy (as you would with copper) did not fix the problem so I had to increase the bend radii.

Originally Posted by kraits

perhaps ive been doing something wrong for the past 14 years but, as i recall the last bit of brass i heated and hammered crumbled like the west coast eagles at a semi final.

Yep Kraits,
you have.
Choosing the wrong brass.
Here are two pieces of brass.
BOTTOM piece.... "Cartridge brass" #260 It is nominally 70% copper 30 % zinc, and is called that because it has the PERFECT working characteristics for gun cartridges. The end can be opened and closed over a projectile, and re-used many times before it needs to be annealed or melted. It's cold working properties are rated as Excellent...not good, not just "alright"...it is excellent. It's hot working properties are FAIR, so it is best not to work it hot.
It will deform cold, without cracking or fracture more than 60% of its cross-section. That is not leaving 60%.... that is leaving 40%.
So if you have a 5mm x 5mm x 100 mm long piece of #260 brass which is fully annealed properly.... (that is, heated to red hot and held for about 10 minutes, than allowed to cool in air, NOT quenched in water) you can roll it out to a piece 3.16 mm x 3.16 mm x 260 mm long before it will need annealing again.
TOP piece #380 Brass, extruded. Cold working Capacity - POOR


Here I rolled both in my hand rolling mill. The cartrige brass went through to 280mm and could go more. The #380 crumbled, as expected!





Brass is great stuff, and logic might tell you that if you put a red metal with a white metal you would get ...what...bright yellow....didn't expect that
Logic would tell you that if you add traces of soft metals like lead and aluminium to a soft metals like those in brass (copper and zinc) you would maybe get a softer metal.
Not at all.

Non Ferrous metallurgy is an interesting and complicated topic, and the internet is full of "not quite right" information on it.
Copper can have lots other stuff added to it like zinc, lead, tin and aluminum to make it very good for different uses and manufacturing processes. Sometimes, that is to break away nicely when it is machined, to crumble if you like. Sometimes, to get one property, another non important property comes with it, it crumbles when hit..... Should be no surprise at all when those brass alloys crumble.
Just get one that doesn't, and anneal it properly.

Regards,
Peter

Fantastic info Peter! Thanks for that.
So are we 100% sold on annealing, not hot-working? And will annealing effect the ability of the brass to have threads tapped on the ends?
What kind of torch will do the job best? Propane, butane, MAPP?
Cheers
Will

Originally Posted by lightwood

So if you have a 5mm x 5mm x 100 mm long piece of #260 brass which is fully annealed properly.... you can roll it out to a piece 3.16 mm x 3.16 mm x 260 mm long before it will need annealing again.

Peter is creating matter
Assuming I am reading your post correctly 5x5x100= 2x2x625. 2mm being 40% of 5mm. Is that right? amazing stuff if it is.

"Non Ferrous metallurgy is an interesting and complicated topic" indeed it is.
Very interesting post
Thanks

Stuart

Originally Posted by wsal

Fantastic info Peter! Thanks for that.
So are we 100% sold on annealing, not hot-working? And will annealing effect the ability of the brass to have threads tapped on the ends?
What kind of torch will do the job best? Propane, butane, MAPP?
Cheers
Will

Will,
is there any need for the wire to have acoustic properties? Like transmit the sound wave?
As understand it, the sound comes from the strings vibrating on the saddle and bridge, but on yours it is held with this brass piece.
The wire on your picture looks like about 3mm???
I wouldn't want to use 2 pieces of 3mm brass with standard thickens nuts on the end.... and hang myself (90kg) above the lion enclosure on it....
The metal will hold but the threads would be doubtful.
What is the usual metal used for that piece?
A longer nut, say 12 - 15 long in this style would work on about 3.5mm brass wire I think.
Gold Economy Tailpiece | Allparts.com
What about steel, then gold plate it?
What part of Melbourne do you live? I'm in the Eastern suburbs...I can make brass wire any diameter from about 8mm down to 0.1mm, and give you a quick lesson in working brass when you are here.
Regards,
Peter
Peter McBride Goldsmith Jeweller