Bending brass

[Chris TickTockParticipant @christicktock]

[Chris TickTockParticipant @christicktock]

Hi,

I need to repair / replace this brass part of a 18th century longcase clock. It is called a hour wheel / cannon pinion bridge. you can get a part that may or may not fit but just in case I would like to explore how easy it would be to make one.

The solder you can see is i think soft solder from a previous repairman. it obviously failed at some point.

The first issue is bending brass, how to do this and whether heat is used etc.

as always I appreciate all help.

chris

Edited By Chris TickTock on 14/01/2020 11:50:29

[JasonBModerator @jasonb]

Really depends on the grade of brass, the harder brasses such as CZ120 are not easy to bend, the half hard brasses such as CZ108 will bend without any need for heat.

However looking at the part I wonder if it was machined from a casting or cut from solid which may be your best bet and would be a bit more rigid than a bent up one

[not done it yetParticipant @notdoneityet]

No need to make one. Clean it up, fix it in place and TIG weld it? Plenty of youtube videos on things such as this.

[roy entwistleParticipant @royentwistle24699]

They were usually castings and are still available

Roy

[SillyOldDufferModerator @sillyoldduffer]

+1 to Jason's grade of Brass warning. If the Brass is original, it's composition will be uncertain, but almost certainly soft.

A century after your clock was made, Brass-making was much better understood, and a whole range of different brasses were available. Properties vary from soft (easy to bend) up to hard (bend resistant), so go for a soft one.

However I believe all Brasses work-harden, that is start soft but toughen up considerably every time the metal is moved. Therefore bends often have to be done in several stages, where each interim step starts by annealing the metal to soften it

Not tried it but annealing Brass for simple bending doesn't appear difficult. Basically heat the Brass to about 500C for a few minutes (glowing slightly in a dim room), then allow it to cool slowly. (Annealing gets much more complicated depending on the goal, but KISS applies for this job.) Main thing to avoid is overheating the metal.

When bending, sheet needs to be held firmly along the full length of the turning edge, for a big sheet 2 lengths of angle-iron bolted back to back with the sheet sandwiched between will work. Ordinary vice jaws work for small objects, but don't use the serrated hard jaws normally fitted to a metalworking vice. (To avoid marking work I swapped my hard steel jaws for home-made mild-steel.) The bend may need leverage, or can be done by tapping the work over with a mallet or a hardwood strip whacked with a hammer.

Thin sheet is much easier to bend successfully than thick. As Jason suggests, because your Bridge looks rather thick, milling one from solid may be more satisfactory all round. (Not having a milling machine, the original clockmaker would have been forced to either bend a strap or file a casting. We have more choice – milling machines eliminate a lot of skilled but boring filing…) Bending sheet is generally done for cheapness, but it requires the right gear to do it. Like a furnace and apprentice, or a furnace and a bending machine! In this case, a replacement part can be made to a higher standard (stronger) than the original.

After getting the material and technique sorted, practice, practice… Most of my early attempts at bending are an embarrassment.

Dave

 

 

Edited By SillyOldDuffer on 14/01/2020 13:13:16

[Martin KyteParticipant @martinkyte99762]

Ditch the bending and fabricate from brass angle and strip. Silver solder together, fit the pipe and machine true.

regards Martin

[old martParticipant @oldmart]

If you decide to bend a piece of brass, then start by rounding off the long edges. This reduces the chances of cracks. Then anneal by heating to a dull red and cooling. Then produce the bends. Lastly, re anneal.

It will take a little experimentation to get the bends in the right places, so having some spare metal stock is a good idea.

[Anonymous]

I expect the original was cast. The angles look far too tight for the thickness of material to be bends, and the thickness of the material seems to vary a lot.

Andrew

[Chris TickTockParticipant @christicktock]

Great post Guys much for me to think about

Chris

[J HancockParticipant @jhancock95746]

The very fact that it has failed like that says quite a lot of 'vibration' stress occurs at that point.

Looks like a spider crack is running towards the centre boss too.

[Bruce EdneyParticipant @bruceedney59949]

Have a look at Clickspring Chris' method of 90deg vee and silver soldering on his bluing tray build

[Speedy Builder5Participant @speedybuilder5]

TIG welding brass is a bit specialised let alone having special breathing kit ?? I am for cleaning off the old soft solder and then make a silver solder repair, otherwise fabricate using silver solder and machine afterwards.

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[JasonBModerator @jasonb]

Only problem is I don't think Chris has ever done any silver soldering

[Former MemberParticipant @formermember19781]

[This posting has been removed]

[old AlParticipant @oldal]

you cant silver solder over lead solder. At best it makes a mess.

Looks a simple job to machine and fabricate, but i dont know the size.

best of luck whatever way you choose

[noel shelleyParticipant @noelshelley55608]

heavy wire brushing whilst heating will remove the soft solder. then clean up with emery and silver solder. where are you ? I have oxy propane, soon do the job. PM. Good luck Noel.

[Chris TickTockParticipant @christicktock]

Thanks for the posts, I will have a go at silver soldering and fabrication; will report back

chris

[IanTParticipant @iant]

Posted by Bruce Edney on 14/01/2020 17:43:49:

Have a look at Clickspring Chris' method of 90deg vee and silver soldering on his bluing tray build

I'm not sure how large/small this part is Chris but cutting a 90 degree 'V' on the fold line makes life much easier when doing this sort of work in brass. As a rough rule of thumb, the thicker the material the deeper the cut.

With most small fabrications you need to hold the parts together with pins/bolts/wire – and with thin-edged angled pieces this can be awkward – so having the parts still attached to each other is very useful. I use a hand shaper for this work but an engraving-type cutter in the mill or lathe will do the same job. Brush some flux on before folding to get it where you want it and apply a few pallions of solder along the fold. Apply heat from the outside of the work avoiding the actual fold line.

Regards,

IanT

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