Flattening thin copper strips - what would work best?

[Gerome]

Hello all,

 

I'm trying to com up with a war to flatten thin copper strips for a hobby of mine.  The strips to flatten are about .020" thick, .425" long and about .060" wide.  I have several devices I'm trying to use such as a hammed and a iron anvil but can't seem to get them as flat as I want.  I can provide pictures later.

[Frosty]

Welcome aboard Gerome, glad to have you. If you'll put your general location in the header you might be surprised how many of the IFI gang live within visiting distance.

Trying to flatten copper on an anvil isn't very likely to work unless you have a LOT of experience on an anvil. Try doing it on a piece of wood with a wooden mallet and be GENTLE.

Then again, that thin you should be able to flatten it in your hand. 0.02" might respond well to a rolling pin but it'll have a LITTLE rebound to deal with. What are you using for stock, roof flashing?

Frosty The Lucky.

[bigfootnampa]

Very small strips you are working with!  A polished flatter and a polished anvil block might do it for you.   You won't really need an anvil... just a very smooth block of half inch stock or even a flat hammer face will do.  Another way would be to use a vice to press the strips between two smooth flat blocks.  That is almost too thin to call sheet metal... it's more like foil!  Probably you'd be ahead to just buy stock of proper thickness and cut it with scissors.

[Alan Evans]

If your going to be doing it regularly and cannot buy the size you want, then a set of jewellers rolls would be the best bet.

Do you know any jewellers or silversmiths local to you?

You are welcome to come and borrow mine if you are passing!

Alan

[metalanton]

Rolling mill for sure. Harbor freight used to have a decent one.  I sold my harbor freight one for twice what I paid for it on ebay... I now have an antique one that I bought for a 100$ on craigslist

[Alan Evans]

I have just reread the OP and realise that you are maybe just trying to take a curve out of the strips without reducing the thickness.

How is the curve getting in? Can you prevent it getting in in the first place rather than fixing it?

Is it a curve on flat or edge, or are you trying to flatten a shearing burr?

Are you cutting these from a sheet of copper shim that was in a roll? Try flattening the roll by pulling it over the edge of a bench before cutting, reversing the curve.

Is it the action of the shears you are using to cut them out that is causing the curve or throwing up a burr that you are trying to remove? Try sharpening the blades, essential to dismantle them in order to flatten back the pivot bearing surface in plane with the cutting edge.

I would always try and keep such pieces as big as possible for ease of handling as long as possible in the cutting process. So cut a long thin strip which you can straighten and flatten and then cut your lengths from it.

Have you tried cutting with a sharp chisel using lead as a support?

Clamping the sheet between two pieces of supporting wood and sawing through the sandwich?

It seems small enough to just squeeze flat in you fingers if it is soft enough. If left half hard from rolling, use two serving spoons to overcome the spring back. That reminds me...The rolling squeeze of a pair of shallow curved surfaces like a pestle and mortar could work. If you have a polished full faced or crowned hammer that you can use as the pestle and make a dent in a piece of metal or wood with it to make the matching curve mortar. Then use it by pushing rather then hammering the copper between the two...

Alan

 

Edited June 2, 2015 by Alan Evans

[Gerome]

All,

 

Thanks for the quick replies.  I race toy Aurora slot cars from the 1960's.  The pick up shoes are copper and to get good contact on the rails you need the shoes as flat as possible.  There are bends on both ends so a rolling press would be difficult to use. Below is a picture of the shoes and the portion that runs on the rails is the flat part just behind the slotted front opening.

 

I have a flat surface that I use to try to flatten them on but I need them really flatter than .020".

 

 

 

[Frosty]

Okay, that's a whole different thing than we thought you were asking and a perfect example of wanting a specific answer to a vague question.

What you want to know is how to form the brushes and keep the contact area flat. This is easy peasy. Cut two pieces of smooth wood the same width as the flat contact area of the brushes. Measure and cut the stock and use a C clamp or vise grips to clamp the strips between the wood with the 90* bends on one side the the step bends on the other. Bend the 90*s then bend the other end close to the wood and clamp it to a table top or steel plate, etc. with a piece of stock, wood, steel, etc. the thickness of the step bends flat on the plate against the up bent strips. now just bend them flat against the bottom die. Forming the hinge/hook end is as easy as using a piece of steel wire or a nail and driving it against the copper on a piece of end grain wood.

Keep it straight and or flat is WAY easier than flattening/straightening it afterwards. It's easier to NOT make mistakes than correct them.

And don't tell me you needed me to tell you to unclamp the brushes from between the first two pieces of wood before clamping it to the large flat piece to make the step bends. Awe heck you can do it all clamped to a table top if you like. Seriously there are so many different ways of making this simple piece I'm in danger of getting seriously sidetracked by different methods and mixing them up.

No rolls, special shears, nothing special needed at all, just a bit of basic technique and care. Heck, the last set of slot car track brushes I made was what 50 years ago? I stopped playing with slot cars a couple years before I got my driver's license. I'm almost afraid to ask my sister if my old slot car box is in the piles of stuff my Parents kept. Pack rats, the whole darned family.

Frosty The Lucky.

[ianinsa]

A different approach would be to find a local laser cutting works and ask them to cut out a male and female die out of plate matching the width of your strip, include a 'notch' in the back to suit a 'vice grip' and them just 'press' them. I hope this 'makes sense ' . As the shape is quite simple it would not be that difficult to 'hand make ' the dies using a fret saw and a file.

Depending on the hardness your stock it might help if you aneal it first by heating and quenching in water.     

Edited June 4, 2015 by ianinsa

[Alan Evans]

So unless you are using the word "flatten" in a very creative way could you confirm that you are just trying to flatten that section between the slotted upright and the first joggle? Is this on pieces you have formed yourself or ready-mades?

Are you, as Frosty and Ian supposed, actually having problems forming them from scratch?

I cannot see from the photographs where your .020" is occurring, is that crowning/ burr across the width of that section or along its length? Is the whole piece twisting from one end to the other?

My slot cars used a bit of flat braided copper ribbon, so I am not familiar with these and I don't know how they are held against the track, whether by their own spring tension or another spring. If spring tension then that determines whether you anneal them before or after any process that will work harden them. Are they held fairly loosely by the car so that they conform to the angle of the track contacts? Are the track contacts flat or slightly crowned? 

So my next question is why do want to flatten them? Are you trying to ensure a larger contact area? Will that effect drag? Flat is all or nothing. If the track is slightly warped would not a gentle crown be more certain of constant contact? Would polishing be an advantage? 

Either way if you do just want to flatten that section and you have not been able to achieve by squeezing between a pair of flat blocks you need to hit it harder, an anvil and a flat bottomed punch for instance, which will reduce the thickness but will forge rather than just unbend it. Ian's profile tools would work with this system but wack them with a hammer rather than squeeze them with vice grips.

An alternative is to use the pestle and mortar / pair of spoons idea I outlined above to unbend them without altering the thickness. This would be in the form of a dished bottom tool and convex top tool formed from stock which will fit between joggle and upstand.

I have a 50 year old memory image of my mate with his scalextric cars poking under the contact with a screwdriver and bending with his fingers...I guess you are in a slightly different league if you are racing others in a club situation. Have you asked you fellow racers what they do or is this thread by way of getting a competitive advantage?

Alan

[David Einhorn]

Or you can modify a pair of vise grips by either cutting down and aligning the jaws on vise grips used for sheet metal, or having someone with a welder attach short lengths of angle iron to the jaws of a vise grip.  http://www.amsisupply.com/graphics/vice grips/23-large.gif

Edited June 4, 2015 by David Einhorn

[Gerome]

Okay, that's a whole different thing than we thought you were asking and a perfect example of wanting a specific answer to a vague question.

What you want to know is how to form the brushes and keep the contact area flat. This is easy peasy. Cut two pieces of smooth wood the same width as the flat contact area of the brushes. Measure and cut the stock and use a C clamp or vise grips to clamp the strips between the wood with the 90* bends on one side the the step bends on the other. Bend the 90*s then bend the other end close to the wood and clamp it to a table top or steel plate, etc. with a piece of stock, wood, steel, etc. the thickness of the step bends flat on the plate against the up bent strips. now just bend them flat against the bottom die. Forming the hinge/hook end is as easy as using a piece of steel wire or a nail and driving it against the copper on a piece of end grain wood.

Keep it straight and or flat is WAY easier than flattening/straightening it afterwards. It's easier to NOT make mistakes than correct them.

And don't tell me you needed me to tell you to unclamp the brushes from between the first two pieces of wood before clamping it to the large flat piece to make the step bends. Awe heck you can do it all clamped to a table top if you like. Seriously there are so many different ways of making this simple piece I'm in danger of getting seriously sidetracked by different methods and mixing them up.

No rolls, special shears, nothing special needed at all, just a bit of basic technique and care. Heck, the last set of slot car track brushes I made was what 50 years ago? I stopped playing with slot cars a couple years before I got my driver's license. I'm almost afraid to ask my sister if my old slot car box is in the piles of stuff my Parents kept. Pack rats, the whole darned family.

Frosty The Lucky.

​I plan to give this technique a try.

I took left slots behind when I got my DL AND discovered girls.  When I turned 50 I decided to get back into them as a hobby to keep me from running the streets.  Seems to be working pretty well so far.

 

[Charles R. Stevens]

Beats a convertable and a pair of tweenty year olds ;-) but i guess bull riding wasnt an option?

[Gerome]

A different approach would be to find a local laser cutting works and ask them to cut out a male and female die out of plate matching the width of your strip, include a 'notch' in the back to suit a 'vice grip' and them just 'press' them. I hope this 'makes sense ' . As the shape is quite simple it would not be that difficult to 'hand make ' the dies using a fret saw and a file.

Depending on the hardness your stock it might help if you aneal it first by heating and quenching in water.    

​I have seen a one off tool that can do this, pictured, but I was looking for something simple.  I have heated the quenched but did not try to flatten while heated but it is worth a try.

[Gerome]

So unless you are using the word "flatten" in a very creative way could you confirm that you are just trying to flatten that section between the slotted upright and the first joggle? Is this on pieces you have formed yourself or ready-mades?

Are you, as Frosty and Ian supposed, actually having problems forming them from scratch?

I cannot see from the photographs where your .020" is occurring, is that crowning/ burr across the width of that section or along its length? Is the whole piece twisting from one end to the other?

My slot cars used a bit of flat braided copper ribbon, so I am not familiar with these and I don't know how they are held against the track, whether by their own spring tension or another spring. If spring tension then that determines whether you anneal them before or after any process that will work harden them. Are they held fairly loosely by the car so that they conform to the angle of the track contacts? Are the track contacts flat or slightly crowned?

So my next question is why do want to flatten them? Are you trying to ensure a larger contact area? Will that effect drag? Flat is all or nothing. If the track is slightly warped would not a gentle crown be more certain of constant contact? Would polishing be an advantage?

Either way if you do just want to flatten that section and you have not been able to achieve by squeezing between a pair of flat blocks you need to hit it harder, an anvil and a flat bottomed punch for instance, which will reduce the thickness but will forge rather than just unbend it. Ian's profile tools would work with this system but wack them with a hammer rather than squeeze them with vice grips.

An alternative is to use the pestle and mortar / pair of spoons idea I outlined above to unbend them without altering the thickness. This would be in the form of a dished bottom tool and convex top tool formed from stock which will fit between joggle and upstand.

I have a 50 year old memory image of my mate with his scalextric cars poking under the contact with a screwdriver and bending with his fingers...I guess you are in a slightly different league if you are racing others in a club situation. Have you asked you fellow racers what they do or is this thread by way of getting a competitive advantage?

Alan

​The picture are of pieces already from but not necessarily flat on the contact patch. The .020 is the thickness of the shoe and it is actually closer to .015" when I checked it with calipers. They do get twisted sometimes but that is an easy fix as it is typically on the "hanger" which is at the far end of the picture.

Below is a picture of how they hook up with the springs providing tension.  Notice the are actually disconnected from the slotted front end. And a picture of them connected.

I want to flatten the to improve the widen the contact patch to make the car run smoother and improve electrical contact.  When not perfectly smooth you get arching which produces a blackened are on the contact patch thus further reducing the electrical contact. I have used 400 grit sandpaper to polish and you can actually flatten the patch in the manner is you sand long enough and have the patch flat on the sandpaper.

I have asked fellow racers what they do and some are quite about this and some forthcoming with information.  Racers are always looking for an edge and that's what I looking for.

Thanks again for all the replies and suggestions.

 

 

[Charles R. Stevens]

And dead flat is beter than slightly crowned? Interesting. Do you run them dry or with a thin film of dielectric greas? 

Might i ask if the bend is always in the same direction? Some times changing the material in one die or the other works, as a softer"hammer" against a harder anvil will infact srink the metal. So a plastic, rawhide, leather or wood depending on the meatal used and amount of srink aplied to the "up side of the bend (eithe as part of the die set if it is always to one side) or as a corective mesure. 

[ThomasPowers]

OUCH annealing them may not give them the spring they need which would be based on work hardening them in the first place.

Frosty, you have experience with how springy these need to be?

[Frosty]

The brushes on ours weren't like these. They had a similar hinge section on one end but were a shallow crescent shape to a small vertical tab and maybe 1/2"-5/8" long OA. It was kept in contact with a small spring. The action was like these but the shape was different. Stiff was better or they'd get twisted when the cars got sideways.

We bought blanks in a package of maybe 10 and bent them to our liking with our fingers. A pair of jeweler's size duck bill pliers in my box meant I was over equipped.

Frosty The Lucky.