Sheet metal punch for stove project
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Jon Fong
(jonfong) - F - M

Locale: FLAT CAT GEAR
Custom Punches for Roper Whitney on 10/08/2012 14:31:16 MDT Print View

Ooops my bad. The company is called Cleveland Punch & Die (800) 451-4342.

http://www.clevelandpunch.com/

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Punches on 10/08/2012 14:56:04 MDT Print View

> The die wears out much faster than the punch so in many cases,
I have refaced both punch and die. I put them in the lathe and used a tool post grinder gently.
It should also be possible to reface with a carbide tool if the 'medium tool steel' is not too hard. Depends on the quality of the steel. (Chinese steel machines OK, but don't try it with Swedish steel!)

Cheers

Kevin Beeden
(captain_paranoia) - F

Locale: UK
what's really needed... on 10/09/2012 11:05:47 MDT Print View

What's really needed is a punch that clamps the thin workpiece first between two clamp pieces, and then passes the punch through closely-machined holes in the upper and lower parts of the clamp.

The clamping action will prevent the thin sheet being pulled into the hole, or bending up away from the hole in the surrounding area, which is what causes the puckering & poor edges.

Now, where to find such a punch...?

(I've considered buying a cheap arbor press, and getting some tooling made (mostly for making alcohol burners, rather than Ti foil). They can picked up cheaply; I recall being tempted by a 1/2 tonne press for £14 on eBay...)

Oh, and this is essentially the same technique as clamping the workpiece between two pieces of scrap, and drilling through the lot in one go.

Trying to drill thin foils, especially materials like Ti, is pretty fruitless without this scrap clamping technique.

Edited by captain_paranoia on 10/09/2012 11:18:51 MDT.

Kevin Beeden
(captain_paranoia) - F

Locale: UK
re: hollow punches on 10/09/2012 11:12:18 MDT Print View

I've used hollow punches for making holes in Al foil, and it's fine (I use it onto two layers of cereal packet cardboard, on a quarry tile floor). Even then, the edges of the hole are depressed, and need to be flattened with a rubber mallet.

I've tried using the same technique on Ti foil (3thou and 2thou), but Ti is so much harder to cut than Al, that I've barely been able to make a hole, and, even if I do, the foil is horribly deformed and the hole very ragged. And, because Ti is nowhere near as ductile as Al, you can't hammer it flat again.

It's one reason I got Steve Evans to cut out a prototype for a Ti SqueezeBox stove with his water jet cutter. And neither of us was happy with that result; the pressure of the water jet caused the edge of the foil to buckle, in much the same way as it does with a punch, only more random in how it ended up, leaving a 'wavy' edge.

Edited by captain_paranoia on 10/09/2012 11:24:17 MDT.

Jon Fong
(jonfong) - F - M

Locale: FLAT CAT GEAR
Re: what's really needed... (punching thin metal) on 10/09/2012 11:43:20 MDT Print View

If you think that clamping the outside material will work then a possible solution is to slip a stiff spring over the OD of the punch. Make sure that the spring extends beyound the tip of the punch so that the spring engages before the punch. Cheap idea but it may be hare to find the "right" spring. My 2 cents - Jon

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: Re: what's really needed... (punching thin metal) on 10/09/2012 13:50:38 MDT Print View

There is a knowlegable sales rep at Roper Whitney that goes by the name of John Yeruski. He taught me all I know about punching holes in thin gauge metal. He'll tell you exactly what is needed. Hint: "Stripper Material"

Yon is on the right track.

John Donewar
(Newton) - MLife

Locale: Southeastern Louisiana
Re: Hint: "Stripper Material" on 10/09/2012 17:22:19 MDT Print View

L O L

I run Google Chrome and when I highlight a portion of text it gives me options such as "search Google for" among other options.

I tried this with "Stripper Material" and you wouldn't believe the results that showed up on my monitor. :-0

Party On,

Newton

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Re: Hint: "Stripper Material" on 10/09/2012 17:29:07 MDT Print View

Please post links to "stripper material" : )

John Donewar
(Newton) - MLife

Locale: Southeastern Louisiana
Re: Re: Re: Hint: "Stripper Material" on 10/09/2012 17:32:46 MDT Print View

You're on your own Jerry!

Party On,

Newton

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Googling "Stripper Material" on 10/09/2012 19:35:14 MDT Print View

Principle routes of exposure: Eyes. Skin contact. Inhalation. Ingestion.
Skin contact: Corrosive. May cause permanent damage.
Eye contact: Corrosive. Causes permanent eye damage, including blindness.

Hum ....
:-)

Cheers

Diplomatic Mike
(MikefaeDundee)

Locale: Under a bush in Scotland
Neat holes on 10/10/2012 10:57:54 MDT Print View

Here's my take on the subject re clearance.
A Tool and Die worker will work by this rule, at least in the UK.
For material thickness less than 0.100", the clearance is 7-10% total. For material over 0.100", it is 7-10% per side. This is a % of the material thickness.

So for 0.005" sheet, the clearance should be 7-10% of 0.005", so 0.00035 - 0.0005". This assumes the set up is rigid, fixed and everything is properly ground, ie a Die Set.

Colin Krusor
(ckrusor)

Locale: Northwest US
punch/die clearance on 10/11/2012 22:13:05 MDT Print View

Mike, thanks for that information. That clearance (0.00035" - 0.0005") is very small, though. That's about ten microns. I'm not sure I could obtain a punch/die set with that little clearance on my budget, not to mention a tool that could accurately line them up.

This evening, I did my first electrochemical etching experiment and it seems promising. I think I might focus on this for now rather than looking for a high-precision punch. Etching can produce clean cutouts of any shape or size and it requires only equipment that I already have.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: punch/die clearance on 10/11/2012 22:23:21 MDT Print View

> This evening, I did my first electrochemical etching experiment and it seems promising.

DETAILS!!!
URLs!
Please!

Cheers

John Donewar
(Newton) - MLife

Locale: Southeastern Louisiana
Re: punch/die clearance on 10/12/2012 04:37:43 MDT Print View

Colin,

I can only echo Roger's interest...

"DETAILS!!!
URLs!
Please!"


...in this experiment of yours.

I do have a couple of my own requests.

Pictures and / or a YouTube video of the process and its results, Please!

Party On,

Newton

Colin Krusor
(ckrusor)

Locale: Northwest US
Etching on 10/12/2012 11:17:04 MDT Print View

Roger and Newton, I'll post some photos as soon as I get a chance. I have a presentation and a manuscript submission deadline that will keep me busy into the wee hours for the next week or so.

This is the jist: most of the DIY metal etching tutorials online focus on copper or steel. Hobbyists use it to remove copper from circuit boards and cottage craftspeople (like knife makers) use it to indelibly put their logo into steel surfaces. Some metals, like copper and brass, can be deeply etched (deeper than 0.01") using just NaCl as the electrolyte:

http://www.instructables.com/id/How-To-Electro-Etch-a-Solid-Metal-Plaque/?ALLSTEPS

Other metals, like steel, require acids:

http://forum.caswellplating.com/electroplating-questions/953-electro-chemical-etching-steel.html

There are companies that etch titanium foil parts:

http://www.fotofab.com/cmp_titanium.php
http://www.tech-etch.com/photoetch/materials_titanium_etching_tungsten.html
http://www.kemactech.com/titanium-chemical-etching.html

And companies that sell equipment and reagents for DIY titanium etching:

http://www.etching-metal.com/etching/titanium.htm
http://multietch.com/

And forums that discuss both commercial and DIY titanium etching:

http://www.finishing.com/134/32.shtml
http://mrtitanium.info/2011/08/09/q-what-common-materials-can-be-used-to-etch-titanium/
http://www.researchgate.net/post/What_could_be_the_alternative_for_Hydrofluoric_acid_in_etching_titanium_metal

Titanium, because of the very inert oxide surface layer, is almost always etched with hydrofluoric acid (sometimes up to 50%). I don't want to deal with hydrofluoric acid. The other options are a mixture of hydrochloric and sulfuric acids, or concentrated oxalic acid. Yesterday I tried HCl+H2SO4 because that's what I had on hand.

I used a lab power supply (Mastech HY 3003) set to a constant current of 1 amp, and connected the positive lead to a test piece of 0.005" 15-3-3-3 Ti foil masked with enamel paint except for a small exposed area. The negative lead was connected to a piece of scrap titanium.

The resistance of the oxide layer drove the voltage way up (to about 40V). The etching was rapid and vigorous (lots of bubbling and heat), but the result was uneven pitting of the surface of the foil. I think the oxide layer needs to be removed first. If there is oxide on the surface, the current will find tiny fissures and excavate them, producing pits, rather than uniformly removing material over the unmasked area.

I ordered some oxalic acid, but I've read that oxalate solutions are very slow for titanium etching compared to fluoride. So, I'm going to try a solution of nitric acid and ammonium bifluoride as well. This is the composition of at least two commercial titanium etching solutions (and the subject of this patent: http://www.google.com/patents/US4314876). This should strip away the oxide and give a much better result.

I'll post an update as soon as I find a bit more time to work on it.

peter vacco
(fluff@inreach.com) - M

Locale: no. california
hole punching on 10/13/2012 12:19:00 MDT Print View

in the world of shearing steel we use the "6 to 7" rule, which tells us that a good place to start is 6 to 7% of the material thickness. when shearing harder alloys (in this case A50, as opposed to A36 steel plate and angle iron) the appropriate starting point is closer to 10%.
now : a punch is really a shear, just formed into a circle, so the 6% needs doubled to give approx die clearance.

in the final decision, it is entirely appropriate that die clearance be determined not by formula in any particular application, but by experience and experimentation. there are excessive variables to allow a simple formula to work optimally in All situations.
still , 6 to 7 yields a fine starting point.

Harbor Freight = garbage. top to bottom. if you liked fish, you would find most of their inventory is not fit for reef construction.
HF is a blight on the economy of the planet, and present an excessive challenge to landfill reform.
if peter was president. Harbor Freight in it's corporate entirety would be shoved onto a very old ship, and sent back where it came. if that country refused shipment .. reef time. (pity the fish..)
HF ? .. not a problem.

our own Ken T. once again shows us the way, and this time it's how to drill thin metal.
Ken is correct. a twist drill is not what you want. in fact, a twist drill is exactly the tool most NOT to be employed in thin material drilling. although a noble item, the twist drill is simply not the correct tool in this instance.
what you want is the Step Drill, commonly know as a UniBit.

the U-bit can still rumple up shim thickness materials though.
ohhh.. that to do ???
i'll tell ya what to do. go to Lowes (less bad than HF) and buy a sheet of 1/4" .. they will call it masonite, but it's really a composite of wood fibers that look like masonite.
a 2 x 4' sheet is like what ... 6 bucks. it's nothing, and you can pick it up on the way home from work. the stuff cuts like a dream, drills just as nicely, and has enough balls to clamp and hold your tin properly.
sometimes they call it MDF. but real traditional MDF is a thicker and quite Vile material used by cut-rate mexican roofing contractors to do shlock work.
the material you want will be found at Lowes and Home Depot (currently recovering from criminally bad corporate management) to have smooth surfaces on both sides,and already cut to the easy-to-put-in-your-car 2 x4' sheets.

happy drilling,
peter v.