Sheet metal punch for stove project

I have no experience working with sheet metal, but why don't you just use a drill? In combination with a small metal file you should be able to get very nice holes anywhere you like.

Colin,

Jon at Flat Cat Gear passed on this suggestion to me regarding the same or similar process.

“I use a Whitney-Roper punch and getting a clean hole on 5 mil titanium is a little tough. The die clearence is a little wide for that thinness. You might need to sandwich the Ti between two sheets of flashing, but practice first as Ti is a pretty tough material”.

I used the term similar because this info is regarding .005″ Ti foil and your question references “(Al and Ti in the 0.003″ – 0.01″ thickness range)”.

I would think that his suggestion would help you achieve your goal. I’ll be trying the same project in the very near future.

Rodney Davis made a post on how he uses a similar tool to accomplish our common goal.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=68758&skip_to_post=587865#587865

BTW Can you give me the item number or SKU for that Harbor Freight, Roper-Whitney hand punch? My local Harbor Freight doesn’t have it in stock and none of their sales personnel have been able to help. ;-?

Party On,

Newton

Harbor Freight – bad, bad, bad,… – best to stay away from that place : )

I have the same question. Drilling produces ragged holes also.

I've thought about making a jig with hardwood. Have a piece on top and the bottom. Screw them together with a scrap piece of metal between so there's a gap for your windscreen. Drill a hole through hardwood and another scrap. Now inset your windscreen where you want to make hole, push down hardwood, drill hole. Maybe that would avoid rough edge.

Jerry,

"Harbor Freight – bad, bad, bad,… – best to stay away from that place : )"

L O L

It's OK Jerry. I did a little online detective work and found an item number for the Harbor Freight tool and apparently it is neither stocked or handled by them any more. My wallet and credit card are safe from harm. ;-)

Thanks for the tip though!

Party On,

Newton

I agree completly with Jerry. Softer metals and wide clearences in the punches do not make good punh presses for thin ti. Ti can be tough stuff, especially when the dies are of poorer quality. You might get about 200 holes. None will be real clean. Avoid the Harbor Freight ones, cheap though they are, they lack the capacity you need.

None of the ones mentioned have a 3" throat depth, though. Newton pointed out that the Northern Tool makes an OK one. But, it lacks the capacity you are looking for. A 3" depth usually requires a "C" body and is often used as a bench mount machine rather than a hand tool. I did an online search and found several that WILL handle the depth (took all of about 30sec.) http://www.mcmaster.com/#hole-forming-punches/=jm8e7f was about the least expensive for a fair to good quality tool. About $225 after a spare set of dies and shipping. The next one up costs well over $1000 and is a true bench mount.

Looks like the (B) model is a light duty hole press, about 1/4" hole (9/32") and was fairly inexpensive for a 3-1/4" throat-depth tool. Note that you will probably still need to mount it on a bench for best results with thin stuff, else you will see all the little odd angles and dimples in the finished piece…sort of depends on what you are working with. I think you can also get spare parts (dies) for this, too, at least they are listed below. You would need to call and ask, though, since the numbers don't quite match.

Use the hardwood jig like Jerry suggests, but us a stepped drill bit, like a Unibit, instead of a regular drill bit. You will need a 1/8" pilot hole. Get the real Unibit as some of the copies are pure junk out of the package.

Made for drilling holes in sheet metal. I use one all the time. They don't build cars like they use too.

Thanks for all of the input. To clarify, the punch that I have is this one:

I'm reluctant to invest in the McMaster Carr punch (B) that James suggested, or a Roper-Whitney deep throat punch, because they appear to be identical to the Harbor Freight punch pictured above (which I own). They cost ten times what I paid, but they appear to be precisely the same as the tool I have, down to the most minute details. I doubt that their dies would be sharper or their die clearances smaller given that they seem to be exactly the same tool.

I have tried using my unibit, and found that there was still some puckering of the hole, although less than from the punch. I'll do a bit more experimenting with the unibit.

A heavy-duty paper punch with a sharp, saddle-shaped cutting surface works beautifully with Ti foil. It has very tight die clearance and makes perfect little holes that look like they were cut with a laser. But the holes are very tiny and I haven't found one that can punch more than about 2" from the edge.

If I were a skilled machinist I could just make this tool.

The punch body itself is probably OK, although the retaining screw in the upper part is a weakness. Can't help that I am afraid. Just don't strip the thread. (It probably will strip eventually.)

Your problem is how the inserts are made. Typically they are made for mild steel and thick aluminium, with the necessary clearance between the male (punch) and female (die) bits. These clearances are necessary to allow the punch and die to self-align during use. However, the clearances are too big for really thin foil. Foil (SS, Al, Ti, brass, etc) will drag into the clearance and pucker and … well, make a mess.

You can sometimes punch aluminium foil by laminating it between two sheets of similar aluminium sheet, but you need to clamp them together hard. You could try double-sided tape for this as well. I have done this with SS, Al & brass.

In theory you could also try this with Ti foil, but the usual Ti alloy (eg 6Al4V) used for foil is just too tough. My experience has been that putting Al sheet around it rarely works because the Al is much softer and cannot support the Ti. Putting Ti sheet around it might work with carbide dies, but not with the steel ones which come with the unit. They just get damaged (and I had ro reface them).

Yes, sometimes a paper punch will work, because the clearances on those are much smaller (because paper is much thinner). How long the punch will last – that's another question.

So how does one do this commercially for Ti foil? Laser cutting is often used.

Cheers

Have you considered using a hollow punch such as those in this set ( http://www.harborfreight.com/9-piece-hollow-punch-set-3838.html )? I use similar punches all the time for leather and plastic. You need a smooth, firm surface that will not dull the cutting edge (I use a scrap of HDPE cutting board stock) on a solid work table, and a non-metallic hammer or maul to strike the punch.

I have punched 1000's of holes in both .005 ti and various gauges of SS with my Roper Whitney. When they get where they aren't punching clean, I just replace the punch & die.

Ed,

Where did you source your Roper-Whitney? Is it one of those two-hundred or three hundred dollar units or is closer to the Northern Tool < $25.00 unit?

Did you have to use any specific "sandwiching" procedure or did you just punch the Ti?

Thanks in advance.

Party On,

Newton

Ed, I have punched clean holes in 0.005" Ti with the Harbor Freight punch as well, but only in harder alloys. My punch works great, and I have used it many times, for punching holes in 0.006" 6Al4V and 0.005" 15-3-3-3 alloy (particularly after they have been heated with a propane flame and cooled). But, in my current project, I'd like to use 0.004" 3Al-2.5V or 0.003" CP4, and my punch just tears and deforms these materials. Have you tried your Roper Whitney punch on thinner foils of softer Ti alloys? If yours will cleanly punch those, I'd be willing to invest in one.

Also, in case this might be of use to anyone else for their own projects, it seems (given my reading today) that chemical etching is a practical way to make clean holes in Ti foil. The investment in time and equipment is about on par with DIY aluminum anodizing, and cheaper than buying a $200+ sheet metal punch. And you can make not only circular holes but cutouts of any imaginable shape. The image below is a titanium necklace pendant made by chemical etching (then anodizing) by a cottage jeweler in Australia.

Is a Greenlee punch practical for this?

–B.G.–

> I have punched 1000's of holes in both .005 ti and various gauges of SS with my Roper Whitney.
Hum – interesting. Mine is a (fairly old) Roper Whitney as well. I am wondering whether they actually make punch&die sets with different clearances? Could be useful if so.

Hum – they do. See http://roperwhitney.com/tech/tech3.cfm for more info.

Cheers

Colin,

I have used both the punch from Harbor Freight and more expensive punches in the range of $500+. There is a very significant difference between them although it would be difficult to justify a $500 punch such as the Whitney or Heinrich for hobby use. The Harbor Freight punch has very loose tolerances, requiring lots of shimming and reaming of the pivot arm sleeves for an accurate punch.

When you said that the material gets pulled into the die, it sounds like you are punching aluminum or stainless thinner than .006". To get a cleaner punch, you could sandwich both sides of the material with any scrap you might have before punching. The extra thickness will help it from getting pulled through the die. Titanium seems to be the easiest material to punch (other than paper), its hardness seems to give for a punch with less burrs. Stainless will come out with very noticeable burrs.

BTW, I own several Roper Whitney Jr. punches (I picked them up in the States on Craigslist for ~$25). I needed to order some replacement punches and I had a long talk with the rep. I learned several things.

1) The die wears out much faster than the punch so in many cases, you only need to re-order the punch (~$8 plus shipping)
2) The default die sets are a medium tool steel with a "generic punch/die clearence.
3) Custom dies can be order through Chicago Tool and Die that have harder grades of tool steel and tighter punch/die clearence.

Best regards – Jon

BTW, paper punches work well on thin material (for a while). All kinds of exotic punches can be found at a local craft stores like Michael's. Look on line and you will be amazed at the different shapes availible (stars, half moons, 2" diameter holes, et.) The biggest problem is that the throat depth is in general pretty short. Jon

Roger, thanks for the link to the Roper Whitney die clearance page. They don't make any die clearance recommendations for sheet thinner than 0.0125", but I'll contact them to inquire.

Jon, I wasn't able to find Chicago Tool and Die online. Does that company go by any other name?

I think, though, that Jeff is correct about the moving parts of the Harbor Freight punch. Low-clearance dies might not work with that tool because the swing arm sleeve is too loose to accurately line them up. And I'm not sure that I'm ready to invest hundreds of dollars in a tool that can.

I think I might have to accept that there is no affordable tool that will punch clean holes in 0.004" or 0.003" soft Ti (3Al-2.5V or CP4) more than 3" from the edge.

I found several sites that describe simple chemical etching of metal foils, including titanium, using acrylic paint masking and a room temp etchant paste (no UV light source, photoresist development, chemical bath, or power supply required). If this works, I think it will be a better way to shape Ti foil than shears, a dremel tool, and a punch. I'll post results if I can find the time to experiment with this.

> I think I might have to accept that there is no affordable tool that will punch clean holes in 0.004" or 0.003" soft Ti (3Al-2.5V or CP4) more than 3" from the edge.

Colin, try a hollow punch as I posted above. They are made to be used on metal as well as the leather, plastic and rubber on which I use them. There is no limit on how far from the edge of the sheet you can place your hole, they are easy to resharpen when necessary, and they are inexpensive.

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

http://www.clevelandpunch.com/

> 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

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.

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.

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