[TheForge] Sheet Metal Bender

Tue Sep 19 12:49:43 EDT 2006

galvanized it is. Thank Bruce

Pete Stanitis told me to use it too.  He has always steered me in the right
direction.  I guess I got paranoid after reading about Paw-paw again.  I
stumbled across an article while surfing the web last week and it got me
thinking......too much....Thanks Pete, I should have listened to you the first
time!!!

I'll order the galvanized from Menards this Wednesday.

Dan

Quoting Bruce Freeman <FREEMAB at pt.fdah.com>:

> Dan,
>
> Use the galvanized.  This is a night-and-day different situation than
> that that killed Paw-Paw.  Paw-Paw was deliberately burning off thick
> zinc plating from some objects, using a forge at high temperature in a
> relatively unventilated shop.  Even so he may have survived the
> experience had he not already been suffering from emphasema.  In short,
> Paw-Paw got a very large dose of zinc oxide fumes.
>
> By contrast, the galvanized pipe you'd be using would not generally get
> hot enough for the zinc to burn.  Where it does burn, it burns slowly,
> so will not in the remotest stretch of imagination fill your shop with
> fumes.  Ordinary ventillation will more than suffice in such a case.
> Ventillation is needed anyway whenever you burn coal.
>
> If that STILL doesn't sit right with you, then please recognize that
> the only section of flue that may lose zinc would be that closest to the
> fire.  Above 3 feet over the fire, it just won't happen.  So do this:
> Pickle off the zinc from one section of galvanized pipe using vinegar or
> dilute phosphoric acid (available in the tile dept of Home Depot for
> cleaning up after grouting).  Vinegar will result in immediate minor
> rusting of the steel, whereas phosphorid allegedly won't.  Then paint
> the bare steel, or wipe it with polyunsaturated oil, to retard rusting.
> (The paint will burn off at hot spots.  So will the oil, but oil's
> cheaper.)  Use this de-zinced section as the section nearest the fire.
>
>  If you put a cap on your flue so rainwater doesn't get in, the
> galvanized will probably last long enough to be worth the effort.
>
> Of course, stainless WILL last longer, if you want to go to the trouble
> and expense.  And a slip roll would be easier than hand-rolling, but
> hand-rolling would work if the stainless isn't too springy.
>
> Bruce
> NJ
>
>
> >>> dan at irontreeworks.com 9/19/2006 12:06 PM >>>
> Bruce,
>    I don't want to make it myself.  I want someone to show up at my
> shop this
> weekend and install my new side draft hood, fix the old Champion forge
> I got
> for $100, and install a new chimney for free! :)
>
>   However, this does not seem like a reasonable event, so I priced some
> stove
> pipe.  I can get the 12" dia galvanized 24 gauge round ductwork from
> Menard's
> pretty cheap.  I can't find anyone that sell/makes the plain black
> stove pipe
> in 12 inch dia.  After what happened to Paw-PAw, I am alittle scared
> of
> galvanized pipe close to the forge.  I have students in my shop, and I
> don't
> want them hurt....soooo.....I thought stainless.  I looked into having
> some
> made and found out that it would be over $600 for 12 feet.....so....if
> you
> can't afford it....make it!
>
> I thought stainless would withstand the elements.  I like the plywood
> circle
> idea.  Seems easy.  I still think that using a slip roller would be the
> easiest
> solution for the straight tube if I can find one to borrow this week.
>
> Dan
>
>
> Quoting Bruce Freeman <freemab222 at yahoo.com>:
>
> > Daniel,
> >
> > First of all, why do you want to make this yourself?
> > To have stainless steel instead of galvanized?  Or
> > because stainless steel isn't available in 12"
> > diameter?
> >
> > Next, correct me if I'm wrong, but isn't 24 gauge
> > pretty light stuff?  Like you can easily flex it by
> > hand?  If so, then bending pipe shouldn't be too
> > difficult - roll it around a slightly undersized
> > mandrel (maybe 10" or 11") and let it flex back to
> > 12".  Lock seams are nice for the prefab stuff, but it
> > would be a deal easier just to drill and pop-rivet the
> > edges and ends.  Or even use self-drilling screws if
> > you like them.
> >
> > Someone else advised 45 degree elbows, and I second
> > that.  Whatever you choose, odd shapes can be made
> > according to diagrams available in any text on sheet
> > metal work. Visit a used_book store and peruse the
> > contents.  The Audel's series should suffice, but
> > there are text books for metal shops that are fine
> > too.
> >
> > You can also fake it by means of a clever device Clay
> > Spencer showed me, and which I've since used:  Imagine
> > you want to make a pipe with a 12" diameter end on a
> > vertical axis, and goes to a 12" diameter end on a
> > 15-degree-off-vertical axis.  (Three of these would
> > make a 45-degree bend.)  Construct a device as
> > follows:  Cut two (~1/4") plywood circles, 12" in
> > diameter.  Drill three holes in each, oversize for
> > available threaded rod.  String the two circles on the
> > threaded rods:  nut, washer, circle, washer nut, (then
> > a lenght of threaded rod), nut, washer, other circle,
> > washer, nut.  You'll end up with the two circles
> > separated on the three threaded rods by some distance.
> >  Now adjust the distance as you prefer, and adjust the
> > angle to 15 degrees between the planes of the two
> > circles.  You want the closest approach of the circles
> > to be some reasonable amount (say 2") because this
> > will be the narrowest sheet metal  you'll have.
> >
> > Now roll this pattern along a piece of paper, and it
> > will describe a pattern to be used in cutting the
> > sheet metal. When actually cutting the metal, be sure
> > to leave tabs to overlap the next pipe section so that
> > you can join them with rivets or screws.
> >
> > I have used this technique to develop a pattern for a
> > side-draft hood of unusual shape, and found it worked
> > quite well.
> >
> > Bruce
> > NJ
> >
> > >>> "Daniel Kretchmar" <dan at irontreeworks.com>
> > 9/18/2006 11:17 PM >>>
> >
> > Greetings,
> >            I need 12" diameter chimmey pipe for my new
> > side draft hood.  I
> > looked into menards.  They have galvanized 12"  24
> > gauge chimney.  I looked
> > into having some custom stuff made but it's too
> > costly.....so the next
> > question is.....can I make it myself?
> >
> > What kind of bender would I need to make 12" diameter
> > pipe/tubing out of 24
> > gauge stainless steel?  I want to make it in 2 ft
> > sections. which means
> > investing in a crimper a bender.....and what about
> > elbows?  I'll need two 90
> > degree elbows.  How will I make them?
> >
> > Advice is appreciated
> >
> > Dan
> >
> >
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