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Seeking delft casting info


#1

Hi all, I am looking for on delft clay casting. At a
resent show in London I went mad and bought myself a few new tools one
of which was a delft clay casting kit, the guy giving the demo made it
look so simple, but he has been casting the same ring since I first
saw him 5 years ago. Needless to say when I tried to do it all I get
is half a ring, it wont cast the whole way around. So I am asking all
you delft clay casters out there whets the secret or are there any
tips or tricks that I should know. all info would be greatly
appreciated.

I also bought a diamond impregnated cutting disc which cut great the
first time but now seems to be clogged up with gold. Is there a way to
remove this? How do I avoid this in the future? Is there a cutting
lubricant I should have used?

Thanking you all in advance,

Neil KilBane (mourning the death of the Austin Mini after 41 years 1
month and six days of production)


#2

One very important thing to remember is “AIR VENTS.” This should
help to improve the chances of a complete casting.

Laney


#3

With Delft clay you MUST have adequate vents at the ends farthest
from the sprue hole (and at each extremity/point if applicable). The
sprue hole should be at the thickest mass. You should also ensure
that you pour enough metal to get a sizable button. Be sure your
sprue hole is smooth and clean or tiny peices of clay will fall during
the pour. Good luck. Regis


#4
I also bought a diamond impregnated cutting disc which cut great the
first time but now seems to be clogged up with gold. Is there a way to
remove this? How do I avoid this in the future? Is there a cutting
lubricant I should have used?

G’day; Just don’t use diamond impregnated tools for cutting soft
things like gold, silver, brass, aluminium, and so on. But you have,
so get a piece of the coarsest carborundum stone you can find and -
yes, cut a slice from it! This will clear your diamond wheel like
nothing else will, and will do no harm to your wheel - I promise!
Even holding it against the spinning blade for several seconds will
do most of the work. Same with diamond drills and burrs; first make
sure that there still is some diamond left (a 10x magnifier will show
you that) then drill or cut into the bit of carborundum stone. When
ever the cutter seems to cut slowly, give it a loving carborundum
kiss. But when cutting harder materials than metals, do use a
lubricant. I use plain water with a squirt of DeSolvit - acts as a
detergent and works well. That’ll be 1? please. – John Burgess;
@John_Burgess2 of Mapua Nelson NZ


#5
    Hi all, I am looking  for on delft clay casting. ...
when I tried to do it all I get is half a ring, it wont cast the
whole way around... 

Hi Neil,
For an incomlete casting I’d suspect one or all of:

  • insufficient venting
  • too cool pour temp
  • too narrow feeder sprue
  • too sharp an angle where the sprue meets the ring cavity

Insufficient venting. Delft need venting, not like cuttlefish where
you might get away with no venting because the material is porose
(sp?) or the join is not 100%. Delft needs a good 2mm vent at the
bottom of the object, and the vent is to exit at rhe top of the mold
away from the feeder sprue and button.

Too cool pour temp. The sand is cold. Not like investment casting
where the mold is 500C. It may be that the metal cooled down and froze
halfway through the mold.

Too narrow feeder sprue. The metal has to get into the mold quickly,
so provide a sprus as thick as the part you’re joining to, and attach
in to the thickest part! At least (guesses) 3mm thick.

Too sharp an angle where the sprue meets the ring cavity. Think of
hotrod exhaust systems where the flow frim the engine is given smooth
curves. No sudden turns or performance in reduced. They restrict
metal flow and are vulnerable to coming away from the mold. Maybe the
metal took a little bit (or a big chunk) of sand with it.

Does any of this seem likely? Tell us about your casting conditions.

That’s all I can think of at 7:30am.

Cheers
Brian

B r i a n ? A d a m a n d R u t h B a i r d
Auckland NEW ZEALAND
ph/fx +64 9 817 6816
www.adam.co.nz
www.fingers.co.nz/ruth.htm


#6

Neil, I have had success with delft clay (also known as damascus earth
or clay,at least that’s what I learned) I just posted some info
yesterday describing it under “fixing” porosity heading) Check that
if you can find it. I think your problem is spruing. But would like to
know what exactly the type of ring your making . Only 2 dimensional
pieces can be cast or at least retrieved, being that the model
"pressed"into the clay must of course come out before casting.(I left
my wax model in one time,OPPS)You can push the envelope sometime with
slightly under cut items but must reform in the metal. Anyway the
"vent" spruing is all important! I put my model(usually wax) into one
side, move it side to side, to remove it later,powder for release,put
on the other ring,(flask), hammer the clay down carefully,separate,
remove model, push a rod through where and what I want to be the
casting sprue(on the ‘male’ side of the flask, so you can put it back
together). I also have a thin tapered,round ended piece of thin
metal w/ handle(like a portrait painters trowel(?) I use to form a
cone shaped sprue hole(with a twisting motion,like cutting the stem
of an apple out). Hoping the cone will reach as close to object
casting as possible. Then I turn over to view the other side of same
flask and take the small rod to make at least three “lines” in the
clay coming from the model to the outer edge of the wall of “flask”.
At , say, 10,2 and 6 o’clock.(Sorta like a peace sign , man) Making
more of an impression than scraping a line(I use a nail!).Then from
the end of the ‘line’ push straight through the clay to the other
side where the cone is,BUT, against the wall of the flask! Boy, I
wish we could draw on email! This allows the metal to be poured into
the model cavity directly, the air and alot of the metal escaping
across the middle(inside) to the edges and up through the 'nail’
holes allowing a full cast.Also allow a little cone indention where
the sprue vent comes out, in case too much metal comes through. Hope
that helps. Let me know! Thomas Blair in Hilton Head SC where we seem
to have had a ‘hurricane scare’ proof season! Everybody cross
something!!!


#7

Hello all,

If some one needs to have about Delft clay casting, I can
scan a A4 with picture with describes the hole process. Just mail me.

Martin Niemeijer
MNartin.niemeijer@hetnet.nl


#8

Neil, I know there should be some Delft casting in the
archives. There was a discussion year and a half ago.

About the Austin, I drove a Tiger for some years, it was fun, also
had a Hilman Minx Cabriolet, loved that one too. You invoked a few
memories for me, thanks, Teresa


#9

Hi Neil; I have done demonstrations in sand casting using the Delft
system and others. It’s not something that can be explained simpy
without seeing how you are doing things. But here are some
considerations to look into.

  1. You are casting into a cold mold, with no additional assist to the
    pouring as with centrifugal casting, so the metal has to have a
    large, short pathway into the cavity. And as such, there must be
    somewhere for the air in the cavity to escape ahead of the metal,
    hence, there must be vents at the extremes of the cavity, large
    enough allow the air to quickly be displaced.

  2. Spruing is best if it is to the thickest part of the casting,
    thereby avoiding bottlenecks which slow and cool the metal on its
    way.

  3. Make sure your metal is completely fluid before you pour, sliding
    around easily in the crucible as you gently swirl it to check its
    state of liquidity.

  4. Use plenty of borax for flux to make sure your metal doesn’t slow
    down getting out from under a skin of oxides when you pour it.

  5. Rings are a bit trickier than simple solid or flat forms. Start
    with simpler forms, without cores, and practice intuiting the logic
    of this type of casting.

  6. You might try practicing with Pewter (Brittania metal) for a
    while, then move on the more challenging metals like sterling, and
    bronze is even more tempermental yet. (Can’t afford to cast gold
    that way).

  7. Rent or borrow from you local library, if you can find it, a film
    called “The Gunsmith of Williamsburg”. It is a remarkable film about
    an extraordinary craftsman, and the part where he sand casts some of
    the hardware for the gun he makes it an exemplary demonstration of
    the reasoning used in this type of casting.

  8. Delft provides a video demonstrating their use of the Delft
    system, and you can buy it for about $14 US from Rio Grande
    (http://www.riogrande.com)

Good Luck and have fun!

David L. Huffman


#10

Dear Thomas I caught this tread by accident,but I have been getting
more interested in sandcasting which I think is the same thing as
clay casting,I have my old college papers from a professor ,(Leon
Lugassy/University of the Arts) on the technique,I remember his Demo
on it too ,never forgot the visuals ,the metal frame he was demoing
with was about 8/10 inches big he had a smaller one too,and wooden
models, My question is where can I find a supplier of these frames,I
saw a set in the Rio catalog they sounded small for me ,it seems he
had his a long time from France… Any help on that I would appreciate
thanks Hratch Babikian ATELIER BABIKIAN P.O. Box 54147 Philadelphia,
PA 19015 USA 215 465 9351


#11

greetings, all- Martin in the Netherlands sent me his instructions and
pictures on Delft clay casting, and I have uploaded it to the web
(temporarily) for those who are interested. For those who have never
done it: to save the pictures to your own files, RIGHT click on the
picture and choose “save as” to save to a folder on your own 'puter.
cut’n paste the address below- Anne Stickney


#12

Hi Hratch,

 I remember his Demo on it too ,never forgot  the visuals ,the metal
frame he was demoing with was about 8/10 inches big he had a smaller
one too, and wooden models, My question is where can I find a
supplier of these frames, I saw a set in the Rio catalog they
sounded small for me ,it seems he had his a long time from France..
Any help on that I would appreciate thanks<< 

I’ve never seen larger sizes than the ones Rio shows. However, they
can be made without too much difficulty. Depending on the size &
material at hand, they could be made from wood or just about any
metal. Since they’re being made, they could be made in any size
required. The ones Rio sells are round, but that’s probably for
simplicity of mfg. I’ve seen the ones from Rio & my guess is they’re
just sections of aluminum tubing that’s been cut to length & then both
pieces are keyed so they can only go together 1 way. The tubing could
be steel (pipe or tubing) or any other metal as well. Steel tubing is
available in rounds, squares & rectangular.

If you have any frames for vulcanizing molds, they could be used
providing you have sufficient depth & a way to key them together. The
keying could be done by clamping the frames together & drilling a hole
(say 1/8") through diagonally opposite corners. Insert a metal 1/8"
rod through the holes to keep the frames in registration.

If more than 2 frames are used, attention must be paid to how easily
the top frame(s) (called the cope) can be removed from the bottom
frame(s) (called the drag). The cope must be easily lifted from the
drag or the packed clay/sand could be disturbed resulting in a poor
quality casting.

Dave