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Re: [hobbicast] gates & risers was The bad and ugly, not so much good :(

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  • Foundryman
    CB, There is no simple answer as to where or how big risers need to be or go. But here are some ideas as a starting point. For thin pieces like a plaque
    Message 1 of 9 , Jun 1, 2003
      CB,

      There is no simple answer as to where or how big risers need to be or go. But here are some ideas as a starting point. For thin pieces like a plaque where I'm getting shrinkage at the ingate, I'll put a riser over the ingate just before the metal enters the pattern (over the ingate). When I'm pouring a pattern that goes from thin to thick, with the resulting shrink in the thick section, the riser goes over the thick area. Tough cutting off the excess, but that is the way it has to be. Now the other question, how big? At a minimum, the riser should be double the thickness and volume of the area you need to feed. If possible, hot top the riser after the mold has partially filled and cover the hot top with sand or any other insulation. Another idea, stir the riser with a hot rod as the riser will stop feeding as soon as the surface solidifies. Bottom line is that your risers can't be too big, so if in doubt go for big!!!! Hope this helps.

      Best, Jerry
      Foundryman in Missouri, USA
      Custom Castings by Twaddell
      foundryman@...
      http://members.igateway.net/~jtwad/


      [Non-text portions of this message have been removed]
    • collegemachinist
      Visit this link, http://www.host33.com/casting/ Go to Gating and GAting rules links. For Gating the only mildly confusing thing is that you get a number from
      Message 2 of 9 , Jun 1, 2003
        Visit this link,

        http://www.host33.com/casting/

        Go to Gating and GAting rules links. For Gating the only mildly
        confusing thing is that you get a number from each category so that
        you can have a 1,4 casting, etc. These should help with your
        problems. You could add a blind riser to your pattern, it is just a
        raised portion over your shrink cavity to take all the shrink. After
        cooling, you cut it off and have a normal casting.

        Hope this helps, it helped me,

        Thomas
      • Chris Boyer
        Risers do go on the thick part of a casting. Always feed from thick to thin sections. I got this much :) Now I have seen examples of risers directly on the
        Message 3 of 9 , Jun 1, 2003
          Risers do go on the thick part of a casting. Always feed from thick to thin
          sections. I got this much :)
          Now I have seen examples of risers directly on the casting and gated to the
          casting. I have even seen a riser attached to a spru? From what I can tell
          most gated risers have a gate about 1/2 the size of the riser?

          So those more edumacated please step in here. What works better. If risers
          are gated to the casting how big should the gates be? IF there is more than
          1 riser should they be gated together?

          CB


          > If you attach the riser with gates, the gates need to be large so they
          don't solidify before the casting. I always thought risers went on the thick
          sections of the part.
          >
          > Ron Thompson
          > On the Beautiful Mississippi Gulf Coast
          > USA
          >
          > Email me for current special offers on items from
          http://www.plansandprojects.com
          >
          > Grave yards are full of people who thought the law could, should and would
          protect them.
          > ----- Original Message -----
          > From: Chris Boyer
          > To: hobbicast@yahoogroups.com
          > Sent: Sunday, June 01, 2003 11:11 PM
          > Subject: Re: [hobbicast] Re: The bad and ugly, not so much good :(
          >
          >
          > See below
          >
          >
          >
          > > --- In hobbicast@yahoogroups.com, "Chris Boyer" <boyercl@a...> wrote:
          > > > Well I updated my latest attempt at the headstock casting. Didn't
          > > get the carriage done. BIG headache, still have it.
          > > >
          > > > Its on its own page now under Gingery Lathe - headstock. Will try
          > > 1 more time. Open for suggestions on how to stop the shrink !!!
          > > ARGH !!!! and other words I bet you can figure out ;).
          > > > Some wanted more pictures of molds rammed and set up. I didn't get
          > > them done either.
          > > > Hope tomorrow is better. Have some AL wheels tranny and misc
          > > engine parts coming. NO, not quite free. I have to take the truck
          > > apart to get them and I believe I got suckered into replacing rear
          > > wheel bearings in a T-Bird ??
          > > >
          > > > http://users.adelphia.net/~boyercl/hobbies.htm
          > > > Chris (CB)
          > > I had to cast the headstock twice to get a good part back when I
          > > built my lathe. Some of Gingery's molding methods seem questionable
          > > to me, but anyway, I eliminated the shrink at the r. end of the
          > > headstock by using a 1 1/2" dia. riser at each corner. This is
          > > probably overkill, if I was doing it again I would use two risers at
          > > the right end only, and gate into both risers.
          > > Mike.
          > >
          >
          > If I under stand correctly there were 4 risers? How big was the
          headstock?
          > Mine is about twice the AL as in the book. I know the risers go to the
          > casting. Did you connect the risers together as well? How big were the
          > gates?
          >
          > 1.5" spru is in the plan and at least 1 riser on each end. Hmm might
          have
          > to go 2 risers on the heavy end? I was using about 1/2" deep x 3/4"
          gates
          > about 1.5" from the casting.
          >
          > Thanks Chris
          >
          >
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        • Chris Boyer
          Thanks Jerry I hope to try it next weekend again :) Bigger spru and riser is in the plan. Probably have to go about 2 on the riser to get it right. ... But
          Message 4 of 9 , Jun 1, 2003
            Thanks Jerry

            I hope to try it next weekend again :)
            Bigger spru and riser is in the plan. Probably have to go about 2" on the
            riser to get it right.




            > CB,
            >
            > There is no simple answer as to where or how big risers need to be or go.
            But here are some ideas as a starting point. For thin pieces like a plaque
            where I'm getting shrinkage at the ingate, I'll put a riser over the ingate
            just before the metal enters the pattern (over the ingate). When I'm
            pouring a pattern that goes from thin to thick, with the resulting shrink in
            the thick section, the riser goes over the thick area. Tough cutting off
            the excess, but that is the way it has to be. Now the other question, how
            big? At a minimum, the riser should be double the thickness and volume of
            the area you need to feed. If possible, hot top the riser after the mold
            has partially filled and cover the hot top with sand or any other
            insulation. Another idea, stir the riser with a hot rod as the riser will
            stop feeding as soon as the surface solidifies. Bottom line is that your
            risers can't be too big, so if in doubt go for big!!!! Hope this helps.
            >
            > Best, Jerry
            > Foundryman in Missouri, USA
            > Custom Castings by Twaddell
            > foundryman@...
            > http://members.igateway.net/~jtwad/
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            > This list is for discussion of metal casting
            > and does not accept attachments. For off topic discussion and to share
            photos and stuff: join Sandcrabs by sending a blank message to:
            sandcrabs-subscribe@yahoogroups.com
            > http://groups.yahoo.com/group/sandcrabs
            > or join the Coffee Lounge group (by approval)
            > http://groups.yahoo.com/group/Hobbicast_coffee_lounge/
            >
            > Please visit our sponsor: Budget Casting Supply
            > http://budgetcastingsupply.com/
            >
            > Files area and list services are at:
            > http://groups.yahoo.com/group/hobbicast
            >
            > To unsubscribe from this group, send an email to:
            > hobbicast-unsubscribe@yahoogroups.com
            >
            > For problems that cannot be otherwise solved contact the list owner by
            email:
            > owly@...
            >
            >
            >
            > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
            >
            >


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          • katoutwo
            The objective of a riser is to feed the casting with liquid metal until the point that the casting becomes solid. So, the casting has to become solid before
            Message 5 of 9 , Jun 2, 2003
              The objective of a riser is to feed the casting with liquid metal
              until the point that the casting becomes solid.

              So, the casting has to become solid before the riser.

              There are two ways to do this:
              1. use a large diameter riser
              2. chill the casting by putting a piece of metal nearby in the sand.

              For instance, I want to cast a 10" sphere of SOLID aluminum. Hmm,
              if I make the riser larger in diameter than the sphere (thereby
              guaranteeing that it will remain liquid longer than the casting) I
              am basically going to have a half-sphere with an enormous riser
              sticking out of it. Which I will have to cut off. Big pain.

              So, the only way to do what I want to do is to ram up the mold with
              a bunch of chills near the part. And it still might not work. But
              anyway, that's one thing to try Chris. Bigger the mass of the chill
              and closer it is the casting, the better it should work.

              I haven't had to try this yet, but this is how it's supposed to work
              anyway. Give it a try, I'd like to hear if it fixes the problem.
              Maybe chilling the chill would be a good idea too? Probably not,
              the extra 20 deg C wouldn't do much good, and it could introduce
              moisture problems. On Second Thought, don't try that.


              Katou
            • cdmckeown
              Ok, A little trick I use to prevent shrinkage voids in parts is to keep the riser molten for as long as possible to allow the part to continuously draw from.
              Message 6 of 9 , Jun 2, 2003
                Ok,
                A little trick I use to prevent shrinkage voids in parts is
                to keep the riser molten for as long as possible to allow the part to
                continuously draw from.
                Cut a riser into the main runner gate just before the part. Line the
                riser with `Paper KaoWool'. This stuff is pressed to around 1/16"
                thick and is similar to cardboard to work with although slightly more
                brittle. This liner takes the form of a rolled cylinder which fits
                snugly against the walls of the riser. After you have poured, top up
                from your insulated riser as the part draws metal from it. You will
                be surprised how quickly and how much it drops whilst the part
                cools. You will find the riser is still molten long after the part
                has solidified.
                Hope this helps out.

                Cheers
                Cameron

                http://home.iprimus.com.au/cmckeown/


                --- In hobbicast@yahoogroups.com, "katoutwo" <katou@e...> wrote:
                > The objective of a riser is to feed the casting with liquid metal
                > until the point that the casting becomes solid.
                >
                > So, the casting has to become solid before the riser.
                >
                > There are two ways to do this:
                > 1. use a large diameter riser
                > 2. chill the casting by putting a piece of metal nearby in the sand.
                >
                > For instance, I want to cast a 10" sphere of SOLID aluminum. Hmm,
                > if I make the riser larger in diameter than the sphere (thereby
                > guaranteeing that it will remain liquid longer than the casting) I
                > am basically going to have a half-sphere with an enormous riser
                > sticking out of it. Which I will have to cut off. Big pain.
                >
                > So, the only way to do what I want to do is to ram up the mold with
                > a bunch of chills near the part. And it still might not work. But
                > anyway, that's one thing to try Chris. Bigger the mass of the
                chill
                > and closer it is the casting, the better it should work.
                >
                > I haven't had to try this yet, but this is how it's supposed to
                work
                > anyway. Give it a try, I'd like to hear if it fixes the problem.
                > Maybe chilling the chill would be a good idea too? Probably not,
                > the extra 20 deg C wouldn't do much good, and it could introduce
                > moisture problems. On Second Thought, don't try that.
                >
                >
                > Katou
              • Chris Boyer
                Thank you Thomas Had lost this site :( added to my links page this time :) A quick review says. my 1.25 spru = ok gates = ok runners = too small need 2 riser
                Message 7 of 9 , Jun 3, 2003
                  Thank you Thomas

                  Had lost this site :( added to my links page this time :)

                  A quick review says.
                  my 1.25 spru = ok
                  gates = ok
                  runners = too small
                  need 2" riser

                  CB
                  Looks like Yahoo got the servers back up. finally !!!


                  > Visit this link,
                  >
                  > http://www.host33.com/casting/
                  >
                  > Go to Gating and GAting rules links. For Gating the only mildly
                  > confusing thing is that you get a number from each category so that
                  > you can have a 1,4 casting, etc. These should help with your
                  > problems. You could add a blind riser to your pattern, it is just a
                  > raised portion over your shrink cavity to take all the shrink. After
                  > cooling, you cut it off and have a normal casting.
                  >
                  > Hope this helps, it helped me,
                  >
                  > Thomas
                  >
                  >
                  > This list is for discussion of metal casting
                  > and does not accept attachments. For off topic discussion and to share
                  photos and stuff: join Sandcrabs by sending a blank message to:
                  sandcrabs-subscribe@yahoogroups.com
                  > http://groups.yahoo.com/group/sandcrabs
                  > or join the Coffee Lounge group (by approval)
                  > http://groups.yahoo.com/group/Hobbicast_coffee_lounge/
                  >
                  > Please visit our sponsor: Budget Casting Supply
                  > http://budgetcastingsupply.com/
                  >
                  > Files area and list services are at:
                  > http://groups.yahoo.com/group/hobbicast
                  >
                  > To unsubscribe from this group, send an email to:
                  > hobbicast-unsubscribe@yahoogroups.com
                  >
                  > For problems that cannot be otherwise solved contact the list owner by
                  email:
                  > owly@...
                  >
                  >
                  >
                  > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                  >
                  >


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                • Chris Boyer
                  Katou I was originally thinking about a chill. Part of my concern,. I would need it very close to where I gate into the part. Hmmm, move the gate / spru?
                  Message 8 of 9 , Jun 3, 2003
                    Katou

                    I was originally thinking about a chill. Part of my concern,. I would need
                    it very close to where I gate into the part. Hmmm, move the gate / spru?
                    Well? Thought about that too, but the shape of this casting leaves little
                    room for changing this position. I bet a chill will move the shrink to the
                    other (smaller) end of the casting or prevent it from filling completely.

                    After reviewing some info on the Casting 101 WEB site. I think I might try
                    it without.
                    Looks like I need bigger runners and a BIG 2" riser directly on the casting
                    over the shrink area.
                    The good part is that the shrink has stayed pretty much in the same location
                    on both attempts. So it should be easy to see where the riser "has to" go.
                    :) Yep a pain to cut it off but ... I come to find out this is a common
                    problem with this part even when made the original size. By doubling the
                    size I have doubled "or more" the problem. I will be posting the solution
                    on my site to help future travelers on this road.

                    If the plan goes well it should be this Saturday.

                    Chilling the chill :) Isn't that done with water in commercial foundries?
                    Me thinks I leave that one alone ;)

                    Thanks
                    Chris (CB) too many Chris running round the net.

                    PS In case I missed anybody thanks to their replies as well :)



                    > The objective of a riser is to feed the casting with liquid metal
                    > until the point that the casting becomes solid.
                    >
                    > So, the casting has to become solid before the riser.
                    >
                    > There are two ways to do this:
                    > 1. use a large diameter riser
                    > 2. chill the casting by putting a piece of metal nearby in the sand.
                    >
                    > For instance, I want to cast a 10" sphere of SOLID aluminum. Hmm,
                    > if I make the riser larger in diameter than the sphere (thereby
                    > guaranteeing that it will remain liquid longer than the casting) I
                    > am basically going to have a half-sphere with an enormous riser
                    > sticking out of it. Which I will have to cut off. Big pain.
                    >
                    > So, the only way to do what I want to do is to ram up the mold with
                    > a bunch of chills near the part. And it still might not work. But
                    > anyway, that's one thing to try Chris. Bigger the mass of the chill
                    > and closer it is the casting, the better it should work.
                    >
                    > I haven't had to try this yet, but this is how it's supposed to work
                    > anyway. Give it a try, I'd like to hear if it fixes the problem.
                    > Maybe chilling the chill would be a good idea too? Probably not,
                    > the extra 20 deg C wouldn't do much good, and it could introduce
                    > moisture problems. On Second Thought, don't try that.
                    >
                    >
                    > Katou
                    >
                    >
                    > This list is for discussion of metal casting
                    > and does not accept attachments. For off topic discussion and to share
                    photos and stuff: join Sandcrabs by sending a blank message to:
                    sandcrabs-subscribe@yahoogroups.com
                    > http://groups.yahoo.com/group/sandcrabs
                    > or join the Coffee Lounge group (by approval)
                    > http://groups.yahoo.com/group/Hobbicast_coffee_lounge/
                    >
                    > Please visit our sponsor: Budget Casting Supply
                    > http://budgetcastingsupply.com/
                    >
                    > Files area and list services are at:
                    > http://groups.yahoo.com/group/hobbicast
                    >
                    > To unsubscribe from this group, send an email to:
                    > hobbicast-unsubscribe@yahoogroups.com
                    >
                    > For problems that cannot be otherwise solved contact the list owner by
                    email:
                    > owly@...
                    >
                    >
                    >
                    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
                    >
                    >
                    >


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                  • katoutwo
                    The chill goes on the largest part, somewhere on the part, doesn t really matter. If you were casting a dumbell shape, the chills would go around the bell
                    Message 9 of 9 , Jun 3, 2003
                      The chill goes on the largest part, somewhere on the part, doesn't
                      really matter. If you were casting a dumbell shape, the chills
                      would go around the bell ends. It doesn't matter where they are
                      relative to the runners or sprues. Well, I suppose it would be a
                      bad idea to put it right next to the sprue.


                      --- In hobbicast@yahoogroups.com, "Chris Boyer" <boyercl@a...> wrote:

                      Part of my concern,. I would need it very close to where I gate
                      into the part.

                      Why would you have to have it close to the gate?


                      Katou
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