looking for tips on making masters for sand castings

[whetrock]

Can someone give some tips, pros and cons, etc. on their preferred methods for making dummy butt plates and trigger guards to be used in sand casting?  I’m talking about a dummies/templates/masters that that I would send to a caster. (I’m not interested in doing casting myself.)

I have previously forged my own from iron, and am comfortable with that process. I could do that again and use iron masters, of course. But I would be interested in reading how other guys skin this cat.

For example:
I could cold forge them out of sheet lead and solder them together.
I could carve them out of wood.
I could create a mock-up butt stock of pine and then carve it out as if fitting a brass plate, then fill in with bondo, etc. to build a dummy plate of bondo-epoxy.

Any and all tips welcome. Looking for pros and cons. Hope the discussion is useful to all.

I think it would be especially helpful to see comments from guys who have themselves done sand casting. What sort of dummies/templates do you prefer to work with? What do you find gives the best results?

Whetrock

PS: I have no experience with brass casting myself. I have seen the video by Terry Leeper  http://www.artisanideas.com/product.jhtm?id=793&cid=27

[PPatch]

Whetrock;

Besides the several examples you listed for creating originals there is the direct wax method that I have seen done by sculptors and jewelry makers. This involves creating the original out of wax to be used in the Lost Wax process. The method pretty much resembles forging and soldering except you are working with wax. They used sheets and blocks of wax worked with metal tools heated over a candle flame to sculpt (and join) the piece full-sized or slightly oversized for eventual shaping with files and the like. Here is a link to wax supplies:

http://www.gesswein.com/c-104-wax-carving.aspx

For tools I have mostly seen used are just a small knife and other handmade tools, but there exist special wax carving tools. Here, down the page and to the right (red handles) are what they look like:

http://www.gesswein.com/c-101-casting.aspx

One does not need the $500 tool warmer shown, just similar tool shapes; briefly heating them over a candle flame is quite enough. One can achieve great detail with this process, in fact create an exacting original. One thing to be aware of is keeping the wax within “working” range by not allowing it to get too hot while manipulating it (put it in the fridge for a bit before continuing). You will have to speak with your caster to know where to position the sprue(s), in fact it is best to coordinate and discuss things before hand with your caster so you understand their needs.

Hope this helps.

dave

[Acer Saccharum]

I've taken guards, cut them apart, soft soldered them back together in the way I want, fill with solder, or bondo, etc.

Sometimes the remake requires new finials, or a longer grip rail, etc, and 1/8 brass plate is useful for things like this.

Once it's where you like the form, send it off to your favorite foundry. Or buy the crucible and make your own castings.

[Acer Saccharum]

Eric vonAschwege made patterns from pear wood. Apple would work, dense, hard, takes great detail.

[whetrock]

Dave, thanks for the info on direct wax casting. I hadn't thought about that route.

[whetrock]

With making brass or wooden masters for sand casting, can you guys offer me any advice on how much shrinkage I need to allow for?  

(A while back  http://americanlongrifles.org/forum/index.php?topic=24553.15  someone suggested building up an original part a bit with foil or tape before using it as a master. But how much build up is recommended?)

[docone]

Lost styrofoam is also used.
Make a master, send it out, or do it yourself.
If you have a torch, you can cast.

[whetrock]

Docone, can you elaborate a bit on the "lost styrofoam"?  I've carved styrofoam for other (non related) projects, but always found it to be pretty fragile when it got thin. How does that work if I carved it down to the thickness needed for a trigger guard grip rail?

[whetrock]

Thanks for the tips on jig sawing together pieces, Tom. I guess I was hoping to avoid cutting up other brass parts I have laying around, but I may choose that route before I'm done.
Re the wood option, I'm a little short on pear and apple , but I've got some good chunks of TN black locust. Almost as hard as brass, best worked with rasp and files, and very stringy. It would probably handle the stress without cracking. I can certainly give it a try.

Any tips on the shrinkage question?

[PPatch]

Shrinkage: I believe this is a good question for whomever will cast for you Dave. Differing compositions of metal will shrink at different rates.

dp

btw: Just looked at that ad for the Jerry Leeper video - those guys shown in the picture are taking a HUGE chance pouring molten metal without being properly dressed for the task. I used to help the sculptors in the studio next to mine pour bronze, brass and aluminum and we always wore protective clothing and face masks. You can pour successfully without it a 1000 times but the one time there is the least bit of moisture in the mold it will violently explode.

[whetrock]

Yeah, I'm sure you're right about the different compositions. That amount is documentable and easy to plan for with investment casting. With sand casting, it is also compounded by the fact that the mold is somewhat loose material. I've yet to try my hand at it, but I'll mention that there is a lot of variation in the quality of the castings I've purchased. Some are so rough and full of pits and sand that I've had to file away half the guard before I get to decent metal. (only so much can be filed in with solder.) If the master was big enough, then that's okay--all part of the plan. But I need to plan for it. If I don't, then I'll end up with a overly-thin guard when I'm through.

Yes, on the exploding risk. In the video I watched, he did talk about that risk. I'm also surprised at the lack of protective clothing, etc. (As you say, most trouble starts out as fun...)

[PPatch]

There are casting "sands" sold today that will give a reasonabily smooth finish, they are more expensive of course. Using regular sand with a binder mixed in gives the sort of rough finish you refer to, very Old School.

dp

[docone]

I have only seen Lost Foam Casting on U-Tube. Myself, I do investment casting. I have tried Cope and Drag but didn't have the best sand for it.
I am guessing the foam carving for the part would be thick enough for sand casting. The molten metal will remove the foam while pouring.
Something to look into for sure. I make rings. I would need larger equipment for a trigger guard.

[whetrock]

Docone,
Just read about this LFC process on wikipea. Very fasinating. Thanks.
whetrock

[wmaser]

I make my masters out of aluminum, cast in sand molds using the original parts from dismantled guns. When I make the molds I first dip the the item in wax in order to slightly build it up to compensate for flaws or rough texture. When creating an item from scratch, I make the prototype out of sheet brass, silver soldered together using three heat grades of solder so as to prevent melting the adjacent completed work. I then make an aluminum master from it.
I make the masters out of aluminum because it's easy to melt and pour, its light weight makes it easy to make molds and what else am I going to do with all these beer cans.?

[whetrock]

Wild Bill, thanks for the tips. your comment on using wax is very helpful. your comments on three grades of solder also very helpful. Thanks.
whetrock

[Randall Steffy]

In response to the question about shrinkage factors, I share the following;
brass shrinks 3/16" per foot
aluminum shrinks 5/32" per foot.
This is the normal shrinkage factor, not the excess shrinkage you will get at overly heavy areas which are not fed properly with risers and /or held with chills. You will not normally see this localized and excess shrinkage on parts as thin as a butt plate or trigger guard unless the molten metal is heated significantly above what is necessary to run the casting with an appropriate number and volume of ingates (the areas the metal feeds into the casting cavity.)
As an example, a master pattern of a trigger guard which is 9" long will make a brass casting 0.14" shorter or 8-55/64" long. Use 0.9846 as a multiplier of your master pattern to know what your final brass casting will be. Or use 1.0156 as the multiplier if you know the dimension you need to get in your final brass product (1.0156 x your final casting = your master pattern dimension.)

[whetrock]

...not fed properly with risers and /or held with chills...  

Randall, I have to admit that I don't have enough experience to understand what I read.  Can you elaborate just a bit on the risers and chills?  I'm guessing from what you wrote that this won't be an issue for something as small as we are talking about, but would be for bigger items and are important in industrial casting.

thanks for the math. that helps tremendously!

[Randall Steffy]

Riser, a heavy reservoir of sacrificial molten metal adjacent to a heavy casting section, and fed into the casting through the gate, can prevent excess shrinkage. I say sacrificial because the heavy pool of metal in the riser will shrink excessively as it feeds the lighter, albeit heavy section in the casting.
A chill is a heat sink, often a piece of iron or other metal with sufficient mass to prevent the excess shrinkage which would result in a scrap casting. The chill is placed against the pattern in the process of ramming up the sand mold, located as near as possible to that heavy section of casting determined to cause the shrink defect. The trade off is that you now have a scar from the chill.
Note that neither riser nor chill should be required for casting rifle hardware. More likely a misrun, or metal too cool or  insufficient ingates to run the entire casting will be the flaw.

[whetrock]

Very helpful! Thanks, Randall.

All of you guys have been very helpful with this!

[JCKelly]

There are pattern makers rulers, a.k.a."contraction rules". which already incorporate the shrink for brass, aluminum or iron, so you needn't do the math each time you carve a pattern.
I have an inherited set. I suspect that in our computerized era you will more likely find these as antiques.

[Captchee]

 I make my moulds from  hard wood .
  There can be no  negative angles .  You can  have detail but it must all be positive  with no undercutting .
For things like trigger guards I start with two pieces  of wood . Pinned together . Carve the part , then separate the two haves
 Lay  one side of the part  on a thin piece of sheeting . For this I use  marelight.
 Now using your existing holes  in your part , drill through the marelight .
 Now set 1/8 hard wood pins  into both haves of your part so that  they stick through the  board  . then sand them off flush with the back side . this allows you to set the  board with 1/2 the mould , face up on a hard serface . then place your cope or drag on the alignment pins  and pack .
 This allows you to join one half on one side  of the board and the other  will match on the reverse side of the same  board so you can pack  the cope and drag independantly .
So what your doing is  ½ your pattern on the cope and the other half on the  drag . By laying up one side at a time .
 so  when your finished with one half . flip the board over , set your other half on the board  and pack the other side .
when you have the cope and drag  packed ,, cut your gates, resavore , pour hole and popit .
 if your doing  alot of casting you can make all these  on one side  of your board  so you will have them all in the same place  time after time .
 then  simply join them  and cast one complete part

 For items like thumb inlays , you can carve that in one piece .
As was stated earlier , shrinkage is very minimal  as you use a reservoir which not only serves to  hold the heat  longer  but it also creates pressure  .
 If  your concerned about shrinkage  in cases where your casting to and  existing fit . Make your mold slightly larger if you want .  With sand casting , you have to file things to finish anyway
Its also The finer the sand  the better  your finish  and cleaner your detail will be .
 I would disagree that  casting sand is expensive. Its reusable time and time again . 20 lbs of  fine green casting sand  with binder added  is way more  then enough  to do all the  major castings on most any rifle.
 Last I bought ran me around 25.00 .  
 
 Now when it comes to lost foam casting .
 Foam comes in a lot of different densities. But thicker parts ¼ inch or more can be cast  using  simple blue or pink foam .
  Thinner parts  can also be cast  but you have to use aerated sand in order to  not distort  the foam.
With out aeration, the sand has to be packed  or settled well . As such this can distort  thin , long  moulds like TG and such
A while back I  discussed  lost foam casting  with a young man who wanted to cast a Knife guard .
 Here is a link to the  forum description of the process I  use  for lost foam . The topic also contains   comments by myself and others  on  fixing issues he  had with his first attempts   and a photo of  one of his castings .
    http://muzzleloadermag.infopop.cc/eve/forums/a/tpc/f/5791081811/m/4164024428

[whetrock]

Captchee,
very interesting technique, splitting the master!  I'm assuming that "marelight" is some kind of clear, plexiglass sort of material . Is that right? can't get any hits on the spelling, so just guessing.

I just read the other post you linked to, with the details on LFC method. Also checked out the website on casting. Learned there that greensand and water (yep, water, folks) is used, by some at least, in making sand-cast molds for brass. Lots to learn.

All very, very helpful!

whetrock

[Captchee]

Captchee,
very interesting technique, splitting the master!  I'm assuming that "marelight" is some kind of clear, plexiglass sort of material . Is that right? can't get any hits on the spelling, so just guessing.

I just read the other post you linked to, with the details on LFC method. Also checked out the website on casting. Learned there that greensand and water (yep, water, folks) is used, by some at least, in making sand-cast molds for brass. Lots to learn.

All very, very helpful!

whetrock

Marelight  is just a thin hard fiber board .  Same stuff used to make peg board  but without the holes .
 it’s a interior  fiber board sheeting that  waxed smooth on  either one side or both sides  and around ¼ thick .
 You could use a  piece of plexi glass  .  All that maters is that the area around the half of the mould is matched to the other half so they fit together
  

  When you looked at the website I linked to ,  your should have seen their tutorials .
 In their basic casting  tutorial  they show  the cope being laid on a  flat board . The  mould is then placed on the board and sprinkled with release . Green sifted sand is then sprinkled over the  mould .  This sifted sand is  where the detail comes from . Then   un sifted sand is packed  onto the sifted sand , to the  level of the cope .
 The board  they set the  mould onto is  the one  you want to set ½ your mould on . The pins only insure that  both halves of the mould fit together properly to make one complete  casting  when you join the cope and drag .

As to water . YES  water is used as part of the binder  or in some cases all of the binder . But you have to be careful  because to much water can cause a steam explosion as well as creating  voids in your casting.
 As a note to this  that may interest some .
 Its kind of like  mixing acid and water  it all in the order in which you pour the two together .
  I once watched a Traditional Japanese  sward maker cast  the sward guard  with nothing more then  water and a piece of silk . A section of silk was  draped over a container of water  . Then he pushed the center of the silk down  under the water level about ½ way . The molten metal was then poured directly into the water . The silk caught the  melt  . Its weight against the silk making a nice round  disc .
 Somewhere I have a video that shows a contemporary sward maker  doing the same thing .

As to the binder . There are many different binders . Each with their own advantages .
 I have read where colonial  casters would use horse  manure to bind the sand for making bells .
I also have read where  French liege casters used   water  mixed with sugar  as a binder .
 Many  folks today use Diatomaceous Earth  or Fullers earth   as a binder ..

 What binder you use , is dictated by  the part your casting . If your casting something with a lot of  open detail , then your going to want a stronger binder so that the sand doesn’t pop out  when you remove the mould

[Captchee]

 Here are a could videos showing the contemporary  maker I talked about . In them you will see not only water casting but also  processes of gold plating  its called ;'Following the Iron Brush'
 They may be interesting to some .

http://www.youtube.com/user/ironbrush?v=wGMj7o6AwnM&lr=1
[http://www.youtube.com/user/ironbrush?v=pM0VnL30rDc&lr=1