Stove tool casting

Discussion in 'Sand Casting' started by YakTriangle, May 29, 2019.

  1. YakTriangle

    YakTriangle Copper Banner Member

    So, following on from my stove tool pattern making post in the pattern making forum, I thought I'd post a few piccies of my first attempt at casting this thing.

    Because the pattern wasn't split, I had to pack it into the top of the drag as can be seen here ...

    MVIMG_20190511_123035.jpg

    I also cobbled together a core using some firebrick. The core was in two parts and guessed the limitations this would have in allowing molten metal into places I didn't want.

    So the fully packed drag looked like this ...

    MVIMG_20190511_131146.jpg

    I was happy with this and proceed to ram the cope.

    MVIMG_20190511_145457.jpg

    Problem was, when I then parted the two halves of the mould, this happened ...

    MVIMG_20190511_150649.jpg

    Guessing I didn't use enough parting powder but also wondering whether my ramming technique was flawed too. Anyway, not wanting to be defeated, I pulled it all out and started over, using significantly more parting powder the second time around. This time was more successful and when I extracted the pattern, there was some destruction of the mould as correctly predicted by many on my pattern making thread.

    MVIMG_20190511_160818.jpg

    You can see in the above photo where I have repaired the mould around the head of the tool.

    Running the furnace, charging crucible, and getting ready for the pour ...

    MVIMG_20190511_162515.jpg

    The pour itself was a good pour I reckon ...

    MVIMG_20190511_172014.jpg

    MVIMG_20190511_175148.jpg

    The final result after a little clean-up and de-sprue. Not bad but I can do better ...

    MVIMG_20190514_190927.jpg

    MVIMG_20190514_191007.jpg

    MVIMG_20190514_191026.jpg

    Overall, I'm quite happy with the turn out of the rope effect but I just need to improve that parting line. I got the expected result on the tool head with the dual core, i.e. - not great.

    There will be a second attempt. My plan is to coat the rope with some kind of paint or lacquer to seal it and give the sand less opportunity to adhere or cling to it. I also plan to make the core out of a single piece of clay. We'll see how that goes.

    Cheers,
    Gavin
     
  2. oldironfarmer

    oldironfarmer Silver Banner Member

    I think you did really well. The first picture above looks like the head of the tool has draft which was upside down. I could be wrong, just looking at a picture.

    Start with an empty drag upside down on a board and lay your tool on the board, taper up. Then dust and ram the sand, pressing some under the openings under the tool. The flip the drag over and cut down to the parting line scooping out generously so the parting line follows the widest part of the tool. That parting line may not be flat. It will be flat along the handle but move up as you get to the wide part of the head. Then when you have it all cleaned out dust it, put on the cope, and ram it. It's all a pretty standard process.

    I think your casting looks great. A little more time spent cleaning it up and it will be good. You may even have trouble improving on it much. What did you cast it in?
     
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  3. YakTriangle

    YakTriangle Copper Banner Member

    Many thanks for the feedback. I believe the draft of the tool head was the correct way around so it may just be the photos giving you that impression. I have always assumed the parting line should be flat and follow the line between the cope and drag ... clearly this is not the case. I'm still trying to visualise what you describe above concerning this.

    I may melt this one down and reuse the metal for a second attempt. One other thing that became apparent was the weight of the tool - it is heavy. I'm thinking of using a core in the handle section so that it is hollow.

    This is cast in bronze (90% copper, 10% tin).

    Cheers,
    Gavin
     
  4. Melterskelter

    Melterskelter Silver

    Way to go, Gavin. You did well.

    The technique described (a good one) is called parting down.

    Here’s an interesting demo. Only rather minor criticism is I’d have patted down the runners with my fingers to smooth and solidify the runners he cut. But good demo of what OIF was suggesting.



    Denis
     
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  5. Chazza

    Chazza Copper

    Nice work Gavin!

    Your plan to seal the string with paint is a good one and you should find that the pattern releases well.

    The parting-line doesn't have to be flat; in Australia it is called "Cutting your own joint", which might provide a bit of amusement nowadays. Do as Oldironfarmer describes.

    To avoid burning your cope with excess metal, make a bush using a cut-down tin-can, which sits on a pattern-plate and sand is rammed into it with your fingers. In your case you would need two bushes. If you need a photo of this let me know,

    Cheers Charlie
     
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  6. PatJ

    PatJ Silver Banner Member

    Not bad considering the level of detail in that piece.

    .
     
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  7. Petee716

    Petee716 Silver Banner Member

    Nice work. I think OIF is right. It looks like the part is complete and just needs to be cleaned up. Even if you decide to recast I'd keep the old one. I've found that working with brand new petrobond can be a bit of an uphill battle. Sticky stuff. I try to remove some of the most severely burnt sand, but don't be afraid of mixing the black stuff in. As you use it it will darken and its character will change a bit for the better.
    Ramming is a practiced skill. I tend to ram too hard sometimes and it's a hard habit to break.

    Pete
     
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  8. YakTriangle

    YakTriangle Copper Banner Member

    Many thanks again to you all for the encouragement. Very much appreciated and gives me a sense that I am doing something right! :)

    @Melterskelter many thanks for sharing the video. That demonstrates what OIF described very nicely however I can imagine this becomes more tricky with increased detail in the pattern? I'll give it a shot though.

    @Chazza Thank you ... and photo please!

    @Petee716 I guess it can be useful to keep the first piece for comparison purposes (I was fully intending to recycle it). I found what you said about the character of the sand interesting and is certainly something I hadn't thought about ... in fact I've been trying to keep it as clean as possible but maybe I don't need to be so precious about that. I think I have also been ramming too hard. I also think I need to riddle my sand, which I haven't done so far.
     
  9. Melterskelter

    Melterskelter Silver

    Riddling your sand is important for s couple reasons. First and obvious, is the improved consistency of the sand making it soft and fluffy and helps it conform to the pattern surface. But just as important it removes random bits of metal and debris that tends to unavoidably accumulate in your sand as time goes by. Those bits do no harm in the backing sand but can cause defects if they are in the face sand.

    I like to use a mesh somewhat coarser than window screen. I lay the riddle right on the flask and push the sand over the mesh. That’s a many times faster than shaking the riddle.

    Denis
     
  10. Chazza

    Chazza Copper

    Here you are Gavin,
    Sorry about the orientation:
    First photo, shows the wooden pattern and a tin can taken from the kitchen rubbish and cut down with tinsnips. The safe-edge is left on the top when moulding.

    Second photo, shows the mould rammed full of sand using finger pressure and the excess struck off with any straight-edge, I use a trowel, or an old hacksaw blade.

    Third photo, shows the mould separated from the pattern and sitting the right way up. Easy way to get it off the pattern, is to twist the can sideways; same process when stripping the casting out later.. The bush, after puffing the loose sand out of it, can be placed on top of the cope and another one placed on the outgate/riser if you have them.

    The advantages of using a bush;
    1. Easier to hit the ingate with the pour.
    2. Less likely to spill on to the top of the cope.
    3. Creates good internal pressure inside the mould cavity, to force metal up into all of the nooks and crannies in the cope.
    4. Can be used as a feeder to help control shrinkage in the cooling metal.

    Using soluble-oil as a binder, there is no significant wash of sand into the mould. The bush can also be made using resin-sand, etc.

    Cheers Charlie
     

    Attached Files:

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  11. YakTriangle

    YakTriangle Copper Banner Member

    Ah brilliant! Many thanks for posting that Charlie. Now I see what you mean, I have seen quite a few photos - on this forum probably - where people have used this technique.

    Cheers.
     
  12. YakTriangle

    YakTriangle Copper Banner Member

    Cool, thanks Denis. I am now sourcing parts to make myself an inexpensive riddle. I plan to use the outside of a bamboo wrap/pancake steamer and combine it with some stainless steel mesh. Was thinking ~4mm square hole size which "feels" like it should be a good size. Would you agree?

    Cheers.
     
  13. Tobho Mott

    Tobho Mott Silver Banner Member

    That mesh size should work well IMO. Personally I us a finer sieve to put on the first thin layer of sand directly over the pattern, then a coarser stainless mesh over-sink type kitchen strainer/colander for the next layer or two. It might be a little finer than 4mm, but it's pretty close I think. After ramming that I usually just scoop in mulled sand to fill the rest of the flask.

    Jeff
     
  14. Melterskelter

    Melterskelter Silver

    I suspect you will hear a variety of preferred screen mesh sizes. For me, 4mm is just a bit coarser than ideal. To be honest, I do not recall the exact size I am using, but I think it would be 3mm or a tad less.

    Your frame can be round and I commonly see them round. However, square is definitely better for me (and much easier to make) as I lay my riddle right on the flask and the straight riddle side will line up with flask on a couple sides. Holding the riddle with one hand, I use the other to sort scrub the sand over the screen concentrating the scrubbing where I want more face sand and doing less where I want just a little—like where I may be placing a blind riser. I whipped my frame together in ten minutes using drywall screws, a stapler and 1x4” scraps. If you just build it fairly robustly but don’t put too much fussing in it, you won’t hesitate to change it as you see fit.

    If SS mess is cheap and readily available, I guess it’s fine. But galvanized or uncoated would be just as good especially with Petrobond.

    Denis
     
  15. YakTriangle

    YakTriangle Copper Banner Member

    @Tobho Mott & @Melterskelter ... thank you both for your feedback.

    Making a square riddle is a no brainer and I don't know why this didn't occur to me ... I clearly have no brain. I've found a source for mesh here ... https://www.themeshcompany.com/index.html. SS is about the same price (or cheaper in some cases) as plain or galvanised steel for an A4/A3 sized sheet which would be ample for my needs.

    Cheers.
     
  16. Melterskelter

    Melterskelter Silver

    Looking at the link you posted, I’d guess I’m using 2.5mm.

    Denis
     
  17. YakTriangle

    YakTriangle Copper Banner Member

    Cheers, I'll get something around that size. I notice brass mesh is cheaper than any of the steel variants so may go for that. There's almost something poetic about being able to sieve my bronze casting sand with another copper alloy. :)
     
  18. Tobho Mott

    Tobho Mott Silver Banner Member

    Mine is smaller than 4mm too, it's one of those over the sink stainless steel colanders. Can't find a good pic to illustrate, but if it matters, you can see it being used most recently in my bottle opener video, linked in the 2019openersopen thread. FWIW, C.W. Ammen's Complete Handbook of Sand Casting says "the 1/4 mesh or 4 squares to the inch" is most commonly used to condition sand. I'm not really sure if that means 4 holes in a row measure an inch long, or each square inch contains 4 holes. In my head it's the former, but I could have it wrong. 4 holes to the square inch just seems too coarse to me though.

    Jeff
     
  19. YakTriangle

    YakTriangle Copper Banner Member

    Cheers Jeff. I agree, I reckon that has to be 1/4" squares as opposed to 1/2" squares which is what it'd be if there were only four holes in a square inch. Even 1/4" squares are quite large though at 6.25mm.
     
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  20. Peedee

    Peedee Silver

    Just realised you are UK based. I've found https://www.johnwinter.co.uk/foundry/model-engineering/ are decent people to deal with and their site is quite an interesting read.

    I would still make my own riddles, just thought I'd mention them. (No affilation just satisfied customer)
     

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