FLASKS Wood "SNAP" aka as hing type

Discussion in 'Foundry tools and flasks' started by smithdoor, Oct 17, 2018.

  1. smithdoor

    smithdoor Copper

    I am looking to build FLASKS Wood "SNAP" aka as hinge type

    Does any one have drawings or photo's of flasks that can posted

    Dave
     
    Last edited: Oct 17, 2018
  2. PatJ

    PatJ Silver

    I started to make some snap flasks, but I generally use a custom sized flask for each part, and make them from wood.
    The metal hinges at the hardware store were pricey in quantity.

    So what I do instead of hinges when I want a snap flask is to remove the screws from one corner of the wood flask, loosen the screws on the diagonal corner, and flex the flask open just enough to pull it off the sand.
    Not a deluxe setup, but works pretty well.
     
  3. PatJ

    PatJ Silver

    But to answer your question, there is a guy here who built some cast snap flasks.
    I will post a photo, but it is his photo, not mine, and I will post it so that others can identify who that is (the guy with the indoor casting area, and fume hood).

    And a few commercial flask photos.

    And a 3D flask design I started with (not a snap flask). I would make some changes to it at this point, but for what its worth, here are the screencaps.

    There is a set of flask patterns floating around out there somewhere that have been shared between members (photo attached).

    Note that commercial snap flasks generally only open enough to slip the flask off the mold.
    They do not actually hinge open more than a slight amount.

    And the sand mold gets a sheet metal jacket around it (I forget the exact term for that, I think "slip jacket") to hold it in place after the flask is removed.

    Edit:
    Here is a flask website:

    http://www.hinesflask.com/

    Also, I have changed the interior of my flasks to have a strip bead of wood that protrudes into the sand, instead of using one or more grooves in the interior surface of the flask, and the reason is that for bound sand molds that will be stored on edge, and also molds that will receive a slip jacket, the outside of the mold needs to be smooth.


    01lwpof.jpg


    12x12-Flask-PJ-01.jpg


    12x12-Flask-Side-REV-02.jpg


    12x12-Flask-Side-REV-02-Assembly.jpg


    12x12-Flask-Side-REV-02-Inside.jpg

    Edit:
    Looks like Robert make these flask patterns.
    http://www.alloyavenue.com/vb/showt...Flasks/page4&highlight=Roberts+Casting+Flasks
    13 - 1 (2).jpg


    13 - 1.jpg


    P1000201.jpg


    rIMG_6810.JPG


    rIMG_6813.JPG


    rIMG_6814.JPG


    rIMG_6827.JPG


    spearmoldfill600x450.jpg
     
    Last edited: Oct 18, 2018
  4. PatJ

    PatJ Silver

    A snap flask patent.

    FLASK-01.jpg


    FLASK-02.jpg
     
    Rtsquirrel likes this.
  5. Here's a simple snap flask. It's made of tongue and groove flooring with the tongues and grooves cut off. A 1x4 works too. for a small flask it's not necessary to have keys to keep the sand in. They can be added if you have trouble. For pouring aluminum I get by with no cover on the green sand mold after the flask is removed.

    IMG_4442.JPG IMG_4441.JPG
    Cheap hinges are holding up well. This flask probably has more than forty molds made in it, and most of those poured in the flask. It's not burned because I try to pour the metal in the mold instead of on it. I like bold colors on each end so it's really easy to get it back together right.

    IMG_4444.JPG IMG_4443.JPG

    The wedge guides work really well and don't stick but they are limited to shallow patterns. For a deep pattern it hard to lift straight without a guide pin. This was the second flask I have made, and the first was similar but not a snap flask. Quick and easy. The floor boards had the relief in the bottom which helps the sand stay in.
     
    Rtsquirrel likes this.
  6. PatJ

    PatJ Silver

    Seems like you could fasten two diagonal corners permanently with glue/screws, and then use box joints on the other two corners.
    The two box joint corners would be drilled vertically to take a pin, perhaps an 1/8" steel rod, and the back corner could hinge open slightly if you rounded the inside corner on one side of the box joint.

    Here is a box joint video which uses a dado blade on a table saw, but seems to produce an accurate enough joint.


    Or a router could be used in a similar fashion.


    And for a more durable flask with more room for drilling the pin holes, use a 2x4 or taller material.
    Another benefit of using nominal 2" thick wood (a 2x4 is actually 1.5" thick) is that you can drill a hole on either side vertically through the cope and drag, and use steel rods through these holes to align the cope with the drag. This eliminates the traditional pins and associated alignment hardware on the sides of the flask.
    The steel rods can be made as long as desired to make a long aligned lift when separating the cope from the drag.

    And if two different rod diameters are used, you cannot accidentally get the cope and drag 180 degrees out of alignment.
    I have used perhaps a 5/16" rod on one side, and maybe a 1/4" rod on the other side.
    It is best to use a drill press in order to drill the rod holes, and for exact alignment, drill the first rod hole through the cope and drag, then insert the rod, then drill the second rod hole.
    And if you are using the flask as a snap flask, you only need one set of pins, and can use those pins for all the various flask sizes/shapes (assuming one person will only ram one flask at a time).

    To make the rods easy to insert/remove, bend a short 90 on the end.
    Waxing the holes in the cope and drag also helps with rod insertion/removal, and allows the fit to be snug and accurate.

    A snap flask made this way would not require any store-bought hinges or latches, and use 1/8" steel rod for pins in the two box joints. Only one 1/8" steel rod would be removed to hinge the flask open slightly.

    I think the router method would be easier since I don't know where my dado blades are, and don't want to have to change the blade on my table saw and find the correct throat plate.
    A 3/4" slot can be cut into the top of a sheet of plywood as a guide slot, and the router mounted on the bottom to make a router table.
    A mitre gauge can be made from two pieces of wood glued at a 90 degree angle, with one thin piece riding in the guide slot.

    I will probably start making my flasks with box joints.
    I already use the two different sized steel rods in lieu of the side-mounted alignment hardware, and that works very well with 2x4 material, and is a quick, simple and accurate way to align the cope with the drag.

    And it would probably also work to just use one slot in the center of one piece which has a height equal to 1/2 the height of the board, and have the mating piece fit in that slot, which would limit the amount of cutting to be done.
    Multiple slots would probably give a tighter and more secure joint.

    .
     
    Last edited: Oct 17, 2018
    Rtsquirrel likes this.
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    HMMM, Ya know......
    Ive been trying to figure out what to do for our next casting contest.. Maybe I should open things up some more and make it a general foundry contest and we make ourselves some new flasks??
    Pretty sure we all could use a new flask..... Well maybe not all.... @Jason Sorry buddy...:(
     
  8. PatJ

    PatJ Silver

    Bingo; I am game.

    Edit:
    And the reason I use wood instead of cast aluminum flasks is because molten metal tends to damage a flask if spilled on it, and a wood flask is much easier to replace and a cast aluminum one.
    And the reason I use snap flasks is because that totally eliminates the danger of damaging the flask from spilled metal.
    Molten iron is especially hard on flasks when spilled on them.

    But aluminum flasks are very nice, and I would not mind having an assorted set of sizes of those, especially if they were snap-flasks.

    .
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    I have two patterns that require very precise vertical lifts that have to be controlled for 2 inches or so of draw. I have tried several strategies to maintain vertical alignment and level Des during drawing of the cope from the drag and subsequent closure of the molds. The molds weigh 125 and 350 pounds respectively. I have also used alignment aids on considerably smaller flasks.

    In my hands, I found that trying to use two long pins in corresponding long deep holes is problematic for two reasons. First boring holes that are precisely parallel in wood or metal is very hard even using a capable milling machine. Drill bits , even new accurately sharpened bits, tend to wander and the slightest error in alignment causes very severe binding as you try to separate or close flasks. And, even with well aligned and sightly oversized holes any error in levelness of the cope will cause solid binding of the pins as you draw it from or set it on the drag.

    If the alignment pins are very short---maybe a half inch or so---then pegs in short holes will work.

    For long draws, the most workable solution for me has been to mount 3/8" diameter steel pins on 1.5" lengths of 1x1x1/8 angle iron and attach these to the drag. Then I attach corresponding angle with holes to the cope. But, it is necessary to make one of the two holes slightly elliptical to provide a little tolerance for pin alignment errors. Both holes need a few thousandths clearance in diameter or they will lockup with any tilting of the cope. Greasing or oiling the pins helps as does using a file makes sure the holes are not sharp-edged. The holes work best if they have a generous chamfer top and bottom so that the two chamfers nearly meet Rather than have the pins on the ends of the flask where they would be hard to see, I like mine on the side facing me.

    Finally, with large molds that require accurate alignment, using a spreader bar and chain hoist makes a controlled draw and closure possible.

    Certainly, all that complexity is not needed for the average pattern. But it does help for challenging ones. The ultimate setup would use a double-acting hydraulic cylinder to lift and align the cope. Haven't tried that, YET.

    Denis
     
  10. PatJ

    PatJ Silver

    Here is some flask hardware I made a while back.
    I don't use this style hardware anymore, since the two rods through the flask sides works well for me so far.

    I think li0 (AA guy) mentioned using carriage bolts with the head sawn off, and that is how these pins were made.

    But another trick is to taper the pins so that they only become tight just as the mold is about to close.
    An easy way to taper the pins is to mount them in a drill and hold them against a disk sander at a very shallow angle.
    The taper prevents binding when the cope is being drawn off the drag, and generally you don't need precision alignment until the cope and drag are almost closed.

    The commercial alignment hardware often has a second small plate mounted on the angle iron that has the open hole, and the hole is oversized.
    The hole in the small plate fits the pin exactly, and it can be adjusted slightly over the oversized hole on the angle iron when the cope and drag are joined, to produce an exact fit.
    The small plate is bolted tight to the angle iron once the alignment is adjusted.
    This eliminates the need to make a precision sized cope and drag, and eliminates the need to try and shim the two pieces of angle so that the align exactly.

    Edit:
    I have seen some flasks with two pins on either side, and you could have both short and long pins.
    The short pins would not have taper, but the long ones would be tapered.
    You could put your thumbs on the short pins to evenly start the cope/drag separation process, and then let the longer tapered pins guide the cope as the gap increased.

    For heavy molds this method would not work, so all bets are off, but perhaps a lever with cam (similar to a lid lifter mechanism) on either side to get the separation started, and then hoist the cope off.


    rIMG_4246.jpg
     
    Last edited: Oct 18, 2018
  11. smithdoor

    smithdoor Copper

    After look all post I made drawing of what my flask may look like

    Made wood steel and wear strips with 3 1/2° tapper hinge and 1/2" pins

    Dave
     

    Attached Files:

  12. I would think the taper on the flask would make it hard to lift the cope to remove the patterns. I guess you could remove the drag. Why the wear strips?
     
  13. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    If you have enough sand and plan make multiple molds, snap flasks are they way to go. If you are typically only making one mold they're probably an unnecessary complication and you'd be better off pouring with flasks in place to clamp and keep the mold stable. The wear plates are a good idea for durability but not many home gamers will see enough use to warrant them. The taper on the sides proposed in your drawing will likely cause drop outs without the addition of cleats of some kind on the inside walls. Most backyard casters find it difficult to have one-size-fits-all flasks and are better off making simple wooden frames to accommodate different size projects and just swap the alignment hardware between the simple flasks.

    How big are you planning the flasks to be? This can influence the required alignment system. For 20"x16"x8" deep flasks I used these bushings on my match plates but commercial foundries commonly use them on even larger match plates with good result.

    Bushings.jpg

    They use two 3/4" diameter pins of varying lengths depending upon the depth of draw. Note that only one of the two bushings is a round hole with a close fitting pin. The other is slotted and the pin only closely fits the edges of the slot. This helps prevent binding and allows looser tolerances in positioning the second slotted bushing on the match plate because the slotted bushing only needs to be mounted on the centerline of the match plate whereas another round bushing would require that plus a precisely controlling the center to center distance between the two bushings. Even with precisely located holes, two round bushing will bind with the slightest cocking while drawing the cope. The pins are typically tapered for the first couple inches and not for the last 3-4" for precise alignment. These are hardened commercial bushings and pins but the approach is easy to duplicate in the home shop. Good luck with your build.

    Best,
    Kelly
     
  14. smithdoor

    smithdoor Copper

    For the bushings I planning on UHMW I have a large supply and its cheaper over steel or brass bushings

    Thank you
    Dave

    (UHMWPE is also used in the manufacture of hydraulic seals and bearings. It is best suited for medium mechanical duties in water, oil hydraulics, pneumatics, and unlubricated applications. It has a good abrasion resistance but is better suited to soft mating surfaces.)

     
  15. smithdoor

    smithdoor Copper

    Here is drawing of flasks a 10 x 8

    Dave Flask Oct 21 2018 Model (1) copy.gif
     
  16. Is that the drag on top? Your taper makes sense now. Once you ram the drag and flip it with a board to add the cope and finish your mold, the taper will hold the sand in the cope.

    Why are you tapering it? It seems like a lot of layout work to get it all straight and square.
     
  17. smithdoor

    smithdoor Copper

    The cope is on top
    The tapper sided are for pouring jacket
    There 2 flat bars in center holding the sand and a few saw cutters about 1/16" deep not shown

    Dave

    PS: The handle on cope is not shown need for parting





     
    Last edited: Oct 21, 2018
  18. Thanks! I hadn't noticed the flat bars protruding into the sand. So your lineup pins come out of the drag for initial pattern placement?
     
  19. crazybillybob

    crazybillybob Silver Banner Member

    I would like to see Jason make some lost wax Flasks. He could make them all fancy. They'd be to pretty to use, and heavy a sin when he cast them in Bronze :) but they would be a nice contrast out by the shinny silver pool.
     
  20. DavidF

    DavidF Administrator Staff Member Banner Member


    1 That would be one expensive flask
    2 They would be pretty heavy
    3 Pretty sure Jason is using the pool thing just so he can buy a new welder ;)
     

Share This Page