Making core-boxes

Discussion in 'Pattern making' started by Chazza, Sep 26, 2020.

  1. Chazza

    Chazza Silver

    I have made simple core-boxes either by, turning parts on a lathe and gluing the cylinders together, or by carefully sawing an old casting along the parting line and using the halves as a core-box.

    So how do you go about making a complicated core-box from scratch? Imagine making a core box where the core is round in section and about 1" in diameter, but the core describes an "S" shape.

    I know a 3D printer could be immensely useful but I don't have the software, the machine, or the knowledge to go down that path. I am more of a traditional tools and methods man.

    I welcome your ideas and experience,

    Cheers Charlie
     
  2. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Make a "positive" of the core with an investment port (a feature to make an opening to fill the core), make a wooden box that roughly fits the positive, then use urethane casting resin to cast the "negative" as the actual core box. Cast one side first, install alignment pins, apply release agents, and then cast the other side. Remove the positive and you have your core box.

    This method works for making multiple cavity match plates too but I usually use silicone as the cast of the negative and use that to pop more positives on the match plate.

    Best,
    Kelly
     
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  3. rocco

    rocco Silver

    I made a core box for a VW intake manifold using a method similar to the one Kelly described. I carved a positive out of plywood and used that to make a core box out of plaster of Paris. I only intended to make a few castings so durability wasn't a concern for me, if it had been, I would have used something like a urethane resin.
    You can see that plaster core box in this video.

     
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  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Good point Rocco. I've used that too. Effective and inexpensive if it's not a high use box. You can also add chopped glass fiber and fillers for added strength.

    Best,
    Kelly
     
  5. Chazza

    Chazza Silver

    Ah yes! Makes sense to me; thank you.
     
  6. Billy Elmore

    Billy Elmore Silver

    Plaster works well and is probably the least expensive method, but if you need any fine detail then using a plastic is the way to go. There are some cheap plastics that have fillers already in them just for this type of application. The one we use is called Repro and comes from Freeman industries. Not sure if you can buy direct from them as we use a vendor for all of our plastics and such but worth looking into. Ours comes in one gallon containers part a and part b so you get two gallons of the stuff which will go bad before we use it all.LOL Remember to just use the plastic for the facing of the box and use wood blocks or some other filling for backing material. We generally try to stay around 1/4" thick with our plastic and the rest is filler. You can use this stuff for patterns, core boxes or whatever for good finish. Just watch the heat and abrasions and you are good.
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I have had an account for 30+years with them and they did not use to be very accommodating to small buyers and hobbyists, but now, you can apply for an online account with them and once approved, you will be able to view all pricing and buy direct from them online. They have many great materials and foundry supplies and are a great resource. I think there may be a minimum order but I want to say it's only $25-$50.

    Best,
    Kelly
     
  8. Chazza

    Chazza Silver

    Thanks Billy.

    I am trying to buy some letters from Freeman's agent in Australia so this may work for me,

    Cheers Charlie
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    Be careful of the Freeman plastic letters. I have some 1/4” size that are fine. But not too long ago I bought some1/2” size. The larger size came with mounting holes. That was a surprise and a serious problem. Had the mounting holes been carefully made, they could have been easily filled. But the are very crudely located and distort the letter edges. I used them for the first time recently and have found cleaning them up to be not an easy task. In fact, Freeman is going to get a call from me today. These letters were not cheap. If you are buying metal letter, I suspect, but would confirm, no holes

    . E11C5878-CB42-451F-8A2D-E46964EFD369.jpeg

    Especially bad is the “R” and the “E” is little better. There is little excuse for this poor design from Freeman.

    Denis
     
  10. FishbonzWV

    FishbonzWV Silver Banner Member

    I bought Freemans letters too. The 3/4" set had those holes but the 1/2" set had nibs instead of the holes. It was like the pins on the ejectors were retracted into the die too far. I considered both sets flawed and over priced.
    There are a lot of people selling 'sign board' alphanumeric's that mold exceptionally well after you trim the tabs off the back. Check out the number 8. These are 1/2" and even the little hole on the top pulled fine.
    IMG_3698.JPG
     
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  11. Melterskelter

    Melterskelter Gold Banner Member

    Ya, I saw you guys posting about sign board letters AFTER I bought the Freeman letters for the last time.

    Denis
     
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  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Agree, those are terrible. I'd be disappointed too, though I must say that has rarely if ever been the case in my dealing with them.

    Best,
    Kelly
     
  13. HT1

    HT1 Gold Banner Member

    OK, I got the Freeman 1/2 fubar letters also
    my best way to deal with the high cost of letters, i bought an entire alphabet of the White metal, made a real rubber mold , so in an emergency, I can cast up that stray vowel out of Bondo ,

    But most the time I just order whatever white metal letters I need cast an aluminum pattern, glue on the letters with PVA glue, cast a master pattern now lettered, and then soak off the letters for reuse.

    But make sure you get a ful alphabet and punctuation. for emergencies, Freeman has sent me letters that did not match older letters. they blamed subcontracting

    V/r HT1
     
  14. Chazza

    Chazza Silver

    Thank you for the warnings; it is not too late to cancel the order.

    Fishbonz I searched for hours for an alphabet and only found Freeman. Have you a link to where you got yours please?

    Cheers Charlie
     
  15. 509Maker

    509Maker Copper

    Chazza, I snagged some of these "Link" from a family members craft room last I made a plaque pattern. Just had to snip the pegs off the back. I believe they make a number of different fonts and sizes as well.

    I mostly use Freeman for picking up renshape so can not really comment on their letters. The RC store I use to frequent in Spokane sold plastic letters in alphanumeric sheets aimed at scale modelers for cheap that would be useful for this purpose as well.
     
    Last edited: Oct 15, 2020
  16. FishbonzWV

    FishbonzWV Silver Banner Member

  17. I've had a look at local crafts and art supply shops locally and can't find anything suitable so I'm going to make up some etched badges with a good deep etch and then paint with primer to get rounded edges with no undercuts. I figure I can make a whole batch in aluminium sheet and then cut out names and logos to glue to the patterns. With a bit of practice I should be able to get letters that stand proud as well as in relief.

    FrontPanel2 1280.jpg industrious 2 1280.jpg industrious 1280.jpg
     
  18. So I had a quick trial run with 1/4" tall letters with limited success: the etchant overheated the film and I started to lose letters after only 0.004" of etch. I think it'd work better with dilute etchant to keep things cooler as it's prone to thermal runaway. Alternatively I could just make a negative etch with recessed letters that are mirrored and make epoxy copies from one master.

    name mask 1.JPG Name etch 1.JPG
     
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  19. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Mark, those look very nice but you need to get yourself a small 3D printer and just print the resist on your sheet........seems like that would be great for photo etching.

    Best,
    Kelly
     
  20. Billy Elmore

    Billy Elmore Silver

    We use painted magnesium plates that have the paint removed in the art location... in a machine that is much like a printer... and then turned upside down in an acid bath for a set amount of time. The longer the bath the deeper the artwork. The acid leaves draft as it is being cut upside down. We just cut out the desired shape of the plate for whatever we are inserting it into and give it a good wire brush and its good to go. Only like 100$ a plate. Acme engraving does it for us and all we have to do is send them the artwork and tell them which part is raised and which is cut...black usually cut and white left uncut/raised.

    P.S. Look at any Lodge logo skillet for examples...every logo is made this way.
     
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