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how to bore a tapered hole for a core box

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  • how to bore a tapered hole for a core box

    Hello... Looking for suggestions on how to bore a tapered hole for a pattern core box. The sand core element is cone shaped about 1 in diameter tapered down to 1/2 in diameter and about 5 to 6 inches in length. I thought about using a boring bar with my taper attachment on a metal lathe but dont want to get wood dust everywhere. Is there an easy way to bore a tapered hole on a wood lathe? Thanks.
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  • #2

    Re: how to bore a tapered hole for a core box

    Yes you can do it on the wood lathe free hand but you would require a steady rest for a precise cut and at 5 inches my Marples chisels would be right up against the tool rest. A faster way to do it imo would be on the drill press. Mark your centers on a 21/2 X 21/2" X 6" long piece of pine or poplar, center on drill press table with 1/2" twist drill in chuck drill to 5" depth, next drill to exactly 33/4" with 5/8" twist drill, next 2 1/2" with 3/4" bit, then 11/4" depth with 7/8 drill and lastly just start the bore with a 1" drill bit. Next saw the 21/2" block in exactly half and using a few carving chisels, carve out the steps in the bore.

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    Next rap various grads of sand paper on a 1/2' dowel and sand the taper smooth to your liking. Next glue an end piece on both halves, then install alignment pins on one half to match up with the other half. Apply a good sealer two coats are better and you are done.

    You may be tempted not to cut in half and withdraw the core length wise, imo you will likely damage the core that way.

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    EDIT: If you have a drill chuck for your lathe tail stock you can do this on the lathe as well. I can here the naysayers now "but the tail stock will not feed 5 " ". As a matter of fact neither will most drill presses. For the first hole you may need to drill to 4", shut the drill down, raise the table a couple of inches or move the tail stock on the lathe., lock everything down and finish the 5" hole. Most drill presses will handle the rest ok but you may have to move the lathe tail stock for one more hole.
    Last edited by Carlosinthesticks; 02-23-2020, 09:26 PM.

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    • #3

      Re: how to bore a tapered hole for a core box

      You didn't say, but if you are looking to make this core box to actually make a casting, there are a few extra details involved. For one thing the taper will need core prints to suspend the core inside your mold, this will change your dimensions somewhat. Here is a better drawing to scale 1" = 1". If it's a one of, you can go with solid pine or poplar, If your going to use it alot you are better off making up your 21/2 X 21/2 X 6" block from thinner layers of laminated pine or popular for greater stability over time. It would be better to add 1/2" end pieces on both ends, would also allow you to drill from both ends and would be easier to sand smooth. Hope this helps.

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      • #4

        Re: how to bore a tapered hole for a core box

        Thank you.. this is almost exactly what I need. It's a valve body core. The main core is straight but has this tapered core coming g off the center. So the core box needs a left section, center section and right section with three core prints. Easy to make but the tapered sections. Is the challenge.

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        • #5

          Re: how to bore a tapered hole for a core box

          You have me wondering what type of valve it is. A gate valve crossed my mind, the faces of the gate are tapered but the gate is not round. A pet cock type valve sounds closer but they usually have 4 core prints and I have never seen one as large as your planning. Even on the 8' high barrels of wine I saw in a bar close to my uncles apartment in Lisbon. A bunch of us kids were playing tag in and out the doors of the bar one day, and someone opened a petcock and flooded the floor with wine, thank goodness I didn't get blamed for that one .

          So after a long look through some of my foundry book collection I found this pet cock type pattern in the 5 vol. set "Shop And Foundry Practice" by ICS Textbooks. The core would look like the cross hatched section in the illustration on the right.

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          Don't know how much casting you have done but if you want some good info, this is one of the best books out there.

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          This is my Lindsay Publications reprint but you can asses the original on line here https://www.hnsa.org/manuals-documen...oundry-manual/ or if you do a google search you can find PDF copies.

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          • #6

            Re: how to bore a tapered hole for a core box

            I am currently modifying my blast cabinet and have a new design for a media metering valve. I have been using a sand blaster for my restoration work but it eats bags of media and requires you to blast outside. Blasting in snow and cold is no fun. For many smaller parts, a cabinet works better. After looking at many designs, I noted flaws and set out to fix them. Now I need to build this valve to see how it works. I have done a lot of casting in my younger days. Just never machined a tapered socket out of wood. Done lots in metal with taper attachment. Just wondering if an old school wood lathe can do this. Looking for alternative ideas.
            Carlosinthesticks likes this.

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            • #7

              Re: how to bore a tapered hole for a core box

              Sounds like your being very creative. I have a small import pressurized tank blaster. All the valves are brass ball valves except the media valve which is a 1/2" hardened tool steel ball valve and accepts a couple of different size ceramic tips.

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              • #8

                Re: how to bore a tapered hole for a core box

                Try one of these.

                https://www.lumberjocks.com/mafe/blog/50137



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                Attached Files
                Last edited by Egon; 02-24-2020, 07:15 PM.
                Egon
                from
                The South Shore, Nova Scotia

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                • #9

                  Re: how to bore a tapered hole for a core box

                  Do you actually need a tapered core? You will need to precision bore and presumably ream the finished casting in any event so a straight core or even no core might work? What material are you looking to cast?
                  Rob

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                  • #10

                    Re: how to bore a tapered hole for a core box

                    You could look at the taper cutters Lee Valley have for chair making. They approach the size you are looking for if your design can be adjusted to accommodate.

                    https://www.leevalley.com/en-ca/shop...-taper-reamers

                    https://www.leevalley.com/en-ca/shop...o-taper-reamer

                    Pete

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                    • #11

                      Re: how to bore a tapered hole for a core box

                      These look like the cats pjs. Thanks

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                      • #12

                        Re: how to bore a tapered hole for a core box

                        What are you a bunch of Luddites ! where’s the 3D printing advice on how it’ll just fall out the ‘A’ of your ‘puter
                        But seriously ? Why not turn exactly what your core shape will be in a fine timber, in halves dowelled together.
                        Probable best to coat with an appropriate finish whilst in lathe.
                        When done separate the halves and sand taper on ends of prints.
                        Mount on a suitable scrap of melamine coated board.
                        Make sides from more board scraps to form a box around model.
                        Apply a release agent.
                        Mix and pour in whatever casting resin you can get cheap or simply use some car bog as this is quite a small corebag.
                        You can use some small timber scraps to fill some of the area to reduce the amount of filler used.
                        When set remove box and make taller sides to box the cast piece and extra above.
                        Locate the other side of the model on the dowels.
                        Apply more release agent and pour the other half.
                        Remove any flash, attach ends and your corebag is done.
                        Pattermakers Guide. by the American Foundrymens Society is worth a look if your into this sort of stuff.
                        H.

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                        • #13

                          Re: how to bore a tapered hole for a core box

                          Sure if your going into production just go out and sink a pile of money into a 3D printer.

                          You can use the resin method you described but:

                          - core is T shaped you will only be able to turn the ends on the lathe.
                          - cut it in half after not before turning, unless you want to glue the haves together in which case you will have to seperate them again after turning.
                          - Materials are 2 or 3 times as expensive as opposed to just easy to work pine.
                          - patternmaking is all about woodworking, most woodworkers could produce that core box in a mornings work, as opposed to a couple of days drying resin mixes, at least twice as much work etc.
                          - this method was probably developed for automated production, a little woodworking in pine is cleaner, alot cheaper and more suitable for the home shop.
                          - good pine core box is good for 100's of cores, if you need more, a small production foundry contract might be in your future.
                          - as for cutting the taper in the core box, come on were woodworkers, a little drilling, some carving and sanding is not rocket science.

                          IMO

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