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Post by dinger73 on Jan 30, 2019 11:52:39 GMT -5
I am a complete newb to casting. What I want to do is to cast a zero-clearance table saw throat insert plate for my cheap Skilsaw table saw. The table top is aluminum. I am wondering if I couldn't just place something underneath the throat opening and then spray a release agent directly onto the aluminum table then cast the resin into the opening to create the insert plate. Is this possible or advisable? Is there a better way? Also, I would prefer to have the plate bright red like the phenolic resin plates that come on the more expensive table saws. Any suggestions on the best type of resins and dye's for this application? Obviously the main concerns are hardness and flatness. Attachments:
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Post by notoes on Jan 30, 2019 20:18:31 GMT -5
Actually, you'd probably be better off to order the part online instead of trying resin. It's what I would do and I'm very much on making what I need. Try this site for a starting place for the replacement part : www.ereplacementparts.com/ |
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Post by Brian on Jan 30, 2019 22:30:00 GMT -5
....By the time you purchase the RTV Silicone for the mold and the resin for casting , you would be money ahead buying the part for the saw, that I'm sure of.
Getting a +- tolerance (Zero clearance) with resin is next to impossible....the manufactured part would use a special process where the liquid material is pressure fed into a casting mold...all of which would be cost prohibitive to the average person. |
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Post by dinger73 on Jan 31, 2019 10:34:54 GMT -5
The problem is that the OEM part, which I still have, does not cover the entire opening of the throat. This allows narrow boards such as 3/4" or less to fall into the opening when sawing dado's/grooves/rabbets on edges. I am trying to make an improved version of the throat plate to fill the entire opening and the create the zero clearance saw blade opening by simply raising the running blade through the cast part.
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Post by Brian on Jan 31, 2019 14:01:15 GMT -5
Do you think that this could possibly be made with a piece of Lexan or some other Polycarbonate...maybe Delrin... verses casting the piece. Another possibility, if your set on casting, would be to build up your original piece with Styrene Plastic...such as Evergreen Plastic...to the size you need and make a cast from that master since it appears that the piece is not weight bearing but more of a plug to close an opening.
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Post by dinger73 on Jan 31, 2019 15:06:56 GMT -5
Do you think that this could possibly be made with a piece of Lexan or some other Polycarbonate...maybe Delrin... verses casting the piece. Another possibility, if your set on casting, would be to build up your original piece with Styrene Plastic...such as Evergreen Plastic...to the size you need and make a cast from that master since it appears that the piece is not weight bearing but more of a plug to close an opening.
Brian, Of course as the saying goes there's more than one way to skin a cat. Many people simply use a piece of plywood or hardwood and cut it and shape it to fit the opening. But, if I were going to do this any other way than casting though, it would probably be by using a piece of already cast phenolic resin and then machining it with a mill or router to create the recesses so that it would fit into the opening and lay flush with the table surface. The only problem with either of these methods though is... a. I don't have a mill or router b. It seems that it would be cheaper for me to be able to cast the part than buy a mill or router. I also would just like to learn how to cast parts. P.S. It wouldn't necessarily have to bear a lot of weight, however, for precision cutting I don't want there to be any flex in the plate as that could lead to variations in the depth of cut in my workpieces. |
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Post by Brian on Jan 31, 2019 22:47:10 GMT -5
I also would just like to learn how to cast parts. O.k this would be as good as any place to start learning ,then. If it where me, I would make a mold and cast of the original piece verses taking the original and adding additional material to it to achieve the correct size that is needed. With the copy/cast of the original, make whatever changes are needed to make it what you need. Using Styrene plastic and CA (super glue) make the necessary changes to modify the cast/copy....I suppose you could also use wood in this case if its more readily available than plastic. Once your satisfied that you have made all of the necessary changes, then make a mold and cast that piece. For the rubber mold (RTV Silicone), I would go with HS-2 ......you could use HS-3 which is available at better hobby stores everywhere, but the HS-2 is going to be a little bit firmer which is better suited for larger molds.
For the resin I would use RC-3 .....I have done quite a bit with cured RC-3 ....drilling, boring, light grinding, sanding, cutting. Once it has cured, it's plenty dense/hard for what you are wanting to do. Sand it as you would wood for a relatively smooth finish. For color you can either paint the piece or paint the rubber mold as the resin will draw in the paint and once it has cured will be the color of what ever paint you used. I've used everything from high dollar automotive paint thru an air brush to the cheap rattle can stuff on resin pieces....I would advise you to clean the resin pieces prior to painting to remove any petroleum based residue that might be present.
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Post by dinger73 on Feb 1, 2019 9:09:12 GMT -5
Brian,
Thanks for the advice. I just have one question. Wouldn't it be easier to just seal up the bottom of the cavity in my table saw (it is flat across the bottom of the opening), spray in some mold release and just cast the part using the tablesaw itself as the mold? I was thinking maybe I could just get a small piece of melamine or something like that and use something to adhere it to the bottom to essentially create a mold cavity. Of course I would also need to plug the screw holes. Is this not possible or just not advisable?
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Post by notoes on Feb 1, 2019 9:13:01 GMT -5
For machining resin, I use a Dremel with all kinds of different heads. It' tough enough to do a good job (I use the 3000) and still under $100. You'd be surprised at how much you can use it. I bought the one I use for my other half and pretty much have taken it over I use it so much.
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Post by Brian on Feb 1, 2019 20:04:43 GMT -5
...For some reason I was thinking that the bottom was an un even surface...anyway, yes, if its a flat surface do this....
use a suitable flat material to seal off the bottom. Make sure that it extends past the opening on all four corners an aprox. 1" to 1 1/2" at a minimum. If you have a way to clamp, bolt or screw the flat piece to the bottom, that would be a preferred method....if that is not possible, use a flat piece that is aprox. 3/4" thick. It should be solid enough so as not to bend or flex, but not so thick and heavy that it wont stay in place once silicone has set up and cured . Apply a liberal amount of RTV Silicone sealant to both the bottom of the saw and to the flat piece ....this could be an automotive type like Permatex or a tube type like you would use if you where sealing the windows or shower surround in your home. Support the piece in place until the silicone cures....leave it in place if you can when you pour the resin to help keep the flat piece immobilized and in place. The silicone is serving 2 purposes...preventing seepage of poured resin and to hold the flat piece on the bottom in place. Be sure and use a release on the metal surfaces that the resin will come in contact with when its poured so that you can remove the resin piece once it is cured....unless you want it possibly bonding with the metal surface. |
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