Can casting resin be used to create a custom mortise jig for routing?

I am wondering if casting resin can be used to create a custom mortise router template? As some background, I have a slab table that to be "reverse engineered". Let me further explain. I recently made a Nakashima inspired coffee table using Japanese joinery. Unfortunately, I want to remove the slab top because it was too small.I am going to use a router to remove material close to the tenons that are sticking through the top of the table, and then carefully pare back to the tenons with a chisel. Once the slab is off, I will need to route a mortise in the new (larger) slab to exactly match the custom tenons, like I did in the first place. However, I will no longer have access to the router mortise template when I built the table.
I have been trying to determine if I could pour casting resin over the exposed (after I route down say 3/4'' into the slab and chisel) tenons to produce a "negative", which I could then use as a mortise (router) template using a pattern bit?
I will attach a few pictures to give you a better mental picture than my words can describe.
Thanks for your input!!




Joe Meadows

I guess you could do that. Rout out a big enough recess to make a resin template that will support your router, wax the bejeesus out of everything and cast some handles into the pour so you can get it out of the recess. I've never poured a plate of epoxy like that- you might want to make it a composite by embedding some ply or fiberglass cloth or something else to stiffen it up. What kind of resin are you considering?

Instead of resin you might want to look into something like machinable wax.
It's made for stuff like you plan to do & then some.

https://machinablewax.com/

I ran across it a few years ago when I was looking for something to use to make zero clearance inserts for my table saw. <--i used MDF for that due to cost.

Rich,

What do you see as the advantages of machinable wax in this application?

Cost - ease of use - more than a single shot at doing it.

With resin, you have one hot at getting it right. With the wax, if it doesn't come out right, you just dig it out and melt it for another try. With the way, you can also use your negative to cast a new positive - one you can use if/when your template wears out or is damaged.

The only downside to the wax is the initial startup costs for the heating equipment & the learning curve.

Machinable was melts at 350* F - so it's something you need to be very careful around.

Quote:

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Originally Posted by Kevin Jenness

I guess you could do that. Rout out a big enough recess to make a resin template that will support your router, wax the bejeesus out of everything and cast some handles into the pour so you can get it out of the recess. I've never poured a plate of epoxy like that- you might want to make it a composite by embedding some ply or fiberglass cloth or something else to stiffen it up. What kind of resin are you considering?

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I am going to try using Alumilite Casting resin, wish me luck!

I already have the Alumilite casting resin, so I am going to try that route first. Thanks for the suggestion.

Quote:

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Originally Posted by Rich Engelhardt

Instead of resin you might want to look into something like machinable wax.
It's made for stuff like you plan to do & then some.

https://machinablewax.com/

I ran across it a few years ago when I was looking for something to use to make zero clearance inserts for my table saw. <--i used MDF for that due to cost.

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Good luck!
Make sure you let us know how it works out. I have any number of things I'd like to cast - and/or 3D print that I haven't taken the plunge on yet.

I also want to make one of these:(3D router pantograph)
https://www.youtube.com/watch?v=vtm4u583YOQ
So I can cast things, then make them in wood using the casting as a source.

Machinable wax can be made at home. Look online for recipe I belive it is just wax and DPPE melted together. Note that much stuff sold as wax is not wax it is solidified oil and not as solid as a wax. The bad stuff feels greasy/soapy at room temp.
Bill D

Quote:

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Originally Posted by Joe Meadows

I am wondering if casting resin can be used to create a custom mortise router template? As some background, I have a slab table that to be "reverse engineered". Let me further explain. I recently made a Nakashima inspired coffee table using Japanese joinery. Unfortunately, I want to remove the slab top because it was too small.I am going to use a router to remove material close to the tenons that are sticking through the top of the table, and then carefully pare back to the tenons with a chisel. Once the slab is off, I will need to route a mortise in the new (larger) slab to exactly match the custom tenons, like I did in the first place. However, I will no longer have access to the router mortise template when I built the table.
I have been trying to determine if I could pour casting resin over the exposed (after I route down say 3/4'' into the slab and chisel) tenons to produce a "negative", which I could then use as a mortise (router) template using a pattern bit?
I will attach a few pictures to give you a better mental picture than my words can describe.
Thanks for your input!!




Joe Meadows

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Joe, those mortises look like those from the bench designed and taught by Taeho Kwon -- is that what they are? Looks incredible -- might you show some photos of both the original and your revised bench?

I use to use alumalite for offshore fishing lures. The water clear is pretty dam hard so it will probably be ok. You could build a little 1” dam box around the tenons and fill it with their mold making silicone. Then use the silicone positive to cast your template.

Sorry Joe, I was thinking backwards, my response doesn’t make sense for what you need. I do know that your casting will be very tight so lots of wax as mentioned above is a good call. Best of luck with it