How To Make a Soap Cutter and Soap Mold Combo for Homemade Soap

In this video I will be showing you how to make a soap cutter for soap making. This device will combine a soap cutter and soap mold in one. This interesting woodworking project will yield a very nice working soap cutter that can be used for cutting homemade soap, as demonstrated in this video on a fresh batch of coffee scrub soap.

Video transcript:

Hello ladies and gentlemen, welcome to Tony Needs Hobbies. My name is Tony and I wish you all a happy, healthy and safe 2021. And with that out of the way let’s dive into the actual content of this video. Some of you who have been following me for a longer time know that once in a while I make a batch of soap and I have always been struggling with cutting the bars at equal sizes. So in this video I will fix that by making a soap cutter which will also serve as a soap mold. Have fun watching.

I will use one of my previously built molds as a starting point. I will extend the bottom and make an adjustable cutting guide. A slot will be cut for the cutter that I will make out of this old hack saw blade.

Almost all the pieces of wood that I need for this device are 90mm wide, so I’ll start by cutting a long strip out of 15mm thick plywood. Since I don’t own a circular saw, I try to cut this as straight as I possibly can using a jigsaw. Then I mark the lengths of the individual pieces and cut all the parts to size and also cut the slot for the blade to go into using the same jigsaw blade, since it’s width matches the width of the blade that I will use for the cutter. If you want to know all the dimensions then please download the plan to make this soap cutting device from my website,, link in the description. It’s free, and it’s available in both metric and imperial measurement units.

That looks about right. Obviously, I’m not going to use the blade as it is right now, but I’m going to make a nice supportive handle out of some thinner plywood.

The thickness of this board is 9mm but in the end two pieces will be glued together with the blade in between to get a combined thickness of 18mm. First I will cut the two handle halves. The pieces are clamped in my small bench vice and in order to protect the wood I have put two scrap pieces of veg tan leather in between the vice jaws and the wood. Then, using files and sand paper I refine the shape to make sure both parts match each other. When the filing is done I give all the wooden parts a good sand paper treatment to get rid of splinters and sharp edges before starting combining all the pieces.

The parts have their main shape now so I will start with the construction of the mold part of the device and when that’s done I will construct the cutter itself.

Putting this together is really easy. First pre-drill the holes, then countersink them, apply wood glue and put the screws in. Repeat these steps for the other side and back end of the mold. Make sure everything is aligned well, so the base is flat and everything looks good when it is finished. It is especially important that the cutting slots are both aligned, otherwise the soap bars will all be cut at an angle and the point of this tool is to cut nice and equally sized bars, not crooked ones.

That’s finished, now I need to make the adjustable cutting guide. Basically two pieces of wood glued and screwed together with a slot in the bottom one. This slot will be made by drilling adjacent holes, also, a hole in the bottom of the mold will be drilled for the bolt to go into. I’m drilling 6mm holes, because of the size of the bolt. After drilling the holes, I use files to open the slot until it’s nice and smooth. This time I also protect the wood with some pieces of scrap leather.

And I made a small mistake. The location of the hole is incorrect so I drilled a new one at the correct location. But before fixing that, I will cut out the hexagonal hole for the bolt to go into with a sharp chisel. The only thing left to for the mold part of the project is gluing and screwing this guide together.

Now I’m going to repair the other hole. This will simply be done by plugging it with a dowel and filling the rest of it with wood colored filler. The only color I have in the shop is oak, which doesn’t match this plywood, but I’m making a tool, it doesn’t have to look perfect. This specific filler needs to cure for three hours and when it is cured I will sand it flat. Then a quick dry-fit before continuing to work on the actual cutter.

I already had the scales made, so the thing I will do now is cutting the blade to size and removing the teeth with a grinding disc on a Dremel tool. Wonderful to see all those nice sparks, indicating that this is high carbon steel, which will give me some trouble later on… After grinding I smoothen the edge and sand all rust off of the blade with coarse sand paper so it looks somewhat nicer. Then I mark where the recess should go and sand that part of one scale 1mm thinner.

This will all be glued together and to make sure the blade is fixed it will be secured with steel pins. In order for them to fit I first drill four holes through the wooden scales and then through the steel. But that is more easily said than done since this steel is hardened so I can’t easily get my drill bit through it but I came up with a solution for that…

I messed up two things: the first being the hole that I drilled at an incorrect location but I already fixed that, and the second mistake is that I forgot to put the SD card back into the camera after making a backup which is a pity because that is the reason that I don’t have much footage on making the actual cutter. It was a very interesting process so let me show you in a little bit more detail what I did to make this cutter before finishing it, giving it a few coats of varnish and preparing a coffee scrub soap batter to test if this device actually works.

Alright, here’s what I did. Before trying again to drill the holes through the steel I tried to anneal it by heating it with a blow torch. After cooling down I sanded it again and was finally able to drill the four holes. I fixed the blade to the wood with five minute epoxy and four 2mm nails. The wooden parts were glued together with wood glue. Now I’m going to sand the corners off and make it all nicer to handle.

Now after sanding it all for one more time I’ll coat it with some varnish and then it’s finally time to test whether or not this project is a success by making soap and trying to cut it in nice and even bars. But first, I’ll have to finish coating and let the varnish dry overnight.

If you want to learn how to make soap, I have other videos about that. I’ll post some links in the description box and link in the top right corner as well. Also, if you subscribe and hit the notification bell button you will not miss any of my future updates. I’d really appreciate that. But now, let’s demonstrate how to use this tool.

For this recipe I will use coconut oil, sunflower oil and palm oil. I’ll put the exact recipe that I used for this batch in the description. When everything has the same temperature I add the lye and start stick blending until the mixture reaches trace. Then I put it in the oven which is pre-heated to 75 degrees Celsius and wait for 45 minutes while checking regularly if it has reached gel phase yet. If so, leave it out and add the fragrances, and in this case, spent coffee grounds for a scrub-effect. Mix it thoroughly, pour the batter into the mold and let it cool overnight before cutting.

And now the moment of truth…

The soap has had the opportunity to cool down for 24 hours, now let’s see if I can cut this big block into nice equally shaped and sized bars.

The soap cutter works just great and I had a lot of fun making it. If you want to make one to, then please go ahead and download the free plan form my website. I’ll post a link in the description box. I had a lot of fun making this video and if you enjoyed watching it then definitely let me know by hitting that like button. Please also consider subscribing to this channel for more content like this in the future. That’s it for now. I’d like to thank you for watching. Bye, bye!

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