Sunday, March 17, 2013

A simpler way to make the Schellert-Tool Handle

Hi, I just want to share a much simpler way to do the Schellert-Tool handle. 
To remember: The "Schellert-Tool" is a tool tip holder with exchangeable sculpting tool tips. 
The sculpting tool tips are fixed into aluminum clamps that are taken from hobby knifes to form the endparts of the Schellert-Tool handle. You can find an in deep explanation about building the Schellert-Tool here (link).

I confess, it's not the simplest tool to build. Especially cutting the threads into an aluminum tube might be challenging even if you own the needed thread cutter and impossible, if you haven't one. So I thought about a way to make this tool easier to build. The easiest way would be to find somewhere an already cut thread-piece that could be used for that. But I had no luck in finding such a pre-fabricated piece untill lately:
Now I've found in a hardware store a simple and cheap piece that is ideal for my needs. In German this thing is called "Messing-Spreizdübel" and the translation into English I found so far is "brass expansion bolt" or "brass straddling dowel". On the picture you can see this fine little thing.

This brass dowel has a m5-thread and is made for drilled holes of 6 mm diameter. This is ideal in combination with an aluminum tube with an outer diameter of 8 mm and an inner diameter of 6 mm (material strength: 1 mm), like the one I used for the original Schellert Tool (link). You don't even need to glue a second smaler tube into 8 mm tube, because the brass dowel will take that part.

So all you have to do is to cut off a pice of the 8/6 mm aluminum tube with a length of about 7.5 cm. The easiest way to do this is by using a tube cutter, that makes perfectly straight cuts (look here). Then all you have to do is to put one brass dowel into each side of the tube. Be sure to push it a few mm below the edge of the aluminum tube. Otherwise the clamp-piece wouldn't fit in later.

In some cases the brass dowel is a little thicker than the inner diameter of the aluminum tube. In this case you have two options. You can widen the aluminum tube be using a drill of 6.1 or 6.2 mm. The other option, especially if you havn't got those special-sized drills is to grind down the knurled surface of the brass dowel. The easiest way to do this is to fix the brass dowel into a power drill and press it slightly onto a oiece of grinding paper while rotating. You can also use a metal file and grind down the brass tube by hand.

To fix the brass dowel into the aluminum tube you have also 2 options:
You can simply glue in the brass dowel into the aluminum handle with a good metal glue or you can fix it by using a 5 mm hexagon socket set screw like you can see on the next picture.

That's all. All you have to do ist to take the clamp-parts of two hobby knifes (Martor, ecobra etc…) and screw it into the tube ends.

Note: The brass dowels I use have a m5-thread. into the threads of these brass dowels you can only fit the clamp-parts of the hobby knifes that have also a m5-thread. The m5-sized screws and threads are standard in Germany where I'm from. In other countries there are other standards like "unc" in the United States for example. There are Hobby knifes available with m5-threads from Martor and Ecobra for example. I know, that other hobby knife have a UNC 10-24 thread, like x-acto, I think (I told a little bit more about this here)
So be sure to use hobby knifes with an m5 thread. You can find these knifes and also the brass dowels on google/ebay.

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