Wednesday, July 29, 2009

THE SCHELLERT TOOL - the hard way, part 1

THE SCHELLERT-TOOL –the hard way -part 1-

Welcome back. Today I want to show you how to build the "Schellert-Tool". The Schellert-Tool is basically nothing more than a small tube with a metal-clamp-system on each side, where you can fit sculpting tool tips in. The tooltips could be stored inside the hollow tube (pic. 1). This tool has some advantages over the pencil tool because it is a two-sided tool and the sculpting tips are fixed more tightly in it, so they won’t rotate. You can make versions of this tool for all steel wire diameters (more about that later). I called this tool "Schellert Tool" because I didn’t found another name. "The-two-sided-sculpting-tool-with-exchangeable-tool-tips" was a little bit long for my taste. So I gave it my last name, that’s all.

If you ask yourself why I wrote in the title of this post "the hard way", it’s because you have to do a little metal working like cutting threads for example. There is also an "easy way" to get a kind of a Schellert Tool which is nearly as good as the original one with a minimum of work. I’ll tell you in a later tutorial how to do this.

The basic idea behind the Schellert tool is to grab two of those hobby knifes (like x-acto, excel, proedge, martor or ecobra to name a few), get the clamps from these knifes where usually the blade is placed in and fix them on each side of a small aluminium tube by cutting threads into the tube. Of course you can just use the hobby knife as it is and fix a tool tip instead of a blade in it, but that’s only a one-sided tool, you can’t store the tips inside the handle and hey, it’s not so cool.

Material and tools needed:

Two hobby-knifes (pic. 2):
First you need two hobby knifes to get the clamps. Here’s where the "trouble" begins.
These knifes are produced in different countries and therefore the threads of the clamps of these knifes are different. The knifes from Germany like those from Martor and Ecobra are using a metrical thread-system. In fact they have an "M5"-thread. The knifes from Excel and I guess even the knifes from x-acto and proedge (I guess they are from the US) using another thread-system. They have a UNC 10-24 thread. You have to know which thread your knifes have because you need the right thread-cutter (threader) for cutting the thread. I recommend using 2 knifes from the same manufacturer.

Regarding these knifes it is worth to look a little bit around for the prices, as there are great differences even for knifes from the same manufacturer. So for the ECOBRA-knife for example I found the range from 2.10 EURO to 9.90 EURO and it was always the same kind of knife. So google until you find an acceptable price. As far as I can see (here from Germany), the prices for those knifes (especially EXCEL and PROEDGE) are a little bit lower in the US, so lucky you, if you live there.

Thread cutter and holder (pic. 3):
As I said before, you need a thread cutter (threader) with the right size. Depending on the knifes you use you’ll need either a thread cutter for M5-threads (German) or one for UNC 10-24-threads (US).

You have to take those thread-cutters for cutting threads by hand, not those for machine-thread-cutting.

There are two types of hand-thread cutters around. The first exist of only one drill-like tool, and you can cut the complete thread in just one turn with it.

Then there is also a set available that exists of three drills- like tools. One for pre-cut (marked with one line), one for the second cut (marked with two lines / cuts a little deeper) and the last one for the final cut (marked with no lines / complete thread).

If you have the choice, take the 3-piece-set. It’s a bit more work because you have to cut three times instead of only one time, but cutting is easier with the set because you’ll need less power. And because the forces that work on the tube while being cut aren’t as high, it’s not so likely, that the tube will rotate in the bench vice while cutting the thread.

And of course you’ll need a holder for your thread cutter like you can see in pic. 3.

Aluminium tubes (pic. 4):
You need two aluminium tubes like those you can found in hardware stores or building centres were you can buy them in 1m or 2m length. The 1m size is more than enough.

You’ll need

- one with an outer diameter of 8mm and an inner diameter of 6mm and
- one with an outer diameter of 6mm and an inner diameter of 4 mm.

The strength of the tube walls is 1mm on both tubes (just to make it clear).

There are two kinds of aluminium tubes that can be found, those with a pure aluminium surface and those with an anodized surface. In hardware stores or building centres (in Germany) most of the times the anodized ones can be found. You can use both versions. The anodized ones have the advantage, that the surface of the tubes has already a finish, so it’s less work later. The "pure" aluminium ones have to be grinded and polished to remove scratches, but this will result in a very beautiful shiny surface.

But one thing is very important about these tubes. The smaller 6mm one should fit easily into the larger 8mm one! That’s not always the case, because those tubes have never exactly the sizes, they claim to have. So before you buy the tubes find a pair that will work. I mean you need a quite large 8mm tube and quite small 6mm one. Try every 8mm tube with every 6mm tube until you find a 6mm one that fits into the 8mm one. If you don’t do that you’ll get into trouble because you have to widen the 8mm tube later, so the 6mm will fit in. And believe me, this is something, you didn’t really want to do if it can be avoided, because it’s really a mess (you shouldn’t make my mistakes).

Bench vice with protection bars (Braces) (pic. 5)
You’ll need a bench vice, where you can fix the aluminium tube in while cutting the threads.
To protect the surface of the aluminium tube, you need some kind of protection bars (braces).
The one you see on pic. 5 I made on my own from strong felt.

Fine metal saw or tube-cutter (pic. 6)
You have to cut off pieces from the aluminium tubes. To do so you will need a fine metal saw or even better a tube cutter or pipe cutter (see pic. 6). The tube-cutter is a very fine tool and not even is cutting much easier with it; you’ll always get a clean 90-degree cut from the tube. So when using the tube cutter you’ll have less work to do to clean up the cut.

Electrical drilling machine (power drill) and 4,2mm metal drill:
If you use the knife-clamps with the M5-thread, you will also need an electrical drilling machine and a drill with the size of 4,2mm. This must be a drill for metal (not for wood) of course. You’ll need this drill to widen the inner diameter of the small aluminium tube from 4.0mm to 4.2mm because for cutting a M5-thread you need a base hole of 4.2 mm.
If you use the other knife clamps with the UNC 10-24-Thread, you are lucky, because for this thread-size a base hole of 4,0mm is fine and that’s the diameter, the small aluminium tube already have. So no need for a special metal drill or the electrical drilling machine in this case.
Good glue for metal:
You’ll also need good glue for metal. It’s not important, that it is fast, but it is important, that it is really hard and strong in the end. I recommend those two-part epoxy glues.

Abrasive paper:
You’ll also need some fine coarse grinding paper to clean the cuts on the tubes.

When you cut the threads into the aluminium tube, you need to dip the tube cutter in oil before. Otherwise cutting is much harder and the tool might get stuck into the tube, so ALWAYS use oil when cutting threads. When I did the first thread cuttings, I just used ordinary sunflower oil that is used in the kitchen. Later I bought an expensive special super metal drilling and cutting oil. But believe me or not, I found the sunflower oil works better, so I’m now back to that. Maybe some metal-working-professionals will get a heart attack now, but that’s what I found out for me. So there’s no need for you to buy special cutting oil. Just try what you’ll find in your kitchen (and don’t tell your wife).

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