Tools for Engine Turning | CRATEX Abrasives

The overlapping circles can be pressed into any metal by using different tools, and the choice depends on the type of metal (i.e. thickness) and work surface. In case you are working on large projects, you’ll need to use large brushes, and in case you’re working on smaller, more delicate projects, you’ll use smaller brushes or smaller abrasive bits that can be inserted into a drill press, hand drill or a Dremel.

Engine turning can be done with a lot of different tools, and it’s quite possible that you've tried most of them by now, unless you were fortunate enough to come across the perfect tool that gets the job done without much wandering and disappointment. Some use a wire brush or buff with an abrasive compound, such as Mag Wheel Polish. The swirls are made by the abrasive action of grinding compound and the brush provides pressure and motion. Brushes have their advantages on curved surfaces and sharp edges, but the problem is that some wires are longer than the others, so it they end up digging deeper into the metal, so your design might not get the smooth and shiny finish that you imagined. Besides that, since the wires tend to spread during the usage, a lot of craftsmen put rubber or hose clamps to achieve a tighter pattern, which is unnecessary work if you think about it.

When it comes to engine turning aluminum, for example, tools like sanding discs can also be used. However, you’ll end up spending a fortune on sanding paper, as they get worn out after three or four burnishes in a row. Sanding paper on elevator bolt is proven to be too hard, and it doesn’t conform to the flat sheet enough to produce uniform circular swirl. Double sided tape creates a pattern that is too faint, so you get ghosting on the overlaps. And if you apply too much pressure, the paper slides off. Some use hardwood dowels, and indeed, decent results can be reached. However, the problem with that is that you’ll constantly worry about adding compound – about every half of the row or so. An additional problem is that the compound would get too much after a while, the dowel would plunge and leave a dark ring on the next swirl.

And it is true – some people managed to get some decent work done by using a pencil eraser and a grinding compound (toothpaste even), but would you really want to do that? 

A much more convenient and efficient option would be using two things, basically: a drill press and rubber abrasive stick of CRATEX. Just a little of any convenient lubricant would be welcome in case you are looking to create a bit deeper swirls. This option also requires patience and focus, but it is a quick and inexpensive way to put truly nice surface finish on your parts. 

 

 Engine Turned Finish on Aluminum Aircraft Panels

Working on the mill press is a bit easier, since you have an X, Y table and all you have to do is keep track of the distance when moving in a certain direction. Possibly the easiest option would be using a CNC machine. It shortens the engine turning process and thanks to the precision of the CADCAM software, a perfect layout can be achieved quite easily. Besides being more accurate in terms of creating a pattern, it is also more consistent with the pressure on eachswirl pattern.

Depending on the type of the machine, you can set parameters, like the speed RPM, tool diameter, dwell at depth, tool number, clearance removing, Z feed rate and Z depth, the direction of the pattern and so on and generate a code. The machine’s normal coolant is quite enough, and you can turn it on or off if you like, and there is no need for adding oil. But of course, you can add an abrasive compound in case you want to achieve deeper marks.

Creating Engine Turning Patterns with PCNC 1100 Tormach & CRATEX Abrasive Stick

How to Engine Turn Stainless with CNC and CRATEX Stick

So, lapping compound is something you’re most probably going to use at some point. It’s a mixture of hard abrasive particles and lubricants which can be either oil-based or water-soluble. The way the compound works is that the abrasives increase the rubbing while the oil tends to reduce and control it. There are different lapping abrasives with different grit numbers that can be used for different types of metals, so important is to find the one most suitable for your work.

A very light mist of 25 parts of water to 1 part of oil mixture (any oil from cooking to motor) is highly desirable for best results. The compound helps avoid metal discoloration and deterioration of the abrasive stick, so recommendation would be to use it after every spin. Of course, as mentioned previously, it is possible to do engine turning by using only a drill press and abrasive sticks, but different abrasive compounds (90, 120, 220 grits, etc.) to achieve deeper or better-looking swirls can be used in the process (the higher the grit rating, the finer is the paste).

The thicker compound, e.g. the 90-grit, is great for any job, as it can be mixed down with lubricants, and made thinner if necessary.  On the other hand, thinner compounds, like the 120 or 220-grit, cannot be made thicker. One must be careful when adding additional lubricants as more lubricant means that the effort and cutting action of the abrasive particles is reduced and they can easily get washed away in case too much lubricant is added.

The compound can be applied with a toothpick or similar on smaller pieces and you’ll need to be careful not to get your vise or drill press dirty, as abrasive compounds are quite messy and a lot of them tend to fly all over the place. Make sure you cover and protect your tools before you start applying and be careful when taking the compound off the piece after you are done as there is a risk of damaging your work by wiping. Use a soft tissue, toothpick, clean the surface with compressed air, wash it off with a suitable solvent or water and detergent stream, or paint thinner.