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View Full Version : Engine Turning (was "variations on a theme"



Lynn Standish
02-18-2005, 09:47 PM
Okay, I said I'd try to post a close-up and perhaps an explanation. My digital doesn't do very close-up, and I'm too lazy to go to the 35 mm, close-up rings, processing, scanning, etc., so this is the best I can do (until I can get an EOS Rebel or Nikon and get back in control). Here are 2 photos, one is a fuzzy closer look at the swirls, and the other is what I use to make them.

http://img.photobucket.com/albums/v738/Standish/engineturn.jpg

http://img.photobucket.com/albums/v738/Standish/Nginturntools.jpg

In the photo of the swirls, you can see that it generally appears to be a series of 1/4 or 1/3 of a swirl that is overlapped by the next 1/4 or 1/3 swirl. You can vary this somewhat by the amount you advance the work before creating the next swirl. The way I do it is to advance the work a little less than 1/2 the diameter of a swirl before making the next one. This applies to both axes. That way, the center of the swirl is obliterated by the following swirl, which in turn has it's center obliterated by the swirls in the next row. Takes longer, but that's how I like them to look.

In the second photo, the equipment to produce the swirls is shown (again poorly). I have used wooden pencils in the chuck, pieces of dowel, electric eraser cartridges, dental tooth polishing cups (rubber), etc. but those in the photo have given the best results. I initially got into this as a method of "jewelling" rifle bolts, and then doing it to other things. As you can see, the main piece is a small stainless steel (I think) brush with a 1/8" shaft. This allows the brush to follow contoured work (rifle bolt) to an extent to produce the swirls. In order to keep the brush from splaying (spreading) too much, either O-rings are slid down the shaft and onto the brush to hold it together, or shrink tubing (as used to provide insulation on electrical wire splices) is shrunk over part of the brush so that only 1/16" or so is exposed. A combination of the two can also be used, and you can use one or two O-rings at your option, depending on how tight you want the swirls (I like them tight, small and well defined). Depending on where you buy the shrink tube, it may not be strong enough to hold the bristles in under pressure. In the photo, you can see the brush with 2 O-rings that was used on this project, and a new brush with a couple of O-rings beside it. The brushes are available in a couple of diameters.

The other item in the second photo is the compound that cuts the swirls. It appears to be silicon carbide in an oil paste, about 200 grit. A suitable grade of valve grinding compound, like Clover brand lapping compounds can also be used. Our local rockhound shop has the silicon carbide in various grits, and I think you could add cutting oil or vaseline to make a paste. You can get this stuff from Brownell's or B-Square -- look for bolt jeweling equipment.

In practice, I use my drill press and cross vise to do the work. The brush (with O-rings and/or shrink tube is put in the drill chuck. The work is clamped in the cross vise, and everything adjusted so the whole length and width work can travel beneath the brush. A thin coat of the abrasive is spread on the work with a finger. Starting at one end of the long axis of the work, the vise is positioned so the brush will create a swirl that is about 3/4 of full diameter on the work (so there aren't any gaps showing around the edges. Then the work is advanced on the long axis a little less than half the diameter of the swirl and another is made. This process is continued until the other end of the work is reached. I don't set a stop on the quill feed, but rely on feel and sound of the drill press to tell me I'm doing it the same way on each swirl (5 seconds is plenty of time to dwell on the swirl). With the size of brush and the cross vise I use, it takes 3/4 turn of the crank to advance the work the right amount. A full or half crank would be easier to keep track of.

When you reach the end of a row of swirls, you then crank the work an equal amount over on the other axis, RETURN to the end of the work you started on, and begin again. If you don't return to the starting end, things will look a little strange, because you won't be getting 1/4 circle overlaps, but some may find it interesting.

These swirls are not very deep, so the surface finish needs to be pretty good before you start, say 320 grit. You can start with a rougher finish, and the swirls will help hide some imperfections -- it's up to you.

Sorry, but the reflection card and stripe on the front of the camera won't work for this because it's kind of like a diamond -- it needs a point source of light like the sun or a spotlight to reflect, so it won't show well under bright fluorescents or a diffused light. Back in the early 60's, they sold "jewelry" for a while that was aluminum turned at a specific speed and feed that caused it to create defraction patterns when reflecting light that looked like a rainbow. No rainbow here, but the light has to be reflected from a point source back to the viewer or camera. By the way, that's how birds get their colors, i.e. refraction, not pigment.

Anyway, long and boring post, and I'm sure I've left a lot out (Friday night, long week at the office, etc.), but I'd be more than happy to discuss it more and try and fill in any gaps.

Thanks for the interest and positive feedback. Sorry for the spelling errors (do we have spellcheck here?).

Lynn Standish
02-18-2005, 09:51 PM
I'm sorry. I have apparently done something to make the post overly wide, which will mean a lot of scrolling left and right to see it. Problem is, I don't know how to fix it.

matador
02-18-2005, 10:11 PM
thanks for the great explanation,lynn.i've often tried to pretty things up with this type of finish,but only succeeded in making an unholy mess http://bbs.homeshopmachinist.net//frown.gif.i'll most certainly give your method a try.

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Hans

zl1byz
02-18-2005, 10:42 PM
Lynn, thank's for the pic and the explanation. You have developed your own style anduse it to good efect.
This will probably make everyone laugh but the top bar design in your version of the nut cracker reminds me of the Romulin's in Star Trek. They wear costumes with a course hatch weave type patten and very square sholders. Your design with the engine turning and the two turned sections with the colums underneath remind me of this.
So the cat is out of the bag, my hobbies are amateur radio, machining/welding, and star trek. Doesn't matter my family think I'm crazy too.

John.

Joel
02-19-2005, 12:32 AM
Nice work.

If you resize your picture to a width of 800 pixels or less, it will fit on the screen without having to scroll over.

Mike Burdick
02-19-2005, 10:29 PM
Very interesting! Thanks for the explanation too.

hoffman
02-19-2005, 11:17 PM
Thanks Lynn! I've always loved engine turned parts but never done it. Great explanation. Finally a good use for one of those cheapo cross slide vises.

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Hoffman in Warner Robins Ga

Buckshot
02-20-2005, 08:27 AM
Basicly done the same way:
http://www.fototime.com/CBEAAE5A40D244A/standard.jpg

If I recall it took 2 of the Dremel stainless cup brushes. I put 2 layers of shrink tubing to help keep the bristles all bunched up good and tight. Course Clover valve lapping compound. Brush held for a 5 count on the work.

Done in a $39 HF compound vise on the drill press. The smoother the polish beforehand, the better the swirls stand out. No, the underside of the bolt isn't done :-D.

Best,
Rick