Getting into bed

So, I can't remember if I've said this or not yet, but I scrapped the steel I-beam as a bed, it was too bowed, and wasn't going to deal with the torsional strain. I've changed to a metre-long piece of 75mm box-steel. This will deal much better with the torsional forces, and also I can fill it with concrete to add to the lathe's mass, always a good thing.

The problem with it is that it's not very flat. The biggest milling machine I could get my hands on had a maximum pass of 700mm, not long enough. So I have to do it by hand. I filed it back to get the longitudinal bow so common in box-section out, but it's still way off flat. I started scraping as per Gingery's instructions, but soon realised that it would take years to do it that way because of the amount of material that needed removing.

Then a thought occurred to me: why not use an angle-grinder? Just for roughing-in of course. I had a lot of material to remove, and wanted to get it close to flat, as close as possible. So, here's my method of roughing in. It's not finished yet, but I've done enough to see that the method has legs.

Lay your surface plate out (mine is the cold rolled steel that will one day be my ways). spread a thick layer of oil paint onto it, keeping it as even as possible.

Clean your steel and remove any burrs. Place the steel upside-down, very carefully, on the painted surface plate.

Do not apply pressure! It's cheating. Instead, gently push the steel forward a few centimetres, then pull is back again. Remove the steel and place it on your workbench. (Your workbench should be a good distance away from the surface plate to prevent grit landing on it.

Get out your angle grinder and make sure it has a grinding wheel in it. Now gently grind the spots with paint on them.

Rinse and repeat, taking a break every three or four passes.

A few important warnings:

Make sure your surface plate is well supported - mine wasn't, so I spent a good amount of time diligently ruining my own hard work. I fixed the problem, but am still trying fix the results of the problem.

Make sure you take those breaks - they're not for you, they're for the steel. You don't want the steel heating up too much, otherwise it will deform. Then you will be wasting effort on a bent piece of steel that will cool back to a different shape.

Make sure you clean the steel thoroughly before you put it on the painted surface plate - if there is any grit or burrs, it will render your markings meaningless.

Repeat this process until you have a pretty even spread of dots on the steel, reasonably close together. Once you have that, you can start scraping and it should be a lot faster.

Experimenting with etch resists

Today I tried two substances as etch resists for electrolytic etching. Etch resist marker, designed for chemical etching of circuit boards, and black acrylic paint. Neither were great, I must say. The etch resist pen worked, but came off very easily when I brushed the surface to remove copper crud. It could work, but I'm not doing any fine art with it. The second, acrylic paint, was a TOTAL FAILURE. Tip: Never use water-based substances as resists. They dissolve in the bath. Photo one is before etching, photo two is after.








I didn't touch the front surface on the second one before taking the photograph. Once I scraped the paint off, I noticed that the whole surface had been etched the same amount. I reiterate: Never use water based substances. Ever.

On inking

I said I'd tell you about inking earlier, so here it is. This is basically a description with the different inking methods I've tried.

The application method for methods 1, 2 and 4 are essentially the same. You apply some of the ink (or paint), make sure it's in all the etched lines, then squeegee ink off the top with a scrap of copper that has a straight edge. Once you've done this, let the ink/paint set for however long it needs, then rub it down with steel wool until you're left with ink in the etched lines, and nowhere else. Cover with a protective lacquer if you want.

Method 1: Lithographic/etching ink. About $20 a tube from Eckersley's. This is an oil base soft ground used for etching hand drawn images. Because it was what I had available, this was the first ink I tried. While it sticks in the etching reasonably well, it takes days to dry, and the lacquer that I was using at the time dissolves it. It's also really messy. I was finding black oily stains for weeks afterwards.

Method 2: Because of the waiting time involved with the Lithographic ink, I decided to try with black spray paint. Simply spray onto your plate after etching, squeegee the excess off, and allow to dry. I found that while this was quick, the lacquer, once again, dissolved the paint. It's a lot cleaner though.

Method 3: Permanent marker. Basically, colour the etched lines in with a thick black marker, the ones made by Staedtler are the best. The problem with this method, is purely the recurring lacquer problem. This is a very easy method.

Method 4: This is the best one of all. It's the same as method 1, but use black acrylic paint instead of lithographic ink. This paint dries really quickly, after squeegeeing it takes about 15 minutes. It's cheap, about $3 a tube, and it's lacquer resistant because it's water based.