Various ramblings – Electronics, radio, old computers, cars & other junk…

Monthly Archives: July 2011

Change gear cover knobs

The change-gear cover on my lathe was held on using some very poorly made allen/hex style bolts. These were a pain to remove each time you wanted to change gears, but I’d seen on a few websites that people had made some knurled knobs with a threaded shaft to hold the cover down instead.

I made these in two parts, after machining both sections they were pressed together. The knurled knob was made from 20mm round aluminium; cleaned up, faced, 9mm hole drilled down the middle and then knurled. The knurling turned out very well, this was the first time I’d used the tool and I think luck played a large part in getting the size right. I made the 2 knobs from the one bit of stock, did the rough shaping and then parted them off. This let me match the size and also get the chamfers to match as I did them at the same time without changing tools.

The shafts were made from 10mm round aluminium; cleaned up, faced, took the size of most of the shaft down to 5mm, threaded the end and then took the remainder of the shaft to a fraction over 9mm ready to be pressed into the knurled section. Making it this way saved on aluminium stock and reduced the time needed to take the size of the stock down to the required size.

First Chips

While I had messed around with the lathe while setting it up and getting the hang of using it, this was my first “real” bit of turning.

I wanted a simple first project so I was looking around the garage for some inspiration, I spotted an old fire extinguisher my brother found a while back and an idea popped into my head. We had planned to turn it into a portable compressed air tank but the fitting in the top of it had too many holes to plug and no room for a new thread. “Perfect!” I thought, “I’ll make an adapter to fit the thread on the tank, and drill a hole in the middle to tap a thread to match air compressor fittings!”

My first attempt was was done with a bit of aluminium I had been messing around with and was already a bit small. I got a bit gung-ho while threading and it ended up undersized. It threaded OK but had a bit too much play in the thread. The second one is nearly perfect, I even cut a small notch in it to fit the O-ring from the original tank fitting.

If you look carefully, you can spot my dodgy setup for running the motor while I was sourcing a new power supply. While removing some of the annoying safety guards and replacing the emergency stop I managed to blow up the motor controller. A 40v-0v-40v toroidal transformer, bridge rectifier and a filter cap running into the direction switch on the front panel is how I was using it while making these parts. This was replaced with a real motor controller that I installed shortly after.

To change speed I had to swap between taps on the toroidal transformer between series and parallel. Not the best solution, but it worked surprisingly well. I had the ammeter hooked up to keep an eye on current to make sure I wasn’t going to damage the motor or cook the bridge rectifier/wiring.

Lathe bench build

I’d been eyeing off mini-lathes on eBay for years, and finally caved in and purchased one mid-late 2010.¬†While waiting for the lathe to be delivered I started looking into buying or building a bench for it to live on. I decided to build one so I could make it to fit exactly where I planed to setup the lathe. A quick sketch on some paper and some more time finalising the dimensions on SketchUp and I’d figured out what I needed.

I stopped in at a steel shop on the way home from work on a Friday and picked up the steel. I got them to cut it to the right lengths for me as I don’t have a drop saw that can cut steel. My only method of cutting steel is with a hacksaw, why do that when you can get it cut much more accurately with the right tools? I welded the frame together and painted it over one weekend, and finished the tops and draws the weekend after. Here is the finished product and a few pictures while building it.

The bench is very simple in it’s construction, a steel frame made with 25mm box section for the bulk of it and some 20mm strap for bracing. The top and draws are made from 16mm MDF, coated with some 50/50 thinned polyurethane¬†to give the MDF some protection from swelling. The frame was painted with etch primer and then some black gloss spray enamel paint. All up the bench cost me about $150 including glue/screws and surface finishing.

The draw handles and a few other things I had kicking around the garage but they wouldn’t add a great deal to the total cost.