Friday, January 17, 2014

Steady Rest Redux, and some misadventures

I really started out to make a feed screw for the Taig lathe. Really I did. What I have found out about this machining business is that to make A, you have to first make B. However, that entails making C and D and so on, so sometimes you lose track of where you are.

I actually did make a feed screw. It was a 1/4"-20 RGU feed screw, approx. M6x1. It was far too flimsy.  I knew it had worked for Dean over on (look under "feed screw for the Taig lathe") but I found it very wobbly. So I needed a bigger screw. I am limited by ready availability, so maybe M10x1 would do it. Not for sale at Home Depot. Maybe 3/8"-16? This is about M10x0.75. But, here comes the problem, I cannot get a 3/8 screw through the bore of a Taig, so ... we need a steady rest. I made one before, see label "steadyrest", but it is too flimsy, just like the 6mm feedscrew. 

I had used a wood-turning attachment as the base of the old steady. It worked. But not really steady enough for what I want. So first I have to make the slide. This is a 45 degree dovetail slide, about 7mm on perpendiculars. So I set out to make the slide.

I had some 1/2" (12+mm) steel so I traced the outline of the old slide onto the new stock. Then I had to mill it out. And now we come to making C. I wanted to use my new Christmas present, a 4mm endmill. The bigger the endmill, the less work. But Cecil B. de Mille cannot chuck a 4mm bit.The biggest chuck is 3.2 mm or 1/8" RGU.
Now you cannot possibly turn down a 4mm mill shank down to 3.2 mm, even with carbide tools. The stuff is much too hard. But you can grind it down. So I mounted my trusty Dremel on the cross-slide. The adapter you have seen before, it is part of a chainsaw sharpening attachment. It ate the grinding wheel to a nub, but it worked. Sort of. Alas, I had a taper on it. It is very difficult to get the Dremel exactly parallel to axis of lathe. I finally set up a dial indicator.

I am getting far too much runout. (Off-center error), 0.1mm or so.  I actually did grind it down to 3.2 mm at base, but it tends to squeeze out of the chuck. Disaster. Time for another plan. 
I set up the vertical milling attachment on the Taig and put a really big (12mm) bit in the chuck. This is a no-no. You are not supposed to do this. I did it anyway and it worked.  So I "hogged out" most of of the slide by this method. I must say it was a pleasure to take really big cuts. By my standards anyway. So now we can clean up on Cecil. I put the bar right on the table and held it down with toe clamps, just like the big boys on YouTube.

The next job is to cut the 45 deg slots for the dovetail. The big boys use dovetail cutters. I haven't one; and it would never fit in my mill anyway, so we improvise. Using a protractor we tilt the piece to 45 deg and mill straight down.
Here you see the first dovetail cut. I am setting up for the second. Tomorrow, all deities willing, I will start cutting it. Then I can worry about the rest of the steady rest. Then I can worry about the feed screw. Whay did I ever take up machining? Because, in the end, it is fun. Getting to the end may not be so much fun, and is sometimes very frustrating. Life, after all. 

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