Make sure your tool post is not rotating slightly under the pressure of a carbide cutting tool. If it is a piece of paper between the tool post and the compound will give you more traction. Cutting on the flat with carbide may be causing more back pressure than your setup can tolerate without moving.
I'm cutting mild steel. I have HSS blanks, but I still don't know how to cut them yet. I don't know what gibs are as of now and no idea how to check them. I"ve got the lathe torn apart for cleaning.
Number 92 is the gib for the carriage, number 94 is the cross slide gib. The compound also has a gib. The six # 91 screws and four #18 screws adjust the gibs. They are adjusted for zero up and down play of the carriage, yet the carriage must move smoothly without too much friction. The three #91 screws adjust the cross slide gib for zero play and smooth sliding. It takes a while to get the gibs adjusted for as little play as possible without causing a lot of resistance to movement. You do the best you can. If they are too loose you loose rigidity and get chatter of the cutting tool. Keep the ways and gibs lubricated. Most use way oil, Mobile Vactra #2. In a pinch any oil is better than none.
There are a number of reasons that your finish may not be great. I've listed a few below and it's just a case of eliminating them one by one.
Check that the cutting tool is sharp. If you’re using carbide try a new insert and see if that improves at all. They don't last that long especially if less than ideal feeds and speeds have been used.
Try different feeds and speeds. Carbide often cuts better at higher speeds. Just experiment here to see what works for you. Personally I’ve never bothered with the recommended speeds & feeds – I do too much turning up to a shoulder and at the recommended speeds I’d be crashing the tool left, right & centre! I just run the machine at a speed I am comfortable with and that gives an acceptable finish.
Check that the lathe is properly adjusted. As has been mentioned before the gib strips may need adjusting. A quick google will bring up countless articles / videos of how to do this. It’s always a trade-off – especially on smaller machines – between getting them just tight enough without excessive binding.
Try a different material – mild steel doesn’t machine brilliantly. It’s quite prone to long stringy chips and has a habit of fusing to the tool tip. It often looks like the metal has been torn from the surface. I found that I could get a much better finish on higher quality steel, brass or aluminium (although aluminium is awful for long stringy chips that wrap around the workpiece and fuse themselves to the tool tip!). If you can try to use free machining steel grades as these often have modified chemistry which promotes better chip formation.
Hopefully working through some of the above may help you to improve your finish!
It's round bar from Curtis Steel, a metal supplier here in Las Vegas
Also, I figured out why my work pieces have rough finishes. My carbide inserts keep breaking.
When I'm turning a right hand cutting tool, going from right to left, should I back out the cross slide before going back to the start area? I've just been using the carriage wheel when I''m turning. I set it to .005, then move the carriage to the left, then move it back to the starting point without pulling back the cross slide.
I'm still trying to figure out how to cut HSS blanks.
You can put together some type of grinder with a motor and a grinding wheel. You have a lathe so it should be an easy project. In the mean time haunt garage sales and yard sales for small bench grinders; that's how I got mine
Having a grinder opens up all kinds of possibilities for making tools and parts- gotta have one
My mini lathe does the same thing. You could try tightening the gibs, but I just learned to apply a little pressure on the carriage wheel when facing. I had to add a plastic shim (~.010”) behind the dial in order to get it to rotate with the knob.
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