Rough finish.

[vimes1984]

Hey there I'm machining my fist steel on my mini lathe, and I can't seem to get a smooth finish.
I've tightened everything the most I can, I'm ground my own HSS tools, to the best of my ability so far I'm running the lathe at about 500~ RPM's.
I'm attaching some photos.
Any advice is VERY appricated.

 

[cathead]

How about a photo of the cutting tool?

 

[vimes1984]

@cathead here you go and thank you!

 

[Tony Pisano]

From photo of the part, it looks like the tool bit might be rubbing or isn't sharp. It's hard to tell from the tool bit photos, but you should have a good sharp cutting edge, and make sure the toolbit is not above center of the workpiece. If it is, the area below the cutting edge will be rubbing on the workpiece. Is it mild steel that you are cutting?

 

[vimes1984]

Ye sit's mild steel, this is so confusing I've read somewhere that a touch above center is good and a touch below is bad
of the joys

 

[vimes1984]

@Tony Pisano how do I go about sharpening it, I don't have a hone I've run them through the grinder and rounded the edge slightly afterwards.
I do have a little file, can I use that to hone.

 

[T Bredehoft]

There is a class of mild steel, (Hot Rolled) that machines as you found. That's not to say you lucked onto some, but it is a possibility.

rounded the edge slightly

This is not a good idea. You want a razor sharp edge, albeit at 60º or so.

 

[savarin]

If your file will actually cut the tool bit then the tool bit is not hard enough to keep an edge.
I've found that a very sharp edge honed with a simple diamond tool/plastic stick helps immensely. I use these EZE-LAP-3pc-Diamond-Hones
Hot rolled mild steel is usually horrible to turn
http://www.conradhoffman.com/advancedsharp.htm and try out the shear tool, My goto tool bit on a cantankerous part.
When facing off some hot rolled plate I wound up the lathe to its fastest speed and used a braised on carbide tip that I diamond honed to a sharp edge. My HSS bits just wore away from the weld and heat scale.
start at post 114 to see the start and finish of how smooth it became https://www.hobby-machinist.com/threads/the-giant-binocular.55688/page-4#post-618084
a word of warning, the chip peels off in one continuous fast razor sharp and blue heated chip so keep well clear.

 

[talvare]

this is so confusing I've read somewhere that a touch above center is good and a touch below is bad

Just the opposite. Never above center.

Ted

 

[WCraig]

I'm a brand new newbie as well and I was having similar difficulties yesterday so I'm following this thread with interest.

I wondered about the quality of the random steel offcut* I was playing with. When I filed it--500 rpm or so, first with an 8 inch and then a 6 inch file--it filled up several of the teeth on the files. Is that an indication of difficult-to-machine steel? BTW, the surface after filing still wasn't that good. I wasn't sure if I needed to remove more of the prior rough cut surface or if the file was also producing a poor finish. Ran out of time before achieving an decent results.

Craig
* box lot from an auction including a bunch of brass and aluminum flat and round stock.