What am I doing wrong

[azshadeguy]

Okay I know that this little Craftsman Lathe is to small but still.
I have a 3/4 thick x 3-1/2 round disc.
I put the disc in a 4 jaw chuck got it centered and turn it on.The disc is a36 steel
All I had was one 1/4 inch tool steel I shaped it according to something I read.
Any way all its doing is grinding the cutter. Not even scoring the disc.
What am I doing wrong?

 

[francist]

A picture would really help here, there are many variables that come into play especially for a first-timer. A few that you could check right away though:

-you say you ground your own cutter. Make sure it is indeed sharp and that you have it set up in the holder so that there is clearance underneath the cutting edge. No clearance there = no cutting there.
- are you turning or facing? I am guessing facing, but not sure. At any rate, is the mill scale still present on the surface you are trying to cut? If so, you need a sharp tool and agressive depth of cut to get through that. It can be challenging, especially for a small machine, and it does make short work of a sharp tool if you just peck at it.
- is your cutter on the centre height of the spindle? Put a centre in your tailstock, bring the cutter up to that, and make sure the two points are lined up. If not, adjust. There are other more fussy ways to get closer, but for starters that should get you into the ballpark of making some form of cut.

-frank

 

[dulltool17]

A description of what operation you're performing would help. I'll second all that Frank said.

 

[azshadeguy]

Here are some pictures
I am trying to turn this down to 3"
I have a tubing bender that has 3" shaft collars on it. It is missing one.
I will pull in the tailstock and check the height
Thanks



Paul

 

[ELHEAD]

Disc appears to be torch cut. If so you may need to grind to the heat affects hard edge before attempting to turn.
Good luck.
Dave

 

[mikey]

I agree that a flame cut disc can be quite hard at the edges. A turning cut at the edge to get under the top layer might do it, or you can anneal the entire disc to soften it before cutting. It should face okay, though, at least past the edge.

 

[markba633csi]

Is that a good quality tool you are using? Also with a large workpiece the surface feet per minute will be high at the outer edge so use a slow enough
spindle speed and some cutting oil- carbide tools are great for that flame-cut stuff
Mark S.

 

[682bear]

What spindle speed are you turning at? A rough surface like that should be turned very slowly until it cleans up... also, being torch cut, it may be a lot harder on the edge than in the center.

It may help to slow it down and, starting at the edge, feed toward the center until it cleans up, back out, move to the left .010 thousandths, then feed back toward the center... repeat.

In other words, rather than feeding across the cut edge, feed into the cut edge... being sure not to cut past your finish diameter of course. When you get the edge cleaned up, it should cut easier.

Also, I can't tell for sure in the pics, but it looks like you may have too much relief below your cutting edge, making the edge weak. For an interrupted cut, you need just enough relief to prevent 'rubbing' the workpiece.

-Bear

 

[Hawkeye]

I have one such disk that a file won't cut. It's either all hardened, or, as mentioned above, the flame cutting may have hardened the outer layer. Have you tried scratching it with a file?

 

[tq60]

Get the largest brazed carbide that cuts on the left side that you can hold in your tool post.

Adjust so tip of tool is as close as possible to tool post so it has less leverage to it.

Put in back gear and slowest speed and start the cut on the face.

Depth of cut should be such that it is consistent and not interrupted if at all possible.

Use power feed set to smallest available, you may need to manually feed it if the motor stalls.

If motor stalls it may chip the cutter.

Cut until close to chuck then flip it over and do other side.

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