Mellor lathe.

[Richard.]

I think aluminium is best to start out learning on. It’s more tolerant to mistakes and tends to cost you less in chipped inserts.

 

[Richard.]

You are welcome to come and see me if you want to pick up some off cuts of alu bar and tube.

 

[God mode restorations]

Evening guys .
I got some new stock of different sizes. All mild steel. The lump I have in the chuck is 20mm thick. I am just running some tests. I have new insert tools on the way. But until they arrive I have to make do with these new hss tools. So the first few runs are poor. Very rough and as you can see from the pictures. Nothing is consistent .the cut lines are hit and miss. I have set the back gears up and it's the first time I used them. But the gears work well. But still very rough finish .everything on the machine is good and running as should be.

 

[Seadog]

Does the tool need a grind/hone perhaps? I wouldn't bother with back gear, that'll be too low i'd have thought. What is the workpiece, mild steel, hot rolled...?

 

[God mode restorations]

Does the tool need a grind/hone perhaps? I wouldn't bother with back gear, that'll be too low i'd have thought. What is the workpiece, mild steel, hot rolled...?

Tools are brand new. Perhaps not sharp enough. I was testing the back gears as I never used them after I stripped the machine .normal mild steel. Unless am running it to slow

 

[God mode restorations]

You are welcome to come and see me if you want to pick up some off cuts of alu bar and tube.

Appreciated thankyou Richard.

 

[God mode restorations]

Running at high speed does nothing. I think the tool must be blunt as looking at the swarf it looks like it's torn rather than cut

 

[eLuSiVeMiTe]

Got a pic of the tool?

Sure I shared before
Worth reading.
http://www.steves-workshop.co.uk/tips/toolgrinding/toolgrinding.htm

 

[Seadog]

Is it on the centre line of the workpiece?

 

[God mode restorations]

Is it on the centre line of the workpiece?

Yes. That was the first thing I checked

 

[Richard.]

I’m not an expert but I will take an educated guess at travel feed speed too fast in relation to the rpm and tool too pointy.
It almost looks like you’ve cut a thread.

 

[Ian James]

@spencer 427 have you tryed it with a tail centre fitted at that length to seeing it will improve the finish I am no expert but am speaking from experience with my old laith

 

[God mode restorations]

@spencer 427 have you tryed it with a tail centre fitted at that length to seeing it will improve the finish I am no expert but am speaking from experience with my old laith

I have not tried it yet. Was literally just a few test runs. Will try that .

 

[God mode restorations]

I’m not an expert but I will take an educated guess at travel feed speed too fast in relation to the rpm and tool too pointy.
It almost looks like you’ve cut a thread.

That's another thing I was looking at Richard. It's as if the apron is moving before the stock as done a revolution.

 

[Richard.]

That's another thing I was looking at Richard. It's as if the apron is moving before the stock as done a revolution.

The apron will always be moving but how much does it move per rev
It’s difficult to get the balance right as you need good positive feed to take your cut but you need it to remain slow enough to get that nice fine feed finish.

 

[God mode restorations]

The apron will always be moving but how much does it move per rev
It’s difficult to get the balance right as you need good positive feed to take your cut but you need it to remain slow enough to get that nice fine feed finish.

That's why I tried it with back gears.just to see what happens. Stood there five minutes waiting for it to finish it's travel. A bit to slow.

 

[addjunkie]

At 20mm diameter you want quite a high speed. You have quite a bit of stick out, id suggest having about an inch out the chuck, put it on your highest speed, and slowest feed. See what you get.

With that amount sticking out Id be using a revolving center.

Back gears are really for large items at a slow speed, so it cuts, dont forget as you increase diameter you increase surface speed. Also for screw cutting, again you dont want any slip.

To be diplomatic you are getting a record finish, often acceptable for some things, because your feed is too high

 

[God mode restorations]

At 20mm diameter you want quite a high speed. You have quite a bit of stick out, id suggest having about an inch out the chuck, put it on your highest speed, and slowest feed. See what you get.

With that amount sticking out Id be using a revolving center.

Back gears are really for large items at a slow speed, so it cuts, dont forget as you increase diameter you increase surface speed. Also for screw cutting, again you dont want any slip.

To be diplomatic you are getting a record finish, often acceptable for some things, because your feed is too high

I will use the centre just to see. I can't reduce the travel speed as it runs off the gears through the tumbler.

 

[Richard.]

I will use the centre just to see. I can't reduce the travel speed as it runs off the gears through the tumbler.

Then try running it off the lead screw in much the same way as you’d cut a thread. I think it needs reducing spencer looking at the cut.

 

[Pete.]

Run the lathe more slowly and put a larger nose radius on the tool.

As a general rule you want to limit stick-out to 6x diameter. Even that much can cause issues.