Is the majority of mini lathe information on the internet bad?

[S. Heslop]

I've got the lathe back together now. It seems to be cutting a bit better (less tearing on this mystery steel) but I now need to buy a new wheel for my grinder so I can grind some better tools until I can really tell for sure.

Just need to fiddle with the apron a bit to stop the half nut clanging into the leadscrew when disengaged, and it'd probably be good to check the alignment on the tailstock (with the way this lathe is made I don't think just lining up two dead centers is going to cut it. I'll probably have to fix a DTI to the barrel and run it along a test bar). I also bought one of those engineer's spirit levels at a boot sale a while ago and was thinking id build a better stand for the lathe before bothering to level it. It seems like a big job though, and I really just want to get back to the electric bike. 

[chipenter]

To tast the tailstock wind the barrel all the way out clamp it , mount a DTI on the saddel and run the saddel along the barrel .

[Stilldrillin]

I got my new mini lathe, 10 years ago. Owned very little kit to go with it. Certainly, no dti......... 

The "only" thing wrong, I couldn't align the centres. 

I first made sure the chuck jaws were running true, at quill diameter.

Slackened, then lightly snugged up, the tailstock adjustment screw. (Underneath the tailstock base casting).

Quill, into chuck jaws, at full depth of jaws. Grip very gently.

Lightly, lock tailstock to bedways.

Settle into place with a bump from lead tup, on top of tailstock casting.

Sensibly, tighten chuck jaws. Lock quill.

Settle again with lead tup.

Carefully remove tailstock, and tighten locking screw.


Four years later, when I got a dti, which was able to clock around the quill...... It was within .0005". 

David D

[S. Heslop]

I'm getting a pretty good surface finish now. It's a huge improvement at least.



It looks like chatter in front of the bearing but its just aliasing from resizing.



This was cut using the mini lathe's slowest screwcutting speed. I think with a slower autofeed it'd look better but I don't mind it as it is now. I think chips getting into the apron gears were causing those bands too.

[Pete.]

If you put a small radius on the tool and lapped a fine edge you'd improve the finish by a significant factor.

[Chuck in E. TN]

This was cut using the mini lathe's slowest screwcutting speed. I think with a slower autofeed it'd look better but I don't mind it as it is now. I think chips getting into the apron gears were causing those bands too.

I built a dedicated fine feed banjo for my SEIG lathe using Mod 1 80 tooth and 20 tooth gears salvaged from a laser printer. It runs the leadscrew the speed to cut 256tpi.
That and a 1/32" radius on the tool bit produce an excelent finish.
Chuck

[S. Heslop]

If you put a small radius on the tool and lapped a fine edge you'd improve the finish by a significant factor.

I'd put a pretty large radius on it. Maybe it's not as close to a radius as I thought though.

[S. Heslop]

Turned out my lathe bedways were pretty twisted. Turning between centers was giving me a 0.15mm taper over 100mm.

Lucked out at a boot sale a while ago and got an engineer's level for a decent price, and I just used it to get the ways 'close enough' to level. Now i'm getting 0.03mm taper over 100mm. This is being measured with a pair of digital calipers though. It's surprisingly hard to find decent metric micrometers.

For that matter it's hard to find decent metric machines second hand. I think when it comes to buying a mill I think i'd prefer to go with imperial and put the effort into adjusting up a neat old machine than into an import.

[Pete.]

Good job on finding the fault. Un-twisting the bed has reduced your error by a factor of five!