What could I possibly be doing wrong?

[Oliver19619]

Hi there ladies a gentleman, just wondering if anyone could guide me in the right direction, I’ve just got into hobby machining about a year ago, started with a mini lathe, have just possibly downgraded to a 10x22 bench lathe…no the rigidity etc is fantastic compared to my previous one really happy with it apart from… okay so here is the issue.
Change gears for threading.
Okay so I believe I’m setting the gears correctly however I don’t believe this is the case because the thread pitch isn’t correct I’m aiming for 1.25 as you can see from photos the pitch isn’t correct on the scratch pass, do the drive gears look correct? Haven't a clue any help would be much appreciated, also I’ve done a little test with all the gear combinations, how I believe they’re set up anyway! you can see the pitch per 1 revolution of the spindle, some of them are correct but some are wrong. Any ideas let me know. Thankyou

 

[DAT510]

Welcome to H-M.
Can you share the Brand and Model of your lathe. I'd like to see if I can find the manual online so I can better understand it's setup and try to help.

 

[Oliver19619]

Welcome to H-M.
Can you share the Brand and Model of your lathe. I'd like to see if I can find the manual online so I can better understand it's setup and try to help.

Hi there, the lathe is an asian model sumore sp2124-I can’t find a manual anywhere myself, i can find the perhaps more modern one that has the lead screw reversal where my “a b c” lever is. If you have any ideas do let me know. Thankyou

 

[brino]

It looks to me like you have the change gears set up properly, according to that diagram.

However, we have seen examples here where the diagram on the lathe itself was not quite correct.
Also, we don't know the history; if the lathe is used a previous owner could have changed the spindle gear or the lead screw, or if new, perhaps the factory changed one of those but it still got the label from the other model.

Two key pieces of info would allow us to calculate everything:
1) What is the tooth count of the gear on the spindle that drives the first gear in the chain?
2) What is the pitch of the lead-screw?

Thanks,
-brino

 

[brino]

They do have a website:
http://www.sumore-machine.com/sp-i-china-variable-speed-manual-bench-lathe-machine-1694.html

Have you tried the "Contact Now" button there to get a manual?

-brino

 

[Oliver19619]

It looks to me like you have the change gears set up properly, according to that diagram.

However, we have seen examples here where the diagram on the lathe itself was not quite correct.
Also, we don't know the history; if the lathe is used a previous owner could have changed the spindle gear or the lead screw, or if new, perhaps the factory changed one of those but it still got the label from the other model.

Two key pieces of info would allow us to calculate everything:
1) What is the tooth count of the gear on the spindle that drives the first gear in the chain?
2) What is the pitch of the lead-screw?

Thanks,
-brino

Hi Brino, okay so the lead screw pitch Looks to be 2mm, the drive gear your asking about attached to spindle is 40tooth I believe this is the gear you are talking about if not please correct me. Thanks for your reply!

 

[Oliver19619]

They do have a website:
http://www.sumore-machine.com/sp-i-china-variable-speed-manual-bench-lathe-machine-1694.html

Have you tried the "Contact Now" button there to get a manual?

-brino

Also yes I have sent them a message regarding manual. No reply as of yet. Thank you

 

[C-Bag]

It looks like the knob on the left that has the Roman numerals is set on lll, it should be on ll.

 

[Papa Charlie]

It looks like the knob on the left that has the Roman numerals is set on lll, it should be on ll.

CII is for .125 for 1.25 it is CIII according to the label. It also calls out a 70/56 gear tooth which all seem to be correct along with your settings.

@Oliver19619 Are you engaging the lead screw at the 8 mark? That appears to be the only mark that you can use for this pitch.

Not sure what the difference is between the 40T and the 45T Scale it is referring to. Appears that one of the gears has to be a 45 tooth. Not sure but the only gear shown in your gear set that comes close is the one marked 40, you may have to change that gear for a 45 tooth.

 

[markba633csi]

I think the problem may be the spindle gear- the chart says 30 but yours is 40. That would make sense as the scratch pass shows a coarser thread than desired which would indicate a too fast leadscrew
-Mark