# What could I possibly be doing wrong?



## Oliver19619 (Aug 4, 2021)

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


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## DAT510 (Aug 4, 2021)

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.


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## Oliver19619 (Aug 4, 2021)

DAT510 said:


> 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


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## brino (Aug 4, 2021)

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


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## brino (Aug 4, 2021)

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


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## Oliver19619 (Aug 4, 2021)

brino said:


> 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.
> ...


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!


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## Oliver19619 (Aug 4, 2021)

brino said:


> 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?
> ...


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


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## C-Bag (Aug 4, 2021)

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


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## Papa Charlie (Aug 4, 2021)

C-Bag said:


> 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.


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## markba633csi (Aug 4, 2021)

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


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## Lo-Fi (Aug 4, 2021)

As mentioned, it's not unheard of for charts to be wrong. This may help:









						Change Gears for Threading
					

This calculator determines the correct change gears for any thread pitch. Works for all mini lathes and HiTorque Bench Lathes.




					littlemachineshop.com
				




It's well worth investing a little time in truly understanding it all from first principals, though, then the calculators (or indeed charts) are much easier to use and understand. 

Hope you're happily threading the correct pitch soon!


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## Oliver19619 (Aug 4, 2021)

Papa Charlie said:


> 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.


Hi there papa Charlie, I will upload some more clear photos of the gears/dial indicator.  The first few are the dial indicator so you can raise and lower it for the tooth count on dial. Okay so as for the gear train, the main spindle is 40t the one attached to Chuck etc, then there’s 3 gears interlinked that I don’t believe can be altered because they’re kind of fixed on the lead screw direction knob, so if I were to put a 30t cog it wouldn’t reach the other two gears responsible for reversing the lead screw. The position of the 40t cog pictured can not be altered. As for engaging the dial on 8. Would that make a difference on the pitch? I thought that was just for engaging at the same point to catch previous thread? Thanks for all of your recommendations/help.


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## Oliver19619 (Aug 4, 2021)

Oliver19619 said:


> Hi there papa Charlie, I will upload some more clear photos of the gears/dial indicator.  The first few are the dial indicator so you can raise and lower it for the tooth count on dial. Okay so as for the gear train, the main spindle is 40t the one attached to Chuck etc, then there’s 3 gears interlinked that I don’t believe can be altered because they’re kind of fixed on the lead screw direction knob, so if I were to put a 30t cog it wouldn’t reach the other two gears responsible for reversing the lead screw. The position of the 40t cog pictured can not be altered. As for engaging the dial on 8. Would that make a difference on the pitch? I thought that was just for engaging at the same point to catch previous thread? Thanks for all of your recommendations/help.


Just had a little mess about where I engage the lead screw has no difference on the readings of final travel of carriage. I just don’t understand it.. if i were to leave the gears set under cover and change the knobs on the front to A + 3 for example I get a 1mm pitch exactly. Strange one.


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## Oliver19619 (Aug 4, 2021)

Papa Charlie said:


> 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.


Okay I removed the pulley spindle etc so I could get this..There is a photo of the whole gear train


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## Oliver19619 (Aug 4, 2021)

Okay so the gearing from the the ratiois 1:1 followed by the gearing 30-100-70-56 so I’m under the impression that the only gears to be changed are the bottom 4. Which is what I have done..set the turn knobs still to the required settings, so I can use this gear setup to get a pitch of 1.0mm as the diagram says. But not 1.25mm strange one it really is.


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## Oliver19619 (Aug 4, 2021)

Okay thank you all so much for your help I swapped out the 56 tooth gear for a 63 and the jobs a good’un bloomin charts.. honestly I can’t thank you all enough for your suggestions etc.


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## Oliver19619 (Aug 4, 2021)

We got there in the end once again thank you all for your advice. Greatly appreciated.


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## Oliver19619 (Aug 4, 2021)

not too sure if the threads are deleted after a certain time but for reference..if anyone ever had the same problem with lathe, the gear train runs 40t spindle/ 30/96/70/63 gears and the same knobs to correct the pitches 0.7mm-1.25mm-1.75mm.


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## extropic (Aug 4, 2021)

Oliver19619 said:


> not too sure if the threads are deleted after a certain time but for reference..if anyone ever had the same problem with lathe, the gear train runs 40t spindle/ 30/*92*/70/63 gears and the same knobs to correct the pitches 0.7mm-1.25mm-1.75mm.



I've been following along. I didn't make any suggestions because I didn't have any better opinions to offer.

Good to see you sorted it out.

However, now I'm confused. What happened to the 100 tooth gear indicated on the chart?
Did you count the teeth and only found 92 (another chart error?)?
Is 92 a typo? please elucidate.


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## markba633csi (Aug 4, 2021)

I'm interested too- what possessed you to swap the 56 tooth gear for the 63?  Intuition?  Wild guess? 
Also wondering about the 92 tooth, where did he come from?
-Mark


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## Oliver19619 (Aug 5, 2021)

extropic said:


> I've been following along. I didn't make any suggestions because I didn't have any better opinions to offer.
> 
> Good to see you sorted it out.
> 
> ...





extropic said:


> I've been following along. I didn't make any suggestions because I didn't have any better opinions to offer.
> 
> Good to see you sorted it out.
> 
> ...


Yes typo I meant 96! My apologies, Okay so after a lot of messing about, as you see i took the recommended gear setup, which I doubted until today once I removed the spindle pulley etc I realised that the 3 top gears were irrelevant and the headstock and them gears had a 1:1 ratio, then I realised I was fitting the gears correctly, however as you can see from my previous diagrams with all the drive gear set ups and knob selectors, you can see some of them on the supplied chart were correct but some of them were off. Someone on this thread mentioned that not all the diagrams are accurate and can sometimes be off so I played about with the gear cogs leaving the gear knobs on C-3 to try and find my thread pitch with different gear combinations. So at first with the recommended gear setup I was getting a reading of 1.32mm pitch, I then put the 63 tooth cog on the lead screw took another reading and I can’t remember what it was now but was marginal, I had to slow the chain down and thought changing to the 96t gear would do this To be totally honest it was all abit of luck trial and error a few days of messing around with it…. Possibly even more hair loss! Most of the chart is correct I highlighted green for the ones that were correct, and red for the few that weren’t, the gear combination 30t-96t-70t-63t with all the selector knobs being in the position they should be in seem to fit (highlighted in green) I know there were some discrepancies with other gear combinations, I will have a look at them another time, it’s quite time consuming. I’ve started to make my own chart which I know is precise for future reference.    However  the recommended gear combination for let’s say a 0.75mm thread pitch, 30/100/54t/72t  selector knobs C-3 isn’t correct however I found that the 30/100/70/56 on A-1 is in fact 0.75mm pitch not the stated 0.7… I’ve written my findings on a piece of paper to keep note of them because the diagram written on the lathe is completely wrong in a lot of cases. The chart I’ve made so far is 100% accurate, will be trying different gear combinations in the future and will upload my findings. It’s 5am I hope I’ve made some sense. Thankyou


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## Oliver19619 (Aug 5, 2021)

If you can’t make sense of that I fully understand, I will clarify things when I’m not half asleep, yes the 100t cog is 100t to answer your original question. Thanks again. I’m off to catch some flies.. goodnight.


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## Oliver19619 (Aug 5, 2021)

markba633csi said:


> I'm interested too- what possessed you to swap the 56 tooth gear for the 63?  Intuition?  Wild guess?
> Also wondering about the 92 tooth, where did he come from?
> -Mark


Hi mark that was a typo I’m Tired of change gears haha, after a few days of playing around I guess I was never going to achieve the results with the combination on the chart so decided to try and make my own combination leaving the selector knobs for a pitch of 1.25 C-3 and trying different gear combinations as well as testing the pitch for the changed gear,  Luckily enough I cracked the code second time round, I suppose intuition/wild guess all play a role. Thank you for  your time.


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## Papa Charlie (Aug 5, 2021)

Be sure to double check the chart on the half nut gauge to ensure the line to use will generate the correct output with your new gear configuration. 

Good job on sorting this out. Hard to do over the internet.


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## markba633csi (Aug 5, 2021)

Wow, this is the worst case of lathe gear problems I have seen.  They say these import lathes are "kits" and require some fettling/fiddling but this is ridiculous.  And of course it's something which is not immediately apparent until you have the machine set up and running.
Kinda makes me appreciate my humble Atlas even more
-Mark


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## Oliver19619 (Aug 6, 2021)

markba633csi said:


> Wow, this is the worst case of lathe gear problems I have seen.  They say these import lathes are "kits" and require some fettling/fiddling but this is ridiculous.  And of course it's something which is not immediately apparent until you have the machine set up and running.
> Kinda makes me appreciate my humble Atlas even more
> -Mark





markba633csi said:


> Wow, this is the worst case of lathe gear problems I have seen.  They say these import lathes are "kits" and require some fettling/fiddling but this is ridiculous.  And of course it's something which is not immediately apparent until you have the machine set up and running.
> Kinda makes me appreciate my humble Atlas even more
> -Mark


I completely agree, makes you wonder if it had the wrong diagram stuck on or something at the factory..because half of them are practically wrong anyhow.. Well we got there in the end, once again I say thank you to everyone who helped was very much keeping me sain. Thank you all.


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## matthewsx (Aug 7, 2021)

I believe what they do in China is just copy the example provided unless someone is looking over the work. Just reference the cheap 123 blocks we all have that don't bolt together, one mistake replicated a million times.........

John


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