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Author Topic: Mini-Lathe woes  (Read 23844 times)

Offline Twinsquirrel

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Mini-Lathe woes
« on: March 14, 2009, 07:23:56 AM »
Disaster, well maybe not a disaster but certainly very annoying!!

I've managed to strip 3 teeth from the main gears on my mini lathe.



You'll notice the lack of any kind of grease inside the headstock, I know that a lot of people may say that those GRP gears are self lubricating but I have my doubts about having no form of grease in a high torque environment like this?

I wasn't even doing any heavy work, just a light facing cut on some 50mm aluminium roundbar, no 2mm interupted cuts on stainless or anything like that :(

To be honest, I never really wanted to see inside the headstock on this lathe as I'm not at all confident that I can regain any accuracy when I reassemble it.

The problem I have now is sourcing a new gear, I havent spoken to my supplier yet though.... Also the spindle seems to be "locitited" into the bearings and I have no idea how to remove the spindle from the casting without damaging either the bearings or the spindle.....Has anyone here ever done this on a mini?

 :( :(

Still, it's all good fun,

David
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Offline Darren

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Re: Mini-Lathe woes
« Reply #1 on: March 14, 2009, 07:33:06 AM »
David,

I did that to mine very early on, I was parting 20mm brass at the time.

Don't panic, I have a pulling kit for this very lathe that i had to import from the US. You are welcome to borrow it.
Just get a couple of metal gears, they are not expensive. You might want to change the bearings to tapers at the same time as they have to come out anyway. Well at least one does.

I have the part No's if you have a local bearing supplier, might be cheaper that way.

It's not that difficult a job....don't panic..... :thumbup:
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bogstandard

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Re: Mini-Lathe woes
« Reply #2 on: March 14, 2009, 07:39:37 AM »
David,

What part of the country are you from?

If you are within striking distance from me, and you get the parts and puller together. I don't mind doing it for you while you wait. I can't do it as a leave it job because my workspace now is getting very small and haven't got the necessary storage space any more. I could then reset the head for you after the job is done.


John
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ja2on

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Re: Mini-Lathe woes
« Reply #3 on: March 14, 2009, 07:44:38 AM »
arc ero list metal gears at the bottom of this page http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/Model-C3-Mini-Lathe

but are out of stock

the little machine shop list metel and plastic  as well http://www.littlemachineshop.com/products/product_view.php?ProductID=3453&category=5
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #4 on: March 14, 2009, 08:11:02 AM »
Wow, What a response, you guys are fantastic ::)

Quote
David,

What part of the country are you from?

I'm in darkest Wiltshire so about a 4 hour drive from you. Shame it's just that little bit too far, although I am coming up to Harrogate for the show on the friday (I have been informed that we have a wedding to go to on the Saturday  :( ) so if I haven't got it sorted by then I may take you up on you very kind offer, thank you again.

Quote
Don't panic, I have a pulling kit for this very lathe that i had to import from the US. You are welcome to borrow it.
Just get a couple of metal gears, they are not expensive. You might want to change the bearings to tapers at the same time as they have to come out anyway. Well at least one does.

I have the part No's if you have a local bearing supplier, might be cheaper that way.

It's not that difficult a job....don't panic.....

Again I'm overwhelmed, do you have a pic of the puller? I have a number of different pullers available to me which could possibly be adapted to suit, If not a loan of your puller would be very greatly apprieciated. It would be sensible to change the bearings as well while I'm at it so if you do have the part numbers to hand that would be great too.

Quote
arc ero list metal gears at the bottom of this page http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/Model-C3-Mini-Lathe

but are out of stock

the little machine shop list metel and plastic  as well http://www.littlemachineshop.com/products/product_view.php?ProductID=3453&category=5

Thanks for that Jason, I hadn't realised that it was so common for these to shear but I am glad to see that it's not an expensive fix.... Just a bit of a B*ll-ache..

Thanks again all,

David
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ja2on

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Re: Mini-Lathe woes
« Reply #5 on: March 14, 2009, 08:26:23 AM »
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #6 on: March 14, 2009, 08:30:35 AM »
Hi Jason,

Thanks for that, I see on the mini-lathe.com "how to" he beats the spindle out with a soft mallet, I have access to a hydraulic press do you think that may be a better option?

David
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ja2on

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Re: Mini-Lathe woes
« Reply #7 on: March 14, 2009, 08:51:45 AM »
Should be easy with a press be careful though  with the thread on the end of the spindle
Please bear in mind I have never done this  :dremel:
I just have a large folder of mini lathe links that I amassed when I was doing my home work before buying one.
I ended up buying a c4 instead as it was on special offer  :doh:
« Last Edit: March 14, 2009, 08:53:41 AM by ja2on »
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Offline sbwhart

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Re: Mini-Lathe woes
« Reply #8 on: March 14, 2009, 09:03:38 AM »
Hi David

Thats a bitch your gears have broken, looks like the lads have pretty well got you sorted, the only thing I can add is that Loctite can be broken with heat, about 150 deg C usually does it.

Good luck
 :wave:
Stew
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Offline Brass_Machine

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Re: Mini-Lathe woes
« Reply #9 on: March 14, 2009, 12:03:06 PM »
Quote from: Darren on March 14, 2009, 07:33:06 AM
...You might want to change the bearings to tapers at the same time as they have to come out anyway. Well at least one does.

I have the part No's if you have a local bearing supplier, might be cheaper that way.

...

I would be interested in those part #s Darren.

Eric
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #10 on: March 14, 2009, 12:30:09 PM »
No time like the present....

Pressing out the spindle was surprisingly easy, not the ideal setup but the best I could do with the bits and pieces laying around.



Then the bearing on the motor side, luckily I had a blank which was an almost perfect fit for the outer race of the bearing with just enough clearance for the casting.



And here is the unit in its component form.







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Offline sbwhart

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Re: Mini-Lathe woes
« Reply #11 on: March 14, 2009, 01:08:35 PM »
You're cooking on gas now David  :thumbup:  Nice job  :clap:

Now all you've got to do is get it back together.

Stew
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bogstandard

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Re: Mini-Lathe woes
« Reply #12 on: March 14, 2009, 01:12:11 PM »
Isn't it amazing David, with a little help from friends you have never met, if you had the new bits in your hands, it would be going back together again, all within a few hours from your initial cries for help.

Amazing site we have here.

Bogs
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ja2on

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Re: Mini-Lathe woes
« Reply #13 on: March 14, 2009, 01:17:51 PM »
arc have a guide for fitting taper bearings
http://www.arceurotrade.co.uk/projects/C3_BC/pages/index.html
they mention a spacer that you might not be aware of
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Offline Darren

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Re: Mini-Lathe woes
« Reply #14 on: March 14, 2009, 02:19:54 PM »
Sorry David I've been out all afternoon picking up a new toy..... :ddb:

I see you have pretty much got on with it whilst I had my back turned. It doesn't look like you need a puller now. But if you do get stuck the offer is always open. Just give me a shout.

Let me get through the door and have a cuppa and I'll sort some info for you.
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Offline Darren

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Re: Mini-Lathe woes
« Reply #15 on: March 14, 2009, 06:22:59 PM »
Hi David, here's the puller kit for the 7x12,

Nothing more than a couple of tubes, a few spacers (of which you only need about two of) and some bolts.

Cost me $152 + £22 import duty, oh, that inc the gears.



The bearing No' 30206JR for the inner race and 30206 J-N for the outer race. Those No's are all you need for any bearing supplier.
You do of course need two sets.

The spacer you need to modify is already on the lathe. I managed to shorten mine on my lathe before fitting it. When you get to that part you will realise what I mean. It's part of the bushing at the back of the spindle just under the pre-load nut. Just lathe it with no pre-load. Easy cos it's plastic, if it where metal I doubt you could do it without another lathe.
I had no choice at the time as I only had one lathe.

Hope this helps
Darren
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Offline cedge

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Re: Mini-Lathe woes
« Reply #16 on: March 14, 2009, 06:27:32 PM »
David
Good time to consider an upgrade to metal gears. Here ( https://thehobbyistmachinestore.com/catalog/proddetail.php?prod=HS0001 )is where I bought my metal change gears and the quality was very good and customer service was excellent. You can get all the gears for a mini mill for $128.00 plus shipping. Not too bad in my book.

Steve
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Offline Darren

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Re: Mini-Lathe woes
« Reply #17 on: March 14, 2009, 06:31:23 PM »
Nice link Steve,

Did you find they made any difference?

BTW, they are out of stock...shame... :doh:
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #18 on: March 14, 2009, 06:55:39 PM »

Thanks guys, will bang off an email to both suppliers and see when they are likely to get re-stocked.

Darren,

The bush to be machined is the one between the pre-load nut and the inner-race is that right? Did the taper bearings make a big difference?

A very quick search gave me this cup and cone set http://simplybearings.co.uk/shop/p47169/30206+Metric+Taper+Roller+Bearing+30x62x17.3mm/product_info.html Not sure whether this is the right one so I will go into my local place on monday and have a chat.

Thanks again

David
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Offline cedge

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Re: Mini-Lathe woes
« Reply #19 on: March 14, 2009, 07:08:49 PM »
Darren
I only purchased the change gears for the thread cutting. No particular difference noted, but the added sense of security. The mini lathe is designed to allow the motor pulley to fail first, in most cases. It almost acts as a "fuse"in the gear train.  I'd suspect a bit of previous stress was the cause of the failure of your main gears. I've managed to explode that little pulley about 3 times but never had a gear failure on the mini lathe.

You can also get the metal gears from Little Machine Shop and Micromark, which probably explains the why of the out of stock issue. Until very recently, this guy was the only place to get them. Still might be worthwhile to contact him.

Steve
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Offline Darren

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Re: Mini-Lathe woes
« Reply #20 on: March 14, 2009, 07:18:58 PM »
Quote from: Twinsquirrel on March 14, 2009, 06:55:39 PM



Darren,

The bush to be machined is the one between the pre-load nut and the inner-race is that right? Did the taper bearings make a big difference?

A very quick search gave me this cup and cone set http://simplybearings.co.uk/shop/p47169/30206+Metric+Taper+Roller+Bearing+30x62x17.3mm/product_info.html Not sure whether this is the right one so I will go into my local place on monday and have a chat.

Thanks again

David


Yes at the back of the headstock. The taper bearings are sligtly thicker than the standards, that's why you need to skim this bush slightly. It's not much.

Those will be the right bearings, those numbers I gave you are an absolute in the bearing world.

Did the tapers make any diff, couldn't tell you really, my lathe was cutting badly, it always did from new. I put the tapers to try to cure it.

But it wasn't until recently till Bogs got his hands on the lathe was it finally cured. And cured good an' proper too.

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Offline Darren

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Re: Mini-Lathe woes
« Reply #21 on: March 19, 2009, 07:59:34 AM »
How did you get on with this David.... :ddb:
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #22 on: March 19, 2009, 09:28:42 AM »
Hi Darren

recieved the bearings and PLASTIC gears today, I couldn't get hold of the metal versions but I'm going to keep an eye open for them.

I will do a post later when I try to fit it all back together, I'm "in the field" at the moment.

Cheers

David
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Offline Twinsquirrel

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Re: Mini-Lathe woes
« Reply #23 on: March 21, 2009, 04:00:46 PM »
Well this all turned out to be quite simple really, the bearing outer cones were easy to press into the headstock casting..



The inner race was pretty easy too.... the second time around as I forgot the bearing cover the first time :hammer:



once the gear, spacers and the other bearing was fitted, the spacer on the outside was obviously (as you guys predicted) about 4mm too long.



But after some careful fettling without the preload, the key fitted perfectly.



All reassembled and run for a few minutes on at a lowish speed and the re-adjusted I'm amazed at the results, a much smoother cut with no chatter on facing cuts which is where I now realise I was having problems before.

It amazing, I've ended up with a much better machine thanks to you guys.  I only wish I could have got hold of those metal gears but hey, you cant have everything can you  ::)

Thanks to all those who offered help and advice

You guys are the dogs danglies.

David
« Last Edit: March 21, 2009, 04:30:39 PM by Twinsquirrel »
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