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  #61  
Old 10-06-2020, 03:01 PM
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Great project Bojan.
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  #62  
Old 10-06-2020, 03:02 PM
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Quote:
Originally Posted by bojan View Post
One pair of calipers (now on standing drill cross vice) was really hardened and not easy to drill.
Another one (currently on that home-made lathe) was made of "white brass", so easy to work with. I would like to get some more, but when I ask vendors about material they swear their products are made of "best quality stainless steel"...
My son was a Welder/Boilermaker until some one talking on there phone rammed his bosses work van and broke his back -- at last he is still on his feet. They got in some best quality steel girders from China. At one paint you could see the engine number of a Car engine block that was made into that girder. Parts of the steel were very hard, other parts were soft.

So wondering if your "Bst quality Stainless steel" has the same problems.
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  #63  
Old 10-06-2020, 04:35 PM
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Quote:
Originally Posted by JohnF View Post
... So wondering if your "Bst quality Stainless steel" has the same problems.
My calipers were made of "white brass" (copper alloy with zinc added).
When I was cutting them, the material behaved exactly like brass (it felt like slippery) - only it was silver-white colour.
Casting signatures are easily visible on attached images...
Those calipers were cheap ($10) but very easy to modify...
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Last edited by bojan; 10-06-2020 at 04:45 PM.
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  #64  
Old 12-06-2020, 06:39 AM
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Yesterday I discovered a potentially dangerous bug in original motor controller firmware..
Something went wrong while I was cutting a metal rod and my instinctive reaction was to quickly turn the potentiometer knob to the left to stop the spindle rotating (instead of hitting the emergency button..)... but there was no expected effect - the spindle continued rotating.

Later I experimented a bit and yes - only relative slow(er) movement of pot controls the spindle, but quick change doesn't.

This is another reason to replace original processor with AtTiny..
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  #65  
Old 14-06-2020, 10:24 AM
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While searching for ideas for DRO (Digital Read Out) for lathe (because calipers are not long enough), I remembered I saw something about PCB strips for them...

Some more search and I found this:
https://www.ebay.com.au/itm/Replacem...53.m2749.l2649
The pattern pitch is the same as used with cheap Chinese calipers... Perfect solution for my case.
I plan to stick this strip to 16x3mm aluminium flat bar, available at Aluminium Trading Centre, and use it with one of standard caliper reading heads.
Perhaps connect it to Arduino LCD display which could then be conveniently placed somewhere on the machine...


Something like this:
https://www.thingiverse.com/thing:1731982

Last edited by bojan; 14-06-2020 at 10:38 AM.
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  #66  
Old 17-06-2020, 10:08 AM
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DRO prototype works...
For now only one sensor, and only one readout (displayed as x and y).


I noticed when caliper is in imperial mode, DRO displayed value doesn't match reading on caliper LCD.. so, this f/w version works only in mm mode.
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Last edited by bojan; 17-06-2020 at 10:43 AM.
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  #67  
Old 17-06-2020, 12:04 PM
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This is absolute artwork that you have done on this machine Bojan.

In a better world, you would be able to sell your design back to the manufacturer. Bugs like described in post #64 are unforgivable on their account.

In practise, they'll keep selling these units as is, to everyone ongoing. Only you have a good one now
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  #68  
Old 17-06-2020, 01:00 PM
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Quote:
Originally Posted by AndyG View Post
.. In practise, they'll keep selling these units as is, to everyone ongoing. ...
Yes, unfortunately this is true..
However, there is a lot more to do, I've only started..

For example, I am still not sure about both slides precision.. most likely I will have to ground them.. There are lots of videos on youtube discussing those issues.
I did offer the processor solution to them, but they ignored it


Attached below is where to mount the scales....
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Last edited by bojan; 17-06-2020 at 01:12 PM.
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  #69  
Old 21-06-2020, 06:45 PM
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I just found this thread, very interesting bojan. There are two versions of what is commonly referred to as the Chinese mini-lathe. Yours is the slightly bigger, and supposedly better, version. A chap on another forum I'm on bought the same one you did and had no problems with it. I bought the smaller, more common version. My controller lasted two weeks! The seller couldn't supply a replacement board, which I asked for. I won't go into the details but I fought long and hard with them (and ebay and Paypal) and got nowhere! In the end I bought a stand-alone controller off ebay ($30) and fitted it to the lathe. It's been fine since then.



I spent time on mine taking out high spots on the ways, smoothing and adjusting the slides, modified the compound slide so I don't have to remove it to change the angle and fitted a tacho. There's lots of info on the 'net about these lathes and the controllers. The best option for these lathes is to replace the motor and controller with a 3-phase motor and VFD as this is their weak point.


I was extremely annoyed with the dealer I bought this off so bought another one! My intention was to replace the controller and then send the faulty lathe back for a refund. Long story short after three months fighting with ebay and paypal and after involving the Australian finance authorities Paypal grudgingly gave me a refund (and I kept the lathe).


A bit of advice to anyone buying off ebay, if you have problems only use ebay to fight any claims, paypal policies are NOT consumer friendly and once you seek help from paypal ebay will no longer help you.


My little lathe is very useful for working with small items, much better than trying to work with small stuff on the bigger lathe.
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  #70  
Old 22-06-2020, 09:48 AM
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Quote:
Originally Posted by dikman View Post
... My little lathe is very useful for working with small items, much better than trying to work with small stuff on the bigger lathe.

Yes, it is very useful.
The last hurdle will be obtaining the new cross lead screw, as the original is eccentric...
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  #71  
Old 22-06-2020, 01:17 PM
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It's a real lottery when you buy one of these as to how it's been built. There are several factories that build these things, supposedly to the same specs. The second one I bought, from the same seller, looked the same physically but was noticeably different in quality. It came from a different manufacturer, the ways were smoother, with no binding, the controller board was built differently but was a straight swap and the motor was only 400w. This was the point of contention as it was advertised as 550w (the seller told me it didn't matter what was marked on the motor - 400w - it was really 550w!!!!!). I have realised that most of these Chinese sellers on ebay are, in general, crooks.


I was going to sell the second one but instead gave it to my son-in-law.
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  #72  
Old 22-06-2020, 01:31 PM
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Well, that depends on definition of "crook".
I think they are just sellers who want to make a buck, without knowing what they are selling and doing really.. at least in my case.
The outcome is the same...

But.. at the end, the machine will be worth $900 I paid for (I think..)
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  #73  
Old 22-06-2020, 04:05 PM
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In some cases you are right, but it's when you have problems and contact the seller that you discover what they're really like. You haven't done too badly because at least they tried to help.
In my case the lathe was made in China but stored and shipped to me from a warehouse in Sydney. One would assume that a return would be to the shipping address it came from (which, I believe, is what the ACCC says). In order for Paypal to give me a refund they require it to be returned first and the return address I was given was in England??!! Shonky? Just a little bit.


The other chap I mentioned that bought one like yours is very happy with it and found it to be quite accurate, given that it's not a high precision build. It's certainly a better design than mine, I looked into them but it was going to cost double what my little one did and seeing that I already have a larger lathe I didn't want to spend that much. As you've no doubt found there is a lot of info on youtube and the 'net about using these little lathes, plus various mods to do to them. I bought a quick release toolpost, which I see yours has, and a set of replaceable tip carbide tools, both of which make life much easier.


Once you get it sorted I'm sure you'll feel it was worth it. If you like making things then a lathe is almost a necessity, in my opinion.
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  #74  
Old 22-06-2020, 04:45 PM
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Quite so.

The quick release toolpost I had from my DIY lathe. As well as some tools I accumulated when working with it...
Well, this one is certainly better than DIY
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  #75  
Old 22-06-2020, 07:07 PM
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I just read your thread, that is an impressive bit of fettling you did!
Now you start all over again modding this one.
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  #76  
Old 22-06-2020, 09:31 PM
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... Now you start all over again modding this one.
So it seems..
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  #77  
Old 30-06-2020, 11:48 AM
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While waiting for new cross lead screw (original one is eccentric.. obviously done on couple of different not so good machines, seller finally promised a new one), I am working on steady rest.... at the same time trying to improve my currently not-so-good welding skills..
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  #78  
Old 01-07-2020, 06:48 PM
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Welding tube like that with an arc welder requires lots of practice and a delicate touch - I am also very good at blowing holes in metal!!!! I eventually bought a MIG (much easier to weld thin stuff) and then went to shielding gas. Not a cheap option but worth it, particularly for doing small jobs.
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  #79  
Old 08-07-2020, 02:43 PM
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The lead screw arrived today, I installed it and since it is concentric, I was able to reduce the backlash down to 0.01 mm, with knob still moving smoothly.
Now the machine is ready for hyper-tuning :-)


EDIT: backlash is not 0.01, it is ~0.04 mm, this is probably the limit (screw/nut play)

Last edited by bojan; 09-07-2020 at 09:52 AM.
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  #80  
Old 09-07-2020, 08:40 AM
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0.01 mm! You've got to be happy with that.
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