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Author Topic: Warco mini lathe / Control board  (Read 2382 times)

Nordlys

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Warco mini lathe / Control board
« on: June 21, 2017, 03:38:51 pm »

Do any members have / used this lathe?
I have blown up two control boards now due to stalling the chuck rotation whilst parting off. 90 a time.
I am on my third  control board ( and last attempt to use the lathe) but I fear the stalling factor is going to occurr
again  -  even with just a small cut it wants to slow down rotation.
Any clues to why this is happening?
Nordlys
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grantl

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Re: Warco mini lathe / Control board
« Reply #1 on: June 22, 2017, 12:38:44 pm »

Parting is a problem for many people, the blowing up of control boards must be very frustrating though.


Seems like you have two problems, the stalling and the blowing up when stalled.


For the stalling, what is the height of you parting tool relative to centre? If it is on or below centre then that is most likely your issue. If the cutting tip of the tool is below centre when cutting then the tool will most likely get pulled in and either break or stall the motor. On light lathes the tool/holder will flex when cutting and a tool that looks on centre will be cutting below centre when under load. If you're in any doubt then shim it up a bit higher, but no more than say 30thou above centre.


Also keep parting tool overhang from the tool holder as short as possible, rigidity is everything when parting off. Google 'gibraltar tool post' for an example of how seriously people take rigidity for this task.


Finally some people swear by using a rear mounted parting tool, but that's probably not really necessary.


Regarding the control boards is there any possibility of fitting fuses between control board and motor? Even if you blow them quite often it might be better than a new board.


Good luck, Grant.




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grendel

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Re: Warco mini lathe / Control board
« Reply #2 on: June 22, 2017, 01:05:21 pm »

I usually part off with the machine running, using a hacksaw, much easier, then if needed the part can be trued up afterward.
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aeronut

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Re: Warco mini lathe / Control board
« Reply #3 on: June 22, 2017, 05:39:16 pm »

Yes, do your parting off with a hacksaw, then re-chuck the piece and face it off.  Normal tooling should be mounted on or just a hair below centre - draw it out and you'll see that any tool deflection will cause the cut to become shallower.  Mount it above centre and tool deflection cause the cut to become deeper, risking a dig-in and a jam up.  If you're boring a hole, then the tool need to be mounted a hair above centre for the same reasons.  A rear mounted toolpost can make parting off much easier, with the tool mounted upside down.  There are people on this forum who have repaired control boards, so might be worth seeking one of those people out.
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Gordon

Nordlys

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Re: Warco mini lathe / Control board
« Reply #4 on: June 22, 2017, 08:07:06 pm »

Thanks for your help.
There is a fuse in the circuit that blew first time this occurred  - subsequent time it did not blow.
I have been pretty careful with lining the parting tool up on centre.  Its nerve wracking winding the tool in to part off
then seeing the cutting stop! Winding in with a bit more force at this point is where the stalling occurrs and board
failing, followed then by max rpm of the chuck!
Since then I use a hacksaw to complete the job - then face up afterwards. Bit amateurish but as you rightly say -  it works.


Warco offer no circuit board repair service and know very little to be of any help. Middle men.
N
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microgyros

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Re: Warco mini lathe / Control board
« Reply #5 on: June 22, 2017, 09:05:11 pm »



Do any members have / used this lathe?
Yes. The very same Chinese one with the Clarke label
Quote
I have blown up two control boards now due to stalling the chuck rotation whilst parting off. 90 a time.
I am on my third  control board ( and last attempt to use the lathe) but I fear the stalling factor is going to occurr
again  -  even with just a small cut it wants to slow down rotation.
Any clues to why this is happening?
Nordlys
Set the High-Low lever to low.
I've repaired a couple of control boards for other owners. You probably cooked one of the two drive mosfet transistors but it is a pi$$ easy diy repair job.
If it happens, take out the controller and identify the two heatsink mounted power components that interrupt the motor drive. Use a resistance meter to test for low resistance between the outer pins which will show up a gate-source failure. If there is a short circuit reading, snip one of the mosfet gate legs and see if that removes the fault. I have a spare transistor but it is a commonly available industry standard mosfet transistor costing a couple of quid.
You may find a "how to repair" on YouTube and others asking on model engineer forums.
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grantl

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Re: Warco mini lathe / Control board
« Reply #6 on: June 22, 2017, 11:30:29 pm »

Normal tooling should be mounted on or just a hair below centre - draw it out and you'll see that any tool deflection will cause the cut to become shallower.  Mount it above centre and tool deflection cause the cut to become deeper, risking a dig-in and a jam up.  If you're boring a hole, then the tool need to be mounted a hair above centre for the same reasons.  A rear mounted toolpost can make parting off much easier, with the tool mounted upside down.  There are people on this forum who have repaired control boards, so might be worth seeking one of those people out.


No I can't agree with that. If the tool is below centre then as soon as you get a dig in the tool is pulled lower and into the workpiece, and the backlash in the slide screws means the tool will readily move further in and become fully jammed/broken. Carbide insert tools are particularly prone to this, and some manufacturers specifically recommend a height just above centre. The info with the tool I use specifies 0.004" above.

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derekwarner

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Re: Warco mini lathe / Control board
« Reply #7 on: June 23, 2017, 12:41:31 am »

"Normal tooling should be mounted on or just a hair below centre"

Well aeronut...all of those years ago...in Australia our Trade Technical Apprenticeship Instructors were more specific at ~~~~ 0.003" below DC when using HSS parting tools

However at work I was fortunate in being under the watch of an older English Toolmaker  ...his specific recommendation...

 "was place the tip of the tool just below DC by about the thickness of a roll your own cigarette paper"   O0

I did measure the cigarette paper & the best average was between 0.002 & 0.003"  :-))

This chap also suggested that HSS parting tools with a flat tapered top rake were rubbish, as the tapered top rake must also include a chip curling radius....[with the radius being about 10 times the thickness of the parting tool]

Still works......one issue not covered here is the cutting fluid specific to the material being machined....

In todays world, tooling manufacturers recommendations for CNC applications [computer assigned speeds, feeds, material grade, coolant flow etc] is text book reference reading only and should not necessarily be confused for a home workshop Myford or SAIG model lathe work

In the end is a Vauxhall better than a Volkswagon?  {-)

Derek
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Derek Warner

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Nordlys

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Re: Warco mini lathe / Control board
« Reply #8 on: June 23, 2017, 10:42:00 am »

A technical question and perhaps Microgyros may have some knowledge as you have the same chinese takeaway!
Since installing the first new board my lathe runs in opp rotation to before.
Of course , I can get round this by using the other rotational button on top ie reverse instead of forward and its ok
Question is why would that have occurred? I thought I took care when reconnecting all wires.......


Nordlys.
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microgyros

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Re: Warco mini lathe / Control board
« Reply #9 on: June 23, 2017, 11:30:34 am »


You might find a few model boat friends have this lathe too. Control box and wear and tear issues are discussed in model engineer forum and the circuit diagram is hand drawn in one thread.
If it is a permanent magnet motor then reversing the motor polarity will change its direction.
The controller version that I have has a reversing switch. If you have the switch it was possibly rotated in the panel cutout.
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Nordlys

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Re: Warco mini lathe / Control board
« Reply #10 on: June 23, 2017, 11:41:46 am »

Hi Micro,
My circuit board has a 1-2 on/off red switch on the board which I know little of its purpose , so did not alter the switch settings.
Im interested in your suggestion to run on  the low speed setting  - what does this acheive please? Is it more torque?
I'll take a look at that forum now.
Thank you.
N
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microgyros

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Re: Warco mini lathe / Control board
« Reply #11 on: June 23, 2017, 12:01:00 pm »


Hi Micro,
My circuit board has a 1-2 on/off red switch on the board which I know little of its purpose , so did not alter the switch settings.
I only briefly looked at a circuit on a model-engineer controller replacement thread long enough to confirm it was the same version that I had. I referred to the top panel on/off/reverse toggle with the usual groove in the threaded neck so that it won't rotate when panel mounted. This is what you may have rotated by a half turn
Quote
Im interested in your suggestion to run on  the low speed setting  - what does this acheive please? Is it more torque?
I'll take a look at that forum now.
Thank you.
N
The lever is a manual gear ratio changer. It will double the torque on the low speed setting. It should be 2000/1100 rpm on hi/low at maximum pot rotation.
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microgyros

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Re: Warco mini lathe / Control board
« Reply #12 on: June 23, 2017, 12:52:21 pm »

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