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Warco wm 250,cutting and motor problems

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sam Freeman31/03/2022 15:10:11
5 forum posts

I have a Warco WM 250 lathe, its mounted on a very robust frame of heavy box section steel Tubing, that came with the lathe. also this is the model with only one drive belt.

Problem one. After buying this lathe S/H, I was quite disappointed with its Performance in regard of depth of cut and surface finish. It had been fitted with a quick change tool post, This was the cause of some problems. As the original TP had been cut cut off low down and drilled and tapped with a stud (I assume to accommodate the higher tool holder. The problem was that the new stud mounting was not only drilled off centre but in material that couldn't accommodate the size required it was only a few thou bigger that the thread on one side.You could move the tool post by hand. To rectify this I have removed the compound slide assembly (for later repair) and replaced with 2 one inch blocks of steel mounted in theT slots of the cross slide, the tool post now consists of a 9/16 UNF bolt and is quite solid or so I thought. Last night I was removing some weight from a rotating drum assembly and not only could only take cuts of a thou or so it would also dig in suddenly and stall the lathe. Has anyone any thoughts on what could cause this?

I have plans to fit new headstock bearings sometime.

Problem two, Due to the cutting tool digging into the material a few times it has probably over heated the motor because at one point the spindle stopped and I could not turn it at all by hand, I stripped out the gear cover and removed the belt.by this time had cooled down a bit and the spindle turned freely by hand.Tried the motor with belt off and that runs fine, Not sure about under load though.

Later on I am going to remove the motor and check the brushes etc. Advice welcome.

Thanks in advance,Sam

Bill Phinn31/03/2022 23:40:53
768 forum posts
114 photos

Can you possibly link to a brief video clip, Sam, showing us what's happening when you experience the first problem you describe?

Hopper01/04/2022 00:11:39
avatar
6729 forum posts
348 photos

So the spindle seized up and could not be turned by hand?

Either spindle bearings or motor bearings could be nipping up.

I would not continue stalling your motor. It seems to be a weak point on some Chinese lathes that doing so destroys the motor control circuit board and is expensive to replace.

Did the spindle bearings or motor bearings feel very jot to the touch?

Edited By Hopper on 01/04/2022 00:12:25

Tony Pratt 101/04/2022 08:51:14
2035 forum posts
12 photos

Try running the motor with no belt & see how that feels, also rotate the spindle by hand, as previous reply a video paints a thousand words. Not sure why a 2 thou cut would make the tool dig in unless you have serious tool post flex, loose tool, tool sticking out too far, etc. etc.

Tony

Edited By Tony Pratt 1 on 01/04/2022 09:05:46

sam Freeman01/04/2022 13:12:55
5 forum posts

Thanks for the speedy replies. No video I'm afraid was already in bits by that time.

Motor was Hot, spindle had a slight tight spot when rotating by hand, bearings were not as bad as I thought they would be, replacements have been ordered,

Motor removed, bigger than expected and also cleaner, pulled it apart, brushes look ok and equally worn, one brush had several coils closed up so has been very hot sometime. Armature looked rusty one end looked as it it had rubbed on the magnets. it was paint! Bearings seem fine, the commutator was black. I put it in the Myford and gave it a 5 second rub with green scotchbrite and it looks fine. there was bit of a rattle when turning the motor I was a loose plastic fan on the brush end of the motor.

Bad news from Warco is that it is an early model that is no longer produced, I'm sure I can find some brushes and probably a fan too. to get it up and running while I get the parts together to convert it to 3 Phase and inverter set up.

I have pictures just need to figure out how to put them up.

thanks everyone

Edited By sam Freeman on 01/04/2022 13:13:21

SillyOldDuffer01/04/2022 14:54:22
Moderator
8913 forum posts
2000 photos

Welcome to the forum Sam.

Pictures help with this sort of problem, and how to post them on this forum is described here <link>.

My first reaction is the two problems are connected:

  • Motor overheats because the tool digs in, Noting that the previous owner probably had repeated dig-ins, and may have kept going regardless.
  • Assuming a sharp cutter is correctly set at centre height with minimum overhang, digging-in is usually caused by the tool-post flexing. I'm not clear how your temporary steel block and big bolt are arranged but I suspect it's not stiff enough either. A photo of the arrangement would help even if the lathe is bits. The force exerted on a tool-post by a properly positioned sharp cutter is surprisingly high, and much higher if the tool is below centre, blunt, well away from the tool-post and is hacking into a nasty lump of scrap such as work-hardening stainless steel.

Maybe the motor's damaged, but don't rush to change it until the mechanical tests advised by Tony and others have been tried. Be really annoying to fit a costly 3-phase and VFD only to find the real problem is something else...

Never mind, every cloud has a silver lining - diagnosing and fixing the problem will be highly educational!

Dave

not done it yet01/04/2022 15:27:14
6891 forum posts
20 photos

Have you read the review by ‘Journeyman’? That should be enlightening - he is a forum member.

At a current new-price of over two grand for a variable speed jobbie, the lathe should be worth up-grading to a three phase motor with VFD, IMO. Providing there are no other insurmountable problems, of course.

WCTPs are not perfect. They can provide problems with light-weight lathes and inexperienced users. Large diameters.

High power at low speed is a potential killer of electronically driven brushed DC motors. A loose cooling fan would obviously exacerbate that situation. Every motor run at low speed will have less than designed cooling air flow.

A spindle with a single tight spot may indicate something is bent or a wrongly clearanced (or out-of-round) gear. Was this with the lead screw being driven?

Howard Lewis01/04/2022 15:38:37
6317 forum posts
15 photos

Brushes.

Take them along to a local motor repair shop. They might be able to find you suitable replacements, intended as spares for something like a pistol drill.

Send the dimensions of the brushes to Ketan at Arc Euro. They might have something suitable in stock.

If the tool dug in with only a 0.002" cut, something is seriously wrong.

1 ) Rigidity of tool [post / Cross Slide

2 ) Tool not on centre height (Lack of rigidity could give the same effect

3 ) Grossly excessive feed rate

4 ) Possible excess top rake on the tool., I do a lot of work with Zero Top Rake. (The parting tool in the rear tool post is one such example. ).

If it were me, I would seriously explore ways of reverting to a four way tool post, if possible. This should be more rigid than a QCTP, because of fewer interfaces and reduced overhang.

You could make a four way post by laminating suitable pieces of plate (I made a four way indexing rear toolpost for my lathe (Take a look at my albums for a couple of pictures )

Like me, you may not be able to locate each position by a spring loaded pawl, I used a long dowel to do the job!

Howard

BC Prof01/04/2022 17:04:10
169 forum posts
1 photos

As Howard suggests lack of , rigidity .is the key . Can you lift the cross slide vertically. ? Possibly due to poor

assembly . On my gh600 the cross slide lock is supposed !!! !to work by tightening up the right hand hex head

to clamp on the underside of the bed .

If your lathe uses a similar system you could try locking the cross slide before moving the tool in to touch the bar

or try taking a facing cut..

Brian

Journeyman01/04/2022 18:28:48
avatar
1174 forum posts
236 photos

Sam, it sounds as if your WM250 might be even older that my 2007 version. The lathe still works well although probably quite lightly used compared to some here. The DC motor does indeed run hot despite the fan, being tucked away at the base of the headstock there is little in the way of free air circulation, I considered fitting a computer style cooling fan to help but never got round to it. Where possible I keep my lathe in the low speed range so that it can run with higher motor speeds, this helps both for cooling and for power.

A few things I found which help rigidity:

  • Check the rear saddle gib strip mine was loose on delivery, this stops the rear of the saddle lifting.
  • Check the guide blocks at the front of the saddle these will probably need fitting by filing, machining or rubbing on abrasive paper. Unfortunately not adjustable so it's a one way trip don't overdo it.
  • Check the cross-slide gib strip and adjust carefully. Stops side to side play and snatching.
  • Check the top-slide gib strip. If not in use clamp up with the allen head screw.
  • Adjust the change gears to ensure they are not too tight, use paper between the teeth.

I use a QCTP on mine without any problem but sounds as though yours might be a bit awry. I made a cross-slide toolpost to avoid any chance of play or rigidity problems from the top-slide.

As NDIY has kindly already given me a plug above here are some relevant links to my website:

WM250 review (this is a bit long in the tooth now) 4 pages
QCTP 1 - cross-slide toolpost
QCTP 2 - top-slide modes

There are a few other bits on the lathe, I will leave you to find your way around, hope it helps.

John

bernard towers01/04/2022 19:55:49
693 forum posts
141 photos

How can the tool dig in when turning if tool is at centre height????

Edited By bernard towers on 01/04/2022 19:56:25

Emgee01/04/2022 20:13:15
2446 forum posts
291 photos
Posted by bernard towers on 01/04/2022 19:55:49:

How can the tool dig in when turning if tool is at centre height????

Edited By bernard towers on 01/04/2022 19:56:25

Too deep cut with lack of power to the spindle.

Emgee

JasonB01/04/2022 20:24:51
avatar
Moderator
23088 forum posts
2774 photos
1 articles

If the tool is being pushed off the work because it's blunt or not on ctr eventually there will be no more flex for it to be pushed off and it will take a big bite

Mick B101/04/2022 21:08:36
2227 forum posts
125 photos

I've stalled my WM250V several times over the 7 years I've had it. It's saved me a few broken tools and more damaged workpieces, and I've had no electrical or electronic problems with it at all.

It's not a bug, it's a feature!

laugh

Howard Lewis02/04/2022 07:52:34
6317 forum posts
15 photos

Bernard,

Parting tools, sharp and set exactly on centre height, will occasionally dig in, even with feed rates as low as 0.002" (0.050 mm) per rev.,.

Higher feed rates are even more likely to cause a dig in, in my experience, even with a rear toolpost.

Howard.

sam Freeman02/04/2022 08:48:45
5 forum posts

Wow, thanks for all the replies,I will work through them later as I have a transmission to build today.

Sam

Tim Stevens03/04/2022 11:39:31
avatar
1623 forum posts

I wonder - was your 'rotating drum assembly' possibly made of brass? Very inclined to grab, brass is, pulling the tool into the work. Just a thought.

To stop this effect, take the sharp edge off the tool with a fine stone - 5 to 10 degrees of negative rake - taking off as little as possible so you can restore the tool for steel. Or, keep a few tools for brass, ready stoned, if you use it regularly.

Cheers, Tim

SillyOldDuffer03/04/2022 12:52:05
Moderator
8913 forum posts
2000 photos
Posted by bernard towers on 01/04/2022 19:55:49:

How can the tool dig in when turning if tool is at centre height????

...

Easy, just follow this bad advice:

1. Wind the top-slide fully to the left

dsc06580.jpg

2. Clamp the cutter in the tool-post at maximum extension:

dsc06579.jpg

3. Grip a long job in the chuck, and don't support it at the cutting end

dsc06578.jpg

Aficionados can improve on this by fitting a QCTP, loosening the gibs, not locking unused slide-ways, using a blunt cutter, turning a grabby metal like Bronze, and attempting a greater depth of cut than the lathe is fit to take. What a lathe is fit to take varies considerably - might have been lightly built in the first place, have an old-fashioned narrow saddle on a twisty bed, and the bed and spindle bearings might be worn sloppy.

Considerable force is needed to cut metal. As every force has an equal and opposite reaction it's important not to multiply it by creating anything resembling a lever in the set-up. Everything bends, so avoid accidentally crowbarring the lathe as shown in my photos!

Dave

 

Edited By SillyOldDuffer on 03/04/2022 12:53:20

Howard Lewis03/04/2022 16:35:43
6317 forum posts
15 photos

Yes! See what you mean, make things an flexible as possible. That should prove the benefit of maximum rigidity in work holding and tooling.

Strange how reducing tool overhang by a little can change things from poor finish with screaming chatter to a good finish in comparative silence, or at least pleasant sound effects.

For anyone who is interested, in my shop, parting off is usually done with a slow drip feed of soluble oil,on to mthe tool, sypnoned from a bottle above the lathe, to a nozzle held on a small magnetic base on the cross slide.

Howard.

Niels Abildgaard03/04/2022 20:33:27
431 forum posts
163 photos

The rigidity of the Emco/WM tool compound system is a practical joke/offence.

Standard EMCO copy

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