New lathe arrived today : The ongoing saga

[Brian JohnParticipant @brianjohn93961]

At least you HAVE lock screws…I do not

I know it is not possible to get it set correctly the whole length of the rails. It has not been machined well enough for that. I just want it set correctly around the middle and close to the chuck ; that will be good enough.

 

Edited By Brian John on 24/10/2015 08:43:14

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 24/10/2015 07:21:13:

… but then there is wobble in the carriage. By ''wobble'' I mean I can wiggle the carriage when I grab it with both hands.

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Brian,

I am struggling to understand what you mean by this ^^^

Give that the carriage runs on two inverted vee rails, I can't see why it would "wobble"

For the sake of my sanity; could you please describe in terms of the standard 'six degrees of freedom'

https://en.m.wikipedia.org/wiki/Six_degrees_of_freedom

Thanks

MichaelG.

Edited By Michael Gilligan on 24/10/2015 09:02:09

[JasonBModerator @jasonb]

Michael as it runs on the rails if the bottom clamps are not tight by grabbing it the carrage will lift which is the "Wobble" Brian describes.

J

PS its one Vee and one flat

Edited By JasonB on 24/10/2015 10:11:19

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 24/10/2015 10:09:47:

Michael as it runs on the rails if the bottom clamps are not tight by grabbing it the carrage will lift which is the "Wobble" Brian describes.

J

PS its one Vee and one flat

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Jason,

"its one Vee and one flat" … Noted

Sorry; I was writing in haste, having ordered Breakfast for 09:00

That said: If the "Wobble" is as you describe, then I think the problem may be largely imaginary.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

It is worth noting that item 219 is identified as 'Klemmplate' or 'Clamping plate'

… i.e. it is not identified as a bearing surface.

It would be interesting to see photos of the surfaces.

MichaelG.

[Brian JohnParticipant @brianjohn93961]

The problem is not imaginary : the reason I had to tighten the carriage in the first place was because of the lousy finish I was getting. Once tightened the finish was perfect. But this tighter carriage situation results in the hand wheel being hard to turn. Trying to loosen things so I can turn the hand wheel freely cause the carriage to wobble again…and so it goes on !

[AjohnwParticipant @ajohnw51620]

The saddle drawing in the manual doesn't make much sense.

I assume 202 going in from the top is for locking the saddle. The other 202 and 220 look like a very crude sort of push pull arrangement. It only makes sense if 220 is used to alter the angle of the plate and both 202's are used to set the fit. The plate doesn't seem to be supported at the other end which is rather odd but there is signs of a hole.

Maybe a photo from underneath might help.

I suspect it will show that some bits have been dropped from the design.

John

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[JasonBModerator @jasonb]

John, Brian has already said that from below there are tow cap heads screws (202) and four grub screws. The grubs open/close the fit and the cap heads lock things into place.

[JasonBModerator @jasonb]

Brian, you were asking the other day about parting off with tailstock support. today I needed a short 7/8" piece of 40mm steel so took a couple of pictures for you.

The 500mm length of bar held in teh 3-jaw and with tailstock support in a small ctr drilled hole. Parting close to teh chuck as its more rigid than doing it down at teh tailstock end

Stop the cut with about 5mm dia left to go, take it out of the lathe and finish with a hacksaw.

[Brian JohnParticipant @brianjohn93961]

I have spent the afternoon pulling the lathe apart to take some photos as everybody wants to see under the carriage and the clamping plate. As you can see, the surfaces are not smooth at all…they are extremely rough but I suppose they do not make contact with each other so they do not have to be. The sliding parts of the carriage that run on the rails are also quite rough. I was surprised at this as I expected them to be finely machined to a perfectly smooth finish.

While everything was apart I took the opportunity to remove the awful purple paint which scraped off easily (it was applied with no undercoat or etch primer).The end result is not in the photos. I also drilled and tapped (3mm) the tail stock side of the carriage to take a lead screw cover when I make one in the future. How did I live without a drill press ?

The carriage does slide smoothly along the rails but as I have said before, the problem is the adjustment mechanism ; it is always too tight or too loose. There is nothing wrong with the lead screw or the clutch.

I have left everything disassembled as you see in the photos. I doubt that there is anything much I can do to improve things before reassembling but somebody may have some suggestions.

I wonder if I have voided my warranty yet ?

NOTE : those  serial taps from Arc Euro are wonderful. It is like tapping into brass !

 

 

 

Edited By Brian John on 25/10/2015 07:05:49

Edited By Brian John on 25/10/2015 07:59:40

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 25/10/2015 06:39:38:

I have spent the afternoon pulling the lathe apart to take some photos as everybody wants to see under the carriage and the clamping plate. As you can see, the surfaces are not smooth at all…they are extremely rough but I suppose they do not make contact with each other so they do not have to be. The sliding parts of the carriage that run on the rails are also quite rough. I was surprised at this as I expected them to be finely machined to a perfectly smooth finish.

…

The carriage does slide smoothly along the rails but as I have said before, the problem is the adjustment mechanism ; it is always too tight or too loose. There is nothing wrong with the lead screw or the clutch.

I have left everything disassembled as you see in the photos. I doubt that there is anything much I can do to improve things before reassembling but somebody may have some suggestions.

 

 

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Brian,

Thank you for taking the trouble to do this … the photos are very informative; especially the one that I have reproduced.

You say:

"…they are extremely rough but I suppose they do not make contact with each other so they do not have to be."

But, it is very clear, from your photo, that this plate is making sliding contact with the underside of the bed rails, and I don't think we have a picture of those … 

If you could manage to photograph the underside of the bed, it might complete the set.

MichaelG.

Edited By Michael Gilligan on 25/10/2015 08:24:56

[Brian JohnParticipant @brianjohn93961]

I am more worried about photo 2 : those sliding surfaces under the carriage should be perfectly smooth shouldn't they ?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 25/10/2015 08:21:53:

I am more worried about photo 2 : those sliding surfaces under the carriage should be perfectly smooth shouldn't they ?

.

On a better lathe, yes … but you get what you pay for.

This is the 'kit of machined castings' scenario, I'm afraid.

MichaelG.

[HopperParticipant @hopper]

Hmmm, looks like you have the basic rough-machined casting kit one hears of.

The very edges of that rough machined "clamping plate" are what runs on the lathe ways at the bottom of the bed. That area really should be a) dead smooth, either scraped or ground, and b) much larger, hopefully there is room on the bed to make a wider plate.

What is the finish on the lower bed ways where that clamping plate runs? Is it rough machined like the plate, or smooth ground the like ways on the top of the bed?

It looks to me like the main top ways have been ground to a reasonable finish. This now needs to be used as the template to hand-scrape the sliding ways on the carriage to match it.

Then the bottom ways will need checking/scraping to make sure they are parallel to the top ways, so you dont get tight and loose spots.

Then the bottom clamping plate needs scraping to match the bottom ways so it bears on a large area that will not wear down quickly.

Then, hopefully either the cross slide ways on the carriage, or the ones on the cross slide itself, are well enough finished to be used as a template to scrape in the other half to match and get it all tightened up and straight etc.

Absolutely not something a beginner can tackle. When you bring it around we can give it a bit of attention and get it sorted properly though. Thankfully the machine is so small it will not take massive amounts of scraping to get it significantly better than it is now. (Bloody hell, an angle grinder could almost get it better than it is now!) In fact, a good seeing to with a millsaw file by an experienced hand will do that clamping plate the world of good and not take very long at all.

 

Edited By Hopper on 25/10/2015 08:39:34

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 25/10/2015 08:36:54:

Hmmm, looks like you have the basic rough-machined casting kit one hears of.

The very edges of that rough machined "clamping plate" are what runs on the lathe ways at the bottom of the bed. That area really should be a) dead smooth, either scraped or ground, and b) much larger, hopefully there is room on the bed to make a wider plate.

What is the finish on the lower bed ways where that clamping plate runs? Is it rough machined like the plate, or smooth ground the like ways on the top of the bed?

.

Hopper,

It looks like we are in broad agreement, but:

Although Brian has rejected my hypothesis; I am still not convinced that 219 was intended as anything more than a 'Clamping plate' [see my post of yesterday]

I suspect that it should be adjusted to run [just] free when the lathe is taking 'sliding' cuts.

MichaelG.

[Brian JohnParticipant @brianjohn93961]

Michael : perhaps I am just tired (only 4 hours sleep today) but I still don't follow. Can you expand your theory a bit for me ?

Trying to get it to be ''just free'' is the problem ; it is always either too tight or too loose.

(I hate picking this thing up. The only thing to hang onto at the heavy motor end is under the flimsy plastic gear box cover !)

Hopper : I just had a look now. The finish on the lower beds is as rough as everything else…perhaps even worse. The interesting thing is that these surfaces are painted and the paint has not worn off. I think this indicates that there is no contact. Aren't the jacking screws supposed to keep these surfaces apart ?

Edited By Brian John on 25/10/2015 09:14:57

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 25/10/2015 09:12:00:

Michael : perhaps I am just tired (only 4 hours sleep today) but I still don't follow. Can you expand your theory a bit for me ?

.

Brian,

I'm ready to be shot-down by anyone with expert knowledge of these lathes, but:

I am suggesting that 219 is meant to be only a 'Clamping plate' [not a bearing] and that the grubscrew adjustment is there to position it at the optimum [] point to serve that purpose … note that the plate appears to be cast iron, so the locking tab will not be very flexible.

You have been trying to use it as a bearing surface, in the hope of improving the lathe's turning performace, but I am not convinced that it's needed, or intended, for that purpose … The cutting forces are taken primarily by downward presseure on the inverted vee slide.

O.K. … That's my version … Bring on the experts !!

MichaelG.

[Brian JohnParticipant @brianjohn93961]

Sorry Hopper, I was looking at the wrong thing. The lower ways are machined but to the same poor standard. Forget what I said about untouched paint…NOT ENOUGH SLEEP !

I think 219 is a clamping plate. I cannot see how it  would work otherwise.

 

Edited By Brian John on 25/10/2015 11:13:10

Edited By Brian John on 25/10/2015 11:13:53

[HopperParticipant @hopper]

Posted by Brian John on 25/10/2015 09:12:00:…

Hopper : I just had a look now. The finish on the lower beds is as rough as everything else…perhaps even worse. The interesting thing is that these surfaces are painted and the paint has not worn off. I think this indicates that there is no contact. Aren't the jacking screws supposed to keep these surfaces apart ?

Edited By Brian John on 25/10/2015 09:14:57

A pic of the underside ways would be real helpful. There appear to be light wear marks on the two edges of the clamping plate, so it has been bearing on something.The jacking screws are supposed to do the same as gib adjustement screws elsewhere on a lathe: to hold the two sliding surfaces together with no excessive slack but with maybe a half to one thou clearance to allow for oil space, not tight. Getting the right balance between free movement and firm seating is a fine art. It goes much better between to smooth, matching surfaces and is pretty much impossible between two rough milled surfaces.

[Brian JohnParticipant @brianjohn93961]

Sorry Hopper, I was looking at the wrong thing. The lower ways are machined to the same poor standard. Forget what I said about untouched paint work…………NOT ENOUGH SLEEP !

I am sorry to confuse everybody.

I think 219 will have to be machined but I cannot see how the lower ways can be improved ; just not enough room. I tried to take a photo but the results are always blurry at night. The flash does not help.

Edited By Brian John on 25/10/2015 11:24:02

Edited By Brian John on 25/10/2015 11:24:23

[frank brownParticipant @frankbrown22225]

That locking tab is an embarrassment, it needs leaving loose and being dealt with as a separate job. I would remove the grub screws and use one shim, because you know where you are with them. If the fixing bolts are left slack then a pair of tool makers clamps can be used (one on each side) to clamp the clamp plate to the underneath of the saddle until the slop is down to a few thou' then try tightening the actual clamp bolts.

I would cut off the locking tab and relieve its thickness at the clamping edge and beyond the hole in it, so it compensates for your shim thickness. Putting the clamping bolt in and tightening it will cause the block to rotate a bit but lock up by interference.

This machine is not a very good advert for far east machines is it?

Frank

[HopperParticipant @hopper]

Posted by Brian John on 25/10/2015 11:18:43:I cannot see how the lower ways can be improved ; just not enough room.

Edited By Brian John on 25/10/2015 11:24:02

Edited By Brian John on 25/10/2015 11:24:23

A careful rub with the right file might be all it needs, or a small scraper.

If you look at the ArcEurotrade articles on fettling mini lathes, it appears the bottom lift plates are designed to be a neat sliding fit on the lower ways.

See points 94-99 here http://www.arceurotrade.co.uk/machineguides/C3-Mini-Lathe-Dismantling-and-Reassembly-Guide.pdf

Slightly different lathe but same basic principle.

Edited By Hopper on 25/10/2015 11:44:16

[Brian JohnParticipant @brianjohn93961]

Frank : What is the ''locking tab'' ? You have lost me there. Do you mean the clamping plate 219 ?

Having had a close look at the working parts of this lathe, I am appalled that this machine could be sold. Had I know it would be this bad, I would never have bought it. It would only have taken them a few hours at the factory to machine everything properly and given the low Chinese wages it would have not added much to the final cost. What we have now is a machine that is good for nothing unless you know how to fix all the problems which should have been fixed at the factory.

I will concede that this is a new model and perhaps later versions will be greatly improved.

Edited By Brian John on 25/10/2015 11:50:04

Edited By Brian John on 25/10/2015 11:51:33

[AjohnwParticipant @ajohnw51620]

It's not that simple a thing for them to do Brian. You have milled ways. To improve that they would have to grind them. They could also improve the milling by doing it more slowly. Both would increase cost and in these days things being sold on the basis of there being a market for items at a certain price doing so would upset the apple cart.

I suspect you would find more or less the same on all hobby lathes.

It looks to me like the plate doesn't actually run on the underside of the rails – just the grub screw tips. Am I correct? In that case the finish on underside of the rails is what matters. The bed is ground so it shouldn't be too much of a problem for them to grind those as the facility to do that would be on any slide way grinder.

John

–

 

Edited By John W1 on 25/10/2015 12:23:50

[JasonBModerator @jasonb]

John the grub screw tips go nowhere near the rails they just set the gap, if you look at the photo of the underside of the carrage marks the grub screws have left

I got curious and rubbed my finger where the similar sort of plates on my 280 bear against, also quite rough milled finish compared to the rest of the bed, now as I can get a good finish on my lathe and a freely moving carrage then is there a need for this surface to be smooth?

A shim is all well and good when packing between two flat surfaces, the 4 grub screws are likely to be a better option if the plate and carrage underside are not flat.

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