Turned out nice

Martin Shaw

Western Thunderer
Steve
The backplate comes pre machined and drilled and in theory should be a bolt together exercise. There are really two problems, the recess in the backplate for the spindle register is v slightly oversize, maybe 0.1mm cos it's difficult for me to measure it more accurately which has a bearing, and the unsymmetric drilling for chuck mounting. I've to a large extent solved the second problem, the first remains. Ideally you are wholly correct that backplates should be machined in situ, howver the state of the machine would have precluded this until recently. I purchased the machine to make model things with, thus far I have been far too intimately involved with fixing the poor assembly of all the bits, which individually are actually made quite well. I do now know a lot about the innards of Sieg lathes.

I had a long conversation with Arc this afternoon about the state of play, they readily admit that assembly of the components of a lathe/mill is too variable but that changing that and keeping the machines affordable is probably a non starter. I said I would check the runout of the 4" chuck assembly and depending on that outcome they would happily supply an unmachined and undrilled backplate gratis, so good customer service. The other problem is that a lot of their sales are to persons who have limited or no knowledge and experience and as such are unable to undertake the sort of work I found necessary, not that I claim to be anything other than a beginner with a modicum of common sense. Hopefully I can get back to modelling in the not to distant future. BTW the little Decauville is sweet.

Regards
Martin
 

JimG

Western Thunderer
The other problem is that a lot of their sales are to persons who have limited or no knowledge and experience and as such are unable to undertake the sort of work I found necessary, not that I claim to be anything other than a beginner with a modicum of common sense. Hopefully I can get back to modelling in the not to distant future.

Martin,

Arc Euro used to offer a setting up service for Seig machines for an extra charge. I think I remember it being around the £75 - £100 mark and I believe that they checked over and cleaned the new machine before sending it out. But I think they withdrew that service a year or two ago and I don't see it offered on their site these days.

I got my Seig KX1 mill from Arc and that was in excellent running condition from new. I'm not sure if that was down to Seig or Arc but I didn't pay a set up charge and I can only assume that the CNC mills received more attention.

Jim.
 

Martin Shaw

Western Thunderer
Jim

Arc no longer undertake setting machines up, I gather from them that despite charging for it sometimes it also ate into the probably quite low profit on the machine itself.
I think the quality of assembly of a machine is a bit of a lottery, two workers in a Shanghai factory despite starting with the same collection of parts will produce vastly differing end products. I think I have just been exceptionally unlucky with mine.
Regards
Martin
 

Steve Cook

Flying Squad
Sounds like a very trying time Martin, I suppose the silver lining is that you'll certainly not be afraid of using the machine when its ready! I see what you mean about the register being slightly oversize, that really compounds the issue. I'll keep my fingers crossed that the runout on the 4" is satisfactory, although I'd still be tempted to take ARC up on the offer of an unmachined backplate and prepare it properly - with any luck (and you are due some) the register will be OK and you can then have a dedicated backplate for each chuck.
Thanks for the comment on the Decauville - its sitting in front of me as we type :) A friend of mine had said he was tempted to buy another just to look at (the first one is for running) - I didn't understand then....

Steve
 

Martin Shaw

Western Thunderer
with any luck (and you are due some)
Frankly this has been the least of my worries this year. The executry I am dealing with has had major property issues, and my father, bless him, is failing rather quicker as each month passes. The passage through this life is sometimes rocky, at least WT keeps me sane.

I'd be interested in what you think is an acceptable run out on the chuck?

Regards
Martin
 

Martin Shaw

Western Thunderer
Just a small update, I've had a rigorous measuring session on the lathe. The radial run out on the spindle register is 0.01mm, not perfect but acceptable. The run out on the back plate register is 0.09mm, definitely not acceptable. The chuck itself shows a run out of 0.12mm, which seems to be the back plate plus a little bit for the chuck. If the backplate were running concentrically we might be looking at a run out of 0.04mm, or 1.6thou in old money. This isn't stunning but for a Chinese made lathe for £700, isn't too bad and I don't think anything I'm going to do is going to compromised too much. Whether this is achievable without resorting to making back plates I don't yet know. Anyway I've written up the whole saga for Arc, basically telling them that whoever manufactures the backplates is either not doing it accurately enough, or they are not quality inspecting, or probably both, and asking if they can supply accurately made parts. We'll see what they say, I suspect I know the answer.

The lathe bench is now far too small, and in reality the wrong height so more woodwork soon.

Regards
Martin
 

Brian McKenzie

Western Thunderer
Martin,
I'm not sure just what options you may have in assembling the chuck/backplate/spindle components. Can you rotate the chuck on the backplate, such that one error might help cancel out error in the other?
Another solution might be to re-machine both backplate and chuck registers, and fit feeler gauge material of the appropriate thickness as spacers.
-Brian McK.
 

Martin Shaw

Western Thunderer
Hi Brian
Unfortunately I think I have explored all the available options with the parts I have, there is no doubt that the back plate is poorly made and in that respect I feel the remedy lies with the supplier. Yes I can remachine things or make from scratch, and I have a friend who has offered to rough out new backplates on a big Colchester leaving me to do final finishing on my machine if necessary. Just at the moment I have done enough to try and rectify shortcomings of the supplied parts, I'm going to let the supplier earn their corn for a bit.

I would feel really sorry for a complete newcomer faced with all this though, it would put them off machine tools completely, I rather lost patience with it all at one point.

Regards
Martin
 

Martin Shaw

Western Thunderer
It's been a month since the last set of ramblings but I can report a major positive breakthrough, but firstly the 4" backplate saga. In discussion with Arc I informed them that both of my backplates had an over sized recess for the spindle register. This obviously rang an alarm bell in Syston, and it appears that their whole stock of finished 4" backplates had the same problem, and rather more surprisingly they had them made in China. To establish where the problem lay was inevitably going to take some time, so Arc kindly sent me a backplate with the spindle register cut but otherwise unfinished. This fitted the spindle perfectly, which I like to think justifies my approach. As an aside I find it difficult to believe that it is more economic to import what is essentially a steel disc with holes from China, than find a CNC workshop in the Midlands to do it, or has manufacturing in Britain been so massacred.

Since the 3" chuck fitted properly I thought over new year to make a couple of thumbscrews to hold the gear cover. This started well, until there was an almighty dig in, that stalled the lathe. I was unchuffed to the point of almost heaving the whole lot out through the skylight, having calmed down and despite a lot of previous effort to make the compound and top slide gibs work well, the real problem was with the saddle and it's retention or lack of, to the bed. The original uses two set screws to set the height of the retaining strips from the saddle, and is retained in place by three cap screws. The strips are supposed to be hardened but judging by the wear on my hardly used examples, don't figure on the Rockwell scale. The other issue is that if you snug up the cap screws to remain tight they lock the saddle, and if you leave them loose enough for the saddle they unscrew themselves over time, coupled with the rather generous lack of engagement of chinese threads makes the whole thing utterly hopeless. The final insult is that the optimum set up tips the retaining strips so that they run against the corner of the underside of the bed. Basket weaving loomed as an alternative hobby yet again.

Whilst realising that this needed solved before I could attempt machining the backplate and pondering what to do I came across a gentleman on Youtube by the name of Steve Jordan, who was an aeronautical engineer, and he had a series of vids on sorting out Chinese mini lathes, including rather helpfully one on sorting out the saddle. It looked simple enough, some bits of steel bar, some drilling and tapping and assembly, so I watched it again and realised I could do this. I visited a local steel stockholder and said to the boy I need some bar 25 by 10, "how many metres sir", so I said about a foot which confused him. We found a bar end which he generously said "its worth washers so have it", some decent folk out there.
IMG_0464.JPG
This is a bit of 10mm bar fixed to the rear of the saddle, I had planned to counterbore for the cap screws, it would have been a good idea to check which side was uppermost in the vice before anything was done, I didn't so they are remaining proud. The grub screws lock down on the retaining strip helping to prevent any lift under load.
IMG_0463.JPG
This is the finished end view, the bar in the upper pic is to the right, the cap screws have been replaced by studs and the whole assembly is retained by nyloc nuts which have a reasonable chance of remaining in position The shims were a bit trial and error, in the end they are 0.8mm. As you can see the retaining strips now sit parallel with the underside of the bed providing maximum support and the adjustability of the nuts by a spanner is much more user friendly than set screw and locknuts. It works beautifully, the saddle lift is better than half a thou front and back, I can lock it harder at the back, say when parting off, yet it retains a sweetness of operation, certainly better than the original. I'm rather pleased with this. Onwards and upwards, might try cutting something tomorrow and see whether it's been all worthwhile.
Regards
Martin
 

JimG

Western Thunderer
Martin,

That looks like a good job.

On getting a backplate machined in the UK, that would be possible but the problem would probably be the price. A company like Arc Euro might only require a stock numbered in tens and if you want runout and fit limited to a few microns, then the unit price would probably be well above what people might want to pay. I have had some discussions with suppliers when seeking turned parts for the S Scale Society parts department and one of the key criteria are the tolerances required. The tighter the tolerance, the higher the unit price goes. I bet there is probably one factory in China churning out thousands of these backplates to supply all the lathe producing companies and hence the unit price can be quite low. The accuracy of machining probably depends on whether it was a Monday morning run. :) Quality check is by you, the consumer. :) It probably makes better financial sense for Arc to have a selection of these inexpensive Chinese backplates to exchange with customers rather than supply locally made, but quite expensive, parts.

My own gripe with these Chinese machines is with their tapered gibs. I have one on the head of my KX1 mill and I can't get it set to my satisfaction. To work correctly it must be absolutely straight and the taper match the taper of its seat and I suspect that really demands the same tolerances as your chuck backplate to work correctly. I would dearly love to change it to a "normal" gib with a set of adjusting screws but I suspect that would need some hefty work on the head which I can't really handle - i.e. re-machining the seat for the parallel gib.

Jim.
 

adrian

Flying Squad
In discussion with Arc I informed them that both of my backplates had an over sized recess for the spindle register. This obviously rang an alarm bell in Syston, and it appears that their whole stock of finished 4" backplates had the same problem, and rather more surprisingly they had them made in China. To establish where the problem lay was inevitably going to take some time, so Arc kindly sent me a backplate with the spindle register cut but otherwise unfinished.
If it helps I have a spare 100mm (4") backplate, the recess on the rear is 55mm and 72mm step on the front.

A nice job on the saddle - I might have a look at doing the same mod.
 

David Taylor

Western Thunderer
You must feel great satisfaction in having made your machine better than when it arrived. It's annoying these things are so dodgy out of the box - I have a milling machine with various problems I have not managed to fix yet, and a 3 jaw chuck with a sticky jaw, will have another go over winter this year - but I'll feel good if I do manage to sort it out!
 

Martin Shaw

Western Thunderer
David
Thank you for your kind words, I am indeed somewhat satisfied by overcoming the deficiencies of the machine. By contrast the milling machine hasn't really had any major problems other than some of the choices made in the design process are sub optimal. I think the major limitation with this class of machine is that the customer, you and me, want a Rolls Royce for Mini prices, if they worked perfectly out of the box then the price would be way beyond most of us. Caveat emptor as the Romans said.
Regards
Martin
 

Rob Pulham

Western Thunderer
I went along to Leigh show today, and chanced upon a small Unimat SL on the bring and buy within the budget that I hadn't planned so home it came with me.

It came with a 3 jaw chuck a spare Jacobs chuck (which actually doesn't appear to fit it but hey ho) a small machine vice which is current mounted where the tool post should be but when I got it the machine was set up as a milling machine which I suspect it's so. It also had a few clamps and a collet holder and some collets for holding small diameter bar or tube.

What it doesn't have and I will need to source are some cutting tools and a tool post. I suspect that I could use the vice but I would prefer a tool post. Any ideas on sources would be gratefully received. Ideally those that won't entirely break the bank in the first instance....

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Rob Pulham

Western Thunderer
This does mean that once I get set up I should have to prevail upon the good graces of Adrian in the future (I hope!)
 

adrian

Flying Squad
What it doesn't have and I will need to source are some cutting tools and a tool post. I suspect that I could use the vice but I would prefer a tool post. Any ideas on sources would be gratefully received. Ideally those that won't entirely break the bank in the first instance....

Congratulations a really nice little unit, especially with the post for milling.


RDG Tools have a couple of toolposts.

A simple and cheap toolpost

Model Engineering and engineering tools online from RDG Tools Ltd Home Page (Engineering Tools) Tel 01422 885069 /884605

Or a quick change one although slightly more expensive.
Model Engineering and engineering tools online from RDG Tools Ltd Home Page (Engineering Tools) Tel 01422 885069 /884605

with additional tool holders
Model Engineering and engineering tools online from RDG Tools Ltd Home Page (Engineering Tools) Tel 01422 885069 /884605

Regards

Adrian
 

Martin Shaw

Western Thunderer
Well done Rob, good find. You need to be aware that the motor is not rated for continuos running, shouldn't really be a problem for the sort of work were doing, but nonetheless ca canny. Adrian's post is defintiely the way to go however if you can stretch the elastic far enough go for the quick change toolpost, shimming tools for the correct cutting height becomes a real pain very quickly.
Regards
Martin
 

adrian

Flying Squad
however if you can stretch the elastic far enough go for the quick change toolpost, shimming tools for the correct cutting height becomes a real pain very quickly.
To be honest I think to get started the plain toolpost is sufficient, especially if you are turning brass.

I have a quick change tool post for my mini-lathe but the locking mechanism for setting the height doesn't seem to be that good. I always seem to be double checking and adjusting the centre height every time I change a tool. So now on my "quick" change toolpost I have my parting tool on one holder (adjusted to be slightly above centre height), my Scale7 form tool on another holder and everything else is fitted to the 3rd holder.

As you don't need any rake angle on the cutting tool for brass once you have sorted out the shimming required for one tool then you can use the same shimming on all the other cutting tools fitted to the toolpost. You may need to adjust it if you start turning other materials.
 

Martin Shaw

Western Thunderer
Fair comment Adrian, perhaps you should be looking at the quality of your QCTP, I wouldn't revert to fixed arrangement and why limit yourself to one metal unnecessarily.
Regards
Martin
 

adrian

Flying Squad
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