Quality issues with a SIEG SX2.7 mini mill

Yes it was your videos Jason, but there was more than just that. I agree I could continue using it on smaller items and never notice any difference in my results.

Unfortunately, I decided to build a 130mm 2 jaw/off-center chuck for my lathe and wanted to get it as good as possible to reduce the total error when it’s gonna be used.

The slot ended up being more than 0.1mm offset even though I centered it carefully. Does the 0.15mm make a difference that would prevent an engine from running, probably not. I still want to have it central

I see my lathe and mill as tools to be used; provided they do what I want I'm not fussed about cosmetic shortcomings. Nor am I surprised that my inexpensive hobby kit isn't as well-made as it might be. I work relatively slowly, in an untidy workshop, and I don't think any of my tools are heirlooms or cultural icons. For me, Far Eastern kit has proved 'value for money' despite minor imperfections.  With care, it's entirely possible to get good results.

Others are irritated by shortcomings, treasure 'good' tools, value tidiness, and want everything to be spot-on. Nothing wrong with this point of view unless you also believe £3000 is a lot of money to spend on a new lathe or milling machine!

I wonder why none of the critics have set up a business to fix the problem? Seems an obvious opportunity - loads of dissatisfied customers straining to spend their money on better machines. Or is it everyone knows it's hard to make a living selling lathes to hobbyists most of whom have short arms and deep pockets? Very few of us buy new high end machines.

Dave

Edited By SillyOldDuffer on 19/02/2019 15:12:32

Martin,

To understand this, you need to understand assembly of these type of machines - manual process- as well as history (i am not trying to patronize). 'Back in the day', machines were checked in the same way 'in Europe' when 'we in the West' made machines.

If machines were made 'by manual process', there were variables. The machines when they left the manufacturer, left in similar way as they do from China. There were gremlins in many of them from new - even Myford (regardless of what some may say). Once the machines were delivered, a machine tool fitter came to the place where the machine was to be installed, checked the place it was to be installed, on what, levels, as well as the the machine, did the adjustments to the machine as necessary, before commissioning the machine, as who know what the machine went through in transit. The user never opened up the machine to look for gremlins. As long as the machine worked as the user needed, that is all that mattered. Most of the users were practical engineers.

The certificates issued by most reputable factories are correct and issued after the machines have been assembled and accuracy adjusted after assembly, at the factory. We are regularly offered these certificates, and I have seen the checkers do their job to check the accuracy. But ARC refuses to accept these certificates because we don't know what will/will not effect the machine until it is installed. So, in this respect, the certificate is only true at the point just before the machine is packed in a 'reputable' factory, wherever it is from in the world. This holds more true for 'lighter' machines, built in this way. e.g. SX2.7 is light, and a Bridgeport is heavy.

Now, instead of a machine tool fitter, the end user is expected to handle, lift the machine out of the case - properly, put it on a level surface/location, and carry out adjustments. If an experienced person does this (I don't mean a person with a piece of paper degree out of university) carries out the checks and does the adjustments, all is well. We have 'respected people' out of industry, with decades of practical experience in machine assembly, with good knowledge of tolerances and accuracies, who have bought and used the machines as supplied, over the years. I don't say this to just inflate my ego. Nor do I say this to patronize. This is just an observation. My reputed competitors some of whom have been around much longer than ARC have similar experiences.

So, to suggest that they are trying to fool you with the certificate is a little wrong. Perhaps they could clarify how and where the tests are made. Perhaps they could clarify that things could change in transit/handling, temperature, installation by you - the customer, adjustment by you the customer. If left unadjusted what could happen even perhaps?... who knows?... At the price you pay, you have to decide if you feel it is good value for money. In most cases, the machines are accurate and fit for hobby use. If you want something which is outside these remits, it will cost a lot more.

Ketan at ARC.

Hi Hopper,

You could try astronomy or making music.

Yes any telescope and mount or guitar straight out of the box will work, just as any milling machine will.

But if you want something at modest cost you have to decide on a balance of features versus quality.

Telescope mounts of comparable cost to bench milling machines need similar levels of 'tuning' including adjusting bearings and re-greasing or replacing gears with toothed belts to improve performance. You don't have to do this, but if you pursue the very best performance you may want to. Affordable scopes can have exceptional optics, but the 'mechanics' typically need fettling or upgrading to get the best performance.

You can get very good electric guitars and basses for around £200, but expect to put some time into setting up intonation and action and basic specification if getting a good build quality. Pay half that and expect something that needs significant 'tweaking' and is possibly a bit ropey.

Of course you can pay vastly more and get any level of quality and performance you want, but in these two other hobbies it's the same situation of people on limited budgets wanting as much as possible for as little as possible. Interestingly, they are both hobbies where products are sold in vastly greater quantities and although that does help make things a bit for affordable because of economies of scale, the same principle certainly applies.

Neil

P.S. it applies to bicycles to - all bikes need to be safe, but some cheap bikes are virtually unrideable with heavy steel frames, cheap gearsets etc.

A lot of discussion has happened on this thread and cold water has been poured on the premise that temperature would not be an issue with manufacture/assembly of our hobby machines. Those who have had careers working in engineering will have undoubtedly come across thermal issues when producing parts, if certain close tolerance parts are made on a cold day and parts assembled with it are completed on a hot day then you can very easily have a conflict with tolerances, I speak with experience on manufacturing components and assemblies with sometimes challenging tolerances. In respect of castings they are nowadays machined mostly when green I.e. straight from the foundry, no weathering or time to stress relieve, this can cause a lot of problems after the component has been machined and is removed from the production fixture; in one factory that I worked in we had problems with cast iron gearbox casings moving after they were finish machined, we found that they were twisting as the internal stresses relieved themselves, the amount of movement was significant enough to cause misalignment of assembly dowel positions. We investigated it thoroughly and decided that we needed to alter the casting patterns to thicken certain areas to strengthen the overall casting, when we machined the modified castings there was imperceptible movement which in our case was acceptable. Stress relieving after machining is not confined to cast iron, it happens with the grades of carbon steel and stainless grades as well, in fact some of the more exotic grades of stainless alloys can be very challenging. Our hobby machines are built to a price and we usually purchase the best that we can afford, they are not going to perform to the standards of toolroom machines, they use castings which are dictated by price and are in comparison to heavy machine tools are relatively flexible as has been demonstrated in this post by the movement detected when bolting on a wooden base and a steel base, I would be surprised if they didn’t show any movement when the castings used are by definition adequate but viewed as unstable when compared to heavy machinery . I am not denigrating the manufacture or standards employed in building hobby machines, they are what they are, built to a price to perform a reasonably accurate function. Machines that perform precision machining processes are available but they are way out of reach of any hobby machinist, if by taking the mill or lathe apart we can improve upon the tolerances then this is a way forward for those who have the expertise to fettle or modify just as the assembly fitters used to do in our manufacturing industries but nowadays parts made in the western world are made on machines that produce to very close tolerances so only minimal work is needed upon assembly, gone are the large fitting shops where, dare I say it, sometimes items were butchered so they would fit. I own a Champion V20 mill and a Warco BV20 lathe, I accept that they are not perfect but live with their inadequacies, the mill has dro’s fitted and that makes life much easier , couldn’t do without them, the lathe is in line for fitting dro’s, just researching to find suitable candidates. I think we should all remember that our hobby machines, usually Chinese, are built to a price that we can afford and without these machines being on the market many of us would struggle to take part in model engineering.

Dave W

Hi Piotr,

Without knowing the details (cutter size and type, speed, feed rate, depth of cut, use of coolant, was the y-axis locked etc.) it's hard to be sure, but a likely reason is trying to cut the slot to size in one pass, possibly at too great a depth causing the machine to flex. I would argue such flex is a limitation of, rather than a fault of the machine.

Even a bridgeport would probably show some flex if you cut a slot that size in one pass, for example.

My approach to that slot would be to cut it to depth in a number of passes with a narrower cutter, then taking a sizing skim from each side.

Neil

Hej Neil!

I cut that slot in what was perhaps 100 passes. I started with a small slot cutter 6mm, and cut it 6mm deep taking 1mm per pass. No cooling as this is regular cast iron and machined very well, just a vacuum cleaner not to breath in the dust and clean the slot while machining. Then I widened the slot using that very same end mill to 10mm, taking 1mm on each side during one pass. Later I repeated the same procedure and deepened the slot to 12mm total, and again widened to 10mm. Changed the enill to a 8mm carbide one and took 0.5mm on each side.. I could continue describing it but I think it’s enough to prove I did not in any way overstress the machine. Everything was done with a DRO and gage blocks for verifying progress.

Besides, after I discovered the offset I did check the column squareness with a grade DIN875-0 square and it was off. I already accepted the limitations of the machine. I will fix what I can, and the rest I will just have to work around if I ever want better accuracy.

Edited By Piotr Gertz on 19/02/2019 19:43:45

I was using a tool that produces a similar pattern finish to that shown in the OP today - a "soft" backing pad with fine abrasive disc on an angle grinder. The Biax power scraper (the machine tool fitters I used to work with refered to these as "diggers" ) produces a very different pattern, as Jason's picture shows.

I would be interested to have more details of the "scraper" that Sieg use, as I have not come across anything other than the Biax type in the UK. Given the price of Biax machines, something that does a similar job more economically would be of interest, though I suspect that I already have it.

Nigel B

Edited to banish the unwanted "smiley"

Edited By mgnbuk on 19/02/2019 19:46:19

Next time I am in the factory, I will try and remember to take a video of the machine in use, and ask them where they got it from. To be honest, JS and I saw it in use some years ago, and educated ourselves to the fact that it was a scraper which the factory is using, rather than an angle grinder (which was our initial impression). As both of us are familiar with the correct use of a hand scrapper, this came as a surprise which we weren't expecting at that particular time.

Ketan at ARC

Problems like these occur with every manufactured item.

In my RAF days the aircrew would have their favourite aircraft and go out of their way to avoid flying some. There would be aircraft that were forever in the hangar being fixed and others would go days, weeks without anything other than the regular servicing being done. No amount of changing components and fixing things would make a bad aircraft good. Maybe better but not good. The same went for the various components, some units would always be coming back in the servicing bays.

I’d suggest that very piece of equipment in our workshops is a compromise from rulers, through micrometres, callipers to the large machines. Fortunately, there’s enough info out there for us to be able to make an informed decision on what to buy within our budgets. Many of us were beginners and when we outgrew our initial choices we either fixed or replaced.

We purchase this Chinese equipment because it is cheap. If they didn’t supply the market we’d still be using vertical slides on our Myfords and probably not being as accurate or productive as we are now. Fair go to Ketan for fronting up and telling us how the supply chain works many other suppliers would shy away from making any comments.

Pete

Edited By Doubletop on 19/02/2019 20:37:59

We can all afford a Box Brownie, but the best that I managed in later life was a secondhand Canon F1n, not the Leica 111G or M3 that I had yearned for all my life.

All through my various cameras, I got what I paid for. The more costly ones had more functions and performed better.

A machine should be "fit for purpose" but with respect to Neil, a Super Adept won't do what a mini lathe can.

For our hobby machine price range it is unrealistic to expect industrial standard of performance and accuracy. In any case, the levels of accuracy and repeatability would be beyond what we normally need, and the machine would be more reliable and durable. BUT it would show in the price..

I am not condoning a badly finished machine, (I have experienced cracked castings that have been painted over, in a machine from one of our fairly well respected importers. It went back for a refund! )

Maybe, Piotr's machine had some very rough handling in transit to Sweden, and before it reached him.

We shall never know. I have witnessed goods being dropped a couple of feet onto a concrete floor. Cannot imagine how that improves the goods.

Whether we realise it or not, at the time, we constantly seek to make a purse of some better material, (hopefully silk) out of a sow's ear.

If we accept less than perfection, we have to make allowances for the characteristics of that particular machine.

I do not expect every lathe like mine to deliver exactly the same performance. Some will be better, some will be worse. I happen to think that for what it cost me, mine is a pretty good machine. From time to time it exceeds my expectations, and very very often, my abilities.

The objective of Statistical Quality Control is to produce a product where a high percentage fall within one standard deviation of the mean.There will be, hopefully, only a minute percentage that fall into the outer ends of the bell curve. That task becomes more difficult as the product contains more parts and becomes more complicated.

Even space ships go wrong, sometimes with fatal consequences.

Rant over!

Howard

Getting back to basics -- and leaving aside the philosophy of hobby equipment in general (my $200 Nikon camera works just fine out of the box for taking hobby photos.) -- I just had a look at the full video above, alleging a .1mm difference in height at the rear of one cross slide dovetail.

But I believe the test methodology is flawed and exaggerating the error by a factor of maybe 10 times or even more.

Hard to tell from the closely cropped video but it appears the DTI is mounted to a sliding block on the right, similar to the one on the left. The DTI is then mounted on a long arm. Further distance is added by the body of the DTI itself.

So what is being measured is most likely a very very very small twist in the right hand dovetail way, or even just a very slight burr on the rear right hand edge of the way surface. It would only take a variation here of less than .01mm to then be amplified by the leverage of the distance from the base to the tip of the DTI pointer. Easily a 10 times or more increase, judging roughly by eye.

So the .1mm reading obtained in the video is essentially meaningless. The ways are quite possibly just fine.

A more accurate way of measuring would be to sit the base on a surface table, set y up level as measured from table to way surface with a DTI on a sliding base, then compare it with the other way in the same manner.

But in the home shop in the absence of a large surface table, best method is probably as said in previous posts, set the machine up and measure the actual movements in action and then test cuts etc.

The important thing is to get the vertical column square in two planes to the cross slide way surfaces, then get the table X movement also square and the top of the table also in the same plane.

Setting up a machine tool is an extremely complex business. MC tool fitters spend four years as an apprentice learning on the job and at tech college so its not something you just sit down and do.

Reading "the bible" is a good starting point: "Machine Tool Reconditioning" by Connelly. Avoiding YouTube gurus is a good follow up. There are some absolute acts of ignorant barbarism being spruiked out there in relation to these small Chinese machines that you should avoid like the plague. (Eg lapping slides to ways with abrasive paste etc.)

If it were me I would put the machine back together, shim the vertical column square in both planes, tram the head and see how it went.

Edited By Hopper on 20/02/2019 00:00:03

Twelve hundred quid for a brand-new precision machine, and from China? Sounds too good to be true.

From what we see and read on many fora, manufacturing and inspection is so hit-and-miss that there are bound to be a few good 'uns escaping, but yer pays yer money and yer takes yer chance. A friend has a small Chinese CNC mill clone and thinks that it can work to micron accuracy. I haven't the heart to offer to do accuracy checks of the machine for him, let alone investigate cutter and work deflection under cutting loads, etc. Interestingly, the maker's spec. quotes 0.01 mm accuracy and 0.015mm repeatability. Not exactly jig-borer spec., is it? Neither is the price.

Hi,

I have an SX2.7 mill and it has a peculiarity I'm not sure is a fault or not.

If there is a drill in the chuck but the mill is not turned on, and the quill is lowered using the handle on the right until the drill hits the work, it is possible to continue turning the handle a bit (say 2 degrees) until it comes to a hard stop. It's like the rack and pinion is really loose and a spring is used to keep the pinion at one end of the rack on the quill. This results in a tendency for the drill to suddenly drop a bit when the pressure comes off and grab when it breaks through the bottom of a hole. Is this normal. I did try to pull it apart to see if I could see what is wrong (if anything) but with the electrics in the handle to enable power tapping (a truly useless complication) I chickened out half way through and put it back together while I still could.

When I first got the mill, it came without the little bit of brass between the locking screw and the quill so I couldn't use it as a mill. The local supplier got onto Seig and as the part only weighed a few grams I expected them to mail the bit. No - they waited until they had a container full for the supplier - so it was about 3 months before I got it.

The other problem with the mill is the lack of oiling points. Unlike the SC4 lathe I was silly enough to buy which seems to have had a shotgun involved in the decision where to put the oilers, the SX2.7 only has one oiler - on the bushing end of the x axis screw for the table. It's really awkward trying to get the ways a screws lubricated.

Regards,

Alan

This is true, it could be twist. It doesn't, however explain why when tramming the column for left/right tilt I would get different readings depending on where on the table I put the reference square or if I move the table towards the column or the other way round.

I will put it on the surface place again when I go out again. Upside down on the ground middle surface and measure the difference of the sliding surface from underneath. The problem here is that it doesn't need to be flat as it's not a working surface, but there's no better reference to use. Alternative approach is to use jacks to level the four extreme points and see how it looks when swiping indicator across the ways then.

I haven't noticed any problem with the quill. I can try that when I am in my garage again. I did however noticed similar behaviour with the head. It can suddenly drop when wound down, especially after the head lock was used.

The lack of oiling ports also surprised me too, but since the ways are exposed anyway it's not such a big problem to me.

It's just a bit of backlash, between when the spring stops supporting the spindle as the drill makes contact and when the rack actually starts to apply pressure. The SX2.7 I have here does it as does my X3 and my drill press.

Thanks Piotr,

In that case it was indeed probably 'nod' of the column.

It's easy to see how travelling around the world in a container could result in movement in this joint, especially if this releases stress in a casting.

If you search on line you will find discussions of how to correct such tilt many brands of mill, it's not a situation unique to Chinese machines.

Neil

As an ex machine tool fitter I would not be allowed to issue calibration certificates until the machine in question had been checked at the factory by the customer and then after it had been installed at the customers site after manufacturing test had shown the machine was as described and depending on the size and type of machine it could take days or weeks to acheive.

Martin P

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