|Michael Gilligan||28/09/2020 14:19:38|
16397 forum posts
I apologise, Tony ... You were correct in your first assertion.
I have just returned from a good long walk, and some pondering; and it became quite clear that the mis-aligned chuck would simply form part of the “any shape you like, provided it’s stiff enough” trammel beam.
By way of demonstration : here is the scrappy little sketch that I doodled whilst I was out.
|Tony Pratt 1||28/09/2020 15:02:22|
|1236 forum posts|
Michael, thanks for the apology, your arguments certainly made me think which is a good thing
1515 forum posts
Me too. Sorry as i got it wrong.
|Nir Somthing||28/09/2020 17:42:53|
|23 forum posts|
ChrisB & SillyOldDuffer, I thought about your comments about cutting a metal or squaring something, and I honestly don't think this is the way to go, for one, when squaring properly, if my face cutter is tilted 10 degree to the front and I rotate the piece on its axis, it will still turnout to be perfect. even the sides! so long as my x axis is spot on - and ~0.03 mm is spot on. Also, I don't have a big enough stock of material. And My point is that when times comes and I will have a project that will need this few hundreds of accuracy all problems will arise... Will it cut metal? I don't see why not, I already squared a small aluminum piece of 20 mm thick to 18.6x17.4x15.6, but this won't help me judge my mill at all, first of all I don't have a proper grounded granite table and a height gauge, and my machined square and caliper will only give good results as my vise, which is a cheap Wilton vise with an accuracy of doubtedly 0.001". I plan to buy a Kurt 4" vise, and a granite table and so on, but only after I know my mill worth it. ***By squaring I assumed you meant making a cube:
Anyway does someone has an idea from from what I advised earlier? Thank You.
|Tony Pratt 1||28/09/2020 19:01:52|
|1236 forum posts|
Absolutely no problem
|Nicholas Farr||28/09/2020 19:07:11|
2442 forum posts
Hi MichaelG, I like your scrappy little sketch.
|Tony Pratt 1||28/09/2020 19:11:19|
|1236 forum posts|
Mr Nir Somthing, is there anyone you know personally near your location who can advise you? I say this with the best intentions as there are many people on this forum who could evaluate your machine if they had eyes on it but diagnosing a problem via a forum is nigh on impossible, are there any model engineering clubs near you for example or do you know any mechanically biased co workers? Please don't take this as a negative posting.
|Pete White||28/09/2020 20:28:23|
|114 forum posts|
Plus one Tony, if only I could have said that in my own words.
This hobby? is great fun, not supposed to cause us big problems............??? , leads me to sleepless night sometimes though. lol
6331 forum posts
Look at it this way, measuring hasn't achieved anything positive yet. It's created lots of suspicion, but not confirmed the mill is a dud, or suggested what ought to be done to fix it.
On the other hand cutting metal achieved something - you made a cube! The point is, if the mill with Nir at the controls made a cube successfully, then Nir's mill can make other objects correctly. Rather than rejecting it, perhaps it's good enough. Judge the mill by what can be made with it, not on measurements that could be misleading or irrelevant. What can't the mill do in practice?
I wonder if there's a misunderstanding about how accuracy is achieved with these hobby tools? It's not done by dialling in dimensions and expecting the cutter to be spot on under all circumstances across the full range of travel. Rather the operator becomes skilled in getting the best out of the machine, allowing for shortcomings rather than expecting them to be eliminated by the manufacturer. Even if the Seig passed all the DTI tests, it's too lightly built to be highy accurate - even monster machines bend slightly when cutting.
Early craftsmen produced superb work without accurate machines - they had to substitute technique for advanced tools. A milling machine makes it possible to work faster, and industry spend big money on mills that the operator can trust without constant checking. However, with care similar results can be got with ordinary kit, it just takes longer.
What do you intend making? It matters and in the absence that information I don't know what to suggest at the moment. Hobby mills are good for most amateur purposes, but probably not suitable for a busy professional workshop, or making watches! Very high milling accuracy (0.001mm) suggest a Jig Borer and tool-room facilities - truck loads of money. I mill for fun but perhaps Nir really needs a jig borer, or a much heavier machine.
|Nir Somthing||29/09/2020 07:21:43|
|23 forum posts|
Dave, thank you comment this is exactly the point.
"I wonder if there's a misunderstanding about how accuracy is achieved with these hobby tools? It's not done by dialing in dimensions and expecting the cutter to be spot on under all circumstances across the full range of travel. Rather the operator becomes skilled in getting the best out of the machine, allowing for shortcomings rather than expecting them to be eliminated by the manufacturer. Even if the Seig passed all the DTI tests, it's too lightly built to be highly accurate - even monster machines bend slightly when cutting."
We "material engineers" normally speak in microns and below. My press drill (modified) was in the range of 0.1-0.3 mm, and I believed that if I spent x8 more money I don't only get better dedicated quill and rigid column but also improve on the accuracy. According to videos I have seen online they always talk in terms of 0.001" or 0.02 mm so I believed that I will improve my accuracy it 1-2 orders.
In terms of what I want to build, my first project is to finally finish a CNC machine out of Aluminum (or from polypropylene and then cnc the Aluminum). when I built the model, many times I had two different parts with holes and I hoped that they will match but they didn’t, so I always had to choose a few holes and widen them up. I used a DRO and an edge finder and the deviations came from the press drill quill which has an enormous play.
In term of what I want to build after words, this is a difficult question, I build with my imagination and my imagination is limited to the tools that I have. The more possibilities the more Ideas come to mind… Now that I will be able to actually mill many ideas will follow, but at the moment I start from the simple things – will it allow me to make 90 degree edge spot on? Will I be able to get holes on a single plate 500mmx160mm spot on? Will I be able to make face mill surfaces spot on? One project that I had in the past involved making a vacuum chamber, If I had a mill I could have made many parts myself… especially the tunnels for the Teflon strips.
|Michael Gilligan||29/09/2020 08:06:43|
16397 forum posts
May I suggest a very simple practical test ?
Take two thick strips of of your Aluminium alloy and clamp or glue them face-to-face
Now drill through the pair at two locations
Separate them, and de-burr if necessary
Turn the top strip over, and try passing a couple of close-fitting rods through the assemblage.
If all is well, you can proceed to doing something similar, but with four holes on a square grid.
The two plates should then match in eight pairings [four positions, and two ways up]
If you find any errors ... investigate.
6331 forum posts
Good looking workshop Nir!
Your pillar drill should allow a simple practical demo of what I mean by 'technique'.
The drill's fitted with a milling-style table and vice allowing work to be held rigidly in position, but the combination doesn't deliver accuracy. It's because the pillar drill is designed to push down and isn't rigid side-to-side. In particular the spindle bearings are often sloppy. If when the drill starts cutting the spinning axis is misaligned with the work, the spindle moves and bends the drill slightly and the hole wanders off.
Rather than hold the work rigidly, sloppy pillar drills work better if the job is held loosely enough on the table to float into the spinning axis. My pillar drill (much inferior to yours) works well using old-school methods:
The method relies on a spinning spindle taking up a particular axis, and then aligning the axis with an accurate point on the job. It doesn't depend on the pillar drill being a precision tool because measuring is independent of cutting. Once the drill's cutting it's important to work within the set-up's limits. Applying too much pressure is liable to bend the drill and shift the axis, causing the drill to wander.
The method takes too long in a workshop where time is money. If a lot of accurate holes are to be drilled in a hurry, the professionals go for a better class of drill. because a pillar drill costing £2000 or more is cheap compared with paying a skilled worker to drive it.
My WM18 milling machine is rigid enough to drill holes accurately straight into the job, but I always position the cutter relative to known reference points on the job, and check frequently.
Similar tricks of the trade work in other situations, and there are other opportunities. It's often possible to minimise alignment problems by designing them out. For example, the bolt holes in a commercial pipe flange are deliberately oversized to provide enough wiggle room to take up manufacturing errors. Works for screw fasteners, but not dowels. The latter problem can often be overcome by machining the two parts together; if there's an error, at least they match!
What I'm describing is called 'Fitting'. Rather than making accurately measured parts, the parts themselves are used as gauges to obtain the required fit. For example, rather than boring an axle block to 15.01 + 0.01mm and separately turning the axle to 14.99 - 0.01mm, the block is bored to about 15mm and the axle turned to fit the whatever sized hole is in the block. The approach is good for amateur work, prototypes, one-offs and repairs. Not difficult to get within to 0.02mm ( 0.001" ), but producing parts within close tolerances takes for ever with many rejects.
Interchangeable precision has long replaced fitting in industry. They work to tolerances, so axles and axle blocks can be made separately anywhere in the world from drawings and still fit together. The classic method is to set up a tool-room equipped with calibrated machines and high-end measuring gear where skilled men make highly accurate jigs, fixtures, and gauges. Jigs and fixtures provide shop-floor accuracy, rather than operators, which is confirmed with the gauges and by inspection. This approach is expensive at the outset, but costs drop rapidly when tens of thousands plus identical parts are needed.
I'm getting the impression Nir's requirement is in the awkward gap between fitting and precision manufacturing. If so, I suggest machines like the Seig (good for fitting) are too crude; probably necessary go upmarket. In the UK it's possible to pick up ex-industrial machines at reasonable cost: CNC caused industry and education to dump thousands of manual machines long before they were worn out. Also easy, apart from the high prices, to buy new industrial class milling machines. I don't know what's available in Israel - having to import anything yourself in any country is a always a pain but I'm sure it could be done.
Cost is the main obstacle.
An answer might be to use the Seig to develop prototypes by fitting and once the concept is proved have the finished parts outsourced to a CNC shop working from CAD. The pattern is common enough: designs developed in the West and manufactured abroad.
Edited By SillyOldDuffer on 29/09/2020 11:16:05
|879 forum posts|
Nir also looks as if he has an expensive 3 axis DRO fitted to his pillar drill; I have the same DRO but fitted to a mill/drill, and absolutely love it. Luxury indeed!
But is this DRO inappropriate for a pillar drill? Or over-kill?
If it were me, and such kit expensive in an expensive world like Israel seems to be, that DRO would be fitted to the Stig where perhaps its expertise would be better served.
Just saying!! Merely a suggestion, an observation,
|Nir Somthing||30/09/2020 09:40:51|
|23 forum posts|
MichaelG, Very cool test, shame I didn’t think about it myself! I will indeed try this one out!
Dave, thank you for your long and interesting post, I might do it out of curiosity once but not on a regular basis anyway I should say that for centering I would really recommend buying one of this:
It is extremely accurate and it never let me down!
I had to opportunity to get an old heavy duty mill from the university for free once and it even still worked, but as I said, If I try to put it in my apartment it will right-away go through the floor of mine and another 5 along the way… Here, living in a private house is only a dream…
For me weight and size is even more of a problem than cost…
ChrisH, Indeed, when I bought the DRO I bought it in parts, so for a change, I didn’t pay any TAX, and it is indeed the expensive one, 1 micron resolution. But I bought it to serve a mill in the future in mind, the press drill is only temporary, I don’t have space so I am supposed to get rid of it and replace it with the Sieg.
|Neil Wyatt||30/09/2020 17:10:08|
18241 forum posts
He's mentioned several times that he's in Israel where the hobby is rather thin on the ground.
|Tony Pratt 1||30/09/2020 17:12:55|
|1236 forum posts|
I do realise that he is in Israel, there are a lot of good mechanical engineers there so just a thought.
|Nir Somthing||01/10/2020 08:08:08|
|23 forum posts|
Ok, so to summaries, after adjusting the gib on all axes, when I lock the y axis I can see the dial moves 0.01mm which is perfect, when I do the same on the x axis the dial moves 0.05mm which is also great. But since on the z axis, as I said, I lowered the gib all the way in, and when I lock the head it moves 0.27 mm and I cannot move the head all the way up – it is obvious that my z column needs machining to make it parallel. So for me, it is easier to adjust the column in the first mill than machine the column. So I decided to call the dealer and ask him to ship back the first mill which I checked without touching the gibs (I pay for shipping) or send a third and I will pay extra. Apparently he is not on my side. He tries to convince me to release the gib so I get full motion in my z axis and have even a bigger of play. By doing so I ignore the purpose of the gib completely! What’s the point of having one if I cannot lock it properly? I understand that many of you think that the z axis is not as important as the x and y axis. But having a gib which is spaced by about 0.3mm (After I move it back up again) is just ridicules! If someone here agree with me - please share your comment so that I can show him that not only I think that way, If you think otherwise please explain way.
|Nir Somthing||01/10/2020 09:03:26|
|23 forum posts|
BTW, I asked my dealer to ask Sieg if it is possible to pay them up to twice the item price and in return get a proper calibrated mill. He claims this idea is not an option. And that he buy the mills as they are...
6331 forum posts
As far as I know that's true. Seig (and others) make hobby mills. Rather than spend money on deep inspections, they make more and accept a percentage won't be up to scratch. If the customer is unlucky enough to get a dud, it's replaced. In the UK with no quibble, but buying direct from China is risky.
Arc Euro in the UK used to offer a tune up service but stopped because - I think - very few people used it.
No problem buying Far Eastern machine tools for the professional market, but I've yet to hear of a hobbyist who's bought one! Price on Application generally like Chester, but Buck and Hickman are more open. Their web page covers both hobby and professional machines, prices ranging from £495 to £38,556 (plus tax and shipping.) I think you should be looking to spend at least £5000, maybe much more. Watch the weight, precision machines tend to be heavy!
I don't know of any Western manual mills still in production; apart from hobbyists, buyers have long shifted to CNC.
Doesn't help I know, sorry. I think you've been unlucky to get a couple of iffy machines, whilst also having a high-end requirement and local difficulties. One way out is to throw money at getting a better machine; another is to work with what you have. What does your supplier suggest? Maybe he's picked up a bad batch*, and should be sorting it out with his supplier, maybe a third machine would be good enough.
* something a little suspicious about the repairs, rust, and paint job on machines that don't measure well either? Could be Seig messed up, could be they're private enterprise - someone doing up factory rejects. Don't know.
|Ketan Swali||01/10/2020 11:19:36|
|1300 forum posts|
I would like to suggest that you look at this video from Blondiehacks. If you don't have access to an experienced 'practical' machine tool fitter, this is a good video to see, if you decide to keep the machine.
If you are having issues with the Z axis, again, a 'practical' machine tool fitter can guide you. To beat your distributor with speculative discussion on here is wrong as it is difficult to make a clear judgement for your distributor or you.
If there really is a problem with the Z axis, there are ways of dealing with it, but without physically seeing the machine in front of you - all guidance is just speculation. There are checks I can suggest, but I would only do so if and when I feel it is appropriate. This would be the wrong time for me to get into a discussion on the subject, because again, I would be just speculating.
Machines are calibrated before they get into the packing case. From then on, ALL machines are subjected to changes in temperature in transit, combined with shake, rattle and roll, until you put the machine in its final resting place in your apartment.... there after, the machine needs to settle in its final place of operation for at last a month, before you decide to do any major adjustments to meet your specific requirements. This is a general purpose - general use light weight/light duty hobby mill. It is not a heavy weight, heavy duty industrial machine, nor is it a tool room machine specification.
So, even after the 'light weight' machine is calibrated before it left the assembly table, you will be extremely lucky if it remains the same by the time you instal it. There is less adjustment to be made with machines which have a heavier casting, smaller table, along with some other factors.
Jason and many others have the same machine, supplied through respective SIEG distributor channels around the world. They are all working as needed, be it with or without adjustments, to meet the users requirements. Where they fail to meet the users expectations, they are simply returned for a refund, after discussion and mutual agreement with the reputable supplier.
I respect your enthusiasm. However, to carry out some of the adjustments to meet your specific requirements requires experience with skills gained over decades. If you decide to keep the machine, I would suggest you use it, let it settle in its final place of operation, and only consider to make very small adjustments over time, as your skills develop. Although I have given you the link to the Blondiehacks video, I would suggest you consider certain bits of it, slowly over time, as your machine starts to settle, and as your skills develop.
If you continue to approach this matter in the manner you are - with speed, it could turn out to be a problem as the machine settles over time.
Ketan at ARC.
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