|von dutch||11/02/2021 23:34:18|
|53 forum posts|
Hi all,I'm having some problems doing the set up tests,to get my myford ml7 up and running.Ive been thorough and checked most things to the best of my begginer ability!.There appears to be little.wear on my machine,I've checked the spindle bearings with a dti on the register and a 12" long bar in the chuck,gave it a damn good wiggle and the only movement was .001",it runs smooth and quiet and the slides,saddle etc all operate smoothly with no binding anywhere on the bed.Now the fun bit,I've levelled the stand and bolted it to my concrete floor and now I am attempting to do the turning test on a piece of a bar.Ive ground a hss steel tool blank to make a turning tool,(probably not the best!),checked centre height it's ok.I can face the end of the bar but if I attempt to turn the diameter I should add its very hard steel it chatters like mad and I suspect my tool needs another look,and the bar itself appears to be deflecting it is 1" diameter steel 6" protruding from chuck.It doesn't like any sort of cut along its length and seems to "push" the crosslide away?! When I attempt to put a cut on,gonna have another go at regrinding a tool or am I using to tough a piece of steel for test ?
|von dutch||11/02/2021 23:36:11|
|53 forum posts|
The chatter was so bad and noisy I looked to the side and saw the tailstock sliding away from me🤣
|2158 forum posts|
Sounds like you are trying to turn some very hard steel, get a piece of EN1A (pb)
|Grindstone Cowboy||11/02/2021 23:46:12|
|713 forum posts|
Probably the steel, possibly the tool, maybe a combination of both. Would be worthwhile sourcing a bit of known easy-machining steel as your first option. I'd also check adjustment of the gibs, need to be snug but not too tight.
Emgee types quicker than me
Edited By Grindstone Cowboy on 11/02/2021 23:47:17
|von dutch||11/02/2021 23:57:05|
|53 forum posts|
I should add piece of steel bar was cut to size by myself with hacksaw,it's hard though I was being polite to my machine,but unless you took nearly nothing on a cut all it did was high pitch chatter,crap tool.grinder I think and am hoping surely it's not that namby?!
Edited By von dutch on 12/02/2021 00:00:14
|von dutch||11/02/2021 23:59:01|
|53 forum posts|
I did check the crosslide gib ,but I only nipped one of the screws a little more and it was solid to turn so I left it as it was
|Chris Crew||12/02/2021 01:35:58|
135 forum posts
You don't say how far your bar was protruding from the chuck. Perhaps if you centre-drilled it and supported it with a centre from the tail-stock you may be a bit more successful or only had a couple of inches out from the chuck. Also, if you are such a raw beginner why not buy some ready ground turning tools or some cheap tipped tools from such as Ebay. There are a lot of people who will tell you the cheap Chinese tools are rubbish but I can tell you the shanks are as well machined as any more expensive item I have examined and the tips cut well enough for me. I bought a set of seven for under £20 for the Myford from Ebay and found them to be so good I bought a larger shank set for the Colchester and I expect them to last the rest of my life, at the very least. Price does not always equate to quality only the dealer's profit!
You need to get some known free-cutting steel like EN1A not less than 25mm in diameter to take some test cuts and get the 'feel' of the lathe. Not all steels cut freely with a good finish, black rod for example is very 'gritty' and doesn't form nice swarf or finish. You should get some soluble oil as a cutting lubricant too. I know some people can't bear the thought of it on their cherished machines but I all my machines are equipped with 'suds' pumps. About 20:1 dilution is about right and if you can get some Rocol anti-bacterial to put in it, so much the better as it stops a black gunge forming in the reservoir and the oil and water from separating out over time. It's cheaper to go down to the local oil merchant and buy a 5 litre container of it than the ridiculous prices charged for small bottles of the stuff then you will have almost a lifetime supply.
Edited By Chris Crew on 12/02/2021 01:37:25
|von dutch||12/02/2021 07:11:43|
|53 forum posts|
The test in the myford ml7 manual says to perform the test without a steady and have the bar protuding from the chuck about 4-6".However I feel to turn these collars on a piece of bar I have to have a steady in or else it's gonna deflect surely?,i know the finishing cuts are light for the test,but I still have to rough out the middle ?Ref grinding hss tools I did cover it in my apprenticeship years ago!,I'm just rusty on it!
|Martin Dowing||12/02/2021 08:53:54|
355 forum posts
You should look for wear of bedways, carriage, cross and top slide, check all gib srips, make adjustments as necessary.
1 thou of play on headstock bearings is also quite much. I have not more than 1/2 thou on my own ML7. When bearings are adjusted properly there will be no play (oil film is not compressible).
You may wish to clean bearings and spindle from all oil using petroleum and then check what your *real* play is.
If you get 3/4 up to 1 thou in "wiggle test" run that way, your bearings are fine.
Otherwise there will be shim adjustment or/and bearing scraping.
You also need o check for an *end play* of your spindle as that is a common reason of chatter (if found it is easy to correct by tightening screwed ring on the left side of spindle but do not forget to untight grub screw in that ring before doing so).
Making an old ML7 working as new and better is a never ending project. I have my ML 7 for ~20 years, refubished it from a scrap like to "as new" condition and have done plenty of upgrades. So bedways and mating surfaces were scraped in, headstock alligned (easier than many think - there is much of false mythology that it can only be done properly in factory setting), spindle and bearing replaced for phosphor bronze and hardened version, countershaft remade from hardened material, one of worn pulleys remade, oilers remade, tailstock barrel first remade but then I got S7 tailstock and now this one is used etc.
And of course old, not hardened spindle was not thrown away at all. Former owner have damaged tapered socket by boring it parallel (lathe crash) but for one job this spindle have proven invaluable.
When I needed to process ends of new precision leadscrew for my ML 7 purchased from McMaster Carr I have reinstalled back my old spindle for few days and damaged tapered socket *just* allowed to pass new leadscrew through the bore.
You will learn a lot of fitting art while proceeding with all such works.
Modern professional guy who operates CNC and nothing else may well look with envy on your skills after few years of such practice.
So good luck!
Regarding "test bar with bobbins".
I have taken a 14 inch section of 20mm diameter hardened linear bearing shaft (they are cheap these days) and locited in 2 of 1-1/4" phosphor bronze bobbins on such a way to get a distance of 12 inch distance between them. They are turning very nicely without any chatter and measuring is pleasant and straightforward.
Edited By Martin Dowing on 12/02/2021 09:03:28
|Chris Crew||12/02/2021 09:01:23|
135 forum posts
Yes, you are right, you scallop out the centre of the bar with it supported and then take the very lightest cuts with the bar unsupported before measuring them with a micrometer. If you can get it to within a thou. you will be doing fine. It's really not that important to me, at least, because it's only on a 'flimsy' lathe like the Myford that any adjustment by flexing the bed is possible. Don't get me wrong, the Myford is a fine machine in its class, I would never part with mine, but you certainly could not make any such adjustment on, say, a Colchester because the bed is like the Rock of Gibraltar so you are governed by the inherent accuracy of the machine or not.
With the greatest respect, like 'Inspector Meticulous' I think you may be being a little too concerned with getting it precisely correct. In the real world it is very unlikely that your chuck will close precisely concentric or the un-ground stock you put in it for most jobs will be exactly round. Most turning jobs are about just reducing diameters over quite short lengths that is why beds wear most nearest the chuck, so even if your lathe is cutting .005 thou. taper over the length of the bed over an inch at the headstock end the run-out is all but undetectable.
I accept I may be criticised for holding such opinions, but I am only an amateur pottering around in a back shed workshop, however well equipped it may be, and everything I make usually fits together or works effectively enough but we all have disasters from time to time and learn from them. I do not work in the tool-room at Rolls-Royce where I would be required to achieve world-class production standards, and rightly so.
|Martin Dowing||12/02/2021 09:26:08|
355 forum posts
Even with 5 thou taper along bedways you will pass by.
ML7 specifications are allowing for 3 thou per foot taper and ispector in the past would pass such machine.
Wear near headstock often leads to minor tapers on jobs held in chuck. Something like 1 thou per inch on occassion, however on longer jobs you do not observe "proportional taper" developing. Without returning shears to parallel condition (scraping of inner vertical surface of the shear near you) not much can be done about it.
In such a sad situation you need set of gauge blocks to measure distance between shears accurately parallel reference slab, scraper and some patience - not that difficult.
Also you may adapt until now unused back shear as a guide (you need to make a gibstrip for that).
|Nigel Graham 2||12/02/2021 09:28:57|
|1712 forum posts|
A length of tough steel protruding 6 inches from the chuck as you say, and without further support as I think you say this was, is pretty severe test of lathe, tool and material.
I'd suggest the problem here is a combination of tool, the particular steel, and that overhang.
I've found sometimes the development of chatter varies with diameter, but in an odd way, worse at some intermediate depth than at the starting or near finishing diameters. I don't know why this would be.
One-inch diameter bar can't be set back much on an ML7 as it won't fit in the spindle, nor indeed on a Harrison L5 about twice the size, for the same reason; and even with free-cutting steel on the latter I'd be wary of machining a long length without a tailstock centre or a steady.
|John Haine||12/02/2021 10:22:51|
|4186 forum posts|
Too many variables. Get some known steel and buy yourself a known good tool, e.g. an HSS tool from Arc. Make sure the tool is on centre height. Then try again,
|Nigel McBurney 1||12/02/2021 10:39:30|
923 forum posts
To test the lathe to produce a parallel cylinder,tailstock centres and steadies cannot be used, sugest use leaded en 1A mild steel and a really well ground HSS toolbit, check that the chuck jaws are not bell mouthed, I have a Colchester master with a well used 4 jaw chuck and brand 4 jaw. Try turning a length of 2 inch en 1a leaded in the old chuck and it will chatter like mad,use the same material ,tooling and lathe settings in the new chuck and the finish is excellent. To find if the ML7 chuck is causing the chatter,try turning the bar between two centres,not chuck and tailstock centre.If it turns with reduced chatter or no chatter then its the 3 jaw chuck jaw at fault.Also grind the HSS toolbit to a sharp point and just stone a small rad on the point.
|Howard Lewis||12/02/2021 11:10:55|
|5328 forum posts|
You sound as if you are making the "bobbin" so that the twist can be taken out of the bed.
You have a ML7 so it probably has Imperial dials and leadscrew..
The machine needs to be in good fettle, and the chuck needs be able to grip the work securely. A chuck that has been abused by holding work at the outer end of the jaws may be "bell mouthed" and so tend to grip work less firmly, because the jaws are now contacting at the inner ends.
Not absolutely vital to be precise to within minutes of a degree, when grinding the tool. A degree or so either way is unlikely to result in disaster.
If yo can produce a tool with about 10 degrees clearance at the front and side, and about the same top rake, you should be OK. The essential thing is to keep a sharp edge. A slight radius on the nose will improve the finish, but maintain the clearance. You don't want the tool to rub below what should be the cutting edge..
Cutting speed, for mild steel, should be 100 f pm (25.4 mpm ) or less, so a piece of 2" or 50 mm bar would be running at 190 rpm or just under.
For what you are trying to do, I would suggest a feed rate of about 0.003"/rev, if you can achieve this. Ideally using a changewheel set up to give a reduction about 40:1 between the mandrel and the Leadscrew. The power feed will give a consistent feed rate.
If you do not yet feel able to make such a set up, do not worry.
Learning how to be able to feed steadily by hand is a good skill to learn
7566 forum posts
Assuming the lathe is in good order, three areas go wrong:
I think von dutch has spotted what's wrong. He's trying to cut hard steel which bends away from the knife rather than cut. His home-ground HSS cutter may be wrong. He's inexperienced and the lathe is new to him and may be worn or out of adjustment. If the work and/or tool are set up with excessive overhang, and the tool is applied with wrong depth of cut, feed-rate or surface speed, then chatter ensues. Each flaw in the set-up multiples the likelihood of trouble, even if the lathe is in perfect condition.
The cure is to eliminate potential problems and try again. Most obviously, replace the hard steel with a material known to be machinable: buy new with 'Free Cutting' or 'Good Machinability' in the product description. Mount the work so the minimum sticks out of the chuck, no more than 2.5x diameter without a steady and/or tail stock centre. Aluminium alloy (of the machinable type) is good for experimenting, and I prefer Brass to Steel, but EN1A is fine. Get a copy of Sparey's The Amateur's Lathe.
With luck decent metal and a bit of practice will fix it. If not, ask again. Could be as simple as loose gibs, or more troublesome the headstock bearing is worn.
Although random scrap can cause a lot of trouble, it's possible to use it once the operator has developed a feel for his machine. Experience reveals the difference between difficult but doable metals, those needing carbide, and the downright impossible. After a while you recognise the symptoms and sort of automatically 'know' what to try to improve the cut as it progresses. It involves finding a combination of speed, depth of cut, feed-rate and lubrication that cuts effectively. (Where 'effective' is a suitable mix of metal removal rate and finish).
As always it pays to learn to swim at the shallow end before tackling the English Channel!
Edited By SillyOldDuffer on 12/02/2021 16:11:17
|Dave Halford||12/02/2021 11:41:54|
|1746 forum posts|
Firstly try a light behind the chuck jaws, any light that increases towards the end of the jaws between a known round & straight bar and jaws (apart from the notches) tells you the chuck is bell mouthed and worn out. A good set of jaws will not show any light at all unless the bar is knobbly. The other set of jaws may be OK.
i would expect any lathe as old as a Myford to have some wear in the slides or bed and therefore if set right for a worn part of the bed should be too tight at each end. Setting it as you have it may be quite loose where you are trying to cut.
The centre height is OK when you don't get a pip on a facing cut.
The cross slide gets pushed away due to backlash in the cross feed screw or the saddle is too loose at that point.
If you clamp the cross slide and use the top slide feed is the chatter as bad?
Edited By Dave Halford on 12/02/2021 11:45:24
|Howard Lewis||12/02/2021 11:57:17|
|5328 forum posts|
Well said, Dave! (Both )
The books by L H Sparey, Ian Bradley, Harold Hall etc all provide good basic information.
Once the basic principles have been grasped the novice can soon gain experience.
Without knowing and understanding the basics, disappointment, frustration and disillusionment are likely to follow.
Zeus charts and Tubal Cain's "Model Engineers Handbook" are invaluable references.
I have seen a mini lathe ruined by trying to take 6 mm cuts with a high feed rate. The repair bill will be nearly half the cost of a new machine!
Yet posters on here produce superb work on machines that are a century old. A former colleague makes things on a pre WW1 Drummond that I would struggle to do on a 2003 machine, or an even newer mini lathe..
My turning instructor, who had earned his living on piece work, used to be frustrated by our taking 0.010" cuts on, by hobby standards, heavy industrial lathes with 5 or 10 hp motors. But we did not injure the machines or ourselves. As we became more proficient, we were able to utilise more of the machine capacity and facilities, with swarf coming off "Like clock springs" to his delight!
We learn every day. This is what the Forum does for us, exposing us to the knowledge of folk with other experiences, on which we can now draw.
Experience allows us to recognise the mistake the next time that we make it!
Edited By Howard Lewis on 12/02/2021 12:04:52
|Gordon A||12/02/2021 12:42:32|
|157 forum posts|
Search for "Rollie's Dad's Method" on the internet. I've used this several times and it appears to work, gets the initial alignment of the lathe bed "within the ball park" even with a worn chuck. Can then be confirmed by turning a test piece (hopefully) just once.
|von dutch||12/02/2021 15:16:45|
|53 forum posts|
Wow thanks for the replies everyone!,just worked a Nightshift so delay in response.I know my cutting of has tool blank probably isn't perfect,but I reckon after some consideration Its my own operator failure! Trying to do this myford test.I think there must be a centre in to produce bell shaped test bar and then remove to take light cuts as per manual for adjustment if needed.Also I probably ran it way to fast for the unknown material(first time back on the lathe in over 20 years!)in my naivety I thought top speed was slow but I possibly needed to be in top back gear at most!.I thought 1 thou movement on the register via a 12" bar being heaved around was pretty good? I did give it some,ref end play on the spindle I did have to tighten initially when I got the machine as it was way to loose but I didn't completely nip it up as the spindle started to bind?,maybe I need to carefully look at the gib again on crosslide but I think it was more the terrible sonic chatter i did actually see the tailstock hum away backwards down the bed doh!,thanks for all your advice ,live centre being ordered (think I have a centre drill!)
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.