AVM MAS 140 lathe

To check Headstock alignment to an alignment bar (Known to be parallel ), should be located in the taper in the spindle, to rule out any problems caused bynbthe chuck, should be used.

Check that both tapers are clean and undamaged!

To check for twist, as Hopper says, turn a "bobbin", as explained by Ian Bradley in "The Amateiurs Workshop" or the "Myford Series v7 Manual".

This is sometimes known as Rollie's Dad's Method.

If the lathe bed is twisted, it will not notb turn parallell. The nadjustments are usually made at the Tailstock end.

The books mentioned above tell where mto adjust / shim, depending on which end of the "Bobbin" is larger.

Once you know that the Headstock alignment is good, and the bed is fre of twist, the tailstockcan be aligned.

For this, the alignment bar is held between centres and checked for being parallel as the clock is moved from headstock to tailstock end.

If it is oiut bof line, anything turned betweem centres will be tapered, so the adjusting screws in rge base of trhe Tailstock should be used to correct the error.

A prtevious owner may have deliberately offset the Tailstock to turn a long taper, or it might even have left the facory slightlyb out bof line (Not unknown 

HTH

Howard

This morning I went to the local Sunday flea market and I found exactly what I needed, a few short pieces of 25mm steel bars. I made the dumbbell test with one of them:

I cut the bar up to 7mm close to the chuck. The last cut to the two wider sections was 20 microns deep. The difference in diameter between the two parts is 10 microns. I made repeated measurements. Is this good enough? Does it make sense to try to make it perfect since anyway the lathe stands on 3cm wood boards?

This time the surface feels like a very fine thread, even if the feed rate was very slow. I think that the HSS tool is no longer sharp. And it has spots, maybe from the oil? It wasn't hot and there was no smoke. 

Edited By Sonic Escape on 19/03/2023 13:01:16

Edited By Sonic Escape on 19/03/2023 13:03:16

Or maybe not! The problem is you have no idea what the specification of the steel is, and it matters. Not all steels, perhaps the majority of them, don't machine well. Unidentified scrap might well be difficult to cut, or to get a decent finish. And some of them are vile, best avoided!

For that reason I recommend beginners start by buying some suitable metal. In the specification look for 'Good' or 'Excellent' Machinability, or 'Free Cutting'. Of the mild-steels, EN1A-Pb (aka Leaded EN1A), is the best. EN3A is OK, but prone to tear and smear.

Exploring a new-to-you lathe three factors can confuse the hell out of a newcomer. They are:

1. Difficult materials (plenty of them about)
2. Tool faults, from blunt cutters, to malfunctioning machine
3. Operator error. There's a lot to learn, including how to recognise trouble caused by the first two!

At the outset, best to eliminate as many unknowns as possible because doing so makes it much easier to work out what's going wrong. Almost the worst case is a totally inexperienced enthusiast buying a lathe in unknown condition, sticking a bar of flea market metal in it, putting a random second-hand cutter in the toolpost, and ploughing into the metal without understanding the need to get the tool-height right, or that feed-rate, depth of cut and cutting fluid all make a big difference. This means reading books (I recommend Sparey), asking on the forum, getting hold of some decent metal and sharp cutters, and then experimenting for best results. You have to get a combination of things right - parting-off is great fun. Much easier with a mentor because they instantly spot baffling mistakes, otherwise set too and try different exercises to find out what works or not! Quite difficult at first. but gets easier once the eye, ear and brain know how to recognise trouble.

There's much to be said for starting to learn on Brass. Most Brasses machine well, which can't be said of steels, aluminium alloys, Bronzes or Copper. Magnesium alloys machine well, but a bit too exciting if the swarf catches fire...

Your dumb bell accuracy isn''t too bad, and the poor finish may be because the metal doesn't machine well, especially if the tool is blunt or the wrong shape. No need to worry yet, unless the same thing happens to a practised machinist with known metal, and everything set up optimally.

Dave

Actually last week I ordered The Amateur's Lathe by H. Sparey from Ebay And a few more.

So far I avoided buying steel from suppliers. All companies are selling only 6m long bars. And most of them don't cut it to shorter lengths. So I have to pay a big truck to bring one single bar... The local hardware stores in my city can cut the bars to any length but the diameter is less than 10mm usually. Plus they have no clue what type of steel they are selling.

A few weeks ago I bought a 5m long bar of stainless steel (20mm). The one that I turned yesterday. That one was from a private person and he was willing to cut it in 3. That material is much better that the steel bar that I bought today. But I think it is much harder.

I was surprised how expensive is brass. Almost 8 times more than steel. Brass is available in smaller lengths but it make sense to buy it only when I'll have a project in mind, not for random play. I think the best choice just for tests is aluminium. It comes in 3m long bars and many choices of diameters for 6082 type alloy. This is a "highly machinable grade of aluminium".

The stainless steel bar from yesterday "killed" the HSS tool:

And the brazed tool is missing a tiny spot also:

Yes. Apologies. Clearly not propetly awake properly this morning!!

Good that you have ordered "Then Amateur's Lathe". WRitten manybn years ago, with the Myford ML7 in mind, it lays outbthe basic principles.

Another good book to get might be "Basic Lathework" by Stan Bray.

Fpr amy measurement to be accurate, the finish needs to be good.

It is good practice to learn how to produce a good steady and consistent feed by hand. Then start tomlearn the effects of varying powerm feed rates for a given cut.

Stick with HSS tools.

Youir pictures show that the tools are not correctly ground and have suffered damage as a result.

If in doubt, tun at too low a surface speed, rather than too high.

As already said, moulded carbide tips are not as sharp as a properly ground a HSS tool and chip more easily.

You can regirind a blunt HSS tool at 9 pm on a Saturday night, but will have difficulty finding a supplier of carbide tips open at that time!   And a HSS toolbit which can be reground many times will cost about the same as one carbide tip.

Carbide tips were develipoped for industry where time is money, so removing metal quickly is essential.

As hobbyists we are not on piece work, and deadlimes rarely loom!

Stainless is not a good material to use for your tests. Some grades can be nororiusly difficult to machines.

Until you know what you are doing, stick to free cutting Mild Steel, possibly containg Lead, (In which case it will have a Pb suffix ).

The tool should be sharp and reasonably correctly ground (It won't matter if the clearance angles are 11 degrees, or 8 degrees when they should be 10. )

BUT to cut properly, the tool MUST be mounted at centre height.

If it is not, not only will not it cut properly, and probably wear. (Try to find copies of MEW for March and April of this year to read ) Also, when you face the end of a bar, it will leave a pip in the middle.

If it does, your fitrst job is to adjust the height of the tool, possibly by adding or subtracting shims beneath it, or adjusting the height bif yoiu have the tool in a Quick Change Tool Post

You can set the tool pretty close to centre height by comparing it to a hardened centre in the tailstock, and then start taking trial cuts with a sharp, correctly ground, tool.

Where do youn get shims? As a temporary measure, you could use feeler gauges, (Biscuit tins, or 2 ounce tobacco tins, if you can find them are often 0.010" (0.254 mm ) thick. Having got the tool to centre height, and it has been used for a few "Suck it and See" cuts to check, it might be worth giving it a very kight grind, but do not do anything that might change the height ofn the cutting bedge, so leave Top Rake well alone.

Once the tool is at centre height, then you can start turning your bobbin on the free cutting mild steel, to compare diameters. If you adjust the machine, to take out anyb twist, so that it turns paralle to with 0.005" or your 10 microns, you should then be O K to carryb out further alignmenmt checks...

Incidentally, how are the dials on your machine graduated, in Metric or in Imperial units?

If the dials have two sets of units, and the Imperail have 118 divisions, you probably have a machine with a Leadscrew with 3 mm pitch, and it is basically a Metric machine.

If the dials have 100 or 125 graduations per turn then it is likely to be Imperial, with either a 10 tpi, ,or a 8 tpi Leadscrew.

If it is Imperial, don't torture yourself tryingn to work in Metric units. You will get RSI from punching the buttons on the calculator. A bar that you measure as 6.354 mm diametr is actually 1/4" or 0.250".

When you have satisfied yourself that everything is aligned, probably within your 10 microns, or less than 0.0005"you can start becoming familiar with the machine, and its controls.

It might be worth becoming famiar mwith the machine, and gaining a little cinfidence by laking a Centre Height Gauge. Yjis well save you time when setting tools, in nthe future. You will see at least one, if you look at my Albums, if you can't find one in one of the books.

Do not rush. It will take time to learn the skills. It used to trake several years to produce a fully skilled turner, and we learn something new every day.

Your ability to ,produce precisely and repeatedly will increase as time goes on.

HTH

Howard

Edited By Howard Lewis on 19/03/2023 21:49:06

Sometimes you can find an engineering workshop or machine shop locally that will sell you some of their left over offcuts of steel bar.

I paid more attention to the tool height this time. There is no need to add shims, the QCTP of this lathe allows you to lock the tool at any height. I measured the diameter of the bar with the caliper. Then I used the calipers depth measurement rod to set the tool to the half value of diameter.

Also I fixed the tools. My grinder has a slow speed wet grinding wheel. It was very easy to repair the HSS tool. For the brazed one I bought a special grinding wheel. I tried to keep the original angles for all faces. Now both tools are very sharp. I turned again the same piece of metal and the difference in surface finish is significant! With both HSS and brazed carbide tool the surface feels smooth. The third tool, the one with carbide indexable insert produces a horrible surface.

While grinding the tools I noticed the significant hardness difference between HSS and carbide. It took almost ten times more to grind the brazed tool. Even if the wheel was spinning faster. But in the end I think you can make the carbide brazed tool as sharp as the HSS ones.

I wanted to try another type of steel, but I didn't have anything except the stainless steel bar. So I took the angle grinder, added a long power cord and cut 10cm of 32mm pipe from a nearby fence. At midnight Same results.

The dials on this lathe are metric. The smallest division is 10 microns. But it has also the DRO. Now it is removed to be able to clean the swarf.

I discovered a local machine shop that can sell you different lengths. You can even use as much as you want and then if you return it they will pay you back for the remaining length. This is a nice way to avoid wasting metals, especially if it is something expensive like brass.

I wouldn't be too discouraged, there's a whole world of complexity when it comes to insertable tools, and selecting the correct insert for the job is a whole other skill-set to learn, generally inserts for Stainless are a different grade and chip-breaker design to those for normal steels.

They also often need high rotational speeds (even relative to brazed carbide) and the correct feed rate and depth of cut to work properly.

For example turning a 25mm steel bar:

• my preferred finishing inserts require 2500rpm to work properly but will take a cut as small as 0.1mm with a feed-rate of 0.12mm/revolution
• my roughing inserts will run at 1000 rpm, but need a depth of cut of at least 1mm (and up to 5mm!) and work best with a feed rate of 0.2-0.45mm/revolution

If I run either too slowly or with insufficient depth of cut, it will inevitably result in an awful surface finish.

​

I have a very similar lathe to yourself, and find that I get the best out of it with carbide inserts, but I had to spend quite some time:

• thinking about the kind of jobs I wanted to do,
• then doing research to work out exactly what inserts suited different tasks,
• then trying to work out what the best two or three inserts to buy would be to cover the whole range of things I wanted to do so I could get started without spending too much.

​If you want to learn a bit more about it all:

• Mitsubishi Carbide gives a really good explanation of the insert codes and toolholder codes, in their basic turning course, which is probably worth a read alongside your recent book purchases.
• Sandvik Coromant gives a good write up of selecting the right insert style for your job.
• Modern Machine Shop has a write up on picking the correct grade and coating of carbide

​​

Over time I have expanded my range of insert-holders and the inserts I keep in stock whenever a particular job called for something special and now have something in the range of 12 different grades of inserts, in 6 shapes and 4 sizes.

Most of which are only used for specific jobs, whilst there's four or five I use pretty much every time I turn the lathe on:

WNMG 080408 GM UM25A - Removing material as quickly as possible.

WNMG 080404 HQ CM20 Cermet - Finishing steel and stainless steel to the best possible finish, final pass when boring holes which need a good surface finish inside.

CCMT 120408 MPN PC25 - Removing metal quickly to form slender parts which would deflect under heavy cutting forces, boring most holes, roughing brass.

CCMT 060202 FP PC25 - Turning very slender parts or taking finishing cuts on small parts, very small boring jobs

CGMT 09T304 ALU AK10 - Finish turning and boring in brass.

Edited By Jelly on 21/03/2023 17:22:47

You're only an apprentice

Good metalwork looks easy because it is done by highly skilled men with years of experience (and a few ladies too)

In a few months you will do nice turning work with a nice finish, but it takes time and practice

practice practice practice

You've got Spareys book coming and it's full of all the nice things he made... after he learnt how to make them

The Carbide you have may not be so good for a final finish... but it may be great for hogging out 98% of a job and then the last 2% can be finished with a sharp HSS tool

You've got all that to learn

Just don't chuck anything out thinking it's useless, put it to one side until your skills improve

Learn how to grind tools properly and how the different materials perform

Edited By Ady1 on 21/03/2023 17:50:11

Thank you for the info about the inserts. Those types look like a good starting point. I'm not discouraged, actually I found interesting the complexity of so many variables when it comes to inserts. But I'll dig into it later. So far I got some 20mm brazed tools. I picked P30 carbide type since I understood that this is less prone to break. But even so one tool was poorly packed and is missing a small piece.

I couldn't help myself and bought another 2m/40mm unknown steel bar. And a 0.5m/60mm one. To my excuse, they were only 1km away. I wanted to quickly cut one slice to try it just before going to sleep. But it took me at least 15 min to cut the 40mm one with a miter saw! There were 2m of sparks, my ears were ringing and I almost set the garage on fire in the process with a nearby plastic bag. And I supposed I woke up everybody again. But this metal is not so bad.

You are making progress, and having some success!

Good, Keep at it. You'll getb the nag of feeds and speeds.

Howard

You mention a wet wheel to grind your tools, for the carbide tipped tools you need a Green grit wheel and/or a diamond wheel, both of these are normally used dry.

Emgee

I have a green wheel. Is interesting that to grind carbide you need actually a softer material that regular grinding wheels. I used it to fix a brazed tool that had a small dent. There is a picture in a previous post in this tread. I was looking also for a diamond wheel but I couldn't find any reason to justify the price. The green wheel was enough to make the tool sharp again.

There is sharp and there is properly sharp! What may look like it is sharp (would cut you) might need a very much finer finish to the cutting edge. Look up ‘honing’.

Today I tried a knurling tool and I noticed that the tool post is rotating. I didn't pushed the knurling tool to much. But there is something wrong with this QCTP. There is no locking mechanism. That central screw has a big nut (removed in the picture) and that's it. There is a large pin marked by the arrow in the left. I can pull it out. But there is no corresponding hole in the compound where that pin to enter to stop the QCTP from spinning.

What is even more strange is that I can't lift the tool post. I remove the nut but the washer (right arrow) can't pass over the threaded part of the screw! How was this tool post mounted in the first place?!

Now I noticed that I don't have the original QCTP:

What is that under the nut - it doesn't look like a plain washer?

It is a thicker washer and it fits exactly in the tool post. It clearly is part of the tool post. I was able to lift it a few mm by rotating it like a nut. But now it is stuck. I would have to use a plier to rotate it further. But it doesn't look right.

Edited By Sonic Escape on 04/04/2023 19:41:15

Looks like the inner edge has been burred / 'spread' by overtightening of the nut, keep going and 'unscrew' it, then de-burr the hole until it will fit over the stud.

If anyone knows otherwise, now is the time to speak.

..you really need to check that the bottom of the toolpost and the surface of the topslide are flat and that there is full contact to maximise clamping friction, and that the thread on the stud is sufficiently long for the nut to be exerting pressure on the toolpost and not 'bottoming out' onto the stud's unthreaded portion.

Edit; just noticed that it looks like the toolpost is hanging out over the sides of the topslide (although could be the angle of the picture) - if it is much too big, it won't help the situation..

Edited By DiogenesII on 04/04/2023 20:13:11