Axminster Engineering Lathe Course – Update

[Andy CarruthersParticipant @andycarruthers33275]

As requested a (brief) update on the Axminster 2 day Engineering Lathe Course I attended recently

The course ran 09:00 to 17:00 on consecutive days with 5 attendees. I felt out of my depth as I entered the training suite, one glance at the workshop immediately put mine to shame. However, Bob Rolfe soon put us all at relative ease – the SC4 lathe is a bit bigger than my WM180 with more features – though still familiar

Apart from tinkering over the past few months I haven't touched a lathe since 1977 at school, the basic principles haven't altered, but my confidence was more the issue, I want to do things the "right" way from the outset

In preparation I had read a couple of books though a couple of others remain unread

When I looked at a sample test piece and drawings my immediate response was that I would never be able to make a similar test piece to the same standard. But that's the point – develop the skills and expertise to make the test piece

Two days passed in a blur, an awful lot of information is imparted in such a short space of time. Of paramount importance is workshop safety, and honestly I had ignored or forgotten some simple stuff so am grateful I haven't injured myself previously and appreciate the *reminders*

Conducting the simplest operations gave me plenty to think about, which way does the tool move when turning the dial, and by how much? because the dials are calibrated in segments with length per segment ie 0.02mm per segment

Digital micrometer has been a revelation too, I knew my digital calipers were ok to a point, but the lack of accuracy really showed up when comparing to digital micrometer – problem now solved

I hadn't realised the calibration rings move either so zero can be set and pieces cut using the calibration rings. And as an aside, it turns out very few, if none, of the entry level machines are accurately calibrated before leaving the manufacturer (broad sweeping statement…) so the only way to get accurate dimensions off the machine settings only is with DRO

I digress…

I left the course thinking my WM180 is a piece of crap, but when I went back to my machine it turns out to be better than I thought, I do need to adjust the saddle but in all other respects – as far as I can tell – it is a pretty much spot on

As the course progressed, and as my confidence improved, I managed to produce a half-decent test piece. Still much to learn, but already with the skills I learnt and improved confidence I feel much more able to deliver precise results

Now my next challenge is to purchase a bigger lathe, because the WM180 just isn't long enough… and until Santa arrives I hope to go on the Axminster Milling course so I can get 2 prezzies, because I can already tell my mini-mill won't be big enough either

To finish, I cannot recommend the Axminster course highly enough. Bob is an excellent – and patient – instructor and throws in real-world experiences to back up the practice. The course has taken me from incompetent novice to competent but inexperienced novice with a desire to learn more

[Andy CarruthersParticipant @andycarruthers33275]

[Ian Skeldon 2Participant @ianskeldon2]

Sounds like you have enjoyed the course a lot, where are the courses held ie which county/town/city?

[NJHParticipant @njh]

Ian

I think you will find that it is Axminster in Devon – the home of Axminster Power Tools. A net search for them will give you a view of all the goodies available and details of courses. I do go over there from time to time …….. but it can get expensive as I always seem to find something that I need!

Norman

[Keith FoxParticipant @keithfox28514]

I went on the same course in August and I have to agree with Andy that I also cannot recommend this course highly enough. I had never done anything on the lathe before, although I had bought a small Chinese one. I was so impressed with the work piece that I managed to produce. I am thinking of going on the 5 day, lathe and milling course some time next year.

Unfortunately, when I cam back from the course I looked at my lathe and decided that it wasn't good enough so immediately order a Sieg SC4 (the same as used on the course) from Axminster.

Keith

[not done it yetParticipant @notdoneityet]

the only way to get accurate dimensions off the machine settings only is with DRO

Andy,

Not necessarily true. They would, of course, like you to purchase one! The accuracy is in the consistency of the lead screw threads, once you take up the backlash. DROs come in various flavours.

Those that highlight readings to 0.01mm may well have a much poorer accuracy (+ or – 0.04mm?), once you read the smaller print. Those that read to 0.001mm should be at least better than 0.01mm absolute – but they are rather more costly than the basic 0.01mm type.

Glad you enjoyed your course. Being safer is a good plus point on its own.

[JasonBModerator @jasonb]

Also depends on what accuracy you think you need, I seem to manage without a DRO on my lathe, plenty of running models can't be wrong!

[BazyleParticipant @bazyle]

Really curious as to what the test piece is – go on show us a picture.

[Andy CarruthersParticipant @andycarruthers33275]

Regarding my comments on DRO – I tried to convey above that the lathes are only accurate to a point, and off-machine measurements give true accuracy. DRO are much better but still not necessarily accurate enough for some work. As I am learning, there are several ways to do things, but the lack of accuracy inbuilt into the lathe came as a surprise

I'll post a picture soon

[HopperParticipant @hopper]

How do you think they made Spitfires then? No DROs in those day, but plenty of accuracy.

Not unusual for lathe work to be done to tenths of a thou using the dials and operator's "feel". One trick they used was to turn the topslide to about 6 degrees. By using the topslide handle to put on the cut, one thou movement of the topslide moved the tool inwards by one tenth of a thou.

[thaiguzziParticipant @thaiguzzi]

Posted by Hopper on 16/10/2017 05:16:41:

How do you think they made Spitfires then? No DROs in those day, but plenty of accuracy.

Not unusual for lathe work to be done to tenths of a thou using the dials and operator's "feel". One trick they used was to turn the topslide to about 6 degrees. By using the topslide handle to put on the cut, one thou movement of the topslide moved the tool inwards by one tenth of a thou.

Exactly!

Top slide trick is an oldie but goodie, especially with a shear tool in the tool post.

[Andy CarruthersParticipant @andycarruthers33275]

@Hopper – please re-read exactly what I wrote and not what you think I wrote. My comment about DRO relates to the machine calibration, not how an operator compensated for the lack of machine precision. I am very aware there are excellent machinists producing superb work on imperfect lathes

[BazyleParticipant @bazyle]

Posted by Andy Carruthers on 15/10/2017 16:37:02:

it turns out very few, if none, of the entry level machines are accurately calibrated before leaving the manufacturer

I think you may be running into metric > imperial compromises. A lot of lathes have a 1mm pitch cross slide screw then mark the dial in a way to make it look like thou divisions so of course they are a bit off. You just do a precise measurement at the last few thou.
However there was one period I believe when Myford used rolled threads which weren't quite accurate.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andy Carruthers on 15/10/2017 21:23:34:

… the lack of accuracy inbuilt into the lathe came as a surprise

 

Interesting point. I've noticed that many Model Engineers like to check their lathes, sometimes as a hobby in itself. Headstock and tailstock alignments, run-outs, bed wear, bed twist, levelling, Rollies Dad, etc. etc.

All very interesting but I don't think I've seen anyone mention careful testing for vibration, or confirming the accuracy of their lead-screws. I've come across both checks in professional sources. Can anyone explain why amateurs don't seem to bother much about vibration or their lead-screw accuracy?

Ta,

Dave

Edited By SillyOldDuffer on 16/10/2017 09:47:19

Edited By SillyOldDuffer on 16/10/2017 09:47:40

[not done it yetParticipant @notdoneityet]

On top of the above post, Myfords with a single lead screw (standing in in for a power feed drive) was a cost cutting compromise. Power feeds do not need to be so precise/accurate, but threading lead screws do. Wear on the threading lead screw, for power feeding, is not an ideal situation and will eventually lead to some inaccuracy along the length of the screw.

[HOWARDTParticipant @howardt]

A DRO or any other device on a lathe indicates distance moved not the size of the part in the chuck. I allways use the dials as indication of movement and used a micrometer to tell me the size of the part.

[Perko7Participant @perko7]

Anyone know of similar courses available in Australia?? TAFE Qld used to have adult ed classes in all sorts of things but they don't seem to offer them any more.

[BazyleParticipant @bazyle]

Posted by SillyOldDuffer on 16/10/2017 09:46:47:

Can anyone explain why amateurs don't seem to bother much about vibration or their lead-screw accuracy

I think both are covered on the forum but couched in different terms such as headstock noise and leadscrew wear.

[Brian WoodParticipant @brianwood45127]

SillyOld Duffer,

I have measured the accuracy of the leadscrew on my ML7R lathe, using the most worn section in front of the chuck to do so and then extrapolate the measurement to the whole leadscrew length

The value I obtained was + 0.0018 inches in 25 inches of leadscrew. The positive figure indicates that the travel induced by the leadscrew is greater than for one of perfect pitch. The comparator for this measurement was the Newall DRO on the machine.

I thought that was pretty good for a well used hobby size machine and certainly not worth worrying about

Regards

Brian

[NJHParticipant @njh]

"Wear on the threading lead screw, for power feeding, is not an ideal situation " –

It's a valid point that, with the Myford, the leadscrew is used for powered feeds as well as for screw cutting – the question is though – how often do you use your lathe to cut screw threads ? In my case hardly ever. On the other hand powered cross and longitudinal feeds I use all the time.

Norman

[Anonymous]

Posted by NJH on 17/10/2017 19:40:53:

the question is though – how often do you use your lathe to cut screw threads ?

Not as often as I use the power feeds, but nevertheless quite a lot, probably over a hundred. I rarely use circular dies on the the lathe. But my lathe does have separate feedshaft so I don't need to worry about wearing out the leadscrew.

Andrew

[NJHParticipant @njh]

I’m pretty relaxed about it – a replacement leadscrew for the S7 is about £120 – and I doubt that I will need one in the near future !

My interest is at the “small” end of things and BA sizes are the “norm” so taps & dies are the usual order of the day.

Norman

[Neil WyattModerator @neilwyatt]

I have yet to meet anyone whose actual requirement for accuracy exceeds that of their lathe in a hobby context.

Plenty of people who worry that their lathe isn't accurate enough.

Lots of people who don't realise that the errors they seek to eliminate may be beyond their capacity to measure them, especially when it comes to angular and pitch errors.

Working with telescope guiding is fascinating, when you need to track something over degree or two's movement to a sustained accuracy of a second of arc and you see how big the cyclical error in a 'precision' worm can be.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Neil Wyatt on 17/10/2017 21:59:15:

…

the errors they seek to eliminate may be beyond their capacity to measure them…

I agree. I think the most accurate thing I can measure is time, closely followed by frequency to about 1 or 2 parts in 100 million. Lots of 'ifs and buts' about it though.

Around room temperature I can measure a steady temperature to about 0.2C.

DC Volts, Amps and Ohms, about 2%, again over a limited range. AC, no better than 10%

In the workshop, the best I can do with length is 0.01mm with a micrometer up to 25mm. My digital calipers are no better than 0.02mm up to 150mm and that depends on feel. I don't have a good general way of accurately measuring lengths greater than 150mm. The worms on my lathe and mill are 'reasonable' compared with a DRO, but a microscope (which can see sub- micrometre differences) reveals that they're only accurate on average. There are inconsistencies per turn if you look close enough. My DTI has the opposite problem. It's pretty good at 0.01mm differences, not so hot adding them up over a few millimetres.

Life gets difficult when you're serious about accuracy. Calibration becomes essential and maintaining accuracy beyond the range of your equipment is a real challenge unless you can do some sort of comparison. Most of the time my metalwork is rough and ready. It is interesting to see how close you can get though. For example, as a challenge, how accurately could you make a rod close to 3.0000 metres in length at 18C?

Dave

[MuzzerParticipant @muzzer]

There are some applications that truly do require precision. Here's an old mate of mine talking about what they can achieve these days with commercial equipment. In contrast, my workshop activities are at the agricultural engineering end of the spectrum.

Murray

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