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michael hobson11/07/2013 19:01:30
7 forum posts

Hi am a beginner to a lathe.I had a go a turning yesterday,I think I did all the right things like making sure the cutting tool was set at the correct height and that the rod I was practising on was sticking out of the chuck no more than about 4 inches.On completion the surface was very rough looking more like a threaded piece i.e. covered in ridges.Any help greatly appreciated including pointing in the right direction of a damn good book,which also gives little projects to get started.Thanks

JasonB11/07/2013 19:07:28
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22574 forum posts
2634 photos
1 articles

What diameter was the rod, 4" is quite a bit to have sticking out of the chuck, also what material were you cutting?

HSS or carbide tool, and what lathe & speed?

J

michael hobson11/07/2013 19:17:16
7 forum posts

Hi diameter about 3/8 " I think it was apiece of mild steel but may have been something else carbide tipped tool, portass 's' lathe ,not sure of speed How do I measure.

jason udall11/07/2013 19:18:51
2031 forum posts
41 photos
Can I suggest a tailstock...when I started out with hobby gear I thought "won't need a tail stock for that"...well I would now suggest any thing more than 5x diameter then definitely tailstock..and if possible even then..also I tended to want to run too slow...my machine at work all enclosed so sort of scary working in the open...so don't be too mean with the rpm...10 000 /diameter ( mm) for mild steel. ..and most of all practice...maybe something first that finished size isn't too important..it will come
jason udall11/07/2013 19:21:43
2031 forum posts
41 photos
3/8?...and4"...yeah a bit rich. .you could use up to 1000 rpm..btw some brazed carbide doesn't perform too well in ms
Steve Withnell11/07/2013 19:23:31
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843 forum posts
222 photos

Look up Harold Hall for a damn good book - "Lathework A Complete Course" He has a similar title for Milling, also good.

One of the old classics is **LINK**

But it is an old classic. He will have you mixing your own marking out fluid from sulphuric acid + copper sulphate solution, when what you need is a big dobber of a spirit marker from WHS. Nothing wrong with his marking out solution, just not the best option anymore, but still a good book.

JasonB11/07/2013 19:26:11
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As the other Jason says 4" of 3/8" stock sticking out is really too much not helped by the fact that carbide can be a bit "blunt" compared with HSS and tend to push the unsupported work away from the tool. Try again with 1" sticking out.

Speed wise you will really have to work it out from the motor rpm and the pullys used as its unlikely to be an original motor. Good news is that 3/8" steel can be run probably as fast as the lathes bearings can take.

My prefered book is " The Amateur'sLathe" by L.H. Sparey, bit dated now but same principals still apply.

J

Ady111/07/2013 19:29:33
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5065 forum posts
734 photos

Try and get a bunch of scrap roundbar and practice practice practice

Think about what you're doing and how you can make it stiffer, easier, faster, simpler

Lathes are like Women(or men)

You can read as much theory as you want but it's only once you get your hands on the real thing that you can get some useful experience

I would recommend "The amateurs lathe" for bedtime reading

Edited By Ady1 on 11/07/2013 19:32:02

Alan .20411/07/2013 20:36:19
304 forum posts
14 photos

Slow the feed down and take a fine cut and go from there thats how I do it.

Alan.

Muzzer11/07/2013 21:17:13
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2904 forum posts
448 photos

I think I mentioned that my first lathe was a Portass S and it served me well for quite a few years. The main problem is that it's not very rigid and has plain bearings, so you have to keep it well adjusted and lubricated and you can't take big cuts. As suggested above, use the tailstock where possible and minimise the overhang from the headstock as much as possible

You should make sure the main bearings are nipped up so they are just not quite about to bind and keep things well oiled (it, not you!). Also tighten up and lubricate the gib strips and leadscrews in a similar fashion. At least there are only 2 slides on the S.

You can't safely run this machine fast enough to use carbide tools properly, particularly on small diameter stuff. I'd stick to HSS unless you are taking the skin off a casting. And get yourself a decent piece of free cutting mild steel!

The guy who sold me mine was an old hand and he ground me a special HSS tool that had a lot of side rake (the angle at the "top" of the tool behind the cutting edge, which is usually zero for brass and perhaps 10-15 degrees for steel), something around 40 degrees or so. Sounds rather a lot but this allowed fine cuts up to perhaps 1/4" depth without judder. When honed properly with an oilstone, I could get a pretty good finish this way.

One key advantage of HSS over carbide is that you can get it sharpened up easily. It seems there are some pretty dodgy carbide tools out there and you'd struggle to do much with any of them. You need to give yourself every opportunity to succeed!

Muzzer

Robbo11/07/2013 22:35:11
1504 forum posts
142 photos

The "old hand" who showed me the way always insisted on using the tailstock for support unless the amount of workpiece sticking out of the chuck was less than its diameter.

Phil

stevetee11/07/2013 23:46:07
144 forum posts
14 photos

I think it's worth pointing out that there are some absolutely dreadful rubbish sold as carbide tools.

Those little sets of carbide tools in boxes are utterley useless and the box is the best part of the set.

Eric Cox12/07/2013 08:55:10
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541 forum posts
37 photos

I was always told never to have more than 1 1/2 times the diameter sticking out without support.

OuBallie12/07/2013 09:39:17
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1164 forum posts
662 photos

Michael,

Welcome to a (the) most absorbing and satisfying hobby.
That rod is whipping around in a fashion that would be the envy of the sadomasochism set.
May I suggest something bigger, say 1", as this will allow you to get the speed needed.
What was the tool shape?
One thing that I learned using my V10P was that, at the end of a cut, to wind the tool in a couple of divisions and then traverse towards the tailstock whereby the tool takes a sliver of metal off.
Result was and still is a finish close to a ground one.
Did this using the tangential tool when making the bearing pins on the axles for my overhead 'crane'.
A special 'slicing'? tool can be made, but I haven't found it necessary yet.
 
Geoff - Working on the 1935 Austin Seven Ruby for the next few days.

Edited By OuBallie on 12/07/2013 09:42:09

OuBallie12/07/2013 09:39:17
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1164 forum posts
662 photos

Apologies for the double post.

Geoff - Internet slow today.

Edited By OuBallie on 12/07/2013 09:40:37

michael hobson12/07/2013 14:03:46
7 forum posts

Hi thanks for the ever so helpful replies so far,the tools I was using were bought from rdg tools,left and right brazed carbide tips.It seems with such a small lathe to use the tailstock wherever possible,hope this is correct.I have been wary to tighten up the bearings but it seems I have been running them far too slack.Will look at this and also tighten up the gib strips a little more as there is a very very small amount of play almost indiscernable.Lathework a complete course is already ordered.Have already got the amateurs lathe but not read it fully yet .Many thanks Mike

GaryM12/07/2013 16:51:31
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314 forum posts
44 photos

Hi Michael,

I'll second what stevetee said above. When I first got my mini-lathe I also bought a set of the carbide tipped tools that are frequently sold by the hobby suppliers because I didn't feel confident enough to grind my own. I had some free-cutting mild steel and couldn't understand why I was getting such a poor finish, even for a beginner. So I decided to try grinding a tool and even though it was my first attempt and I hadn't used a grinder for years, the finish was so much better that I've not used the carbide tools since. My grinding skills have improved as well. Try one yourself and see.

Also this thread **LINK** might help

Gary

fizzy12/07/2013 19:01:18
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1841 forum posts
120 photos

I started on all brass parts and have only recently progresses to getting good results with mild steel - you can read all the books and it still turns out like a pig! As said above, try grinding your own tools and see what a big difference you can get.

Ian S C13/07/2013 13:31:21
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7468 forum posts
230 photos

Use HSS tools, thats the type the Portass was designed for (unless you go for carbon steel), and get hold of L. H. Sparey's book "The Amateur's Lathe", old, but not out of date, it matches your lathe nicely. Use a tail stock centre, and for 3/8" I'd have no mre than 2" out of the chuck. With HSS you can take a much finer cut than carbide(that stuff needs to work hard), use a slow feed, at the top speed, and you should get rid of the threaded look, a thread is just a fast feed, shaped by the tool being used. Ian S C

Ady113/07/2013 13:56:29
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5065 forum posts
734 photos

So I decided to try grinding a tool and even though it was my first attempt and I hadn't used a grinder for years, the finish was so much better that I've not used the carbide tools since. My grinding skills have improved as well. Try one yourself and see.

Once I acquired some HSS ability I went back to carbide, those brazed ones, and ground my own tips on a "green grit wheel"

I now prefer brazed carbide because the tip lasts for so long compared with hss but each material has its place and should never ever be discounted

Edit: Once you can grind stuff ok then maximising your workpiece stiffness becomes the major issue

 

Edited By Ady1 on 13/07/2013 13:58:27

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