Bullet bitten

[paul]

I shelled out for my first lathe today (the Clarke CL300 jobbie) with a great value starter pack from those nice Chronos people (only a 220 mile round trip!).

Expect a huge number of embarrasingly ludicrous questions! I have two or three lined up already but I'm off to google for the answers rather than show myself up immediately

I suppose I am officially addicted now.

[Chris Kelland]

So! you were at the open day as well?

Chris K

[paul]

On Saturday yes Chris. Like a kid in a candy store - mind you I had no idea what half the stuff in there was actually for

[paul]

Here we go!

First I'll post two links I've found that might be of use to beginners (like wot I am).

This one is translated from Japanese but is quite understandable...

www.nmri.go.jp/eng/khirata/metalwork/index_e.html

and this one if from the good 'ole US of A...

www.americanmachinetools.com/how_to_use_a_lathe.htm


My first question arises from this line on that second site...

"For most straight turning operations, the compound rest should be aligned at an angle perpendicular to the cross slide, and then swung 30° to the right and clamped in position."

Is that right? And why does the tool post have lugs on the bottom that seat in the slide only when perpendicular?

Doh, that's two questions! Never mind

[Lurkio]

Hi Paul,

Good luck with your new lathe!
I should ignore the compound rest (compound slide) instructions on the site you mention.
More important to ensure your lathe is set up for the particular job in hand, and to provide your tool-bit with plenty of support underneath (i.e. solid metal), with as little overhang as possible.
This keeps things nice and rigid.
So, to get you started, leave your compound slide at 90deg to the cross slide and get stuck in!
I'm sure you'll get plenty of good advice from the very capable people on this forum. Don't be afraid to ask, we all had to start somewhere.

Just to make you feel better, as a young man I was assigned to work with a skilled turner for a while. I told him I found using a lathe a bit tricky, and he looked me in the eye and said: 'Even a worm can turn." There's nothing like encouragement!

Lurkio.

[starspider]

Hi Paul
Have fun with your lathe. The reason us old turners used to swing the top slide is so that you can put on very light cuts as the tool is advancing at an angle rather than straight into the work piece or youare turninga very small diameter on a large machine and the compound slide is fouling the tailstock.
colin

[ron]

Paul, good luck with your purchase, I think you'll have a lot of fun with it, only thing I can add to the advice already given is after you understand the basics of what the machine can do is practice, turning is a practical skill that really becomes second nature after a while. I hadn't used a lathe for 30+ years since I was taught as an apprentice, when I bought mine a couple of years ago I was surprised how it all came back.
Buy TC tipped tools,preferably the indexing type, for most jobs they are far superior to HSS, wish they had been about all these years ago!
Ron

[Laurie_B]

Good luck with your new lathe.Once you get the feel of it,you'll soon be away.
Like Ron,I bought a second hand lathe (a Myford) about 5 years ago.Hadn't used a lathe in years,but I found it soon all came back to me too.
A website that you might find useful is www.lathes.co.uk/ by Tony Griffiths.You might find the "Lathe Technical Data" really helpful.

[paul]

Lurkio: I made a number of aluminium shims by cutting up some 10mm angle these seem to work just fine - but I can see why the chap recommended a height adjustable tool holder!

I tried a few simple turning operations on some round brass stock - managed to get the depth of cut about right and a nice sharp sholder

Starspider: Of course, why didn't I think of that! While I'm learning though I'll just keep it at 90deg for now so I can see the effect of different tools/speeds/cutting depths/advance speeds (or whatever that's called!)

Ron: I bought a special starter pack with the lathe that includes six TCT tools What is meant by 'indexing' ? To be honest I'm not sure what the spefici purpose of each tool is... maybe I'll post a picture later and someone can tell me!


laurieb: thanks for that link... very useful

Another question:

I was looking at this page on Alan's site...

www.alanstepney.info/page38.html

to get some idea of the speed to use. Why does the speed need to be reduced with larger diameter work-pieces? I would have thought the speed would vary depending upon the material and depth of cut (and maybe the forward speed)?

What difference does cutting faster make? (i.e. advancing the tool from right to left). I tried to vary this speed, cutting depth and turning speed but became not a little confused!

[paul]

Thought I'd post that pic now rather than later

From left to right the tools are stamped D14, C14, M14, A, A, L14. What is each for please and why aren't the two stamped A marked as 1/4" when the others are?

[ron]

Paul, look up 'Glanze' lathe tools in the Chronos or similar catalogue, and you'll see their indexing tools. I've one general purpose and one boring bar and they do about 95% of the time. I've also got a very fine parting tool that takes a replaceable HSS blade about 1/16" wide or so, excellent.
If you are looking for any sort of tooling try Ebay first, the TC tips for Glanze tools are a fraction of the price there that the dealers charge.
Ron

[Laurie_B]

paul said:

I was looking at this page on Alan's site...

www.alanstepney.info/page38.html

to get some idea of the speed to use. Why does the speed need to be reduced with larger diameter work-pieces? I would have thought the speed would vary depending upon the material and depth of cut (and maybe the forward speed)?

Basically,the table of rotational speeds is based on the linear cutting rate for the material concerned.According to my "Machinery's Handbook' (vintage 1943 edition!),the linear cutting speed for mild steel is quoted as between 90 and 150 feet per minute.
Depending on the diameter of your workpiece,its rotational speed (in revs per minute) should be set to maintain that linear cutting speed at the cutting point.So as the diameter reduces,the rotational speed has to be increased to maintain the same linear cutting speed.
The formula is simply expressed as:
Linear Speed=Rotational Speed X Diameter
As you note,the cutting speed does vary from material to material,for example you would turn brass at a higher speed than for steel.Also the depth of cut will have an influence;light,finishing cuts can be made at a higher speed than for heavy cuts.
Also the cutting tooling used makes a difference.For example, tunsten carbide tools are best operated at higher speeds than for High Speed Steel (HSS) tools.
Hope this helps.

[paul]

Ron: thanks for the tips!

Laurieb: most helpful thank you

I've found on a couple of occasions that I've created a 'collar' that gets pushed along while turning a piece of brass - my guess is that I'm trying to make too deep a cut - more experimentation needed!

One other thing; the instruction book (such as it is!) says that 0.25mm is the maximum suggested cut - this equates to 10 marks on the cross slide dial. Is it usual practice to zero the dial betwen cuts or to carry on winding the slide further in each time, going from 10 to 20 to 30 to 40 if I wanted to take off 1mm?

[ron]

Hi Paul, I don't do this millimetric stuff but basically keep winding, you don't need to zero and remember if you take a 5mm deep cut it's 10mm off the dia.
If you have say a 1" dia bar and you wan't it to be 3/4" dia, take a couple of heavy cuts till it's about 10 thou oversize then make your last cut at a higher speed 5 thou to finish it nicely or if you want to be more accurate take a 3 thou and then a 2 thou final cut, hence why you need accurate measuring kit [I'll let you do the metric conversion]
Do you have accurate measuring equipment, you need a vernier or a mic, a digital vernier is probably the easiest for a beginner to use.
Ron

[paul]

Ron - thank you! I'd just about figured that out, I managed to get a 8mm rod down to a pretty accurate 7mm with a nice finish. I also took a 4mm silver steel rod down to 3mm although the finish is rather more 'jumpy'. As the accuracy required for that piece wasn't great I spent a while repeating tiny cuts until I got the best finish I could. Anyway, that was my first practical application of the lathe - I needed a sub 3.5mm D bit but only had 4mm rod.

I only have a rubbish *plastic* vernier at present - I saw some nice ones at Chronos yesterday but thought I'd spent enough for one day

[baggo]

Paul,

Places like Aldi sell digital verniers for less than a tenner! I've had one for about a year and had no problems with it. It's the most useful tool I've ever bought and is in constant use. They're great when you need to turn down to a certain diameter. Just set the caliper to the diameter you want and then 'zero' it. Measure the diameter of your bar to be reduced and the reading is the amount to take off.

John

[paul]

Cheers John - that sounds very cheap compared to the £35+ ones I was looking at!

[Lurkio]

Paul,

Just to follow up on your earlier reply....aluminium packing pieces under the tool are fine for starters, but I'd swap them for something better (steel) when you can as I'm sure you'll find they gradually get 'squashed' with constant clamping.

Lurkio.

[paul]

Lurkio - I'd figured that might happen so I gave them a right good squeezing in the vice first!