New lathe arrived today : The ongoing saga

"There are no modelling engineer's clubs in Cairns ; it is too small." Is that Cairns in Queensland? population 150,000.

It's a huge town - 30 times bigger than my nearest so will have about 300 home workshops. But even better you have a men's shed with what looks like a 12 in lathe and milling machine. They will also tell you where to get material. If you get down there and pit it about that you are interested in model engineering lots of others will start to come forward. Then mentions on here and other forums will also get the message out.

FWIW..From your pic you've got too much shaft protruding from your chuck; and, I assume the you have a tailstock centre fitted & supporting the shaft, what is happening is that with the set up you have your are deflecting the shaft from its rotational axis by pushing it with the parting off tool this will cause the shaft to 'whip' eccentrically about its axis irrespective of the speed / feed used, thus allowing the shaft to climb over tool centre height setting & either snap your tool or bend the shaft, or both, also the groove in the shaft will be opening & closing against the parting blade due to the pressure from the tailstock centre, with the same effect.

Malc Broadbent has given a good general set up write up for parting off earlier to which I use & would agree with, & which I'm sure many others use.

George.

There was too much slop in the top slide : I have made some adjustments to the gib nuts now so things should be better tomorrow. I had not looked at that before. I probably got away with it on aluminium but not with steel.

NOTE : link to the '' men's shed '' has been blocked by my anti virus for some reason.

Edited By Brian John on 29/08/2015 12:22:10

"With the Woodworking area fully functional, we're now concentrating on our metalworking shop. We've just installed a decent size lathe and a new milling machine arrived in early January 2013. We're on the lookout for a folding machine and guillotine, but our 240 volt power supply, does limit what we can use.

We hope to see many improvements to the metalworking shop in 2013, but we could do with a few more fitters and turners to assist our small but enthusiastic metalworking team"

It's not fair, all this, + welding, + woodworking for just $30 which is about tuppence in real money and its 22C and not raining like here.

Don't make things too complicated. You don't need an expanding mandrel. Just chuck a bit of mild steel roughly the diameter of the boss. Turn it down to be a good fit in the bore for a distance of about twice the thickness of the boss. Then turn half of that down to a convenient size for threading for a nut.

Don't remove it from the chuck. Fit the flywheel using a nut and some washers. You can then turn the outside and it will be co-centric with the bore. Just don't take too big a cut.

Russell.

Hi Brian, I've learned a huge amount just watching Chris @ Clickspring's videos on youtube.
https://www.youtube.com/watch?t=11&v=Yt20qj1DHpc

He works to very high standards but his videos are easy to follow. Some of the lathe sequences are speeded up but that helps.

(Plus you'll be able to understand his weird accent )

The reason for using an expanding mandrel is to ensure that both sides of the boss are parallel to each other. Probably not needed in this case but the results would be very close to the holy grail of machining - do all of the machining in one go. That way the basic accuracy of the machine is achieved without any fiddly setting up.

John

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As you said John, probably not needed in this case.

Always use the KISS principle.

Russell;

I tried to cut the 6mm thread today but I had no luck at all. It just would not cut. I will have another go tomorrow. I may have to reconsider the expanding mandrel. I am think of using an M4 socket cap. I will also try to buy some 6mm aluminium round bar but my usual engineers supplier does not stock alumnium. I have none on hand but this will be easier to work with rather than trying to machine 6.35mm silver steel.

In the meantime I found that there was still some play in the carriage (?) There is a large socket cap bolt that I had not tightened. Unlike the smaller bolts on the top slide and cross slide, this one does not have a lock nut so I will have to keep an eye on it. It could be a problem if it keeps moving.

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That's the carriage lock. You only need to tighten that when you want to lock the carriage in one place.

Pete

Brian, what part of Cairns are you in? I'm at Edmonton and could help out a bit if needed. I have not owned a mini-lathe like yours but have been mucking about with lathes in general for a good few years, most currently an old Drummond M type and the principles are all the same. If you are on the southside I could give you a hand anytime. North might require some planning and a cut lunch.

There are a couple of blokes building model engines that I have heard of in Cairns but no club as you say. It seems like due to the lack of mechanical industry hereabouts, there are not as many mechanically-inclined tinkerers as there might be in more industrial centres. There is one bloke who uses the Mens Shed to make model airplane engines so you might be able to make contact with him. I don't think they have regular meetings, you just join and to and use their machinery at your own schedule. I keep meaning to sign up because they have a quite nice Hafco 45 vertical mill that could be handy for jobs too big for my vertical slide.

Edited By Hopper on 30/08/2015 08:58:29

The block is probably just down to the name. Obvious connotations and over zealous blocking.

John

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If you google Cairns none ferrous suppliers you will probably find some one that supplies aluminium locally. Very likely if there is some one who sells steel.

On simplicity you may find that one of your chuck jaw arrangements can grip the inside of the rim of the wheel so that you can machine the OD and one side in one go. In my view there is very little difference in taping a hole and slitting it for an expanding mandrel that running a die down some bar.

Few people would screw cut M6 or 1/4" by what ever. They would use dies. This is the sort of thing that is likely to be anybody who owns a lathe first major purchase. Screw cutting is used when this isn't possible. As far as dies go it's best to buy HSS split ones and taps to go with them. There are some very poor quality sets around. On taps money can be saved by just buying 2nd cut ones but on materials like stainless it would be better to have 1st cut as well. The other type plug is needed when tapping into a blind hole. When I started I bought individually as needed from an engineering supplier. The die stocks in sets can be a bit indifferent as well. It's an area where people tend to get what they pay for especially at the very cheap end. Good quality tool steel ones are ok as well really but most tend to be rather poorly produced.

I tried to find some web pages on screw cutting especially with your style and size of lathe which I believe doesn't have a screw cutting indicator but couldn't find anything at all. I did find a video that was using a mini lathe that did have an indicator for metric threads but that's not really suitable. Maybe some one else knows of one.

John

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You will find a die for this size is a bit difficult to use as it is hard to grip the rod tight enough to take the high cutting force so screwcutting is a good thing to master.
Stainless can be a bit hard and difficult to cut so stick to the silver steel.
But silver steel in its shiney new state is hardish. So cut off a short length enough for the job in hand and heat one end of it up to red hot in a gas blowlamp or cooker when the wife's not looking. After a minute or so hot withdraw it slowly so it gradually cools down. You can run a file over it and will see it is now softer. By heating only the end evenly it should not bend.

Mount it in the chuck with only about half an inch protruding to screw cut it. It is normal to work this close in so get used to it. We established earlier that the pointy first tool you were using is your screwcutting tool. Research on the web and youtube for screwcutting. There is no point in us giving the detailed instructions here. You will be looking for the offset or angled method, not the 'plunge method'. There will be lots of people now jumping up and down saying the plunge method works for me blah blah blah but ignore them. The old timers invented the offset method for the vey good reason that it works better on small lightweight lathes.
Do not try to screwcut under power. You will have to turn the chuck by hand. This is perfectly ok and I am still doing it on some of my lathes for which I still haven't made a mandrel handle (look that up and make one one day). Also you will only want to take a cutting depth of about 3 or 4 thou each time, and 1 thou towards the end. Yes it is slow but again ignore those who will say they take 30 thou cuts as they just want to boast that they were in industry with an elephant sized lathe turning battleship propeller shafts.

Brian, it might be worth your while looking up either the yellow pages, or the internet, there are quite a number of metal suppliers in Cairns.

For some work you can even make do with off cuts of rebar from a building site.

Ian S C

I missed the OP on this.

Brian, Norweld down in Portsmith on Ogden Street sells nice-machining ally offcuts of all shapes and sizes by the kg. Quite reasonably priced. It is "marine grade" which is as far as I can find out, 6061 or 70-something in a soft or medium temper. Machines beautifully. They are the only place in Cairns that sells offcuts. Ulrich Aluminium at Woree will sell you small quantities but at stupid high prices. Best place in Cairns I have found for small quantity steel is Tonkin Steel at Portsmith, unless you have found someone better?

Thank you for all the advice.

Hopper : I have taken note of those suppliers and I will call tomorrow. Yes, I may need your help soon ; I live at Mooroobool.

Why would you want to lock the carriage in place ? Before I tightened this bolt up a bit there was movement in the carriage. Obviously tightening it up a lot stops it moving but a 1/4 turn removed the slight wobble it had. I was still having problems with getting a clean finish today. I am hoping that when I try tomorrow, things will be better now that I have removed all movement from the carriage.

I was warned by the company who sold this machine that it was not really suitable for steel and that it was better to stay with brass and aluminium. I was a bit surprised at this advice because it has a 500 HP motor. The Sieg C2 lathe which is a MUCH bigger 12 X 7 lathe only has a 250 HP motor. Are there other factors in play beside the power of the motor ?

I am using top quality HSS taps and split dies purchased from Arceuro in the UK.  I have found carbon dies to be rubbish. I am machining the 6.35mm silver steel bar down to 6.00 mm because I do not have any 6mm bar on hand at the moment. I will buy some 6mm aluminium bar instead as it should be easier to work with.

I regard screw cutting on the lathe as an advanced technique. If I am having trouble doing basic lathe work then I do not think I should be contemplating screw cutting on the lathe just yet  Cutting a 6mm thread on aluminium should be easier than cutting on silver steel.

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