Metalworking lathe buying advice

[guineafowl21]

Thanks for all the advice - I’ve got hold of a Boxford VSL. Pics will follow!

I did take on board the suggestions for Chinese machines, as I’m not against them. I learnt how to use a spindle moulder on a Charnwood W030, and didn’t regret buying it. Loads of features for the money - I’d have to spend ten times as much to get an industrial quality machine, new, with that kind of functionality.

 

[Fergie 307]

Well done finding that, nice machine. Look forward to the pics

 

[DiyAddict]

You are going to have some fun!! And yes, don't forget to post some pics. Good work.

 

[guineafowl21]

Here it is, installed in a nook with shelf for bits and overhead light:

I’ve made a few things - brass bush for the spindle moulder, turned down a spare bolt to size, cut a BSW thread, and made a thick washer for it, and a prototype quick change handle for the toolpost:

The toolpost handle is a bit rough - I think the insert was for aluminium, and blunt. Got some proper inserts now.

 

[TFrench]

Looks great to me! I've just bought a little lathe for my home workshop - it really annoys me to have to break the flow of a project to go to work to use it. I use the lathes more than almost any onther machine tool in the shop.

 

[DiyAddict]

Very nice, thanks for posting the pics, and nice to see you've already put it to work!

There's a bit of a learning curve associated with insert tools. Carbide inserts tend to be blunt for steel, and sharper for aluminium. They tend to chip rather than wear in lathe use, but the chips can be tiny and aren't always obvious. They're also designed for high speed and deep cuts relative to HSS. Some people say that for smallish lathes, HSS is a better choice, or that inserts designed for aluminium are more suitable for cutting steel. But I use them extensively on my 254s, which is a similar size. Reducing the feed rate can improve the finish.

It's worth looking up Blondihacks' Youtube videos - she has a very good 'starting out' series, one of which is devoted to tool choice.

 

[Fergie 307]

Nice looking old machine. If you want to work with aluminium the most important thing is to use a lubricant to stop the tool tip getting fouled. Paraffin is the best thing to use. Use the power feed where you can for finishing.

 

[clogs]

u bought the lathe, now u need to start saving for the tooling.....hahaha....
my tooling is worth more than the 2 lathes I have.....
def HSS for Brass/Bronze and ally......
from "diyaddict" with carbide, big bites at a high feed rate n no coolant is what they like....proff's get the swarf comming off BLUE....u def won't be doing that......Carbide come's into it's own with very diff metals like hardend St/Steel.... even crappy cast iron has hard spots....
I have a good seletion of carbide tools mostly with changeable tip's...(indexable).....
HSS is really cheap if u buy blanks and grind them ur'self, it's not a black art really....better if u can start with HSS plus cobalt, 5%...they'll do all u want.....
actually the same with drills....
what ever anyone says, parting off is a BLACK art to get it right everytime.....I've used carbide for that but gone back to HSS with cobalt again......

now u'll need a decent bench grinder...u can use the grey stones on HSS but everyone says u need white wheels to finish, I dont bother, anything special I finish with a hand held diamond stick....oh, green wheels or diamond for carbide.....
I can see the money disapearing already...hahaha....
I got lucky and bought a slow speed proff bench grinder....this is parked between my lathes and mills and only used for that tooling...I do have other grinders for sharpening drills plus another for donkey work........
dont bother with those brazed carbide sets off ebay etc....unless u can/have the kit to reshape them...
there is another good tool I'd be lost without is the diamond tool from Eccentric engineering, made in OZz but sold in the UK....u dont need their grinding tool....works very well, u dont need coolant with it....
u'll need to think about cutting metal....heard good results from Lidil/Aldi, they sell a small metal cutting bandsaw, made in Germany......
lastley join the "model engineering forum...loads'a knowlege there....ideal for small lathe owners.....
have fun.....

 

[guineafowl21]

I had another go at the toolpost handle - certainly a deep cut and slow feed seemed to help. I did get lots of long, blue ‘stringy bastads’ coming off. (I’ve been watching Doubleboost).

For sharpening the HSS I have a Wolf bench grinder or a Tormek T7 which should do the trick.

 

[DiyAddict]

I love watching Doubleboost - very skilled, modest and funny. I've learned so much from him.

 

[Daniel2]

I love watching Doubleboost - very skilled, modest and funny. I've learned so much from him.

He's an active member over on the mig welding forum.

 

[guineafowl21]

I have some questions about screwcutting. For smaller, and metric, threads, I tend to use taps and dies. I understand the tapping drill size needed for internal threads, but for external threads, what size do I turn the piece down to?

For example, for M6 should it be 6.00mm? It always seems very tight.

For Whitworth external threads, again which is the diameter to turn the piece to?:

 

[J-G]

I have some questions about screwcutting. For smaller, and metric, threads, I tend to use taps and dies. I understand the tapping drill size needed for internal threads, but for external threads, what size do I turn the piece down to?

For example, for M6 should it be 6.00mm? It always seems very tight.

That really depends upon what you want the finished thread to look like.
Personally I tend to prepare the OD with a tolerance of -0.0 +0.05 mm since this should always give me a full form thread.

The most important dimension for any thread is the 'pitch' or 'effective' diameter which, in the case of M6 is between 5.279 & 5.35mm which is usually controlled by adjusting a split Die but if you are screw-cutting then it's just a matter of adjusting the depth of cut.

If the OD is smaller than the nominal dia. but the pitch dia. is correct then the width of the flat at the crest will simply be wider than normal.

 

[Fergie 307]

J-G is spot on, use a split die then you can find tune the size. And always buy good taps and dies in hss. The kits you get tend to be rubbish. Tracey tools is a good source of quality taps and dies at good prices. For internal threads always use a first and second or finish tap. So the first one has a pronounced taper so it leads in well, and cuts a rough thread. The finish tap does what it says and brings it to final size. This avoids tearing and ensures you get a nice clean thread, especially important the bigger the thread, or the finer the pitch. And make sure you use an appropriate tapping fluid if necessary.
so going back to your original question as J-G says you want to start out with your bar a gnats oversize to ensure you get a full thread.

 

[clogs]

I make quite a few specials, nuts and bolts.....Brass n Stainless.....upto 35mm dia.....
I screw cut to "almost there" then use a good qual split die to finish off....
Biggest failure of diy threading is getting the die the correct way and useing a decent cutting lube....even a better qual die holder makes a difference......
I like old Brit and American makes....
Over the years have found a Rocol thread cutting drip bottle the most economic for hand threading...even smells nice....
I find it quite a work out cutting a fresh thread on anything over 25mmm/1inch now.....just getting old.....
one of my bigger tap wrenches....the smaller one is for upto 8-10mm.....ps bought it like that from a car boot....

 

[guineafowl21]

Thanks. I’ll get some decent dies. I have cut plenty of threads before, but never on something I’ve made myself.

So if I can’t test the fit of the thread during cutting, I’m aiming for the effective diameter as a minimum size.

 

[deema]

Take a look at Machinery Handbook, there is a free copy online, or just buy a copy. You will only ever need one edition; they bring out a new one every year. It covers just about everything you will ever want to know.
I cut the outside diameter close to bottom limit (minimum diameter) so that I don’t end up with the nut thread riding on the peaks. In most cases for my own stuff, I cut the thread to match a nut, rather than cutting to PCD (lazy I know, but I don’t think I’m alone) and it’s sooooo easy to cut the thread too deep due to it catching in the peak.

 

[J-G]

I cut the outside diameter close to bottom limit (minimum diameter) so that I don’t end up with the nut thread riding on the peaks. In most cases for my own stuff, I cut the thread to match a nut, rather than cutting to PCD (lazy I know, but I don’t think I’m alone) and it’s sooooo easy to cut the thread too deep due to it catching in the peak.

If the 'Nut' has finally been cut with a 'Plug' Tap and the 'Bolt' cut with a solid Die, then there is no chance that the thread will be 'riding on the peaks'. Starting with an under-size bar could increase the chance of cutting a 'drunken' thread higher and they are a nightmare!

For external threads I have a habit of using a split Die at maximum opening as a first cut and finish with a solid Die -- and I'll agree with @clogs in regard to using a quality die-stock, making sure it is free of swarf and supported by the tail-stock to make sure that the Die is held perpendicular to the axis.

Matching to a nut is the easiest way of measuring an external thread of course and in general is as close as you need to be. In the aircraft industry, press-tools and measuring instruments of course there may be a need for precision which can only be achieved by measuring with the 'three-wire' method but for the home workshop....

 

[guineafowl21]

Any recommendations for a good metal supplier? I tried Metals4U, who took a week to post my order. Note £16 delivery charge.

I can’t imagine how you can switch off the lights and lock the doors to your business on a Friday evening, with an order from the previous Monday morning still unprocessed.

 

[chaoticbob]

You could try The Multi Metal Shop - they're new boys on the block and are currently (or were fortnight ago at least) offering free UK mainland delivery as an introductory offer. I recently bought 300mm of 1.75 inch brass bar from them - £44 delivered, order placed 10th Aug, despatched RM 48 tracked on the 12th, arrived on the 14th. Metals4U would have charged £85 for a 250mm length of the same with delivery. So I was happy with that.
Bob.