Limitations of my lathe.

[niall Y]

I'm relatively new to working with a metal-lathe, And apart from distant memories from schooldays, I've had little opportunity, until recently, to get hands on experience.
Yesterday, I tried to carry out , what should have been a simple operation. Which was to take a whisker off the inside of an 18mm diameter, brass tube, to allow me to form a couple of 5mm wide rings, which could then be slipped over some thinner tube and be silver-soldered on. All this to help fabricate some whistle, tuning-slides, I am working on.
The first problem I encountered ,was in setting up the tube in the 4-jaw chuck. Up until now I usually do this by eye referenced off the cutter in the tool post. Though in the interest of accuracy for this particular job, I used a dial gauge. Well, that was an education! I gradually homed in on getting it perfectly centred when, as I was turning the chuck, I heard a slight knock and the needle lurched wildly. There is obviously something wrong with the bearing. The bearing problem isn't obvious. If you hold the chuck and try and move it ,it appears rock solid. It's only when you revolve it by hand that you hear the knock - and it's only a very intermittent knocking,
Undeterred. I then set up the boring bar and proceeded with the cut, The first few mm into the cut were OK, but then it stopped cutting. It became apparent that the cutter was pushing the stock out of the way and not cutting. All I was getting was a tapered shoulder part-way into the tube.

Plan B, then fell into place. This was to hold a hand-reamer ( Yes, I was able to find one of the exact size. courtesy of an old neighbour whose collection I had inherited.) in a mini-chuck attached to a revolving centre in the tailstock of the lathe. Then, by hand, I reamed out the tube, before parting off the two rings I needed.

I now need to try and sort the lathe out

 

[TFrench]

Start with the easy things - if the cutter isn't cutting properly it's most likely the cutter and not a spindle bearing. Check it's sharp and on centre first.
If you hadn't noticed the problem before using a 3 jaw could it be that you fitted the 4 jaw incorrectly?

 

[redhunter350]

Niall I think you need to give more detailed information, what tooling were you using, HSS or disposable tipped tools? By a whisker I assume you mean say less than 5 thou ? tipped tooling does not lend itself to small cuts, I would use HSS and for brass a small rad on the cutter plus honed to ensure a keen cutting edge.
Also what make is your machine. From what you say you suggest the bearings are ball or roller bearings? Etc etc.
John

 

[Fergie 307]

Agree with the above, more details needed. But if it is a spindle problem then logically it will appear on each revolution of the spindle. So when you say it's intermittent, what exactly do you mean. I cut a lot of brass and only tend to use tipped tools if I need to remove a lot of material initially, then switch to HSS for the finishing. The problem with carbide tips is they like to work hard to give the best results, not really well suited to fine work in brass. With a really sharp HSS tool you can remove very small amounts very accurately, so much so that the swarf is like fluff.

 

[ChaiLatte]

So when you say it's intermittent, what exactly do you mean?

That is a very good question for him to answer. If the noise occurs in conjunction with spindle rotation but not once per turn, it could be the belt. Hence, in addition to your advice, it would be good to isolate the spindle from the rest of the drivetrain (loosen the belt or put the spindle gearbox in neutral) to aid diagnosis.

 

[Fergie 307]

Agreed, if it happens every so many revolutions then maybe a problem With the gear train, if it has one, or belt drive set up. I would certainly follow ChaiLattes advice and try and isolate the spindle first. If that is ok then connect up the drive and try again. You just need to be methodical.

 

[niall Y]

Niall I think you need to give more detailed information, what tooling were you using, HSS or disposable tipped tools? By a whisker I assume you mean say less than 5 thou ? tipped tooling does not lend itself to small cuts, I would use HSS and for brass a small rad on the cutter plus honed to ensure a keen cutting edge.
Also what make is your machine. From what you say you suggest the bearings are ball or roller bearings? Etc etc.
John

Yes, more details could well help home in on what is actually happening and also what I should be doing better. The tube being turned was being held in a 4-jaw chuck - one of those with the independently adjustable jaws, hence my using a dial gauge to get it bang on centre. The tube in question is 18mm diameter, with 3mm thick walls, and an internal bore of 12 mm. Since this has to slip over a 12.7mm tube to be silver soldered. in the region of 0.35mm needs to come off ( more than the 5 thou, @redhunter350 mentions)
The boring bar was indeed a tipped one. and I will take onboard the advice that HHS cutters will be better for brass.

The knocking that i could hear, and feel that gave rise to a deflection on my dial indicator of about 0.08 mm. I believe was coming from the front tapered roller bearing So, with this in mind I'm in the process of changing the bearings, In fact I posted a query about this with another thread - all since done and dusted with help from @deema, and others
As for the lathe itself, it is fairly rudimentary. It's "Home-made", not by myself, but is one my son was given. Judging by the build the main elements must have been made at the builders place of work. There are good and bad things about it. Design wise it is much more basic than the old round-bed Drummond lathe I have - but this is offset by the fact that it is at least useable .

 

[bourbon]

I have to beg the question. Why were you using a four jaw chuck on a tube in the first place? Of course. if that is the only chuck you have, then that is the one you use. (but it's a lot harder)

 

[Fergie 307]

I have to beg the question. Why were you using a four jaw chuck on a tube in the first place? Of course. if that is the only chuck you have, then that is the one you use. (but it's a lot harder)

Four jaw independent chuck seems a very sensible option. Most so called self centering chucks are nothing of the kind, or not for anything accurate anyway. I am lucky enough to have 5C collets, so would use that system.

 

[niall Y]

Four jaw independent chuck seems a very sensible option. Most so called self centering chucks are nothing of the kind, or not for anything accurate anyway. I am lucky enough to have 5C collets, so would use that system.

@bourbon is correct in assuming that I do not have a 3-jaw chuck. I do, however; have an ER32 chuck with a selection of collets. This is only really useful when turning between centres, as I have no way of holding it back in the Morse taper. Out of interest, I was wondering how the 5C collet system differs from this.

 

[J-G]

Four jaw independent chuck seems a very sensible option. Most so called self centering chucks are nothing of the kind, or not for anything accurate anyway. I am lucky enough to have 5C collets, so would use that system.

That does depend upon the operator - to some extent. I seldom use a 4 jaw chuck though they do have their place. I very rarely use the hard jaws that are generally used with 3 jaw 'seft centering' chucks, much preferring 'Soft' jaws which I machine at least each time I have to re-mount the chuck or swap the jaws and often when I have a need to machine a component which is much larger (or smaller) than the previous one.

I have some soft jaws which have been drilled & tapped to act as 'carriers' for wood, plastic or alum jaws which are again machined to suit the component before it is mounted.

Collets can be good but I've found that even they are prone to error - I don't have 5C type though, just ER32, but I cannot rely on absolute concentricity even though I have made my own collet chuck on the lathe they are used on.

For absolute concentricity (on spindle type components) I would always turn between centres.

 

[J-G]

I do, however; have an ER32 chuck with a selection of collets. This is only really useful when turning between centres, as I have no way of holding it back in the Morse taper.

??? how would you use an ER32 collet systen to turn between centres ?

'Between Centres' means exactly that - a 'Centre' in the headstock and another in the tailstock, with the component clamped in a carrier powered by a drive pin, the component having previously had a 'centre' drilled in each end.

An ER Chuck that has a Morse Taper Shank should have a threaded hole rather than a tang and a drawbar is used to hold it in the headstock.

 

[clogs]

think we need some photo's of the machine and what u are useing.......
unless it's thick wall tubeing anything else will be a trial.....
often u cant hold it tight enough.....
tube is never very accurate either in wall thickness or roundness.....bad word.......at the best of times.....
often with brass/copper it's drawn tube.....
some brass is harder than other making delicate work diff......
HSS is the prefered cutting tool........
to machine down tube it's often better to start with barrel and waste some to get what u want......
hard enough to buy accurate steel tube.....
once u've mastered this have a go at St/Steel......loads'a fun.....
Carbide tipped tools just work better with abuse......but they really need heavy equip.......
Have a look on youtube.......Cutting Edge Engineering, Australia will show carbide tools work.....
wll worth a look.....just for fun....

if it's real thin wall better to use an abrasive mandrel or internal polishing mop....or just make ur own.....

 

[niall Y]

??? how would you use an ER32 collet systen to turn between centres ?

'Between Centres' means exactly that - a 'Centre' in the headstock and another in the tailstock, with the component clamped in a carrier powered by a drive pin, the component having previously had a 'centre' drilled in each end.

An ER Chuck that has a Morse Taper Shank should have a threaded hole rather than a tang and a drawbar is used to hold it in the headstock.

My sloppy terminology........... by "between centres" I mean - held in the ER32 collet chuck and supported using a live centre in the tailstock as well. This prevents the Morse taper from falling out as there is no provision inside the spindle of my lathe for anchoring the ER32 chuck with its internal screw-thread.

 

[niall Y]

think we need some photo's of the machine and what u are useing.......
unless it's thick wall tubeing anything else will be a trial.....
often u cant hold it tight enough.....
tube is never very accurate either in wall thickness or roundness.....bad word.......at the best of times.....
often with brass/copper it's drawn tube.....
some brass is harder than other making delicate work diff......
HSS is the prefered cutting tool........
to machine down tube it's often better to start with barrel and waste some to get what u want......
hard enough to buy accurate steel tube.....
once u've mastered this have a go at St/Steel......loads'a fun.....
Carbide tipped tools just work better with abuse......but they really need heavy equip.......
Have a look on youtube.......Cutting Edge Engineering, Australia will show carbide tools work.....
wll worth a look.....just for fun....

if it's real thin wall better to use an abrasive mandrel or internal polishing mop....or just make ur own.....
View attachment 164520

Thanks, I take on board your observations regarding the accuracy of the tubing, The stuff I'm using for the collars has 3mm thick walls - so quite barrel like- and it's so much cheaper to buy this, than turn from solid bar, where most would end up as swarf.

Having said that - I do have some nickel-silver rod I'm hoping to make into ferrules, though I did manage to get this fairly cheaply.

I'm also working with some thinner brass tubing that has 1/32" walls, though I will be limiting the operations I carry out, with this on the lathe, to trimming to length, only.

 

[J-G]

My sloppy terminology........... by "between centres" I mean - held in the ER32 collet chuck and supported using a live centre in the tailstock as well. This prevents the Morse taper from falling out as there is no provision inside the spindle of my lathe for anchoring the ER32 chuck with its internal screw-thread.

If your headstock spindle is hollow then you can very easily make a draw-bar. Even if you start with a length of threaded bar and add a washer and nut. Better to make a suitable bush that fits the rear end of the shaft though since that will keep the bar centred.

The MT2 ER Chuck will have either an M10 thread or a 3/8" BSW or UNC - 'AllThread' is available in all those variants but it shouldn't be beyond your capability to cut a suitable thread on each end of a length of 10mm steel.

 

[Fergie 307]

5C mount either in their own chuck, or in a draw bar in the spindle, either way very accurate. I use a chuck and can mount and dismount it on my L00 spindle with less than 0.01mm runout repeatably. They differ from ER in that they are through collets, intended for holding work. So for example if you want to make muliple components you can use a long piece of bar or tube, machine one component and part it off, then pull the bar through and repeat. ER series collets are really intended for holding tools, hence they dont have a hollow bore. Even cheap ER holders should be under 0.01mm runout, if you dont get this from one with an MT mount I would think the fault more likely to lie with the lathe itself. If you want to pay more you can get them specified to 0.001, overkill for most things. For tube CDS is good, seamless and generally pretty accurate size wise. I avoid welded tube, rarely particularly round and has a nasty seam to deal with. Ok for stuff where it is to be used as is, horrible to machine.

 

[niall Y]

If your headstock spindle is hollow then you can very easily make a draw-bar. Even if you start with a length of threaded bar and add a washer and nut. Better to make a suitable bush that fits the rear end of the shaft though since that will keep the bar centred.

The MT2 ER Chuck will have either an M10 thread or a 3/8" BSW or UNC - 'AllThread' is available in all those variants but it shouldn't be beyond your capability to cut a suitable thread on each end of a length of 10mm steel.

This is certainly something I would have sorted out earlier, but, sadly I don't have a hollow spindle So, I'm just going to have to work alongside the limitations of my lathe.

 

[TFrench]

Another benefit for 5C - when tightened the collet closes at the very end, allowing you to hold very short workpieces. ER collets tighten along the full length of the collet so you need a much longer amount of material for it to hold properly.

 

[J-G]

Another benefit for 5C - when tightened the collet closes at the very end, allowing you to hold very short workpieces.

True - BUT - this feature actually limits the choice of material that can be safely & securely held.

ER collets tighten along the full length of the collet so you need a much longer amount of material for it to hold properly.

The advantage of ER type is that they can securely hold a range of diameters, mostly -1mm from nominal but below 4mm it's -½mm I'm not sure about the imperial sizes - I only have 2, 1/8" & ¼" (used specifically to hold carbide milling cutters).

Essentially I'm saying that both systems have their pro's & con's - such is life!

Incidentally my ER collets are all 'through bore' so can take longer lengths of material (well up to the limit of my lathe headstock spindle bore). I seldom use this facility since most of my work is 'one-off' prototype but I have used up to 6m lengths in 5C type collets in the dim & distant past when in a production environment. - - - that takes me back to my pre-apprenticeship days!! - - - Ye Gods - 1956!