Q. about mini lathes & 'cutting off'

[rvt]

I've been cutting off some 'rings' from a tube of aluminium. The tube is 8-9mm thick (and needs to be). I'm using a tool, that says it's made for my type/series of cheap mini lathes (SEIG C1).

I'm curious as to whether there is something 'thinner' that i could use to cut off? The tool is 1.5mm at the cutting point, seems to be a lot of waste as I'm only doing quite thin rings often. It also seems to take quite a while, and the noise is quite intense sometimes, I've had to switch to ear muffs after it gave me a insane headache! I've made sure the tool is cutting in the middle and that it's lined up properly, so i guess a certain amount of noise is to just be expected because of the nature of the cut?

Thanks for any thoughts.

[Bluechip]

Hi RVT

Been doing some myself today, 1.25" OD x 1" ID.

Ally can be a bit 'shreiky', I use WD40, other unctions often recommended tho'

1.5mm does not seem unduly wide .. what RPM are you using?
I used about 200 or so, can't remember, no Tacho on a Myford S7.
Part off as near the chuck jaws as possible, about 15 deg Top Rake works for me. Nice deliberate infeed, keep the tool cutting.
PS  only enough blade sticking out as is needed,


Dave BC



 

[sbwhart]

Try a squirt of WD40 on it, also make sure the tool has plenty of top rake about 10 - 15 deg.

Stew

[Stilldrillin]

Wot they said......

Plus, WD40! 

David D

[Bluechip]

Errrr ..

Would a spot of WD 40 help ??

Dave BC

[rvt]

Great advise, thank you all! Will give this ago next time I need to cut something off (next week most likely).

[andyf]

To add to the good advice already offered, I'd suggest clamping the carriage down to the bed, so it can't move as you wind the cross-slide in. I doubt if the C1 has a clamp fitted as standard, but if you can get a (metal, not plastic) woodworker's cramp in there, with some aluminium pads to prevent damage, that would help.

Again, I'm not sure if the C1 has a topslide, but if so it might be worth clamping that down, too.

The general idea is to fasten down everything that moves (except the cross-slide, of course) to minimise play and the chatter it causes.

Andy

[Sorekiwi]

 Well, I might get labelled a redneck here, but here is a mod that helped me immensley with parting off on my mini-lathe... 

I had always had trouble with parting off.  Going to a steel QCTP helped a bit, as did locking the carriage and the cross-slide.  But it still wasnt good.

One day I came across a picture on the nudie-net (sorry, dont remember where) of a bolt, threaded into the bottom of the parting tool holder to give it some support.  I needed a quick-fix right now, so I tried this little bit of "bush engineering", and it worked wonders!  So well in fact that 3 or 4 years later I still havent prettied it up!

The pictures arent great, but you will get the idea.  Here is the tool holder:



and here it is on the lathe:



The head of the bolt was faced off to give it a smooth sliding surface, and a jamb nut locks it rigidly into the toolholder.  The bolt can be lengthened or shortened to allow for tool height adjustment.  The bolt head slides smoothly across the cross-slide as you feed the tool in, and so far does not appear to have worn, marked or "hammered" the cross slide.

Sorry for posting such an ugly mod, I wouldnt have done so if it hadnt worked so well!

[Stilldrillin]

Sorry for posting such an ugly mod, I wouldnt have done so if it hadnt worked so well!

There`s nowt ugly about that mod, mate...... It works..... VERY well! 


I couldn`t get support under mine, as it was too far over, out in space...... 




So, I got rid of the topslide......




Then made a slimline holder for the carbide tool......




I could now fit one of your screwjacks, if necessary! 

Great idea! Thanks...... 

David D

[rog8811]

I couldn`t get support under mine, as it was too far over, out in space...... 

{image of tool holder like mine}


So, I got rid of the topslide......

{image of a different holder}


I could now fit one of your screwjacks, if necessary! 

Great idea! Thanks...... 

David D

I have recently purchased the same tool holder as in your top picture.... I had to modify it to fit my Seig C6 in the first instant.
I am not convinced of its repeatability when swapping holders, did you find it ok? other than the overhang problem.

Regards rog8811

[Stilldrillin]

I have recently purchased the same tool holder as in your top picture.... I had to modify it to fit my Seig C6 in the first instant.
I am not convinced of its repeatability when swapping holders, did you find it ok? other than the overhang problem.

Regards rog8811

Rog,

The lack of repeatability was a secondary issue......

Completely solved by the new toolpost! 

David D

[Jonitus]

Another thing you can do when parting off tubing is to stuff the tube with newspaper before chucking it up.  With the tube stuffed, you won't get the harmonics when cutting and it won't "scream" when you cut nearly so badly.

[Dunc]

Was a mini-lathe (C3 equivalent) user for a while tho I never did try these ideas...

Posts on the net (sorry, don't have an exact ref) suggest the best solution is the use of a toolpost fitted behind the work; however, the minis lack adequate space unless the work diameter is small.

Another suggestion (untried by me) is to mount the cutoff tool upside down in the toolholder and running the lathe in reverse.

Lube/cutting fluid is always in fashion.

[Stilldrillin]

Was a mini-lathe (C3 equivalent) user for a while tho I never did try these ideas...

Posts on the net (sorry, don't have an exact ref) suggest the best solution is the use of a toolpost fitted behind the work; however, the minis lack adequate space unless the work diameter is small.

Another suggestion (untried by me) is to mount the cutoff tool upside down in the toolholder and running the lathe in reverse.

Lube/cutting fluid is always in fashion.

That worked for me Dunc. With my old wobbly toolpost...... 

http://madmodder.net/index.php?topic=932.0

Not needed to try it with my present one.

Oh! Welcome to the collective..... 

David D

[rvt]

Just to update:

I've tried locking everything up tight to reduce vibrations and using wd40. However, there isn't a great deal of improvement. I'm running it at around 1500 rpm just so that I'm not there for 3 weeks trying to cut through around 8mm. The wd40 has perhaps stopped it stalling so often, but even then when it is applied all it seems to do is make the blade 'slide' for a long time, not cut.

I see there is now the suggestion of putting the tool upside down and running it backwards - I will have to try this. Otherwise things are generally still pretty frustrating.

[John-Som]

You may find some helpful tips on parting off here
http://start-model-engineering.co.uk/begin-with-bogs/parting-off-2/

John-Som

[rvt]

You may find some helpful tips on parting off here
http://start-model-engineering.co.uk/begin-with-bogs/parting-off-2/

John-Som

Hey John, thanks for the link. That's a great break down of the sort of position I'm in myself, overall the website seems impressive too, very useful for someone like myself just starting out. I followed the advise on that link and had a go over lunch.... worked well! I'm finally getting a real 'cut' of ribbon, rather than horrible 'chips' along with the noise. This was just on a small rod of aluminium, but I'm sure I've got the technique sorted now. The only small issue is with the blade mounted upside down, being able to move it forwards a touch every now and then (to cut down on vibrations) is a little more difficult, but I'm sure i can work around this.

Thanks!

[John-Som]

Hi RVT - It's good to know it was some help.

John-Som