By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Nov 29

Parting off - again, sorry

All Topics | Latest Posts

Search for:  in Thread Title in  
Mick B113/10/2018 15:11:16
913 forum posts
55 photos
Posted by Neil Wyatt on 13/10/2018 10:41:46:

Possible, that would mean it is being very badly swung around.

If so the holder has been 'sprung' by a bad dig in and that end may now be useless unless you can push the insert further in.

Neil

From the bit of support showing under the insert, looks to me like he already did that. And Jason thinks it's too far back. If the insert isn't broken at the back end, and the blade location isn't damaged, pretty much all that's left is that the insert's a wrong one for the location.

Roy M14/10/2018 00:16:47
103 forum posts
7 photos

I am surprised that nobody has suggested that you take a good look at the swarf. This can tell you lots about what is going on with your cutting. Is it even, is one side ragged, is it chipping or stringing ? All these are indicators of your cutting conditions and tip condition. Don't forget that the tool only makes swarf and just leaves the job behind! With the type of insert shown, the swarf should be coming off in tight spirals, like 'neat clock springs', (as described by an ISCAR rep). Also, if you are just using your parting tool for 'jobbing', you might like to consider using a 90deg tool, as opposed to an angled approach .

Roy M.

JasonB14/10/2018 06:56:56
avatar
Moderator
14864 forum posts
1492 photos

To save further speculation have a look at the end of this video

David George 114/10/2018 08:00:04
avatar
657 forum posts
221 photos

I have looked at the action of the carbide tipped holder and I get a similar effect using the carbide tip holder that i have. The holder is an extension sideways and you get a greater leverage force because of this type of blade holder when you use a HSS tool it is nearer to the support and less likely to become loose I would like to make a carbide blade holder which is a part of the quick change holder not an extension sideways.

David

SillyOldDuffer14/10/2018 10:01:48
3857 forum posts
775 photos
Posted by JasonB on 14/10/2018 06:56:56:

To save further speculation have a look at the end of this video

Yes indeed. Another easy check is to lay the bottom edge of the holder on a straight-edge. If the blade is strained you can see daylight between the edges where it bows.   I've restored order temporarily by squeezing the blade in a vice, though it's not a good solution - metal that's been bent loses much of it's strength. 

I find these blades to be very effective apart from their tendency to open up after a dig in. I've even managed to snap one! Looking at the design of the insert holder, it doesn't leave much metal to support the insert and resist wedging. It may be deliberately intended to fail when excessive force is applied.

Next time I write one off I'm going to switch from the 3mm type to 2mm inserts. The 2mm blade has proportionally more metal relative to the forces applied to the tip and should be tougher.

I think there's a sweet-spot using these. They like to be driven fast and hard but not too hard! Above all, avoid digging in. The operator parting off at a smooth steady rate helps, but of course any lack of rigidity in the set-up is liable to cause trouble. Quite a lot of skill needed in this machining lark. Perhaps one day I'll be good at it...

Dave

Edited By SillyOldDuffer on 14/10/2018 10:03:00

Edited By SillyOldDuffer on 14/10/2018 10:05:58

petro1head14/10/2018 10:31:13
avatar
547 forum posts
102 photos

Having recently bought a Gopro 7 Hero, I thought I would do a video of me parting off and a bit of slow motion just for interest. BTW the Hero 7 is very good with image stabilization

 

Edited By petro1head on 14/10/2018 10:38:45

jimmy b14/10/2018 10:53:26
avatar
434 forum posts
27 photos
How far away from the chuck are you parting off? It looks to be quite away?
Jim
petro1head14/10/2018 11:09:55
avatar
547 forum posts
102 photos

About 2"

fishy-steve14/10/2018 12:24:36
103 forum posts
30 photos

I personally wouldn't part off with that much overhang without tailstock support.

Steve.

Philip Powell14/10/2018 12:47:02
45 forum posts
15 photos

That's just asking for trouble sticking the bar that far out of the chuck then parting off.

Phil

Edit typo.

Edited By Philip Powell on 14/10/2018 12:48:09

not done it yet14/10/2018 12:49:35
2640 forum posts
11 photos
Posted by fishy-steve on 14/10/2018 12:24:36:

I personally wouldn't part off with that much overhang without tailstock support.

Steve.

Neither would I, especially as the perspective, and given distance, makes the item look very much slimmer than the 38mm quoted earlier in the thread! More so, knowing that parting has not worked out well, previously.

Jon14/10/2018 21:19:56
949 forum posts
45 photos

Presume its about 1 1/4" dia, 2" sticking out will or should be ok, done it relentlessly where parts need to be done as one rather than removing and put back in the chuck wrongly.

If you look carefully you will see the tool post moving, coud be all manner of things. Other than that spindles way to slow, deep cuts if ever did get that far will break the cutter and or tip.

That type of tip not the tool you should be able to part 6" dia off in 6082 the worst of all evil. Just be quick when hear tonal change and draw out.

What will help is a 2mm parting tool and tip such as DGN Do Grip my favourite go to tool used for turning, grooving and parting. Saying that broke it after 6 years and cant find another at a respectable price.

petro1head14/10/2018 21:59:17
avatar
547 forum posts
102 photos

 

It’s 1.5” dia.

6082?

I can’t see the toolpost moving

It’s the speed and feed bit that I am very unsure about. When I run it after it does not sound right, to me and am scared of fing another tool.

So would this formula work for the speed:

RPM=SFMx(12/3.142)/work dia inches

RPM=150x3.82/1.5 = 382rpm

Edited By petro1head on 14/10/2018 22:25:41

petro1head14/10/2018 22:06:45
avatar
547 forum posts
102 photos

I have just found Neil’s post with the cutting chart.

That suggest the SFM for Ali is 200. So that would be 509rpm

 

It’s getting confusing

Edited By petro1head on 14/10/2018 22:07:26

Niels Abildgaard15/10/2018 06:12:53
191 forum posts
40 photos

I am owner of 2018 WM250 and 2011 WM280 lathes and both have a rather stupid compound slide system.

It looks like something copied from austrian EMCOs.The made in millions 918 lathes has them as well and the first advice on all 918 pages is to scrap it.

If You want better parting try making a better/stiffer/more direct force path from tool tip to lathe bed.

Avoid the flex of compound slide and quick change toolholder for parting.

The video indicates chattering.

I made a holder of this kind and parted 100mm mild steel routinely on a Boxford and a single 125 disk of seawater resistant aluminium.

 

stepstik 1.jpg

My new 250 lathe with old floppy tool slide system.Lovely lathe apart frpm compound slide system

Ny WM250 paa Hjul

Edited By Niels Abildgaard on 15/10/2018 06:44:06

JasonB15/10/2018 07:36:32
avatar
Moderator
14864 forum posts
1492 photos
Posted by petro1head on 14/10/2018 22:06:45:

I have just found Neil’s post with the cutting chart.

That suggest the SFM for Ali is 200. So that would be 509rpm

That table is a bit useless without the text that went with it where you will see that David said" for Carbide I would double the shown speeds and industry would be 4-5 times faster".

Kind of brings us back to what I said on the first page of this thread 900-1000

JasonB15/10/2018 08:28:39
avatar
Moderator
14864 forum posts
1492 photos

I did think the cut from your video looks a bit rough and inconsistant so quickly popped out to the shed for a quick video.

Speed is not such an issue and sometimes a bit slower can make things more relaxed and easier to keep up with the lube so did a bit a 600rpm and then some at 950rpm. Also using a slow power cross feed so tool is constantly loaded, the only time you hear a hint of chatter is when I stop the feed to move the camera and that is because tool is not being kept under a decent load.

Warco 280VF, Glanze 2mm holder, APT general purpose insert 6082 38mm dia ali, paraffin, 600 & 950rpm. Saddle and topslide locked, topslide well back.

Sorry about the noise, my belt creaks when cold, its not the head honest!

not done it yet15/10/2018 08:30:47
2640 forum posts
11 photos

We have two threads, running concurrently, on really the same subject - the inability of the OP to part off successfully.

I really think it is time for the OP to step back and consider every aspect of his working practice and improve each and every one to its maximum.

Among others, we have, so far:

Possible excessive overhang from the chuck with no additional support.

Possible excessive overhang of the tool from the holder.

Possible excessive overhang of the tool from the carriage.

Non locked-down axes while cutting on another.

Possible drawbacks with the machine design.

Cutting speeds in relation to diameter of work, material and cutter type.

Apparent differences between tool holders and some examples not being secured properly.

A possibly compromised parting-off tool.

Possibly poorly secured, or loose, tool post on the top slide

Likely others, too, not listed above from this or the other thread but that little lot should provide at least some considerable practical improvement in this task.

We don’t actually know which (or combination) of these factors led to the original cry for help. So time, now, for all the possibilities to be examined by the OP? Then, and only then, the OP might try parting off again, because changing one thing (in this case) seems very unlikely to solve the problem in one go!

Neil Wyatt15/10/2018 08:52:24
avatar
Moderator
15581 forum posts
652 photos
73 articles

You've left off strange noises/chatter causing the lathe operator to either slow down the lathe or reduce the feed rate.

Neil

petro1head15/10/2018 08:58:36
avatar
547 forum posts
102 photos
On phone at the mo but will study posts and report back.

I did find a post re double the speed for carbide

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
ChesterUK
Eccentric Engineering
Eccentric July 5 2018
Warco
Ausee.com.au
Allendale Electronics
TRANSWAVE Converters
Sarik
emcomachinetools
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest