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Parting off - again, sorry

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petro1head11/10/2018 14:56:52
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Posted by Mick B1 on 11/10/2018 12:59:16:

My two penn'orth:

Looking at you photo of the tool, I'm thinking I can see a tiny wedge of support on the lower edge of the insert location that suggests the insert is skewed rightwards. Can't tell if the insert is properly vertical or not, but if it isn't the right-hand side of the tool might be rubbing, unable to cut, and so forcing the left-hand side to dig in further and deflect the supporting blade that way.

The fact that there's also a significant bit of the support projecting forward underneath the insert suggests to me that there's summat up with its location.

Thats becuse just before taking the photo I had the tool on the bench so must have knocked it.

petro1head11/10/2018 14:58:08
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Posted by Ron Laden on 11/10/2018 13:59:59:
Posted by JasonB on 11/10/2018 13:16:16:

Speed wise put it in the slower speed range but run towards max 900-1000 and feed briskly.

I recently turned a set of buffers from 35mm dia ali and Jasons advice above is pretty much what I found worked for me using a 1.5mm HSS tool. Moving up to a 3mm tool I would avoid if my experience with one is anything to go by. If you are using a mini-lathe as I am I would argue that a 3mm parting tool is too much for them. I have a HSS 3.2mm tool and the lathe just doesnt like it, even with ali, I tried everything I could but it was not happy.

Edited By Ron Laden on 11/10/2018 14:03:25

Edited By Ron Laden on 11/10/2018 14:18:05

I am using a Warco 290 lahe, not mini more like maxi

JasonB11/10/2018 15:26:53
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Posted by ega on 11/10/2018 12:30:27:

JasonB:

Did you use tailstock support and if so at what stage did you retract the centre?

In that case I did, if you look at the chuck jaws you will see that they are closed up on what is a fairly small chucking spigot hidden out of sight. I did not want to take any chances of the force from the parting cut pulling the work out of the chuck, probably removed the tailstock when I got down to about the diameter of the chucking spigot. This is someone else doing the same thing on the same engine part.

xtype disc.jpeg

SillyOldDuffer11/10/2018 15:28:24
4320 forum posts
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I hit this problem occasionally with blade type holders when the blade is well out. It seems more likely to happen when the slides are unlocked.

My pet theory is that if the tool is slightly off-square, and the blade is extended, and the slides are unlocked, then there's enough leverage to either move the carriage or to flex the blade. Unfortunately I'm not able to prove it!

I've not found it easy to align a parting tool exactly square to the work. More likely one side or the other of the tip will start cutting first putting a sideways force on the blade. How big the force is I've no idea, but it might be enough cause petro1head's problem.

What's the best way of making sure a parting tool is exactly square as opposed to 'looks OK to me guv'?

Dave

JasonB11/10/2018 15:43:05
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I put a tri square or 123 block against the side of the holder (blade) and check against the side or face of the chuck.

Also make sure your toolpost is tight and not getting turn by the force of the cut.

Ron Laden11/10/2018 17:20:09
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Posted by JasonB on 11/10/2018 15:43:05:

I put a tri square or 123 block against the side of the holder (blade) and check against the side or face of the chuck.

Also make sure your toolpost is tight and not getting turn by the force of the cut.

I have a couple of small slip gauges in my box and I used one of those to check that I was presenting the blade square. Seeing Jasons post and thinking about it I checked the blade was square to the work piece when really I should have checked against the chuck, I can see that now. I found the difficult part was grinding the blade square as its such a narrow cutting edge.

Mick B111/10/2018 17:26:05
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Posted by SillyOldDuffer on 11/10/2018 15:28:24:

...

What's the best way of making sure a parting tool is exactly square as opposed to 'looks OK to me guv'?

Dave

I've got T-slots square to the bedways in my Warco's crosslide. I find lining up the parting tool blade by eye with the T-slot works well enough that I don't meet petro1head's problem.

ega11/10/2018 17:45:05
1159 forum posts
95 photos

One advantage of the dedicated rear parting off toolpost is that it can be set nicely square and left in place undisturbed for use when needed.

Front or back it is sometimes possible to face the workpiece and refer the p/o blade directly to the work.

Chris Evans 611/10/2018 19:03:29
1417 forum posts

I use the same parting blade from ARC with a 2mm tip. Rear mounted I can part 40/50mm EN1A (leaded) at 1100 RPM and 0.05mm per rev feed with flood coolant. Feed by hand if not using flood and still dab plenty lube on with a brush. I tend to mix a little machine oil in with the soluble coolant when brushing on.

mark costello 111/10/2018 20:57:36
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You could always use a Dial Indicator to check if the cut off tool holder is parallel to the travel of the cross slide. Overkill but guaranteed results.

David T12/10/2018 10:08:48
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14 photos
Posted by mark costello 1 on 11/10/2018 20:57:36:

You could always use a Dial Indicator to check if the cut off tool holder is parallel to the travel of the cross slide. Overkill but guaranteed results.

When I used to use a front-mounted tool I always aligned it with a dial gauge. I must admit though, since getting a rear toolpost I've never checked it blush

Edited By David T on 12/10/2018 10:09:14

Edited By David T on 12/10/2018 10:09:39

Jon12/10/2018 22:01:07
988 forum posts
46 photos

I only get veering off using decent Eclipse hss blades in the supplied tool post kits.

Dont tend to part or groove deep using 2mm only to 38mm dia using DGTR Iscar. Makes no odds whether use neutral, left or right hand inserts, never veers off.

Whilst at it way too much sticking out the tool holder, may have enough for 4"+ dia.
Blade type you take a cut and keep pulling tool out as you go in, have done 6" dia in 6082, takes some doing with quick reactions coolant or not theres no warning.

In fact any of the other 7 parting or grooving tools non veer off but all are quality brands with quality tips Sco. Iscar, Arno, Teutatec etc.

Neil Wyatt13/10/2018 09:30:11
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There's not enough flex in that tool to give the result in the photo, plus you can see the angle of the cutter tip should be deflecting the cut the other way:

Something is moving under load.

Either lock the saddle or at the minimum see if you can tighten the gibs a bit without over doing it.

Neil

Ian S C13/10/2018 09:49:16
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Neil, although you would expect the tool to cut in the other way, I think the cut is being pulled to the left by the top rake digging in and pulling the cut at right angles to the cutting edge.

Ian S C

JasonB13/10/2018 10:17:56
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More like the holder has got bent open so the tip is not being held correctly and moving as mentioned on the previous page by Mick and me.

Neil Wyatt13/10/2018 10:41:46
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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

Hillclimber13/10/2018 11:17:13
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$5 says Neil is right. Before bothering with anything else, lock the saddle/topslide.

I have seen a very similar result on "a friend's" work....

petro1head13/10/2018 13:10:44
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547 forum posts
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Thanks for the replies.

Update:

I have made a new locking mechanism for the saddle.

On close inspection I think the problem if the quick change tool post. Its a one I got from Warco,and the tool holder is coming slack on the quick change piston type tool post. I have notice this happen a few times over the last few months and can only assume its cheap chineese stuff. So I have started a thred about getting a new quick change tool post

JasonB13/10/2018 14:25:45
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Just had it confirmed to me that on these blades the tip is not supposed to go back as far as your photo shows which again indicated the "blade" holder has been damaged and the tip is moving about. Suggest you use the other end, put in a new tip and try again.

petro1head13/10/2018 15:06:07
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547 forum posts
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Thanks Jason, as always top notch advice

Will give that a try once I have sorted the tool post

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