Parting off – again, sorry

[JasonBModerator @jasonb]

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 LadenParticipant @ronladen17547]

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 B1Participant @mickb1]

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.

[egaParticipant @ega]

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 6Participant @chrisevans6]

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 1Participant @markcostello1]

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 TParticipant @davidt96864]

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

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

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

[JonParticipant @jon]

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 WyattModerator @neilwyatt]

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 CParticipant @iansc]

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

[JasonBModerator @jasonb]

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 WyattModerator @neilwyatt]

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

[HillclimberParticipant @hillclimber]

$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….

[petro1headParticipant @petro1head]

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

[JasonBModerator @jasonb]

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.

[petro1headParticipant @petro1head]

Thanks Jason, as always top notch advice

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

[Mick B1Participant @mickb1]

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 MParticipant @roym]

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.

[JasonBModerator @jasonb]

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

[David George 1Participant @davidgeorge1]

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

[SillyOldDufferModerator @sillyoldduffer]

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

[petro1headParticipant @petro1head]

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 bParticipant @jimmyb]

How far away from the chuck are you parting off? It looks to be quite away?
Jim

[petro1headParticipant @petro1head]

About 2"

[fishy-steveParticipant @fishy-steve]

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

Steve.

[Author]

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