Parting off tool – straight or angled.

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Parting off tool – straight or angled.

This topic has 41 replies, 22 voices, and was last updated 21 March 2019 at 19:59 by Oily Rag.

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31 January 2019 at 17:54 #393955
Former Member
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@formermember19781
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31 January 2019 at 17:54 #9508
Former Member
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@formermember19781
31 January 2019 at 18:14 #393960
HOWARDT
Participant
@howardt
I use the 1.5 x 10 M42 plain with angled sides. Much stronger than the plain hss bit.
31 January 2019 at 18:23 #393963
I.M. OUTAHERE
Participant
@i-m-outahere
I will assume that the horizontal tool is the HSS unit and the angled tool is the carbide insert type they have listed ?
31 January 2019 at 18:28 #393965
JasonB
Moderator
@jasonb
Do you mean the holders? if so the angled one saves having to grind the top of the tool, just touch up the end on a grinder. Down side is that if you advance the tool for a deep cut then that means ctr height has to be reset so pros and cons for each.
31 January 2019 at 18:32 #393966
John Haine
Participant
@johnhaine32865
When asking questions of this sort about items available on the web it makes it much easier if links can be provided so people can see what is being asked about rather than having to guess.
31 January 2019 at 18:34 #393968
Former Member
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@formermember19781
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31 January 2019 at 18:40 #393969
Former Member
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@formermember19781
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31 January 2019 at 18:42 #393971
Former Member
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@formermember19781
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31 January 2019 at 18:45 #393975
Former Member
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@formermember19781
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31 January 2019 at 18:54 #393977
peak4
Participant
@peak4
Well according to the catalogue, the angled one isn't suitable for use with mini-lathes as it raises the cutting edge to high.

Other than that, flat for brass, angled for steel maybe. ????

Bill
31 January 2019 at 19:01 #393980
Former Member
Participant
@formermember19781
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31 January 2019 at 19:28 #393986
peak4
Participant
@peak4
Bill double check yourself from this link

Note: This tool holder is not suitable for Mini-Lathes since the 4° angle raises the tool too high for these machines. Please choose the Horizontal parting tool holder 090-070-00356 for use with Mini-Lathes.

I'm not familiar with Seig stuff, so I don't know what defines a Mini-Lathe.

Bill

Edited By peak4 on 31/01/2019 19:28:29
31 January 2019 at 19:37 #393988
Former Member
Participant
@formermember19781
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31 January 2019 at 23:57 #394060
not done it yet
Participant
@notdoneityet
I bought a QCTP set and regretted it. The parting tool holder was angled. It never gets used now and eventually the holder will likely get butchered to accommodate some other cutter.
1 February 2019 at 07:42 #394077
Hopper
Participant
@hopper
I always use my HSS parting tools dead horizontal, on steel, brass or whatever. No angle ground on the top of the blade either. No problems at all, parting up to 2" diameter steel on an 80-year-old hobby lathe. The do work best inverted and in a rear toolpost though. Seems to let the chips fall out without jamming up the works.
1 February 2019 at 10:59 #394127
larry phelan 1
Participant
@larryphelan1
Hi Hopper,

I too always use the parting off tool mounted in the rear toolpost,but never tried parting off as shown in your picture !! I seldom use a steady but I can see how useful it could be when dealing with big dia bars.

Thanks for the post.
1 February 2019 at 11:36 #394137
Hopper
Participant
@hopper
Posted by larry phelan 1 on 01/02/2019 10:59:02:

Hi Hopper,

I too always use the parting off tool mounted in the rear toolpost,but never tried parting off as shown in your picture !! I seldom use a steady but I can see how useful it could be when dealing with big dia bars.

Thanks for the post.

You're welcome. Yes, handy when dealing with bar too big to fit up the chuck or spindle hole. Also means you part off exactly how much you need for the job in hand from the end of your piece of stock. So you can even machine the job to finish where it sticks out of the steady, then part it off to final length. That way you don't end up with a box full of noggin ends that were left in the chuck after parting off the job.

Even when parting off, or knurling, shorter jobs, putting the steady between the tool and the chuck takes strain off the headstock bearings and spindle, which are a tad undersized on the aged Drummond Flagellator and prone to shimmying about a bit if pushed.

Edited By Hopper on 01/02/2019 11:39:00
1 February 2019 at 13:01 #394155
Brian John
Participant
@brianjohn93961
Why should the rear tool post give a better result then the standard tool post ?
1 February 2019 at 13:07 #394157
Hopper
Participant
@hopper
Hi Brian. Long time no see.

For one thing, the chips fall out of the groove and don't jam up between the sides of the groove and the tool.

For another, more widely debated, thing, forces on the headstock bearings are downwards towards the more solid lower half of the headstock rather than the flimsier top bearing covers.
1 February 2019 at 13:12 #394163
Ex contributor
Participant
@mgnbuk
Why should the rear tool post give a better result then the standard tool post ?

When the parting too is inverted in the rear tool post, if it digs in it can "escape" into fresh air, whereas a front mounted tool will get dragged into (and under) the workpiece and probably break was the reason I recall being given.

Isn't the idea with the angled holder to give easier sharpening of the tool blank ? The top rake is provided by the tool holder, so only the front face of the tool blank requires grinding. On a "flat" holder, top rake as to be ground in, which can lead to more wastage on the tool blank when regrinding is required.

Nigel B
1 February 2019 at 13:21 #394165
Hopper
Participant
@hopper
Posted by mgnbuk on 01/02/2019 13:12:47:…

… On a "flat" holder, top rake as to be ground in, which can lead to more wastage on the tool blank when regrinding is required.

Nigel B

No. If you look at my pic above and as I said in the text, no angled grinding of the top of the tool blank is needed. I grind it dead flat and straight right along , ie zero back rake. Cuts steel just fine like that, despite all the theories.

If you start grinding the top surface back at an angle, the next time you remove some metal from the front edge to sharpen the tool, it is now narrower at the cutting point that at the point where it has not been ground on the top edge. So when that point gets to the groove in the job, it jams.
1 February 2019 at 13:31 #394166
Ex contributor
Participant
@mgnbuk
I use a small diamond ball cutter in a Dremel to put a dimple in the top face, just behind the cutting edge. This mimics the form of a parting insert & distorts the swarf, which comes off narrower than the groove, so no jammimg.

Nigel B
1 February 2019 at 14:01 #394167
Vic
Participant
@vic
I use the T shaped blades in a straight holder, all you need to do is provide a little relief at the front. The top of the blade includes a chip breaker along its length in the form of a slight U shape.
1 February 2019 at 15:54 #394188
Howard Lewis
Participant
@howardlewis46836
A mini lathe is usually, in my book, something like a Seig C2 or C3.in size. Think Clarke Metalworker / Chester Conquest as similar.

Myford ML7, Boxfords and larger do not fit the description.

Being tight (to put it mildly) I use my HSS parting blade, horizontally in the rear toolpost, without grinding any top rake, and have done so for nearly 15 years. Dig ins are almost unknown, and do minimal damage,

(And I invite them by grinding the front edge at an angle, in the hope of leaving the workpiece without a central "pip". This makes swarf wider than the cut, but the swarf usually finds its way out without a problem, in small pieces; possibly because of the zero top rake?)

As long as you are finding your way, I would not advocate angling the front until you are a lot more confident. If you have a problem, you need to have the minimum of possible causes. Don't let me lead you astray!

In addition to all the help that you will get on here, join a Model Engineering Club, where you will probably get face to face advice and first hand demonstrations. Whereabouts are you, roughly?

Someone on here may well be near, and happy to help and advise.

Howard
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