Parting Clearance



Russell, I'll happily bung in a useful heap of bumph if you e-mail me at snipped-for-privacy@n-atkinson.wanadoo.co.uk.
You could make the GHT whole thing but alter it a tad for the Boxford. The clamping idea could be done easily on the shaper( uh huh?)
Cheers Norman
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wrote:

If I can't cut 4" steel stock in under 5 minutes the blade is shagged.
John S.
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And John,
I gave the idea of such things as a snotty nosed little kid out of the gutters of the dirty biggest open sewer in the World in----1944. I sold spinach from the garden and bought myself an education.
I came in from my few pennorth at the local flea pit where the film was the old mining film of 'The Stars look down' and an old wrecked man was in the tin bath and my mother was bathing the cuts that started from the old man's buttocks and went up and up his body as the greasy wire rope had cut and cut almost through to the bone. The cuts stopped thankfully before they severed his neck. That Old Man was my father- Old Bill, the colliery blacksmith. A few years later, I had moved on a bit. My father had been trapped with a colliery loco tube that he had been fitting. Happily, the hospital had found 'something else' but in the next beds in the Royal Victoria Infirmary in Newcastle four miners laying dying with their guts riddled after a misfire with coal and slate.
I must have looked at sight when I got back to the office but dear old Hicky took me under his wing- and the rest is -well, history.
Tomorrow night, I'll get the same nice invite to put on my best dinner suit and climb the stairs- and look at Hicky's name in bronze with the rest of the Masters. I've been offered the Master's Chair many times. Of course, I cannot fill his chair with the same wisdom.
One thing that he taught me was there was more things in life than cutting a 4" billet of steel- not in 5 minutes but in my whole lifetime.
Norman
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On or around Sun, 22 Feb 2009 14:27:56 -0800 (PST), ravensworth2674

I've got that book of that, it's good. As is "The Citadel".
--
Austin Shackles. www.ddol-las.net my opinions are just that
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[]
If I can't cut 4" steel stock in under 5 minutes the blade is shagged.
John S.
Hi John, would that we had your equipment, experience and 4" stock to play with :>) Ned Ludd
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ned ludd
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On Sun, 22 Feb 2009 13:28:21 -0800 (PST), John S

Do threats work on parting tools then?
Mark Rand RTFM
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Ouch! Scary place in my mind now, Mark.
David
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David Littlewood

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Mark Rand wrote:

I've parted 4" EN24 on a minilathe, with a HSS blade, and not worried over much :)
Took a while though - a bit more than Norman's 40 minutes for a hacksaw, but not that much more.
I picked up a couple of spare blades and boxes of inserts of Ebay

yep, same for HSS.
then the inserts last a very long time. Conversely, I have

A minilathe doesn't have th grunt to snap a HSS blade ... :)
-- Peter F

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wrote:

Dunno where you got that from <BG>
regards Mark Rand RTFM
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Richard Edwards wrote:

?? Generally the blade top is horizontal ??

I've found HSS parting blades come in three types - flat topped, step-topped, and w-topped.
I think the w-top is deliberate, and is meant to make the chips curl into the center; the flat top is - well, normal; and the step-top looks like an artifact of cheap manufacture, though it may be that way for a reason - anyone?
I usually grind the step-tops flat, then leave them alone - otherwise I never touch the tops, only grind the end.
then the cutting edge becomes narrower than the shank

ohh, don't grind the sides. Just make sure the blade is exactly parallel to the motion of the cross slide..

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A load of interesting comments however I have some comments with regard to HSS type part off. This post is general but relates to some of the comments made
1 The top of the HSS blade is usually not flat due to the method of clamping. Therefore it must be ground flat before use. 2 If the blade is held horizontal then cutting rake needs to be ground. 3 Once cutting rake has been ground any touching up on the front requires that the top be ground down to match the height 4 If the blade is held at a rake angle then touch up on the front is all that is needed. 5 Either option of tool holder means that if a different rake is required say between brass or aluminium then really a different tool bit is required. The grinding discussed above therefore needs to be repeated. The Horizontal holder is therefore best suited for brass the angled holder I assume gives more grind problems for brass.
All of the above means that the newcomer to machining (and possibly many old hands) has major problems dealing with parting off.
A last point - the concept of "grooving" an inch deep with no side clearance to the tool makes little sense to me.
I appreciate that this type of parting off with HSS has been with us for a long time, but there is now a MUCH better way. If the OP had used an insert blade then I am sure this thread would never have started <G>
Richard
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Hi Russell. In your first photo, the P/O tool seems to be cocked to the right slightly at the top, giving clearance on the left and none on the right, which will not help. The second photo seems to agree with this, and your last photo shows a "lot" of overhang, which I would keep as small as possible. Also, I would think about reducing the top rake, if you can, it looks very steep in the photo. Cheers, Norm5.
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Russell Wrote:

Hi Russell, Obviously things are nearly right if you can part 2" stock, all you need is slight tweaking to make "perfect". Looking at your pictures, two things occur to me. First the "top" of your blade still seems to have its original bevel. Best remove this and make the "top" level (headstock to tailstock wise). Don't grind anymore than needed otherwise you will end up with jamming problems in later life. The second point is, is the blade vertical, ie. are both side angles equal. Come to think of it this should be the first point as it has an effect on point one. If the parting tool's cutting edge is not square and level there is going to be a slight bias when cutting, this shows on a thin blade more than a thick one, also why you want as little of the blade protuding from the toolpost. This is a little difficult to adjust on your holder due to the built in back rake. you have to decide before hand what size you can part off when you are making the thing. Good effort though. Ned Ludd
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ned ludd
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Make sure your carrage is locked .
all the best.markj
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mark wrote:

Second and third that.
The overhang seems to be a bit long too.
Also, can you move the blade back on the cross-slide? By that I mean move the blade holder across the top slide, in the direction away from the chuck, so the blade tip is vertically above the area between the cross-slide V's.
That way vertical forces on the blade tip have much less of a twisting, and thus sideways-moving, effect. Hope that's clear, it's difficult to describe.
However, if something isn't tight ...
-- Peter Fairbrother
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That, I have to say, is NOT George Thomas's design and it does not follow his guide lines. Sorry
Norman
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Ned Ludd said:
Hi Norman, To determine a sharp edge, you first have realize what constitutes a sharp edge. Sharp, ignoring grind angles, means the arris between two flat planes. In simple terms this means two flat surfaces meeting with no rounding of the meeting point. Any rounding blunts the edge, and the simple way to see this rounding is to look in good light, a blunt edge will reflect light, a sharp one will not reflect any light.
Comments anyone? ned Ludd =My dear old Dad was renowned for his tool-sharpening skills. One of his favourite sayings was, "Look at the edge in good light. If you can see it, it isn't there!"
Just as you are saying.
JW ==
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Ned, But I don't have a problem! I have a Clarkson. It's bit of a rattle trap. I made a Quorn- a bit rusty like me. I have a Kennet for weekdays and bought for curiousity and 'shirt buttons' at fabricated smaller Stent. With the help of a more computer literate than I, I made 113 pages of grinding information onto those in MyMyford Group.
I was toddling around the blacksmith's shop in 1933 and I was fiddling about with a friend's watchmaker's lathe in 1941.
Sorry, at 78+, but one gets rather 'Deja vu'
Norm
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ravensworth2674 Wrote:

I think I heard that before. :) Ned Ludd
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ned ludd
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