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Tangential tool sharpening

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Andy_C18/01/2022 18:29:56
47 forum posts
10 photos

I have just resharpened my tangential tool and achieved a good finish on brass but with spiral swarf. Is my sharpening not quite right?

bd22c206-5fae-4280-a329-40f5f257885b.jpeg

Howard Lewis18/01/2022 18:53:17
6005 forum posts
14 photos

A continuous spiral of swarf is indicative of a steady feed rate.

If the surface finish is good on whatever material you are cutting the tool form is good.

That is the deciding factor, not the shape of the swarf..

A sharp Tangential tool should be capable of taking cuts of 0.0005" (0.012 mm) , or maybe even less, and then if it is within the lathe's capability, and rigidity, take a cut of 0.100" (0.25 mm).

Just use the jig to grind the toolbit, when it needs it, until the cutting face cleans up.

Howard

Andy_C18/01/2022 19:05:03
47 forum posts
10 photos

Many thanks. The swarf just looked very different to what is was used to with brass with other tools and before I sharpened the tool. Many thanks for response.

the artfull-codger18/01/2022 21:42:30
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294 forum posts
28 photos

I've had a tangential tool for years & use it for all of my plain turning,& facing but be careful of taking "bonus cuts" in brass unless you grind it with no top rake as it grabs.all my brass tools have no top rake.

Graham.

ega19/01/2022 14:29:23
2487 forum posts
199 photos

Spiral swarf:

In one of his videos Gary (Eccentric Engineering) mentions that he had ground a chip breaker into his tangential cutter; this would presumably yield separate chips rather than a continuous spiral.

Increasing the DOC is also likely to break the chip.

John Haine19/01/2022 14:35:12
4622 forum posts
273 photos

Talking of tangential tools and brass, somewhere on here, years ago, I posted on what angle the end of the toolbit should be ground to to get zero rake for brass. If anyone wants to know then a bit of searching should bring it up.

Howard Lewis19/01/2022 15:39:19
6005 forum posts
14 photos

Have never had a problem using a Tangential Tool on brass!

If anything, a better finish than on steel, with a 0.0025"/rev feed.

0.025" DOC on Stainess produced nice long spirals.

Without regrinding the toolbit, this morning, took spring cuts on 1.250" lengths of Stainless, now 0.198" dia to remove the last thou (0.0005" a side ) The swarf looked like dust, but brought bit down to size!

Howard

Andy_C19/01/2022 17:41:36
47 forum posts
10 photos

Gary talks of grinding a flat on the top I think when machining brass. I will try and find John Haine’s earlier post ref zero rake and will also re look at eccentric site. Many thanks for responses.

Howard Lewis19/01/2022 17:59:53
6005 forum posts
14 photos

Try using the tool "as is" on brass, before doing anything drastic.

If it works O K, "It ain't broke, so don't fix it"!.

If it is set correctly, there is unlikely to be a problem.

The surface finish is as likely to be affected by your feed rate as by the tool.

Learn how to feed at a steady slow rate, to get a fine finish (One of the first things that we were taught as Apprentices )

With a Tangential Turning Tool, a Centre Height Gauge becomes a necessity, and very useful for all other tools.

Howard

Howard Lewis19/01/2022 18:01:31
6005 forum posts
14 photos

Try using the tool "as is" on brass, before doing anything drastic.

If it works O K, "It ain't broke, so don't fix it"!.

If it is set correctly, there is unlikely to be a problem.

The surface finish is as likely to be affected by your feed rate as by the tool.

Learn how to feed at a steady slow rate, to get a fine finish (One of the first things that we were taught as Apprentices )

With a Tangential Turning Tool, a Centre Height Gauge becomes a necessity, and very useful for all other tools.

Howard

John Haine19/01/2022 19:43:41
4622 forum posts
273 photos

**LINK**

Howard Lewis19/01/2022 20:23:03
6005 forum posts
14 photos

For grinding toolbits for the "Diamond" tool on my Worden, I made up a tool holder (Just a piece of Inch square bar with a longitudinal groove milled at 45 degrees and clamping screws ) so that the toolbit was held diagonally rather than horizontal (Avoids all the complicated trigonometric calculations. ).

In this way, the requisite angles can be achieved simply by swinging the tool holder slide an angling the table.

With just a bench grinder, the jig supplied by Eccentric Engineering is quite adequate., and is quite often used, rather than getting out the Worden.

Howard

IanT19/01/2022 21:04:25
1984 forum posts
211 photos

I don't use my Diamond tangential on brass - just too easy to get a dig-in - which I most definately have had when I tried to do so. They were 'nasty' dig-ins too - spoiled the part, quite apart from frightening the bejezzers out of me.

Maybe my old S7 is not a 'typical' lathe in terms of age and wear - maybe a nice new shiney lathe would be just fine. But I certainly don't use my tangential on brass - and as it's pretty easy to grind a HSS tool for brass (with no back rake - just front/side clearance) it's really not a problem...

Regards,

IanT

Howard Lewis20/01/2022 10:24:54
6005 forum posts
14 photos

IanT

I have used home made and Eccentric Tangential tools ( from 1/8 upto 5/16" )on my BL12-24 (manufactured may 2003, used since September 2003 ) on Steel, Aluminium and brass without any dig ins.

I always ensure that the tool is set at centre height.

A feed rate of just over 0.002" / rev usually produces a very good finish, cutting dry. Applying neat cutting oil to steel, produces an improvement, especially on stainless.

It replaced a ML7. The BL12-24 is a larger, much heavier and more rigid machine than the ML7

I hate to say it but has your machine slack gibs and a lot of backlash?

Dig ins suggest that something is not as rigid as it should be.

Initially with the Eccentric tool I had problems with chatter; solved by shortening the shank of the holder to reduce overhang to the absolute minimum.

Howard.

Andy_G20/01/2022 10:39:55
avatar
166 forum posts
Posted by Andy_C on 18/01/2022 18:29:56:

I have just resharpened my tangential tool and achieved a good finish on brass but with spiral swarf. Is my sharpening not quite right?

bd22c206-5fae-4280-a329-40f5f257885b.jpeg

What grade of brass is it?

I acquired a sheet of what I thought was brass (it looked like it), but I believe it’s actually aluminium bronze. It produced similar curly chips.

 

Edited By Andy_G on 20/01/2022 10:41:05

bernard towers20/01/2022 12:02:18
568 forum posts
109 photos

I’d have to go with Andy G don’t think it’s likely to be CZ121. You can get curls with some tools on CZ120.

Andy_C20/01/2022 21:18:24
47 forum posts
10 photos

It was supplied as as brass in a Bengs kit. Swarf produced on a facing cut.

Andy_G21/01/2022 11:55:31
avatar
166 forum posts

Actually, the stuff I have could well be engraving brass - if so, it machines very differently to "normal" brass.

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