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Gazzar

Starting turning on an old lathe

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And another:

What tool holder should I order to fit these inserts?

Are there Chinese versions at quarter the price, but 2/3rds the quality?

When I was cutting the CV axles I held the other end in a center. But the piece was turning, the center wasn't. I kept it lubricated, but I'd there a better way?

IMG_20190422_193037.jpg

IMG_20190422_193058.jpg

IMG_20190422_193107.jpg

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1 minute ago, qwakers said:

you don't start with a drill bit for a start :D

 

use a tailstock center first

 

http://www.technologystudent.com/equip1/mlathe4.htm

Center drill! Perfect!

A solid centre punch sort of thing for a lathe.

I think I'll get one of those.

Thank you.

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Don't worry, I knew what you meant!

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Posted (edited)
23 minutes ago, Gazzar said:

When I was cutting the CV axles I held the other end in a center. But the piece was turning, the center wasn't. I kept it lubricated, but I'd there a better way?

That's the way with a "dead" center. The alternative is a "live center" which has a bearing in it, so the pointy bit rotates with the work. 

Grab a set of center drills - a lathe essential. They're the correct tool for making the whole for a center as well as starting a hole for a twist drill. 

I can't figure out quite what inserts they are, I'll have a look around some charts. Edit: Still can't say for sure, you'll probably have to carefully measure a few angles, then have a look here:

http://www.carbidedepot.com/formulas-insert-d.htm

To figure out what holder, the biggest factor is probably the size shank the machine can take. 

 

Edited by lo-fi

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Ha! I’ve just posted the same on the other thread thinking it was this one :lol:

the angle on a centre drill is also the same angle as a centre for the tailstock :)  

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Watch out with centre drills, their favourite hobby is snapping the end off when you least want them to.  On all the CNC machines I use spotting drills instead, unless I am going to put a shaft on a cente in which case you have to use a centre drill.  Spot drills are 90 degree and have no skinn pilot, they are much stronger.

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I'll admit to snapping a centre drill but you can pick 'em up cheap enough, for hobby stuff you don't need to be buying the industrial-quality gear. I'm living on the cheap Chinese carbide-insert cutters these days - a holder & pack of 10 tips is often cheaper than a single "quality" cutter, and if I'm likely to make a mistake and f*** the tip up I'd rather damage a 50p insert than a £20 tool.

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On 4/22/2019 at 9:44 PM, landroversforever said:

Ha! I’ve just posted the same on the other thread thinking it was this one :lol:

the angle on a centre drill is also the same angle as a centre for the tailstock :)  

Center drills come in more than 60 degree angles. They can be 45 and they can even come as a radius so be careful.

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On 4/22/2019 at 9:17 PM, Gazzar said:

And another:

What tool holder should I order to fit these inserts?

Are there Chinese versions at quarter the price, but 2/3rds the quality?

When I was cutting the CV axles I held the other end in a center. But the piece was turning, the center wasn't. I kept it lubricated, but I'd there a better way?

IMG_20190422_193037.jpg

IMG_20190422_193058.jpg

IMG_20190422_193107.jpg

That looks like an SCMT insert. 

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Cool! Are they for steel? Not being gold, and not carbide (I presume).

Thanks.

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18 hours ago, Gazzar said:

Cool! Are they for steel? Not being gold, and not carbide (I presume).

Thanks.

Without seeing any insert codes or a manufacturer I couldn't say. Colour is irrelevant, that just tells you what there coated with.

 

What I feel must be said is that as your a hobbiest, you may find your time and money spent better on some quality bits of HSS for grinding into tools. Your machine won't run fast enough or be rigid enough to get enough out of a carbide insert. To achieve a decent surface finish in most materials with inserts you need very high surface speeds, reasonable feed rates and a depth of cut you would also be surprised at. With HSS you can take a whisp of quite easily. HSS is also capable of cutting 95% of the materials we machine in industry, it just takes longer. It won't get through the case hardening on the bits you were messing with at the start of the thread.

 

In industry where time is money then inserts are (mostly) the way forwards. 

 

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Thanks, 

I see where you are coming from, I think. I find getting the HSS to do what I want difficult, the inserts have worked better so far. Though I might get more HSS and experiment more.

Out of curiosity, what is a fast speed? I think my machine goes to nearly 1,200 rpm, according to the gear box plate.

 

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2 minutes ago, Gazzar said:

Out of curiosity, what is a fast speed? I think my machine goes to nearly 1,200 rpm, according to the gear box plate.

I think the issue is the outright horespower of the thing - being able to take a very aggressive cut at a relatively high speed that would stall your home/hobby lathe, and there's not really much we can do about that.

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But inserts are so much easier!

I'm being lazy, I suppose, and trying to avoid having to tackle my carp bench grinder. I don't need another project right now.

The lathe is fairly old, probably 1950's, German, 1.5 metre bed and 3kw motor. So I think it might be quite capable, for a hobby machine. It has a screw thread gearbox for Whitworth and metric, which I thought unexpected in a German machine.

I think you can remove the front bit of the bed for greater access and larger chucks, but I can imagine that's a nightmare to realign on replacement, so I'm staying away.

Lots to explore.

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17 minutes ago, Cynic-al said:

Rigidity is a big problem. You can break stuff or get chatter etc. 

Might be a useful link for your speeds and feeds

https://www.wisc-online.com/LearningContent/mtl11802/MLT11802.htm

That's useful, I did think that the quality should change when facing, as I got closer to the centre of the piece.

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27 minutes ago, Gazzar said:

But inserts are so much easier!

I agree, that's why I'm still mostly using them.

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The removable bit is called a gap bed lathe. For turning larger parts as you suggest. Useful if your putting holes in rectangular plates and that sort of thing. If you have a face plate to put in instead of a chuck you can clamp odd ball shape stuff on. 

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I wonder if I've given up accuracy for the ability to handle larger stuff.

Can't see why, though.

And it wasn't expensive, so why not? The previous owner only used it to clean up the inside of thick wall pipe so he could use the pipe as crush tubes in bits he was making. 

It comes with a 12 inch 4 jaw chuck and a pile of alternative gears.

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1 hour ago, Gazzar said:

And it wasn't expensive, so why not? 

Absolutely! I doubt it is any less accurate than the smaller kit, I mean, what good is a lathe that wobbles?

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