Chucks

I'd be interested to know what sort of accuracy those that can set their 4-jaw "in a minute" with a bit of chalk, fag paper, end of tool, etc can get.

There you go, you see. I, me and myself am not a trained machinist. I can often set up a piece of material in about a minute, but not with the accuracy you are thinking of. Certainly sufficiently accurate to knock out a part from an over-sized piece of material because I know that it need not be as accurately centred as your lovely SC chuck! As long as I finish the machining before removing it from the chuck (usually parting off) there is not a jot of difference between the two types, as regards accuracy.

I didn't know it when I started, but soon learned that I could not even re-chuck a perfectly round bar in my cheap chinese chuck. Yes, the ones typically sold with most new lathes. It may take me longer than a minute (often does!) to centre a part accurately in the 4 jaw, but at least I can, if I want/need to.

I do use the 3 jaw, but if the 4 jaw is fitted it is about as easy to centre a workpiece as changing the chuck (and it still not be centred to the accuracy you were suggesting).

As I said earlier, it is with hindsight that I would choose a 4 jaw independent over a 3 jaw if I were only to have one chuck. Very hypothetical, now that there are several chucks stashed away in my workshop. And I still would not class myself as a precision machinist, by any means. I make things to suit a purpose.

A 3 jaw is easier for a beginner, just no more accurate and a lot less useful than a 4 jaw independent. But we are not beginners for long (not talking about ability here) and once you get started, you soon realise the need for a different chuck to that 3 jaw. And mostly, people do not go out and buy another 3 jaw chuck of he same size. They get a 4 jaw independent as a first extra purchase.

Hi Pero, I have checked Taigs website and they do not supply the 3-jaw with steel jaws.

Without a DTI, just using the tool, about 0.1 to less than 0.2mm total runout. 0.2mm runout looks quite terrible when it is running. 0.1 looks not too bad, this is TIR . With a DTI and 2 keys, if the bar is round to start with, getting it to about 0.02mm to 0.03mm TIR is actually quite quick. Getting less than 0.01mm takes more time and care. Then every micron takes more time.

Neil

'2 keys', why 2 keys?

Tony

'2 keys', why 2 keys?

Easier / quicker to set with a key in each of the opposing jaws - you can only push with a jaw, so using one key means having to spin the chuck 180 degrees to get to the other side if that is where the push is required. Using 2 keys allows you to push from either side as required without having to rotate the chuck.

Nigel B (another who was taught to use a 4 jaw independant in an apprentice training school)

4 jaws grip better and can do everything a 3 Jaw can except holding hex bar (well, easily anyhow).

If you are really fussing about price stick to a Face plate and centres.

Seriously though you are probably going to buy the 'other chuck' soon after so I would say it depends on the quality of the chuck they are offering. You can probably put up with a cheaper 4 jaw than a 3 jaw. If it's a lower quality chuck go for the 4 jaw and buy the best quality 3 jaw when funds allow. That way you may not end up buying both.

regards Martin

Hello Brian

My apologies - you are quite right - it's a long time since I have looked at the website.

However, they are still listed as a chuck accessory on the Taig Australia website, which in some ways is a little more informative than the US site.

There is no information provided as to whether they are original Taig manufacture or from a third party supplier.

In any event as the jaws are in two parts and the gripping portion simply bolts onto the carriers it is possible to make your own jaws out of any desired material, truing them up as per the instructions provided with the chuck.

I'm not sure whether your proposed supplier does a pre-delivery set up, otherwise there is a little work to do in getting the Taig up and running. Not terribly complicated and worth following the instructions to achieve the best from the machine.

Best of luck Pero

Four jaw is much safer, way harder for workpiece to come out of the chuck! Take only a wee bit longer to setmup,but gives a much more secure and accurate setup.

"Four jaw is much safer, way harder for workpiece to come out of the chuck"

Well maybe I've been lucky but I've never had a regularly shaped workpiece "come out" of a 3 -jaw -

On the other hand I'm always a bit wary when holding irregularly shaped components in a 4-Jaw !

N

Edited By NJH on 25/05/2017 09:12:34

Surely this is only true if you ignore the possibility of beginner mistakes or carelessness? One problem with using independent 4-jaw chucks is that centring can be achieved with the work gripped properly by only two jaws. In this condition the work will rock as soon as pressure is applied by the cutting tool; I hope we all agree that this is a bad thing.

For what it's worth, I use a 3-jaw most of the time because it's quick, convenient and generally 'good enough'. I switch to a 4-jaw to hold rectangular stock and other odd shapes or when I need better accuracy. When going for accuracy I don't mess about: I'd say a DTI is the best way to assure results. On the other hand I've been in the workshop of a chap with a big lathe. His 4-jaw is about 2 feet in diameter and an engine crane is needed to lift it. No surprise that he uses the 4-jaw for everything, but I doubt he'd advise a beginner buying his first tiny lathe to do the same. When giving advice everything depends on the context. You have a problem if you owe a bank a million pounds. If you owe them a billion pounds, then it's the bank that has the problem...

Dave

Edited By SillyOldDuffer on 25/05/2017 10:29:17

Having seen the heat and light generated by this question, BEWARE we seem to have fallen into the trap of flooding the chap with too much information.

A lot of us have experience, (many more than I) but we are being asked to advise a beginner.

I served my time at Rolls Royce at the Sentinel works in Shrewsbury. In that first year in the Basic Training School, we used 3 jaw, 4 jaw and Collet chucks.

But we started with the easiest to use, and used it for a lot of the time.

3 Jaw: not absolutely concentric. but suffices for much work. If two or more diameters are turned at the same setting they will be concentric to each other. If the work is removed and replaced,it is unlikely that the second operation work will be absolutely concentric with the first, because it has not been replaced in exactly the same position as originally. A "good" 3 jaw will probably hold work concentric to within 0.005inch. Don't think about an old abused one!

4 Jaw: Once learned how to operate, with the aid of a "Clock" and its stand or magnetic base, work can be made to run as concentric as the time and effort that you are prepared to spend. It can be used to deliberately hold work off centre, when needed. It can also hold irregularly shaped objects for drilling, boring or turning.

With a 4 jaw and a "clock" you should be able to set the work to run concentric to within 0.0005 inch or maybe even better. Greater accuracy just takes more time.

Collet Chucks: useful when more than one component needs to be turned. Hopefully, a good one will hold work concentric, consistently.

For a beginner, I would opt for the 3 jaw, since it requires the least expertise, and is least complicated to use.. As you gain experience, you can progress to learning how to improve its use and then progress to the 4 jaw (and have time to save up for the one that you have researched as best value/ most convenient). Then you can start making things as concentric, or as eccentric, as you wish, and hold odd shaped things that a 3 jaw cannot.

A Faceplate requires slightly more skill than a 4 jaw, so save that for even later on, unless you HAVE to jump in at the deep end.

Hope that these comments clarify things a little.

Join a local Model Engineering Club for advice and help, (and hear all the foregoing arguments again)

Enjoy yourself

Howard

The three jaw is a most useful tool, just remember it's limitations. It will always have some error in concentricity and repeatability. If either of these requirements is critical then the three jaw may not be the tool for the job. I am not concerned with the accuracy of my three jaw chucks as I will use a 4 jaw or collets if I need good concentricity or repeatability. Some thought given to the order of operations will often allow a job to be completed without removal from the chuck so the accuracy will not be a problem. For many jobs the slight runout will not be an issue if the job is removed or reversed in the chuck so most of the time the 3 jaw will suffice. It is true that the 4 jaw is the most versatile and potentially most accurate but you will soon lose the will to live if you have to use it for every job even if you do get efficient at setting it up. So get a 3 jaw and put the 4 jaw on your Santa list with the collet set.

Mike

Thank you all again for the advice, I have decided to go for the 3-jaw chuck as this seems to be recommended by the most people.