Chuck size (good idea or not.?)

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The D1-3 fitting 125mm Pratt Burnerd on my Boxford has seen better days.! Although I did get it fine for a short while by fitting some new jaws that were donated to me. It however soon returned to a wayward state.

It's usable, and there is lots more that I would prefer to spent the money on, but I feel it needs to be replaced.

I am considering purchasing a smaller chuck.! ( I can always fit the 125mm back in seconds if needed ) Possibly a Pratt Burnerd 80mm. My logic behind this (possibly flawed) is that a lot of the smaller parts seem to get swamped by the 125mm one and thus an 80mm will suit my purposes better.

The 80mm has a bore of 19mm so will pass most things needed to be turned for a Stuart type engine. Other things will be turned in my 4 jaw or on a faceplate, and as I said the 125mm could always be fitted back if needed.

So is buying new 80mm a good idea or shall I replace it with another 125mm.?

Cheers, Nick

Nick,

Given the requirements that you mention, I agree that a [good quality] small chuck would be nice to work with.

The price of a good one, in D1-3 fitting might be surprisingly high though.

MichaelG.

Hi Nick,

For my lathe I have several chucks, a 150mm 4-jaw (independent), a 100mm SC 3-jaw and a 80mm SC 3-jaw. For small work I find the 80mm better than the 100mm, so I too would recommend you try to find the funds to buy a good 80mm.

Thor

Edited By Thor on 01/08/2014 05:51:06

Hi Nick,

Have you thought of a collet chuck? You should get better repeatability than from a 3-jaw, which will most likely suffer in the region of 3 thou run - out. An ER 25 or 32 collet chuck is available from the usual suppliers. I would get a D1-3 backplate from Roatagrip.

An example of a collet chuck is here:**LINK**

A backplate is here:**LINK**

John

Nick,

+1 for John's comments above.

I have an ER32 collet chuck and rarely use anything else these days. Coincidentally, the other chuck I use most often is an 80mm 4 jaw.

ER32 goes up to 20mm and will close on 2mm. If you do get one, get a proper collet spanner and consider a ballrace nut.

Regards Tom

If you go for a collet chuck I would suggest you opt for an ER40 as it gives you a larger range of sizes from 3mm to 30mm. If working on round bar up to 30mm, I almost always use my ER40 chuck, I also have another ER40 chuck on the milling machine so I only need one set of collets. Although you do not need to buy a set of collets I would suggest you do as sods law says if you don't the one you want you'll not have.

They are available here **LINK** amongst others, standard accuracy 15 Micron accuracy up to 10.0mm, 20 Micron accuracy up to 26.0mm and they also do zero Micron accuracy but expensive see http://www.youtube.com/watch?v=nRjlhAllEGk

Bob

Edited By Bob Brown 1 on 01/08/2014 08:30:42

Hi,

It sounds like you have one of the modern boxfords. The spindle can pass 1". To my mind it seems a shame to use an ER32 chuck rather than an ER40 or 5C solution.

The spindle is designed for a 5C collet adapter and drawbar assembly. These can be purchased from boxford or made. The spindle taper is:

"No 4 1/2 Taper (ASA. B5. 10-1960). 1 deg 29' 22" ON RAD. (0.624" TAPER PER FOOT ON DIA.) Note inside of spindle nose is a Morse Taper of 4 1/2. "

There would be less over hang and you can benefit from the 1" bore in the spindle.

I do not wish to re-open the ER versus 5C debate I simply point out a quick search will find plenty threads.

Steve

As someone with both ER collets and a big and small 3-jaw, in your position I'd go for the 3-jaw. ER collets are not the best solution for things like holding a casting by a chucking piece or anything else other than round bar. Try holding a flywheel on the inside of its rim using an ER collet... Plus an 80mm chuck will let you hold items up to 80mm which is far more useful for general work like the stuart engines. I'm assuming that the frequency you need round work set concentrically is rare enough for using the 4-jaw to be acceptable.

Neil

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Thanks for the replies guys. I will address a few points raised.

Yes I know it will not be a cheap option buying a semi finished quality D1-3 backplate. The Bison 100mm one is over £100 then plus the cost of the 80mm Pratt Burnerd will take it into the region of a readily manufactured Pratt 125mm with a D1-3 fitting. - But nothing  of quality is cheap when it comes to engineering it seems.

Yes I have considered a collet chuck as an option but as Neil says I will get more use from the 80mm scroll I think. So that will go on a future 'wish list'

SteveI :- The STS 10-20 Boxfords spindle bore is 38mm / 1 1/2" not 1"

Many thanks again for the replies

Nick

Edited By Nick_G on 01/08/2014 10:44:31

Hi,

Nick - your right of course! For some reason I was sure it was 26mm... I just checked the website and the spec 35mm. Oh well... Sorry for the misinformation. I don't think I have had stock bigger than an inch down the spindle myself.

I suppose its simply about the scale of what you do and the run out you want. I found I use collets more and more and the 3 jaw chucks more and more rarely. When I don't use collets most of the time its the 4 jaw. The other nice thing about 5C is the hex and square collets.

.

Thanks SteveI you have given me some good information.

I was wondering what the headstock taper was.?

Regards, Nick

As you get older smaller and lighter become desirable attributes. Consider your other equipment eg rotary table and dividing head and what you make and perhaps a small screwed chuck on an arbor with adaptors for the other tools would be better for 80% of your actual jobs. This is the route I am going down at the moment.

I am only 52.!!!!! .............. That's classed as a mere 'wippersnapper' in the world of model engineering.

Ain't it.?????????

Nick

headstock taper is 4 1/2 morse. The specs as per my post. I don't know if this is a common choice but its basically big enough to fit 5C collets down it (with an adapter bush) and a MT3 reducing bush for between centers work.

The STS 10 - 20 headstock taper is a unique Boxford one! You can get an adapter to take 3MT but sit down before you check the price! I did make my own adapter to take 4c Collets with a drawbar.

John

google tells me that a few other lathes have used the 4 1/2 morse headstock taper, but it does not appear to be overly common. Over in the USA you can buy the reducing bush to MT3 from ebay.com amongst over suppliers.

John - was there a specific reason you went with 4C instead of 5C?

Steve - I happened to have a set of 4c collets!! I have a 5c chuck and collet set which I use far more than the 4c. M

Making the headstock bush was more of an exercise really.

John

Edited By John Corden on 01/08/2014 14:12:11

Nick,

I thought you were set on a 3-Jaw, but if you are interested in collets ...

The Burnered MultiSize is a lovely system, especially in D1-3 fitting.

Get a set and you could always mount 3-Jaw and 4-Jaw chucks on spigots if you wanted.

MichaelG.

Collets and chucks aren't alternatives, a youngster like Nick will probably get both in due course. Also there are lots of collet fixtures that mount forward of the nose so spindle taper can be bypassed.

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Bazyle,

I didn't mean to imply that they were alternatives ... it's simply that Nick is facing a paricular purchasing decision at this time ... and John had questioned the practicality of fitting a small chuck to the D1-3.

The possibility of collets having already been raised ... I would personally prefer to buy the the MultiSize collet chuck first; mounting other [small] workholding devices on spigots that fit a [large] collet, as-and-when appropriate.

MichaelG.