Chucks V collets (Little Lorch lathe)

[Yorkie]

I’ve just made another little brass turret terminal for the Ekco AC77 that I’m restoring. Such a simple little thing as turning one of these little jobbies involves quite a lot of work and tool changing. I used collets rather than a chuck and thought I’d add a few pics to illustrate the difference between using a chuck and alternatively using collets.

Three-jaw self-centring scroll chucks aren’t noted for their accuracy and despite my best efforts with a Dial Test Indicator (‘DTI’) to tweak the chuck on my little Lorch lathe to minimise the extent of eccentricity, getting it to run absolutely true is next to impossible.

The smaller the diameter of the object being turned, the more of an issue even the slightest eccentricity becomes. A couple of thou out on something 3” diameter is one thing, but on something ¼” diameter or less it’s quite another thing. Collets are expensive items, but fortunately, my Lorch came with a full set of collets for tool holding and work holding. Using collets instead of a chuck ensures that small diameter stock (up to 10mm diameter in my case) will run absolutely true.

This little watchmakers' lathe dates from the early 1900s, (I wonder if it was ever used for watchmaking?), so can be forgiven for its shortcomings! I don’t really do any turning which calls for a high degree of accuracy, but I don’t like to see things which aren’t as good as they could be within the limitations of my lathe. I’ve attached a few pics to show how collets are used, for anyone who doesn’t know, (which will of course exclude Colin and Al to name just two!):

Pic1: Shows the lathe headstock with the chuck in place.
Pic 2: The collets I used to turn the brass terminal. Namely:
Headstock collet with drawbar, and 6mm brass rod in place. Tailstock end collets with centre drill, drill for tapping 4BA, and 4BA tap.
Pic3: Chuck removed, and headstock collet holder visible.
Pic 4: Centre drill in tailstock end collet holder.
Pic 5: 4BA tapping drill (tape on drill to limit the depth of hole).
Pic 6: 4BA tap in collet holder (headstock turned by hand to tap thread.
Pic 7: Terminal turned to size with groove in it cut with parting tool.
Pic 8: Finished terminal.

Serves me right for losing one!

Hope that's of interest.

[AlanBeckett]

David,

Why are you using that set of Jaws in Picture 1?
It leaves a lot of the material unsupported. When using a Chuck it's best to have the least amount of material unsupported as possible. Also, unless you require the final Diameter to be the same as the Material Diameter, ie un-machined, a bit of eccentricity doesn't matter provided you don't remove the work during machining.

I've got a couple of Collet Chucks for the Chipmaster. Infortunately they're not 'through' so only useful for short workpieces.

Alan

[Yorkie]

David,

Why are you using that set of Jaws in Picture 1?

Alan

Well spotted Al, and thanks for reading the post and for your comments.

Short answer is that I'm not using those jaws - I uploaded the wrong pic - all the rest were taken today - that was a pic I took a couple of years ago, basically to show that a length of rod could be passed through the headstock - a bit of a daft pic in the first place really. As you rightly observe, those jaws are for larger diameter stock, and would be the wrong jaws for gripping 1/4" diam rod. (I do have both sets of jaws). I'd intended to post a pic taken today that just shows the chuck in place prior to removal and fitting the collet.

[AlanBeckett]

Splendid!

You often see Chucks for sale with the Outside Jaws fiitted but no Inside ones with it - hopeless really unless it's a well-known make and spares are available. On the other hand a spare set for something like a Bernerd can cost an arm and a leg, and using new Jaws on a warn Scroll isn't much of an idea anyway.

Alan

[Retired]

Hi,

Many thanks David for adding the pictures and describing how you make your brass turret terminals. This sure is inspiring stuff to encourage a novice to buy a lathe even a small one such as yours because lathes are just so useful and very interesting to use.

The quickest way to learn what works and what doesn't work on a lathe is to have a go but not to be reckless because a lathe is easily damaged as is the lathe operator. It's possible to get away with extra overhang from the face of a chuck using thick material taking light cuts but something like thin brass easily flexes away from the cutting tool so the usual thing to do is to increase the cut then suddenly the work is destroyed as distortion rapidly takes over. Without proper training then a novice simply makes all the mistakes until a bit of experience is gained; after 50 years of playing with lathes I'm still learning; the main things are not to damage the lathe or yourself.

It's the end result which counts and you look to have a nice production line going in making the turrets; well done David and thanks for sharing your story.

Kind regards, Col.

[Alan Douglas]

Lathes are an endless source of fun, and sometimes even useful. My latest project was turning a new handle for the "commutator" of a 10" Marconi spark coil, circa 1912, a gift from my old boss who had retrieved it from a storeroom at the Midland, Ontario Marconi station in 1950. I've had to make a number of parts including the entire spark gap assembly, and now am working on the coil's outer casing which is badly cracked.

The original handle was ivory but a friend also restoring a Marconi coil sent me a piece of bone, which is a very good match.

[Yorkie]

You probably know Alan that should you ever need any, you can get 'alternative ivory' (and horn and bone) in various diameters and lengths, suitable for turning on woodturning or metalworking lathes. It comes in blocks as well as round bar. This firm is on your side of the pond:

http://www.masecraftsupply.com/servlet/t...Categories

http://www.masecraftsupply.com/servlet/t...Categories

http://www.masecraftsupply.com/servlet/t...Categories

In the UK, firms such as Axminster sell alternative ivory/horn/bone:

http://www.axminster.co.uk/alternative-i...oise-shell

Rattlesnake skin pen blanks (and other snakes) seem to have come into vogue among some pen turners. Stripped and tanned rattlesnake skin is encased in acrylic.

Some may find it attractive!

http://www.exoticblanks.com/Prairie-Ratt...I-102.html

[Alan Douglas]

Thanks; I also had a link to an outfit selling fossil ivory or mammoth ivory and pre-ban ivory but it was naturally rather expensive so we opted for bone. The other restorer was missing the two shorting bars with the ivory balls on the ends.

[singlepentode69]

I have recently got a lathe with collets.The chap I bought it off used to teach lathe work for the mod and swore by them , I mY have a try at making some wanda plugs.
Regards
Robin

[AlanBeckett]

Collets, properly fitted and not worn, are generally considered more accurate than a Chuck.
On the other hand they often don't have a through hole so you can only use short lengths of material.
If you can do all the Turning for a job without removing the work from the Chuck, and the final diameter is less than the original, it doesn't matter if it isn't very central.

Alan