Herbert Lathe and domed Drum

Hello again,
I have a 60 year old Herbert preoptive Lathe. It is quite huge and I have a chuck with a very bad case of worn out scroll. My question is:
is it possible to replace the scroll and the jaw carriers, or what ever they are called. or would it be easier to get a whole chuck, - there is no runout on the body of the chuck? I get runout that varies over about 20 thou, depending on which bit of the scroll is in use. What about the chances of finding a 4 jaw that would fit on the 3 stud fixing. Does anyone have anything that is better than what I have that is no longer in use? Anything considered. I am near Norwich.
Also I am trying to make a cone on the bottom of a 40 gallon drum. I have been thinking that it might be possible to pound out the bottom in the style of a calypso musical drum, to get the same effect. Has anyone done it, or know how much of a dome I could beat out, - using a rounded end wooden post for example, before it started to do damage to the bottom ring edge or started to split the bottom. Or maybe I could reinforce the top rim and jack down on the bottom from a strong support at the top, to achieve the same effect.
Any comments would be welcome, thanks and regards, George.
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On Tue, 14 Sep 2010 23:32:34 -0700 (PDT), George

3 stud lathe chuck? Give me the diameter and the pin sizes and Ill see what I have.
My Clausing 1500 is a 3 pin removable chuck and I have extra stuff
Gunner
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Hi Gunner,
thanks for the reply. I have posted a few photos of the Herbert Chuck on my website. http://www.maribelecosystems.com/OldEngines.html There is a calliper shown which I used to measure the diameter of the flange onto which the chuck mounts. I hope you do have something.
Thanks and regards George.
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On Wed, 15 Sep 2010 07:58:51 -0700 (PDT), George

Nope..no fit. Your system is different than the D1-3 and D1-4 chucks that I have.
Sorry!
Gunner
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George, that looks similar to the DIN mounting of the chuck on my little PRAZI lathe, except it uses 4 studs. A real pain to remove and replace. Could your lathe/chuck be some larger DIN standard size?
On the 40 gallon drum, you need to be able to heat the metal, then pound on it a while, then repeat. Should be somewhere on the WWW that explains the procedure for making a calypso drum.
Paul
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On 09/15/2010 01:32 AM, George wrote:

Easier? Sure, replacing the whole chuck is easier.... But, machining a new scroll is not very difficult. The main thing is you need to be able to replicate whatever the spiral thread pitch is on the chuck, unless you will be replacing the lower jaws, too. Your lathe may or may not be able to match that thread pitch with whatever settings are available. Depending on how the scroll is turned by the pinions, that can be the more difficult part. Often they have bevel gear teeth cut in the edge of the scroll.
Making new lower jaws may be more difficult, as they need to be a very fine fit into the chuck body, and have a number of bearing surfaces that need to be ground.

I assume this is a D1-x camlock mount, when you talk about these pins. These are still in current use, and many chucks, backplates and etc. can be found in tool catalogs. Just measure the pin spacing and you should be able to match the correct D1 size.
Jon
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    You know -- while you mentioned the lathe brand, and posted a photo of the chuck mounting plate, you did not say how big a chuck you needed. I know that *I* have never heard of a Herbert Preoptive lathe before. (Of course, I was only 9 years old when it was made. :-) This might be useful information.
    Actually -- often the problem in the scroll-back lathe chucks is that the center of the scroll gets worn -- and it usually uses the center on a pilot in the chuck body to maintain centering.
    To fix that -- at least somewhat -- take the back off the chuck, take out the jaws, and using some feeler gauges, determine how much smaller than the bore in the scroll the center spigot is. Divide that size by two, get shim stock of that thickness, and cut a strip to wrap almost totally around the spigot. Slide the plate over it, and this will minimize the walking off center.
    Note that such chucks are sensitive to which of the (usually) three key holes is used to tighten it, because this determines which way the scroll plate is pushed off center. So -- it is best to mark one of the key holes as the "master" if one is not already marked. (Stamp a '0' in the body near the key hole.) Experiment to find out which one gives the best centering for a common size of workpiece (the error varies with workpiece diameter).
    Once you have found the best key hole and marked it, consider re-grinding (or turning if soft jaws) the top jaws.
    Of course -- if you have the jaws in the wrong slots, or in the wrong order, you will get major errors in centering.
    And a 3-jaw scroll-back chuck will always have some error.
    You can get plain-back chucks, and make your own backplates to mount them to your spindle. (It sounds as though you might have difficulty finding backplate to fit it from the vendors.) A quick Google search comes up with Herbert No. 3, Herbert No. 4, and Herbert No. 7 and No. 8 lathes. And what is huge to one poster is tiny to another. My largest lathe is 12" swing, and I do not consider it large, while those with 3" swing lathes (yes, they exist) might consider mine huge. Personally, *I* consider the ones with 60" swing or larger to be huge. :-)
    O.K. here are the dimensions for a No. 4 -- finally found:
7-1/2' (that's foot, not inches) center height, 17' swing over bed, 8' swing over cross slide, spindle bore 2-1/4", and 32 feet from chuck to turret face.
    This one is huge enough by my standards -- but is it the one which you have? Tell us the size so we have some clue.

    Don't make master jaws -- and if possible, don't make a new scroll plate -- just re-center the scroll plate and then true the jaws. (Turning for soft top jaws, toolpost grinding for hardened top jaws.
    Or -- consider making your own back plate for a chuck which you *can* find.

    From the photo, I think not.
    Good Luck,         DoN.
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Thanks very much Jon, but I am not up to cutting a new scroll, I am afraid, I am very much an amateur. I have just found an old Forkardt F250, 3 jaw chuck which I have carefully taken apart and cleaned and it is in very good condition. The only problem - as far as I can see is that the mounting is different and an adaptor plate will have to be made. I am not sure about this, but the Forkardt seems to run on a ground shaft about 66 mm diameter, and held on by 3 bolts, into a rear flange. I am going to take some more photos of this, and later on today will paste them on to the same page of my website. A more professional view would be appreciated.
What is the pin spacing, is this the attaching studs spacing and what does D1 mean? I put my dial indicator on the flange with the chuck removed and there is virtually no runout. On the body of the chuck, which is worn with dents it is essentially true.
Regards, George.
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Thanks Don, I did not see your post when I replied to Jon. My Herbert (4) lathe is big compared with nearly every other one owned by my friends. It is about 3 metres long and the Chuck is about 25 cm diameter. It has a 7.5 Hp motor with , - luckily, a 3 Hp option. As you say though, it is all relative.
I have found a chuck for sale on Ebay which carries a very good description, it looks and sounds just like the one I have. Is it possible that I can find a ground adaptor somewhere. It seems to be a quite common chuck, as there are many other Google links to them. Here is the other chuck advert. http://cgi.ebay.co.uk/FORKARDT-F250-250mm-3-Jaw-CNC-Lathe-Chuck-Fast-Adjust-/370373745594?pt=BI_Tool_Work_Holding&hash=item563bfedbba advertised in the US for quite a lot of Dollars. (over a thousand) apart from a lot of dents and scratches on the outside, the one I have is hardly worn on the inside.
Regards George
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    [ ... ]

    We'll need to be reminded what the URL is of the web site.

    I think that my post was rather late, so it is not surprising.

    O.K. 25 cm is pretty close to 10" (just a little smaller). based on the normal fit of a 6" 3-jaw to a 12" swing lathe, this would suggest that your lathe swings 20" over the bed -- so a serious sized lathe.

http://cgi.ebay.co.uk/FORKARDT-F250-250mm-3-Jaw-CNC-Lathe-Chuck-Fast-Adjust-/370373745594?pt=BI_Tool_Work_Holding&hash=item563bfedbba
    Auction # 370373745594 extracted from that long URL as easier to cut and paste for viewing. (My newsreader does not invoke the browser (a separate program) directly -- I have to cut and paste between them. This is by choice, BTW. :-)

    And looking at that web site, it is an interesting design. Instead of the usual scroll plate, there are three separate blocks with straight-line duplications of the scroll pattern. At first I thought that it was independent adjustment of each jaw, but it appears not to be so. I think that you withdraw the scroll blocks by turning the key in one direction, and then slide the jaws in to near contact with the workpiece diameter (the "quick-adjust" feature). Then you turn the key the other direction and the scroll plates re-engage and move each jaw perhaps one tooth inward before the end of travel. I guess that there is a plate with three radial slots which engage the "house" shaped objects, one of which is labeled "53" to match the pin on which it pivots. This transfers the motion of one scroll plate to the other two.
    You'll need to find or make a back plate which mounts to your spindle and accepts the three bolts through the chuck body to mount it. In the last image on the auction site, there are drawings of several such back plates. After making the plate and mounting it on the lathe spindle, you turn the OD to be a sliding fit into the recess on the back of the chuck (being careful to allow for cooling after machining before measuring so you don't get a size which is too loose).
    That chuck in the auction is mounted to a strange back plate.
    It is not clear whether the chuck key is included -- and it is an unusual one, too -- the key has a 14mm square *socket* instead of a square projection.
    Good Luck,         DoN.
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In mounting it must be very clean.
While mine Sheldon is different - the chuck was threaded on by Dad after a move. When I got it a year later - the chuck was still there and never checked out. As it turned out, a very small fleck of steel was in the threads and slightly offset the chuck.
Make sure dirt or chips are not running it off axis.
Martin
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On 9/15/2010 1:32 AM, George wrote:

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