The Shop > Tools
Edgwick Lathe
hermetic:
Hi HH, There is a limited amount you can do with a three jaw when it gets worn, but you can usually improve the situation somewhat. first, take the chuck off the lathe, strip it down, looking for any damage or looseness in the jaws and the scroll, clean it, oil it, and rebuild it. Check the lathe nose threads, and the register to for any damage or dings and if you find any, stone them off so you know the chuck is properly seated on the lathe, oil the thread and put the chuck back on the lathe. Get a known good piece of , say 1" plus dia bar, put it in the chuck, with the end right at the back of the jaws, tighten it firmly,and watch the jaws carefully as you do it to see if you can see the jaws rising in their slots and use a DTI to check the runout. Any better? If the chuck has adjusting screws adjacent to the backplate bolts, you need to slacken the backplate bolts very slightly, and adjust them to dial the chuck in on the DTI. If there is play between the register on the backplate and the chuck, you can slacken the bolts holding the chuck to the backplate, and bump the chuck with a hide mallet and see if you can improve it that way, or make a mark on the backplate and the chuck, then remove the chuck from the backplate and see if you get better concentricity by turning it one set of fixing holes, and refitting it. At the end of the day, you can put each job in the chuck, then bump it with a mallet and check with a dti, till you get it "near enough". remember a 3 jaw chuck will have 3 to 4 thou run out when new! Mine, on a Colchester Student mk1 ran out about 17thou, but with care, this could be reduce to about 6 thou which was adequate (barely) but I used it until I was able to get a new (to me) chuck! Don't sweat it, make what you want to make on it, and if the parts aren't accurate enough, look for another chuck. Can you post up some pics, of the lathe and the chuck, especially the side faces of the chuck so we can see if it has adjustment screws or not.
Good Luck,
Phil
AdeV:
--- Quote from: HalifaxHerbert on January 15, 2018, 02:54:02 PM ---Hey Guys,
I am another EDGWICK 6.5-inch Lathe Mk. 1 owner .
Mine is fitted with a Pratt Burnerd 1210-02505 Precision 250mm chuck with 0.015" run out.
Any ideas ?
--- End quote ---
Welcome! :wave: The old Edgwick is a fine lathe, the only thing that's a bit awkward (or, shall we say, less user friendly) compared to some other lathes is the chuck changing procedure....
So, 15 thou of runout, that's pretty serious...
Some questions:
Have you measured the runout on the chuck body? If yes, what do you get?
Presumably the 3 nuts which hold the chuck in place are all tight enough? They don't need to be murder tight, but they do need to be preventing any movement... If they're good, read on...
Put the lathe in it's slowest gear (17rpm), now grab hold of the chuck and try to wobble it up/down and/or back/forth. Any discernable movement (have a dial indicator set up on the chuck body if you can't feel anything). If it's definitely moving about, it may well be wear in the spindle bearings.
If there's no major movement in the spindle bearings, the next step is to remove the chuck. Undo the 3 bolts that hold it to the spindle nose, and withdraw carefully. If it's anything like mine, you have to back them off until they're virtually touching the headstock, then wobble the chuck off, then finish undoing/removing them. Set aside. Now carefully examine the register in the chuck - any crushed swarf in there? It wouldn't take much of a chip to throw the alignment off. Check the spindle nose for similar.
If there's no swarf in there, put your dial indicator up against the spindle nose & check for runout again. If you've got runout at the spindle, the bearings need replacing. if it runs true, your chuck is bad. Try wobbling the spindle again; you should see nearly no movement in the DI.
If you can't find any wobble anywhere, put the chuck back on (but not the nuts at this point). Push the chuck all the way home & try to wobble it on the register. If it moves about, then the chuck backplate is either badly worn, or is not the correct backplate for the machine, or has been over-cut when originally machined. This isn't the end of the road for the chuck, if you don't mind messing about re-fitting it: Basically, re-install and tighten somewhat. Run the lathe slowly under power, note the high spot, tap with a rubber mallet/plastic or wooden hammer. Chase the high spots around until you've got it as true as you can, then carefully nip the bolts up, bit by bit, frequently re-checking runout. With care, you should be able to get it pretty damn close; certainly close enough to work with until you can replace the chuck and/or backplate.
Post some pictures!
Good luck!
Cheers,
Ade.
Another Edgwick owner :)
hermetic:
AAAH! they bolt on! never had an Edgewick lathe, but time yet, although I have two lathes already, but I am not trying to give them up! I have an eye on a Harrison locally............................................
HalifaxHerbert:
Hi ADEV and Hermetic,
Thank you for your comments , much appreciated.
I have measured the run out on the chuck back plate ( Max 0.001" ).
Next, I measured the run out on the chuck body ( max 0.001")
Both measurements were taken with my trusted Mercer DTI.
I have rotated the jaws , cant get better than 0.015" run out.
All the jaws are a good fit into the chuck, no slop and what I can see of the scroll, it looks in reasonable condition but I have not taken the chuck off and stripped it down because it is freezing in the garage/workshop.
Please correct me if I am wrong, do the jaws need re grinding ?
All the mounting nuts back plate to headstock and cap head bolts back plate to chuck are tight.
Pratt Burnerd in the USA inform me that this is a precision chuck, spare parts no longer available.
Is it worth pursuing a second hand chuck ( which might be crap) but I do not fancy paying big £ for a Pratt Burnerd.
Any help and advice would be much appreciated.
This machine is in my opinion a classic icon. I have the "massive face plate " which an owner of and engineering company gave me. He stated his business on one of these and used it for many years. Now retired in the Bahamas. Great!!!!!!
vintageandclassicrepairs:
Hi,
Before considering regrinding the jaws I would clamp a range of different size round parts in the chuck See if the run out is the same at the different diameters and at the same high / low point on the chuck
If the run out is concentrated at or near one end of the range of sizes the chuck will hold then the wear is mostly in the scroll
If the jaws are reground and the scroll is worn it will only hold "true" at one diameter
If the run out is constant at all sizes then it would be worth regrinding the jaws
I almost always use a four jaw independent chuck, with a bit of practice you will never bother with a self "centering" three jaw
John
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