|528 forum posts|
Hi out there, hope somebody can give a little advice......
I have a Colchester Student lathe with a square top, can't find the machine no......I guess this vib problem has just crept up on me ....... I've not had it for too long (5-6 years) I know where it came from and it's not a worn out dog....... I think I need to adjust the headstock bearing's.......this is because of a bad vibration / chatter when parting off or taking a medium cut.....anything heavy is out of the question......my work never goes over 2.5 inches in dia....
the chuck has no play in it that I can feel by rocking it and it is very quiet.....if the gearbox selectors are placed between gears ( a false neutral ) the chuck spins quite freely........the box is also up to the mark with clean oil......
I have even taken to buying new carbide tipped tools (Sandvik) and also after sharpening my normal cutter's I've polished the cutting edge on an oil stone....this has improved the cutting finish but not the vibration.....
when the chuck starts to vibrates I'm sure I can see it wobble.....I'm to scared to take any heavy cut's and am always steady and careful as can be when turning, but it's now getting too bad and I can't say I'm enjoying the experience at all.....I normally machine mild steel and 306 stainless, I 've not tried any ally yet.....as for parting off I obviousley keep the job as near as poss to the chuck....I can help ease the vib's if I use a rotating steady but I can't always use one though......
So my thought's are with the head stock adjustment / preload.......idea's / help, please......
many thanks, Frank Cloggs
|1231 forum posts|
have you tried asking the ColchesterLathe-User group on Yahoo? They may be able to help you.
|Dennis WA||30/05/2013 14:08:24|
|76 forum posts|
I assume you have also checked by clamping a long stout steel bar in the chuck - were you able feel any play in the bearings if you pull on the bar?
I agree with Thor - I own a Student and have found the Yahoo group very useful.
|3251 forum posts|
What state are the chuck jaws? Are they gripping evenly along their full length? When you are between gears and you say it spins quite freely, a properly preloaded and warm taper bearing will have some specified bearing torque setting, which can be measured.
|528 forum posts|
Hi, thanks for taking the time to reply....all time is valuable....
have joined the Colchester forum....no replies yet...
No I havent used a bar in the chuck - will do tomorrow.....
the jaws look real good but will inspect tomorrow (in general the machine has not done a lot of work)
as for the chuck spinning freely (in a false neutral) I'd say there was no drag...ie. bearing pre-load....
my machine no. F2/70869..is there a work-shop repair manual on-line ??
will let u know......many thanks gentlemen.....
|1231 forum posts|
when your membership in the Colchester Yahoo group is approved there is a manual for Colchester Student (from 1967) in the Files section. This is probably for an older model than yours.
You should be able to buy one from lathes.co.
|1504 forum posts|
There is a manual on the Yahoo Colchester_usergroup
|Bob Jordan||18/10/2013 17:17:03|
|2 forum posts|
If as you say your student lathe has not seen a lot of use over the years then the spindle bearings should be OK.
I would start by firstly removing the chuck, cleaning all mating surfaces on the spindle nose and chuck and dressing off any bruising etc., Refit the chuck in the correct manner. ( You have not stated what fitting type you have, i.e. screwed locking ring or the more modern camlock.) Please note that camlock chucks should always be fitted in their original orientation by aligning the reference marks on both spindle & chuck.
Now as Dennis said grip a long bar in the chuck & check for any appreciable deflection in the spindle. Hopefully there will be none. If there is play emanating from the spindle bearings then this will be a very costly repair because these are Gammet bearings that have a fixed preload & are not adjustable.
Hopefully the headstock assembly will be found to be OK & you can then start looking for any slack in the slide assemblies.
|Mike the Bike||19/10/2013 10:17:50|
|16 forum posts|
Following on from Bob's advice, I would suggest that while the chuck is off you put a substantial and long piece of bar down the spindle. Put a clock on the spindle nose and pushing and pulling the bar, observe your clock. Deflection either up and down or side to side will indicate a headstock problem, no deflection would suggest that your chuck may be the cause.
Hope this helps, Mike
|Nigel McBurney 1||19/10/2013 11:09:26|
709 forum posts
Colchester round heads and the early square heads were very poor at parting off,the cross and topslide vee ways are to put it bluntly not up to the job, the later square heads are better,I have a master 2500 which parts off en 8 steel with no problems, I think your problem is a worn chuck where the jaws have been strained and only grip at the back, have you tried using the four jaw chuck to hold the work or turning between centres to see if there is a improvement, A new chuck is probably the answer,the east european Bison chucks are quite good for the price. There should not be any problems with bearings as they are substantial and selfadjusting, the hand book does not give any info on bearings it just states self adjusting,the cost of new bearings would possibly write off the lathe.
I have surface finish problems with my colchester triumph 2000, I thought it was bearing problems until I tracked it down to to the phase converter,the lathes perfect when driven by a single phase motor.though the single phase was ok for testing but not powerful enough for most jobs.
Have you got any friends with a similar lathe ,try borrowing one of their chucks, Or if you are self taught try to find someone who has more experience,you can always learn even if you have spent years doing a job.
|528 forum posts|
mine's a square head....bit like me ......
how right u are, I did find the chuck jaw's gripping at the back...so I held an accurate ring on the inside so that the jaws were locked and cleaned them up with a tipped v/heavy boring tool...it didn't need much......this did seem to improve the parting of but not by much......I now part way turn off the jobs untill I get scared and then finish the job with a hack-saw.....if it the stub is still a bit thick I do it with the chuck spinning slowly.......
does anybody know the machine no's to find out if I have an early machine or not.....
Have checked the turning torque of the chuck - in neautral (between gears) and it takes about 3 - 5lbs / ft to get it moving so by my reckoning theres enough preload on the bearing to eliminate the chuck shakes.....
I'm afraid there's nobody else here to ask, where I live in France, my house is the last chance saloon.....thats unless there's anybody around Bordaux on the forum......if there is let me know, my wife bake a good cake and the kettle is always on !!!!!!
I'll have a look at the Bison chuck.......
does anybody have a copy of "screwcutting in the Lathe" by Martin Cleeve. they want to sell ??
thanks for ur time and trouble......Frank
|Dennis WA||20/10/2013 12:18:17|
|76 forum posts|
Machine no. F2/70869 was manufactured in 1969.
|Sam Haylock||02/06/2020 21:29:25|
|1 forum posts|
Hi have Colchester student 1800 lathe, s/no. 4/0001/02427
couple of questions, on page 16 in parts section of manual it shows an "O" ring (part no. 77590) & locking pad (part no. 77594-0) on the crossslide assy, I have the screw (part no. 77207-0) but no pad or "O" ring, does anyone know what these are for?, also on along from screw for pad/O ring are three grubscrews, does anyone know what these are for?,don't see them in manual,
crosslide looks like one in manual (part no. 77738-0), would anyone have a swivel slide (part no. 77742-0)
4553 forum posts
That's possibly because gripping the inside of a ring pushes the jaws in the opposite direction to what is needed when resurfacing the jaw faces. You need to use a clover-leaf plate or spider that pushes the ends of the jaws outwards while the gripping surface is (preferably) ground.
There are numerous videos on YouTube showing people doing this the wrong way because they know no better.
Something like this is what you need. Or you can make a simpler version from three pieces of flat bar with the hole and slot in each and held in position by hand while tightening chuck jaws.
Edited By Hopper on 03/06/2020 08:48:21
Edited By Hopper on 03/06/2020 08:59:34
|larry phelan 1||03/06/2020 11:23:48|
|726 forum posts|
Surprised to hear that some Colchester lathes were/are bad at parting off !
I though they were supposed to be the cream of the pack?, at the price of them, I would expect something better.
Perhaps my Chinese Monday Morning Product is not so bad after all !
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