|alex lester||27/11/2018 15:20:34|
|3 forum posts|
Hello all, great forum from what I have seen hopeing someone can help. I have just taken delivery of a Colchester triumph 2000. she is all wired in and working. except the tailstock is out of line with the chuck. now what is not to normal is that it is out bottom to top. I have taken a light cut on some 2" unsupported bar and it is cutting no taper but aligning the tailstock. the tailstock is around .020" low from the centre. I have been digging for a while and cant find any details on how to go about aligning it on the web.
I have put a coax indicator into the headstock and that is showing the same measurement. I have taken the tailstock of and cleaned all faces and there is nothing that should be causing this. does anyone have any ideas?
|ronan walsh||27/11/2018 15:57:00|
|539 forum posts|
Is there a base on the tailstock that is removeable from the top ? There is on my colchester, i think shimming maybe the easiest way to get things back in line.
|alex lester||27/11/2018 16:04:40|
|3 forum posts|
thanks for getting back to me ronan, your bang on the money it does split. is it normal to shim the tailstock in this way. ive been playing around with putting shims in and have it running pretty central
|J BENNETT 1||27/11/2018 16:34:19|
|36 forum posts|
Another very interesting post. I have the same problem with my Warco WM 250, where the tailstock centre line is slightly higher than the spindle. I had long suspected there was something wrong with alignment and finally got round to checking it. I removed the chuck and placed a centre in the spindle bore and also one in the tailstock. I then brought the points together with a six inch steel rule between them. First in the horizontal plane where there was a small misalignment that was easily corrected with the offset adjustment. Then in the vertical plane where the tailstock centre is slightly higher than the spindle.
I appreciate this is a fairly crude method and does rely heavily on the assumption that the centres have been accurately ground. It is however very sensitive to small misalignments and I could not think of any other way to do it. The other major problem is that this method does not provide a quantitative measurement of the error. Skimming would therefore have to be a trial and error process!!
I have yet to dismantle the tailstock which does appear to have a horizontal split line and hopefully a flat surface that could be skimmed or ground. I would also appreciate any ideas or suggestions.
|75 forum posts|
To the OP how old is the lathe and how much work might it have done , I worked on a Triumph 2000 for 15 yrs in a very busy sub contract shop and when you think how many thousands of times the tailstock has slid back and forth including in its previous life before we got it I expect enough wear could occur on the bed and tailstock ways to drop the centre height a bit especially if the bed hasn't seen much oil in its life or has been lubricated with suds , shimming is a perfectly good way to bring it back though if its gone below the headstock centre height.
Edited By Kettrinboy on 27/11/2018 17:03:38
|Brian Wood||27/11/2018 17:40:42|
|1942 forum posts|
I had to pack up the split joint on an old DSG lathe that had a nose droop of 0.018 inches, purely due to wear on the bed shoe.
Not a perfect solution it has to be said but we were then able to properly drill 1 inch diameter holes into steel stock without the drill nose diving inside and making an internal taper to the hole. It was also damned hard work cranking the drill in while that condition prevailed.
|Clive Foster||27/11/2018 18:20:03|
|1799 forum posts|
Shimming a tailstock up to compensate for wear in the spindle bore is a fairly normal practice on ageing machines. My wartime Pratt & Whitney Model B 12 x 30 has been so fitted and works fine. Especially so on the lighter variety normally used by Model Engineers. Bed and base wear tends to be uneven so any attempt to compensate for that is inevitably a compromise so it may be necessary to accept "lots better" when "dead nuts" was the aim.
Bed wear seems to be much less of an issue with larger, ex industry, machines than with the small ME variety.
Important to consider the effect of the tailstock poppet locking mechanism when shimming to correct a worn tailstock bore and poppet barrel combination. For example my P&W has an almost 4" long key underneath with a sloping bottom side that both prevents the poppet from rotating and locks the spindle. The keyway in the tailstock acting has a slope matching that on the key base. The key is pushed backwards by the locking mechanism causing it to rise as it runs up the slope in the casting forcing the poppet barrel against the top of the casting bore to lock it. Component wear means there is several thou lift on the poppet when locking. Somewhen I shall make a new , deeper, key to reduce the lift.
|alex lester||28/11/2018 17:44:36|
|3 forum posts|
got there in the end, just seemed a little strange as the last owner said there wasn't a problem. I shimmed it up and its true and central now. thanks for your help
4676 forum posts
Did you check that it is now horizontal? It might have worn more at the front end.
|4587 forum posts|
If the cause is bed wear, worth checking where it is on the ways. For example, if the bed is worn only in the middle due to concentrated hard work in the past, then shimming would cause the tailstock to be too high at either end of its travel. Not what's wanted. A dip in the bed can be detected by looking for light escaping under a straight-edge.
A bed regrind might be necessary unless the wear is evenly distributed. However, it might not matter much for hobby use. Quite often it's possible to compensate for known shortcomings in a machine as required by a particular job, ie you check and set the tailstock height only when a task makes it necessary. Whether something more expensive like a regrind is needed depends on how bad the hollow is and how inconvenient it makes using the lathe in your workshop.
In the event a worn bed is the cause, I'd also check the saddle doesn't alter height as it travels.
Edited By SillyOldDuffer on 28/11/2018 18:36:31
|Jeff Dayman||28/11/2018 19:28:20|
|1591 forum posts|
If previous owner only did short work in the chuck and didn't drill many holes, or bored them all, he may not have noticed there was a tailstock misalignment problem. Or maybe not mentioning it when selling was a sin of omission in anticipation of commission..... Either way, shim it up and enjoy! Many old worn lathes still have a lot of useful life, but it can take a little tinkering to work around the wear.
|martin perman||28/11/2018 19:40:41|
1628 forum posts
I've been racking my brain for past experience and remember that as a Reliability Engineer I used to send our Colchester lathes to a company called Curtis machine Tools, Ardleigh nr Colchester who would grind and re harden the bed ways, if memory serves correctly the headstock comes of the bed ways as one lump and it wouldnt hurt to see if there is any muck underneath that lifted it up.
|988 forum posts|
Correct Martin the bed is one piece, dovetail carries on under the head like any decent well made machine. Theres adjustment for offset and swing of the head as well best done by sending a cutter down rather than a dti on a bit of 2" round checking for runout over the length.
Its likely the tailstocks off another lathe or the beds been redone without the tail stock.
|Simon Williams 3||29/11/2018 13:56:34|
|399 forum posts|
Do please explain further!
I have a Mk 2 Bantam with the tailstock about 7 thou low, as near as I can measure it. I know how to adjust the side to side alignment, but being able to adjust the vertical alignment would solve my problem. Other than setting a shim to pack the upper part of the tailstock up on the lower part, is there an adjustment?
I would love to fix the vertical alignment of my tailstock.
|Frode Nęstad||29/11/2018 18:06:50|
|2 forum posts|
I have the tailstock center 5/100 low on my Tos lathe as well.
Apparently the tailstock on new lathes is bored in an incline, so as the tailstock wears most in front and it drops so it parrallell. after it wears more you need to shim it up.
An easy way of checking the tailstock is to machine a pice of bar to the samme diameter at the barrel. Bring the barrell upp to the piece an measure with an dti.
|Simon Williams 3||29/11/2018 19:26:08|
|399 forum posts|
That's all very well, and I can buy it for a new lathe where the bed is straight and true, but bolting the tailstock on the bit of the bed which is nearest the chuck (on my worn lathe) is likely going to set it low. Having "trued up" the tailstock bore to that low position moving the tailstock to the end of the bed will set it high.
I recognise that this makes assumptions about the state of the bed, but that's my point, this does exactly that. Moreover if the axis of the tailstock is high there's nowt you can do to fix it, at least if it's low (which is where we started) shimming it will let you choose a workable compromise. It's laborious, but I'm going to have to find an optimum position by repeated settings and "home in" on something which is optimum.
Which is more easily said than done. I've managed to measure the out - of - alignment but only in one position of the tailstock on the bed. Measuring it over a range of positions (and making sense of the measurements) is far more difficult, and I wouldn't commit to cutting metal on the basis of some measurements I was unsure about.
It also occurs to me that the boring bar as per the video above isn't necessarily following a straight line path. If the bed is worn the saddle moves in three dimensions, and you could be boring the tailstock in a very odd direction.
So a reversible adjustment - either twiddles or shims - is a lot more attractive as I might actually make an adjustment without being too frightened that I was making it worse.
I'm looking forward to seeing how this could be done.
Best rgds Simon
Couple of edits to make my logic more logical
Edited By Simon Williams 3 on 29/11/2018 19:30:33
Edited By Simon Williams 3 on 29/11/2018 19:33:34
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.