Lathe rebuild


I was quoted about 400-500 dollars if I bring in my lathe bed, to have
it reground. The bed is relatively worn (carriage drops about 0.002 inch
near headstock), and the rest of the lathe is not.
I am ending my ebay selling soon, so I will have some more time.
If applying turcite and re-scraping the saddle is not too much, I will
have them do it too. My thinking is that after this, I will have a
lathe that is as good as a new one.
My current question is, how hard is it to take the headstock off this
clausing colchester master, and, no less important, how to align it
again once I get the bed casting back home.
Reply to
Ignoramus14986
Loading thread data ...
0.002 isn't much for hobby use. Do the math. For a tool on centerline, how much change in diameter does a 0.002 drop produce?
Care to share why?
Don't have an idea on that. Most lathe bed grindings I've read about are 2x the price w/o any fitting.
Well cutting a rod and measuring it will show if it is off as far as taper. Loosen bolts tap it in correcting direction and try again.
If you really have 0.002 wear, just use it as is.
Wes
-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller
Reply to
Wes
It is no big problem to remove the headstock and reinstall it, but the use of a test bar is best for alignment. Machining a test bar indicates error but not direction of error, where a proper predision test bar does. Most hobbyists will not own one, but after having done this job using both methods, the use of a test bar is much easier and more accurate. They can be found on ebay from time to time. I now have a set of them. Steve
Reply to
Steve Lusardi
A description of your test bars , please ? Precision ground between centers bar ?
Reply to
Terry Coombs
Unfortunately, the inverted vee that holds the saddle, is also very worn and so the saddle moves crosswise when I move it along the lathe. I think that it is because the the vee wear. The difference in diameter at various points is perhaps 0.2mm.
I do not like the latest ebay changes. I have way too much stuff to sell, so I will be selling for a few months without buying anything new.
Reply to
Ignoramus14986
I think that eBay is digging its own grave, by trying to become what it could never be, and in the process, losing what it always has been good at.
Reply to
Ignoramus19342
Really, a piece of hardened and ground shafting (like Thompson glide rails) works very well with the types of indicators the typical home shop would have. There is a tiny bit of sag due to weight, but it isn't real bad. The indicator with the lightest touch is best to avoid deflecting the shaft. (Oh, you have to verify the straightness of the shaft with indicator and surface plate, first. You can't assume any shaft is straight.)
Jon
Reply to
Jon Elson
Setting up a lathe is not high tech. You must be careful, keep everything spotlessly clean and make multiple measurements with every step. Regrinding the bed of a lathe rarely produces increased accuracy, but what it does do is allow tight carraige adjustments which reduces chatter and adds overall machine stiffness. This increases consistancy making every step more repeatable. A worn out, loose lathe is capable of accuracy, but takes a lot of patience and experience to do that. When you service a lathe bed, every surface on the bed should be remachined to original specs. Any attempt to do otherwise is a waste of money. For those folks that have never done this, let me assure you that lathe beds look massive and enormously stiff, but they are not. They can and do bend and twist quite easily. That is why the bed leveling operation is so critical. Please do not misunderstand that statement, a level lathe is NOT important. They are quite successfully installed on ships. What is important, is bed straightness and reference to a water level is nothing more that a common base line reference. All lathe beds will twist with the weight of the carraige simply sliding across them. A lathe carraige is not balanced. It is much heavier on the apron side and when moved to the center between bed supports, will exert a twist as much as .004" worst case. Contrary to popular opinion, this will not cause an observable change to the dimensions of the cut because the position change of the tool rotates about the bed center. This is the reason a worn bed does not cause inaccuracy.
Head alignment does effect the lathe's accuracy. It is critical, so getting the spindle line parallel to the lathe bed is the second step in setting up a lathe. That is why a precision test bar is so important, because it easily shows these position errors. Every spindle comes with a precisionly ground inside cone. Typically it is a morse taper and the test bar seats there and provides a spindle extension on which a simple dial indicator is placed. The top of the bar has a ground flat which is positioned during testing, parallel to the bed. Observed deviation is vertical head misalignment. When the indicator is positioned 90 degrees away at the horizontal center any deviation along the bar's length indicates horizontal deviation. This deviation can be compensated with shims under the headstock.
These statements are verifyable with two tools, a precision machine level and a test bar and if you don't have access to them, get access or buy them. These are necessary to install a lathe, let alone repair one. Steve
Reply to
Steve Lusardi
eBay could go back 5 or so years in time and be a fairly decent company again.
I don't care for ebay from the buyers side. Hiding bidding id's, that just turned me off 100%.
Wes
Reply to
Wes
Yes, indeed, everything that they have done, lately, is for their benefit and not for their users'.
Reply to
Ignoramus19342
much change
I love the mix of units. Do you work for nasa?
Reply to
Cydrome Leader
Steve, thanks. I saved your post. I think that my issue is not so much the worn surface of the bed itself, as it is very worn "inverted vee", which makes the carriage move sideways as it moves along the bed.
My plan, for now, is this:
1) Set the lathe correctly so that the bed is properly level. 2) Buy, borrow or steal a test bar 3) Measure everything and check with this group again 4) If numbers warrant, take the bed for re-grinding.
I have a Starrett 98 precision level, but not a test bar. I will look for one now.
Reply to
Ignoramus11155
Yes, very sad, a bunch of greedy people who have no idea what they are doing, ruining the good thing that ebay once was.
same here.
Reply to
Ignoramus11155
Igor - I have a Starrett #199 level in good shape that you can borrow for a week or two. Email me at this address if you are interested.
Mike
Reply to
Mike Henry
I have just noticed this too. The new eBay search system is dreadful. If you want to add any special options, such as "Item Condition: Used" it's now really difficult to find them. As far as I can see, the new search system hasn't added anything useful. It has just made finding items to buy harder.
I also hate those little pop-up windows which aren't proper windows which they've introduced. I think they're probably implemented with JavaScript. If they had thought their interface through, they wouldn't have needed any of those windows.
Best wishes,
Chris
Reply to
Christopher Tidy
Yep.
They are. Turn off JavaScript, and they go away -- but unfortunately, so does other *needed* functionality.
And I really hate the auctions which also require Flash to be enabled to see the images (other than one default image).
They want to be "impressive", not useful. :-(
Enjoy, DoN.
Reply to
DoN. Nichols
The vast majority of things for which Flash is used are totally pointless. Playing video online is an arguable exception, although it should be noted that most videos published online are pointless.
I came across this abominable piece of web design yesterday. A truly gratuitous use for Flash:
formatting link
They appear to be forgetting that people go to eBay to buy stuff, not to admire the latest trends in web design.
Best wishes,
Chris
Reply to
Christopher Tidy
On Sat, 11 Oct 2008 00:04:56 +0000, the infamous Christopher Tidy scrawled the following:
I get REALLY pissed off when someone takes my spacebar 'page down' away from me. Grrrrrrr!
Reply to
Larry Jaques
[ ... ]
Hmm ... what browser are you using? I'm using Opera, which allows you to set preferences on a site-by-site basis (after turning off a lot of things as the default). Among other things, the sub-menu for controlling scripting (aside from just turning on and off JavaScript itself) includes:
====================================================================== [] Enable JavaScript
[] Allow moving and resizing of windows
[] Allow changing of status field
[] Allow script to receive right clicks
[] Allow script to hide address bar
[] Open Console on error
User JavaScript files
[________________________________________] [Choose] ======================================================================
Aside from a separate menu which allow turning on or off Flash (plugins), Java, Content Blocking, and Animated Images
And one which allows selecting which brower your brower tells sites that it is. :-)
It is free -- and it is a fast browser.
Enjoy, DoN.
Reply to
DoN. Nichols
On 11 Oct 2008 22:04:39 GMT, the infamous "DoN. Nichols" scrawled the following:
I have Javascript and Java turned on. The above link kills HTML keyboard characteristics in both Firefox 2 (my main browser) and MS Internet Exploder 7 (which I only use for Netflix because Netflix isn't sophisticated enough to work with the better browser.) Feh!
I thought the free version of Opera had beaucoup integrated advertisements. The earlier versions did, and I nuked it because of that.
-- Guard well within yourself that treasure, kindness. Know how to give without hesitation, how to lose without regret, how to acquire without meanness. -- George Sand
Reply to
Larry Jaques

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