Rd14x40 Bed Twist

Back way.jpg Front way.jpg Mic.jpg Way measure.jpg Crossfeed.jpg You may want to do some simple checks of you lathe bed, I made this alignment checking tool to tell me how much wear and twist there is. Indicator position is critical for getting a good reading and eliminating any vibration with a light oil helps keep the .0001 indicator from bouncing around. My old bed has as much as .008 wear at the head stock, the new one is about .0006. When I checked the parallelism of the dovetail, it was less than .0005 after I got the TDI to stop vibrating when I slid the alignment tool along the edge of the ways. I also have a few ground flat plates (carbide inserts) that I used to put under the ball, it makes for a true flat surface to ride along. There are many ways to get this measured. Now interpreting what it is telling me can be a challenge. Good luck. Tim
 
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WA5CAB,
Thank You for the explanation. That helps a lot to understand the intent of your information. I think this

Hermetic,
Thank You as well, your explanations are a great help to me. I can understand what is going on.
I very much like the idea of putting my efforts into "re-seating" the headstock. I have made a lifting arm that is attached to the headstock cabinet(front corner). I use that arm to change the chucks and lift anything very heavy on/off the lathe. I can position this arm over the head and add a supplemental brace to the end of the arm. With a chain-fall I can then easily pickup the headstock.

ASTJP2,
Thank you for the photos, I like the setup. If re-seating the head doesn't improve things, I will most likely head in that direction.
If you were to make another tool, what improvments would you incorporate?
 
Sorry, got the wrong term, I meant cross slide, not compound! My postulation is that if the headstock is angled slightly towards the rear of the lathe, and you take a cut using the cross slide only, you will produce a flat surface on the end of the bar (eventually, when the end all cleans up) but it will be slightly elliptical, and not perpendicular to the length of the bar. I think maybe less Port and more thinking is required at my end! Having said that, the sun has set behind the yardarm, so it must be time for the remains of the Christmas booze to be finished. Happy new year to all of you!
Phil
 
Hermetic, Makes perfect sense to me.

Happy New Year to all of you.
 
I need more sizes of snugs and a way to keep everything organized better. There is a large and small C, I started with the large but it was too big for the inverted V on my lathe so I made another. They are both gray cast iron. I have something like 4 each .0005 and 2 each .0001 TDI's but they all attach differently so I need to have a way to attach each one and still be useable. I would use the tool with a true alignment tool in the spindle to check the alignment of the headstock, yours is a Short #5 MT, contact Brian (millermachineandfabrication@gmail.com) or you can do the Ebay thing and hope for the best http://www.ebay.com/itm/5MT-Lathe-A...271297?hash=item280a1b93c1:g:XrcAAOSwZd1Vdrvz

This is an accurate way to check your alignment, turning cuts gets you close at one point on your bed, what happens if you move 10" to the right? The alignment tool and a test bar is what you need if you want it real true. If your headstock is off, you need to scrape the bottom to get it aligned. After I am done with my carriage, crossfeed and compound scraping, and 2 new gibs, I am taking on the head alignment and scraping it in also. A mind numbing task but worth it in the end. Tim
 
Hermetic,

No. Given: That the cross slide moves exactly perpendicular to the longitudinal axis of the lathe (bed) and that the spindle axis is twisted slightly toward the rear of the machine and therefore not parallel to the lathe axis and not perpendicular to the cross slide path.

To produce an eliptical end on a workpiece mounted in or to the spindle, you would have to have a motor mounted on the cross slide turning something like a face mill and do the cut with the spindle locked. If you turn the spindle and use a normal cutter in the tool post, you will cut a convex cone. Twist the headstock so that the spindle is pointed slightly toward the front of the bed and you will cut a concave cone.
 
Wa5cab, Thank you for the input, in your opinion , what should I do next?
 
I'm not sure. Do you have or can you borrow a 10x10 or 12x12 surface plate and do you have a 4-jaw chuck large enough to hold it? If you do, you could start by confirming whether the spindle axis is perpendicular to the cross slide axis at the headstock.
 
I have a small 6"X 18" surface plate. I don't think the 4jaw would chuck it, it's a 12" chuck.


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wa5cab said:
I'm not sure. Do you have or can you borrow a 10x10 or 12x12 surface plate and do you have a 4-jaw chuck large enough to hold it? If you do, you could start by confirming whether the spindle axis is perpendicular to the cross slide axis at the headstock.
Click to expand...

You are making the assumption that the wear in the carriage has not changed the crossfeed causing it to be off from perpendicular to the bed. I am still trying to figure out how to measure exact perpendicular between the inverted V and the cross feed dovetails. I know the crossfeed angle is fixed but if there is much wear (my saddle was rocking on the bed due to wear) it will need to be scraped to realign it. I know its in Connleys book but I cant seem to find the procedure in checking the alignment. There is also the alignment of the headstock to the bed, both vertical and horizontal. You need to have both in alignment or what you have is a parallelogram where the crossfeed cuts perpendicular to the headstock but its not perpendicular to the bed. Tim
 
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