PDA

View Full Version : Cleaning up two faces.



plunger
10-24-2013, 05:29 AM
If I wanted to clean up these two faces what is the best set up This plate gets charged with diamond dust of some sort but I don't know how. The mandrel has a 0.1mm run out. Should I be working between centers or if I clean up the mandrel face does it make no difference unless I remove the mandrel? I only have a left hand facing tool with a special insert for aluminium. I notice it works better than if I sharpen my own hss. Could I clean up the tailstock side face and then just turn the tool upside down or should I just turn the plate around and keep working on the tailstock side? My worry with that is that the major face area will be clean but wont the area where the mandrel runs through the center hole make a problem. If I clean up both sides without moving the setup and then set this up in a four jaw I could recess the area where the mandrel bolt was and then it should sit flat on the aluminium face plate shown in the picture
http://i941.photobucket.com/albums/ad254/eugeneeman/SDC13181_zpse9bff5ba.jpg (http://s941.photobucket.com/user/eugeneeman/media/SDC13181_zpse9bff5ba.jpg.html)

JoeLee
10-24-2013, 09:05 AM
If it were me, I would mount the disc up against a face plate. Machine one side, flip it over and machine the other. Looking at your set up in the picture I'm inclined to think you won't get a good finish because the disc is too thin and will vibrate causing chatter. Mounting it against a face plate will ensure a solid mount and maintain even thickness. Now your next question will probably be how do I mount it up against a face plate........
What I've done in the past on a set up like this is run a piece of threaded rod through the spindle with a nut and washer at each end to hold the disc against the face plate. Indicate your OD to ensure the disc runs on center. Light cuts with a dead sharp insert.

JL.........................

Rich Carlstedt
10-24-2013, 12:18 PM
Vacuum Chuck

Rich

Mike Amick
10-24-2013, 01:43 PM
Great Lathe !! . I have the 11

plunger
10-24-2013, 03:46 PM
If you look carefully at my lathe you will notice it has a compound slide about a third longer than standard emco slides. My lathe has a permanent gap and is actually a nuisance as most of my work takes place about 40mm from the chuck This means a quarter of my saddle is hanging in fresh air.I can get around this by winding the compound out but rigidity is compromised. The rubber sheet is to help prevent swarf from getting under the slides.

becksmachine
10-24-2013, 03:57 PM
Looking at your set up in the picture I'm inclined to think you won't get a good finish because the disc is too thin and will vibrate causing chatter.

Light cuts with a dead sharp insert. JL.........................

Probably the most reliable method to do this would be to use "pie" (full circle) soft jaws in a 3 jaw chuck.

This would also allow unobstructed cutting across the entire face, and if they are made correctly would help mitigate the chatter problem while also ensuring good parallelism between the two faces.

You don't say what the material is, but I would agree with your comment about grinding a HSS tool. One reason for this might be that you are (hopefully?) turning much slower than if you were using carbide, the slower speeds usually being less likely to cause chatter.

Also I am sure that you are grinding that HSS tool to a dead sharp point as suggested by Joe above, and this is way less nose radius than is commonly available on any inset.

If you had any brazed carbide tools, and a diamond wheel to finish grind it, you could duplicate the zero radius cutting edge in carbide which sometimes works well. But it has been my experience that any insert, no matter what the specified nose radius is, will generate greater cutting forces, and thus more chatter, than either carbide or HSS tools ground this way.

Dave

elf
10-24-2013, 04:19 PM
[QUOTE=plunger;881423]This plate gets charged with diamond dust of some sort but I don't know how. QUOTE]

You can buy diamonds in grit sizes down to at least 200,000 on ebay. Sprinkle a small amount on the plate, then use a ball bearing to press it into the plate. You'll need a plate for each grit size.

JoeLee
10-24-2013, 05:38 PM
If you look carefully at my lathe you will notice it has a compound slide about a third longer than standard emco slides. My lathe has a permanent gap and is actually a nuisance as most of my work takes place about 40mm from the chuck This means a quarter of my saddle is hanging in fresh air.I can get around this by winding the compound out but rigidity is compromised. The rubber sheet is to help prevent swarf from getting under the slides.
Wow........ I know that the overhanging would have a tendency to cause the right side of the saddle to want to lift off the ways, and it can't be doing the left side of the saddle any good either coming in and out of the edges of the bed ways. It has to be scraping the bottom of the saddle ways out. If it were me, I would look for a larger chuck, preferably a set-tru. Then you would have a back plate behind the chuck and that would space you chuck further out from the head stock, Hopefully that would be enough to keep most of you close work over the bed.

JL..................

firbikrhd1
10-24-2013, 09:01 PM
Your problem reminds me of turning disc brake rotors on a brake lathe. Does your disc have to be turned all the way to it's center? If not, with some fiddling you might be able to rig up a tool that looks something like a tuning fork with a bit on each side of the disc so both sides cut simultaneously. That seems to cancel out the vibration issue you mention on brake lathes.

Jim2
10-25-2013, 10:12 AM
Have you seen this?

http://bbs.homeshopmachinist.net/threads/39202-Shop-Made-Tools?p=641327#post641327

Something like that, maybe with a dedicated bearing to support the chuck on the ways. . . . It would be a bit of investment in terms of time and materials, but would potentially give you a larger spindle bore.

Jim

plunger
11-09-2013, 10:05 AM
I tried doing it on a face plate but realize the guillotining process must have warped these plates . As I tighten the plate up on the face plate it behaves like a belville washer. Could I press this out. I dont want to land up machining these discs too thin to clean them up. Also would it work to heat them up red hot and place a heavy weight on the disc to get rid of the distortion. How do you harden copper if it has been annealed?.

dave5605
11-09-2013, 01:22 PM
How much do you need to take off? If only a few thousandths how about just using some wet/dry sandpaper and a piece of plate glass? Lay the sandpaper face up on the glass, keep it wet with water or your favorite liquid, lay the disc on the sandpaper and move it around with your hand.

Here in the states you can buy the sandpaper in all kinds of grits at any woodworking place or auto parts or paint store.

Of course all that also assumes you can pull the mandrel out..

plunger
11-09-2013, 09:48 PM
I am trying to clean the faces up so the process of sanding it on a sheet of sandpaper is reduced. The disc is 6mm thick but my mate has asked me to try and reduce as much as possible. At the moment I am left with a disc of 5.5m but is still not flat.The idea is to get it flat as possible to save him days of lapping

Arthur.Marks
11-09-2013, 10:56 PM
You have some excellent suggestions already. Just to be clear, I've never done this. I mean, I have, separately, in other applications...

I am figuring you have an honest original faceplate for that lathe? Super-glue the brass disc to the faceplate. Make a flat, broad nose HSS tool and sharpen it to a very fine edge. Set up the tool parallel to the faceplate (perpendicular to the spindle axis). Take a very fine DOC -- like no more than a thou' -- for your entire facing cut. Run the spindle slightly faster than you would normally. See how that works. If good, release the plate with acetone, flip, and glue again. Face the other side in the same manner.

plunger
11-09-2013, 11:36 PM
My problem is not holding but rather the moment I fix it to the face plate it is pulled flat to the faceplate. I can machine it flat but once the copper disc is removed from the faceplate it has a memory and is acting as a spring and the distortion comes back but not as bad. I am using a mandrel to hold the copper disc to the faceplate. I can see as I tighten up the tailstock I can actually see it bowing in or out to the faceplate. It depends which way I attach it to the plate. It is acting as a spring.

caveBob
11-10-2013, 12:37 AM
Friction turning?:

Use Friction Turning to Make Thin Disks and Flywheels on the Lathe
http://www.machinistblog.com/use-friction-turning-to-make-thin-disks-and-flywheels-on-the-lathe/

I've purchased diamond powder and paste from lascodiamond.com a few time, they have a 10% off coupon atm too (THANKS):
http://www.lascodiamond.com/LascoProducts-DiamondPowder.html

Arthur.Marks
11-10-2013, 05:28 AM
I can see as I tighten up the tailstock I can actually see it bowing in or out to the faceplate. It depends which way I attach it to the plate. It is acting as a spring.
That's why I was thinking of gluing it -- to remove the tailstock. Lay the faceplate face up on your bench. Apply a number of super-glue drops around the plate. Lay it down on the faceplate. Don't apply any weight. When the glue is set, mount to lathe and face. All in all, it is just a theory. I don't know if it would work. It really does sound like a vaccuum chuck is ideal for suck a large diameter-thickness disparity. I' just guessing at a workaround.

boslab
11-10-2013, 06:45 AM
It looks to me like a flat lapping plate for metallurgical samples, i have used them with different grades of diamond paste, 5 micron and 2.5 micron, kemet supplied them, warp will bugger the sample, the kemet ones were eventually backed up with a steel plate, or even cast ali.
http://www.kemet.co.uk/products/flatlapping/kemet-lapping-plates
Think the answer is to glue the plate to a faceplate, with epoxy then heat to remove.
Mark

Boucher
11-10-2013, 08:53 AM
I am trying to clean the faces up so the process of sanding it on a sheet of sandpaper is reduced. The disc is 6mm thick but my mate has asked me to try and reduce as much as possible. At the moment I am left with a disc of 5.5m but is still not flat.The idea is to get it flat as possible to save him days of lapping

I have a large lapping machine used to lap air compressor valves. It runs for hours sometimes days unattended. This type equipment is becoming obsolete as compressors are changing to screws. This would be a good piece of equipment to have if you could find one.