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View Full Version : How Would You Set This Up ??????



JoeLee
09-25-2013, 11:23 AM
This is the R8 face mill arbor that we discussed in my previous thread. I have it set up in the work head of my grinder. I have it zeroed in to less than .0001 as far as run out goes. Now I need to set the angle of the work head to grind the taper. On straight shafts I always use a dial, however on a taper it's a little different. If I'm not dead on the center line of the taper I won't get an accurate reading. Any ideas on an easy way to set this up.

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


http://i911.photobucket.com/albums/ac317/JoeLee09/R8%20Face%20Mill%20Arbor/Image002_zps997a1787.jpg (http://s911.photobucket.com/user/JoeLee09/media/R8%20Face%20Mill%20Arbor/Image002_zps997a1787.jpg.html)

TGTool
09-25-2013, 11:36 AM
Although in theory any variation up or down from true centerline will skew your indicator reading, if you calculate it out a small difference in height is almost infinitesimal. So, you can get the size of the large diameter for instance, use a machinists square to get the height to the top when the blade end is flat on the ways, subtract half diameter and reset the square to position the indicator. Or use a vernier height gauge if you have one. Sure, it's maybe slightly off when you eyeball the indicator point position but you'll be off only by millionths.

Toolguy
09-25-2013, 11:41 AM
Put an indicator on the spindle housing with the indicator point on the R8 taper and run the table back and forth to get a zero reading on the taper.
For wheel height you can use the old lathe trick of putting a straight shim between the wheel and workpiece and get it vertical. That will be plenty close enough.

rdhem2
09-25-2013, 11:52 AM
If I may ask. Why are we doing this in the first place. Maybe if we knew the purpose the solution might be more at hand.

Rosco-P
09-25-2013, 12:17 PM
If I may ask. Why are we doing this in the first place. Maybe if we knew the purpose the solution might be more at hand.

Buggered R8 taper.

This would be easier on a Universal OD grinder. Does you table swivel? Can you mount the facemill holder between centers? Thinking that that would be more concentric.

MichaelP
09-25-2013, 12:40 PM
If the spindles of the grinder and workhead are on the same level and the arbor is concentric, in the first place, the wheel will be on center.

Now you only need to place your diamond point on center to shape the wheel.

In reality, you don't need anything centered as long as you indicate the taper, shape the wheel and have the grinding contact all at the same level. Having them on the center just makes the alignment easier.

P.S. I'm not impressed by the lack of support of the arbor shank. Can you, at least, make the chuck hold the large head (the part next to the taper) and zero the shank along the whole length? Holding like this would make the part more stable if tail support/grinding between centers is out of question. I'm not sure your chuck will allow it however (hole size?).

Arthur.Marks
09-25-2013, 12:41 PM
Can you remove that chuck in a repeatable manner? i.e. It has a 4MT shank or something? In that case, an ideal method is to mount a straight, cylindrical arbor in the workhead... something similar to a spindle test arbor. That will allow an accurate, straight shaft to mount a precisionangle block stack to. One of these things is ideal: Mini-Sine (http://www.ebay.com/sch/Business-Industrial-/12576/i.html?_from=R40&_nkw=Mini+sine). Or you can use a basic angle plate set: like this (http://www.ebay.com/itm/ANGLE-BLOCK-SET-MACHINIST-PRECISION-GROUND-1-30-Degrees-/310755731085?pt=LH_DefaultDomain_0&hash=item485a7c268d). Then you run the table back and forth against an indicator to zero. Whenyou replacethe chuck in the workhead, it will be angled very precisely to the table movement. Hopefully I explained the idea well enough to understand.

[EDIT:] 'might be able to use the above method but not remove the chuck. Use the straight section of the R8 taper as the zero reference... or the thick body portion depending on TIR/concentricity (but I sorta doubt that).

JoeLee
09-25-2013, 03:11 PM
Although in theory any variation up or down from true centerline will skew your indicator reading, if you calculate it out a small difference in height is almost infinitesimal. So, you can get the size of the large diameter for instance, use a machinists square to get the height to the top when the blade end is flat on the ways, subtract half diameter and reset the square to position the indicator. Or use a vernier height gauge if you have one. Sure, it's maybe slightly off when you eyeball the indicator point position but you'll be off only by millionths.

Yes, I understand what is quoted in red, been through that in a previous thread.
Toolguy, what your saying is what I had planned to do, that's how I always set a shaft up for inline travel, how ever falling off the center line was my reason for asking. I know everyone has a different method in mind, grinding on centers would not be a good option as the threaded holes in each end of the arbor may present an off center or eccentric problem. I thought it would be best to chuck up on the pilot end of the arbor to grind the taper with hopes that the taper is concentric to the pilot, I'm sure the factory makes sure they are.
I would rather not remove anything from the work head during the process. I guess I'll try to find the center line and indicate it inline best I can.
I can make micro adjustments by pivoting the table.

Thanks all.

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

Arthur.Marks
09-26-2013, 12:39 AM
Huh. I was figuring the taper angle was off. Now I don't know what it is--scored maybe? Anyway, if you use a plunger type dial indicator (as opposed to a lever type test indicator) just install a flat bottomed tip. Round on round is a sort of no-no in metrology, technically speaking. A flat anvil eliminates the center line problem you are concerned with.

Jaakko Fagerlund
09-26-2013, 03:56 AM
+1 for flat anvil on the dial indicator. I have a small flat piece of key stock I've drilled to put it on the end of my DI and it can be secured in place with a screw.

And what I've come across tools that have a threaded hole, theyhave the center point angle as a lead in, meaning the center is there, it is just a larger diameter. Check it, as it most probably is there.

boslab
09-26-2013, 06:08 AM
Cosine error im thinking
https://www.google.co.uk/search?q=cosine+error&oq=cosine+e&aqs=chrome.3.69i57j0l3&sourceid=chrome-mobile&ie=UTF-8&hl=en-US&espv=1#biv=i%7C1%3Bd%7CsgNlhSR-vk1MtM%3A
Mark

JoeLee
09-26-2013, 08:17 AM
I've indicated the center line as close as I can by mounting my tenths dial on the column and running the column up and down a bit. Then I adjusted the pivoting table to inline travel. I'll finish up this morning. I don't think any of these tapers make full contact in the spindle. If I look at some of my other R8's I can see rub marks from where the two surfaces touch. Some look like they make contact at the larger end and others at the smaller end.

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

Doozer
09-26-2013, 08:41 AM
Looks to me like only the small part of the taper is scored.
Why not bias your angle setup towards the acute side and
only grind away the damage part of the taper? Plenty of
bearing there.

--Doozer

JoeLee
09-26-2013, 12:10 PM
That would drastically change the angel unless you mean just grind it out and leave the rest of the taper alone, if so then the bearing surface would be much shorter. Any, it's done, came out perfect. Just have to hope it fits right.

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

Rosco-P
09-26-2013, 12:32 PM
Any, it's done, came out perfect. Just have to hope it fits right.

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

Blue the taper in the spindle and see what contact pattern you get. If the spindle taper is in good shape, no scratches, nicks, pimples, you should get a near perfect pattern if the tapers match. I'm sure you knew that test already.

Doozer
09-26-2013, 12:34 PM
Those Kingmann-White 2.5" magnetic sine bars
sure are nice. I bought mine a few years ago.

--Doozer