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View Full Version : Air Bearing Question..... Spindle & Housing Tolerances...... Anyone....



JoeLee
02-28-2013, 06:21 PM
I have a really nice KO Lee air bearing, however the spindle tends to stick a bit. It's not just in one spot, it can just happen suddenly about any where throughout the spindle's travel. I removed the spindle, wiped it clean and made sure that it was free of any oil, nicks, etc., same with the housing and it made no difference. It actually moves with less resistance with out any air being applied to it.
I've varied the air pressure from 30 psi to over the recommended 80 psi. and it made no difference, actually the lower the preassure the better it feels, but it still sticks. Here is the reason.......I think......... There is a lot of air leakage comming out of the right hand side of the housing where the spindle exits the bore. The leak seams to be concentrated between the 11 and 2 o-clock position. What I think is happening is the uneaven exit of air around the spindle is forceing it against the opposite side of the bore causing it to stick. Thats why it moves with less resistance with no air. I don't know what the tolerances are on these, my guess is a couple tenths. I think I may have a simple fix but I'm not 100% sure if it'll work. My idea is to make a flange to bolt to the housing with a tight tolerance ground ID. The flange doesn't have to be any more than 1/4" in thickness. My thought is this flange will act as seal, altough it won't touch the spindle it will just even up the gap around the spindle and hopefully allow for even air flow around it eliminating any binding.
If any one doesn't quite get what my idea is just let me know and I'll post some pictures.

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

oldtiffie
02-28-2013, 06:48 PM
If the "stick a bit" does not really impede the function of the air quill and if it can be used as required without too much effort or problem, I'd suggest it be left "as is" as attempts to solve a small problem may may it a bigger one and perhaps beyond use or recovery.

Perhaps it will "wear in" over time - and perhaps not too.

JoeLee
02-28-2013, 10:21 PM
It's well worn in altough it doesn't look it. It does impede the function at leat it does to me as that effortless glide of the spindle just isn't there and with out it you don't have the sense of feel.

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

Bruce Griffing
02-28-2013, 10:35 PM
I don't know what the end of that air spindle looks like, but this idea may be a useful test. I would put a clamp across the outside of the spindle in such a way that the applied force tends to close the gap that you suspect and open gaps in the perpendicular direction. If you apply a clamping pressure large enough to produce a small deformation (not plastic deformation) you should see some change in behavior. It is a simple test, you just have to be careful not to produce damage. A better test involves a ball bearing of just the right size - something you probably don't have. A fix involves a ball bearing of the correct size, some lube and a press.

oldtiffie
03-01-2013, 12:05 AM
It's well worn in altough it doesn't look it. It does impede the function at leat it does to me as that effortless glide of the spindle just isn't there and with out it you don't have the sense of feel.

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

As the main use of the air quil is probably sharpening the spiral flutes (end edges as well) the "feel" theat I am after with my quills (air and other) is that I can feel the "finger" on the flutes of the cutter.

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-33.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-35.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-36.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-43.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-42.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/ER-32_C5/ER32-C5-31.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder18.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder20.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder21.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder23.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal_grinder17.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Universal_grinder/Universal-grinder27.jpg

This stuff on other than air quills ir set up to show the principle involved (ie "mocked up") and while on tool and cutter grinders can mostly be done on a surface grinder with a "saucer" wheel anda bit of lateral thinking and ingenuity - and it is just as functionally accurare as the air quill..

My air quill is fine but if it is set level with air supplied it will "creep" and increase longitudinal speed until it hits a stop or a job or a wheel unles it is "nipper"/clamped whennot in use - a slope of less that 1/8" per foot (1 in 96 ~ 0.60 degrees) but because of "stiction" and some "moving" friction I have no "sliding" problem there with the "other" (non-air) quills.

Here is my air quill:

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill4.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill6.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill5.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Air-quill/Air-quill7.jpg

Elninio
03-01-2013, 12:57 AM
Maybe one of the pads has more oil in it or gunk than the other. Try rotating the pads and check for chirality - if yes, then replace the pad(s)

Jaakko Fagerlund
03-01-2013, 05:01 AM
If the "stick a bit" does not really impede the function of the air quill and if it can be used as required without too much effort or problem, I'd suggest it be left "as is" as attempts to solve a small problem may may it a bigger one and perhaps beyond use or recovery.

Perhaps it will "wear in" over time - and perhaps not too.
The idea of the air spindle is totally lost if it drags.

And 'fixing' something by wearing it in is not the way things are fixed. Crap doesn't turn to gold no matter how much it 'wears in'.

oldtiffie
03-01-2013, 05:54 AM
Perhaps so - perhaps not.

If the OP wants to stick to "perfect" and not use the air quill until it is "perfect" then he may not get around to using it at all.

If it is less than ideal but is still quite functional - then if it were me I'd use it.

Its the OP's call after all as it is his air quill.

Machtool
03-01-2013, 07:50 AM
then he may not get around to using it at all.
Pot, kettle, black.

Is there any chance you could possibly stuff any more **** into this stooge Pic?

http://s200.beta.photobucket.com/user/oldtiffie/media/Universal_grinder/Universal_grinder23.jpg.html

Ron Davy
03-01-2013, 08:44 AM
Pot, kettle, black.

Is there any chance you could possibly stuff any more **** into this stooge Pic?

http://s200.beta.photobucket.com/user/oldtiffie/media/Universal_grinder/Universal_grinder23.jpg.html

clean it with car wax. and wipe it with a soft clouth.

Rosco-P
03-01-2013, 08:54 AM
Have you been feeding it "clean" air? Well filtered, no oil, dry air? Did you make the mistake of connecting it using an air hose that had been used for general shop use and was contaminated by dirt, oil, etc.? Did this start happening recently or was this behavior noticed immediately after buying it (used?)?

philbur
03-01-2013, 09:07 AM
The air is usally supplied to the anulus via very small orifices. If you have an orifice blocked at the 6 Oclock position you will get the effect you describe. Look for a means of access to the orifice (one feeding each recess pad) or come up with a way to backflow through the offending orifice with compressed air.

Phil:)

As the previous poster pointed out, very clean air is a must.

Jaakko Fagerlund
03-01-2013, 09:48 AM
Perhaps so - perhaps not.

If the OP wants to stick to "perfect" and not use the air quill until it is "perfect" then he may not get around to using it at all.

If it is less than ideal but is still quite functional - then if it were me I'd use it.

Its the OP's call after all as it is his air quill.
If he wants to use an air spindle, then a sticking spindle is not one to use but to repair. Using a broken tool will end up in more broken tools.

If you would use even half the stuff you pose you would know this kind of elementary thing.

JoeLee
03-01-2013, 10:09 AM
Tiffie, I don't have a spin jig, I've used them before but they don't have the same no drag feel that an air spindle should have. If you can develop the feel for useing one when sharpening your end mills that geat but with the drag thats on this spindle I have it makes it very difficult to maintain the delicate sense of feel that you need to keep the end mill in contact with the finger.
As far as the replies about cleaning and air supply etc. Those were the first things I looked for. In it's first life it was used in a tool sharpening shop, it was used for it's intended purpose but cared for and not abused.
The first picture shows the bore, this one has 3 air holes evenly spaced out around the center of the bore, every thing is clean.
the second picture where I indicate with the red marks is where the heavy air loss is comming from. It must be that there is some wear in the bore that is the cause. My thought is to make a flange like the one shown in the last picture, wit a close fit ID to seal the gap and hopefully evenly distribute the air around the spindle, it;s an easy and simple fix, but I just don't know if it'll work.
The idea that was mentioned about clamping a half or quarter round piece of plastic around the leak area would be a good way to test my idea. If it works then I can procede to the permanent fix.

JL.....................
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image001_zps519c003d.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image003_zps15ffafa9.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image004_zps4ab06bb0.jpg

JoeLee
03-01-2013, 10:11 AM
Note: I've tried reversing the spindle and the leak is still at the same location that is marked so with out a doubt it's in the bore and not the spindle.

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

JoeLee
03-01-2013, 11:31 AM
I measured the spindle. I get 1.7295 consistently any where I check. Indicating the bore I get 1.7315, sometimes I get .732 where the leak is.
I tried to take an average reading.
If the flange idea doesn't pan out the only other option I can think of would be to resleeve the bore. The only problem would be finding hydraulic tube to fit the spindle. If I can get close I could have the spindle centerless ground to fit the tube. Just a thought.

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

phil burman
03-01-2013, 02:17 PM
Those air holes will have small orifices in them

Phil

goodscrap
03-01-2013, 04:13 PM
Half a thou wont be the problem, my home brew air spindex has more variation than that and floats. As mentioned above I think you have an air supply problem. Remove the spindle turn on the air at low-ish pressure and feel the ports, leaving a gap between finger and hole so you don't block them completely,. I think you'll find one or more is flowing less than it should.
Also if you put your finger in the centre of the bore the air should feel fairly even, almost centring your digit.

Try with higher pressure if needed, but usual disclaimers about high pressure air and skin apply.

I don't know if ou can dissemble the housing for cleaning, or use a piece of rubber hose on the end of a blow gun if needed to blow out any obstruction.

Brian

JoeLee
03-01-2013, 06:32 PM
I wouldn't think a half a would be a problem either unless it's like a wear impression along the inside wall of the bore. This bore has 3 air holes spaced 120 degrees apart in the center. They look to be .375 in dia. I don't see how one of them could be clogged. It looks like the bore is set into a sleeve and sealed at one end you can see it in the picture. Air is feed into the housing and flows around the OD of the bore and through the holes, how could one be clogged??????

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

oldtiffie
03-01-2013, 08:02 PM
Frankly. I've never had to worry too much (or at all) about a "delicate" feel as a good set-up is quite robust.

Grinding the external faces/edges (straight and spiral) on slab milling cutters, side and face cutters, slitting/slotting cutters etc. all use a similar "finger" set-up without the benefit of an air-quill.

Provided the OP can develop a consistent but adequate "feel" with the air-quill assembly as it is he should persevere and he should do very well.

There is a risk that any "remedy" may not be reversible.

The previous owner (tool sharpening shop) - in the absence of any evidence to the contrary - seems to have coped with the air-quill as it is well enough in a commercial environment.

But its the OP's call after all.

philbur
03-01-2013, 08:15 PM
HAVE YOU CHECKED TO SEE IF THERE ARE ORIFICES IN EACH OF THE 3 AIR HOLES. And yes I was shouting. All good quality air spindles have orifices. For an air bearing to work at it's best the air supply to the annulus must be restricted. Please check this before you start to butcher it.

There is no reason why the spindle should be worn, when it is working there are no contact surfaces. You would have to be pretty brutal to wear an air spindle to the point where it no longer functioned.

PS: A Darex AS has three air holes (pads) at each end and each of those pads has an orifice.

Phil:)


I wouldn't think a half a would be a problem either unless it's like a wear impression along the inside wall of the bore. This bore has 3 air holes spaced 120 degrees apart in the center. They look to be .375 in dia. I don't see how one of them could be clogged. It looks like the bore is set into a sleeve and sealed at one end you can see it in the picture. Air is feed into the housing and flows around the OD of the bore and through the holes, how could one be clogged??????

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

oldtiffie
03-01-2013, 09:29 PM
As a matter of interest, this is how side and face cutters, slotting saws and slab milling cutters are mounted - on an arbor/mandrel - before going between centres on the T&C grinder - no air quill:

http://i200.photobucket.com/albums/aa294/oldtiffie/HF-45%20Mill%20misc/Stub_arbor2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/HF-45%20Mill%20misc/Stub_arbor1.jpg

The side faces are done on an MT3 arbor in one of the other heads (set at 90 degrees +/- clearance angle) that I have for my grinders. End faces of end mills are done in a similar manner.

There are few rules is T&C grinding as many operators will achieve the same end via different methods and set-ups.

This one is done similarly:

http://i200.photobucket.com/albums/aa294/oldtiffie/HF-45%20Mill%20misc/TC_End-cutter2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/HF-45%20Mill%20misc/TC_end-cutter1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/HF-45%20Mill%20misc/Brake-disc2-1.jpg

The thing that all have in common is that the work is passed by the grinding wheel (saucer wheel) by moving the table back and forth - which is a lot "heavier" than just an air quill - and different set-ups and "feel" are required.

Tool and cutter grinding is pretty well a quite skilled manual art form - similar to marking out and grinding drills (by hand).

End mills with a shank larger than the largest of the air-quill collet set will require to be sharpened between centres - similar to that for a mandrel - but your fingers are going to be a lot closer to the suacer wheel.

A real finger (yours?) caught and dragged down between the work and the wheel is not a pretty sight so full concentration is needed.

oldtiffie
03-01-2013, 09:31 PM
HAVE YOU CHECKED TO SEE IF THERE ARE ORIFICES IN EACH OF THE 3 AIR HOLES. And yes I was shouting. All good quality air spindles have orifices. For an air bearing to work at it's best the air supply to the annulus must be restricted. Please check this before you start to butcher it.

There is no reason why the spindle should be worn, when it is working there are no contact surfaces. You would have to be pretty brutal to wear an air spindle to the point where it no longer functioned.

PS: A Darex AS has three air holes (pads) at each end and each of those pads has an orifice.


Originally Posted by JoeLee

I wouldn't think a half a would be a problem either unless it's like a wear impression along the inside wall of the bore. This bore has 3 air holes spaced 120 degrees apart in the center. They look to be .375 in dia. I don't see how one of them could be clogged. It looks like the bore is set into a sleeve and sealed at one end you can see it in the picture. Air is feed into the housing and flows around the OD of the bore and through the holes, how could one be clogged??????

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

Phil:)

I agree with Phil 110% - think it out and proceed slowly - if you must.

JoeLee
03-01-2013, 10:15 PM
Thanks for all the help guys........... I'm not going to do anything to the fixture that would ruin it. My question now is how can I tell if there are orifices in the three holes???? Looking down the bore all I can see are 3 holes about .375 in dia. Whats behind them????? I don't know, just the outer housing that the bore is sealed in. If there are orifices behind the holes there is no way I can access them. Any attempt to remove the bore from it's outer shell would risk damage. I have a parts break down but it doesn't show any orifices. The spindle and it's housing come as a matched pair.

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

JoeLee
03-01-2013, 10:50 PM
Here are some pictures of each end of the bore. You can see the three holes in the center. There are no orifices behind any of the holes. I stuck a piece of wire through all of them....... nothing behind them except the outer wall. Also are pictures of each end and one where the air inlet is.
It's just what I thought it would be. The OD of the bore has has a grove turned at the center where the holes are. It's potted in the outer housing where the air inlet is. I don't understand why there would be the need for an orifice. When you say orifice I think Bridgeport oilers, metering jets with different size orifices to meter oil flow to vaious points etc. there are no pads or any type of seal at either end. My thought was to make a seal plate to even out the air flow around the spindle.

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

http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image009_zps5866cf64.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image008_zps0dc3c4ca.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image007_zpse1690a7f.jpg
http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image006_zps375e6190.jpg

TGTool
03-02-2013, 12:30 AM
There is a patent for an air bearing where the restriction is provided by linear channels leading to large holes rather than small orifices at the air exits themselves. To qualify as a bearing there must be a self centering force in response to a movement of the spindle off center. In order for the force to be created there has to be a restriction or orifice so a differential pressure can develop and thus a centering force.

OTOH there have been plenty of devices promoted as air bearings which don't actually support the spindle centrally in the bore but simply flow air around it. I'm not venturing any opinions on what you're dealing with there or what to do to make it work better for you.

JoeLee
03-02-2013, 01:00 AM
TGTool, I agree with you about the centering force and how it develops. I'm not aware of any other designs....... this is my first air bearing. It seems simple enough. The spindle would self center, it almost does, if it wasn't leaking so much from the one side that I indicated in my other post. There are no end caps for restriction of air flow. My guess is the restriction of air flow is determined by the clearance betwen the spindle and the bore in which case I have a little too much on the one side which is forcing the spindle off center.
I have a 1/8" piece of aluminum plate, I'm going to turn a hole through it about .001 larger in dia.than the spindle and clamp it to the leaky end of the bore. What I'm thinking it'll do is even out the air flow around the spindle allowing it to center. I can't damage anything in trying this.
If it works than I'll make a steel flange like I showed in one of my first set of pictures.

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

oldtiffie
03-02-2013, 01:18 AM
Grinding end milling cutters and the like are really better off ground on centres as that is more likely the reference surface for the shank and the grinding of the flutes when it was manufactured.

Some of the possible contributary errors in an air quill are: quill bending, 5C (or rother collet) bearing cone not concentric with the the quill outer diameter; collet external tapers (which bear on the quill internal taper) having a concentriciy error (parallel and/or conical); the collet bore which grips the job being conically and/or parallel eccentric with respact to the collet outer locating taper/s.

All of these may be mutually additive or subtractracted and the sum of some others varying between zero and maximum depending on where the collet is loacated in the quill and where thejob is located in the collet.

This is is common in milling spindles where the bore may be eccentric to the quill as well as the collet adaptor and the collet.

Parallelism and zero taper are not all that important when grinding an end milling cutter as it may meet some of the errors in the machine spindle and collets etc.

Same goes for horizontal milling machines where the arbor is distorted or bent such that cutter eccenetricity is very evident by eye and by machine cutting noise such that only a few teeth are actually cutting.

But keep it to a minimum by grinding the cutters as well as can be done.

philbur
03-02-2013, 04:38 AM
Buy yourself a $5 inspection mirror.

Make two plates to fit on both ends, with a tie rod holding them in place. Attach you air supply to one of the plates and blow backward through the holes, or .... or....or use your imagination.


The restriction to the air supply must be upstream of the annulus. When the annulus opens up on one side the pressure in that part of the annuus needs to drop in order to generate a restoring force. If the air supply to the annulus is virtually unlimited then the pressure reduction in the wider opening of the annulus will be minimal and the restoring force will be minimal.
Air bearings look very simple but achieving the correct air flow to optimise the restoring force requires very careful balancing of the air flow.

Phil:)

PS: From memory the orifices in the Darex are in the range of <0.012".

PPS: Ignoring a possibility because it's difficult to check should never be an option.

JoeLee
03-02-2013, 08:30 AM
I have tried reverse air flow as mentioned by plugging each end of the bore with rubber plugs. The reverse air flow is just as free. With out any type of orifice or check valve how could it not be. I'm sure there are other designs for air flow control such as end plates with small dia. holes to balance air flow but this design does not employ any of the fore mentioned. As I mentioned before, I believe the only thing that regulates the flow is the tolerances between the spindle and the bore. If the bore wears and becomes slightly out of round then the result is uneven air flow exiting around the spindle causing forcing it off center. My end cap idea is sort of changing the design.

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

JCHannum
03-02-2013, 10:56 AM
Just a thought here. This style of endmill grinding fixture is an offshoot of the design that was origianlly be Weldon. The first Weldon fixtures were not air bearing that followed. I have seen original Weldon fixtures that have been "air bearinged" by tapping and adding air lines in random places.

I don't know the evolution of the KO Lee fixture, the earlier small machines used a ball bearing collet fixture for doing the flutes. Is it possible that this is a fixture that started life as non air bearing and has been modified, or as an air bearing that has been "improved" at some point.

At any rate, nothing ventured, nothing gained. As it is not suitable in its present state, experimenting with reversable fit ups can't hurt and might help.

JoeLee
03-02-2013, 08:33 PM
I roughed out a flange for the leaky end of the bore out of 1/8" alum. I'll turn the ID to about .0005 over the spindle size. It'll be close fitting around the spindle. I'll put some double stick tape behind it to make for a good seal. The tricky part is going to be getting it positioned so it doesn't rub the spindle, if it does it won't hurt anything but may cause some drag. If it works I'll make a permanent one out of steel ground and finished. All I'll have to do is drill and tap 3 holes in the end of the bore to bolt it up.

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

http://i911.photobucket.com/albums/ac317/JoeLee09/KO%20Lee%20Air%20Bearing/Image012_zpsb40b0efa.jpg

jamesmelville
10-11-2013, 07:34 PM
My first post and just attempting to help. From post #32, appears to be either a Rocheleau or Harig fixture. Roch. was designed to have a front wiper around spindle and if my memory serves correct the family owned company never did a true diamond lapping of their fixtures. Not sure if I still have drawings but seem to remember using the same wool felt/lubricated(same as Cincinnati #2 head) when repairing one yrs ago. I may still have a couple of these fixtures here. Harig used tapered neoprene/butylene? but almost unnoticeable. If your grinding a carbide EM vs. HSS/COBALT, I would suspect the carbide dust as the culprit along with worn spindle. By worn yes it may mike out within tenths but just from grinding pressure of carbide vs.steel will create the necessary pressure or hot dust(diamond +carbide dry impregnates) to ruin those type spindles. Roch. family still doing business and friendly enough. Give them a call if they are the mfg. Always been helpful to me.
Oh, just a 30+++ tool maker/grinder here.