Air bearing for a Tinker cutter grinder

[archers]

I am attempting to replace the bushed head in a Tinker tool and cutter grinder with an air bearing. I am using the Philip Duclos article (1987) as a model. Does anyone have experience with making an air bearing? My first attempt was not successful.

[halfnut]

Got a bushing on each end, some space and clearance beween these 2 bushings. Put air to it in the middle between these 2 bushings.

Now these bushings need to be nicely fitted, no annular grooves to let air escape.

Works good.

[Rotate]

Can you explain in more detail how this air bearing works? Does the spindle move both axially and radially with very little friction? I can't visualize how this can be achieved

Albert

[archers]

Albert

Yes, the spindle rotates and moves in and out. The spindle is bored to a nice fit on end mills so they can be sharpened on both the ends and edges.

[archers]

Halfnut,
Thanks for the posting.

So all that is needed is air to the center of the spindle housing and it will work? Great!

Can you give me an idea of clearances required. Duclose indicates .002 (1987 article). The tinker plans call for something a bit closer.

What air pressure are you using?

Thanks again for the advise.

[archers]

Albert,
If you are a HSM reader, Philip Duclos published an article in the Sept./Oct. issue on the construction of an end mill grinding fixture.

SA

[bspooh]

I have never made an air bushing, but what i would do is make it about .001 difference in diameters...

For the cylinder, add a few grooves that is channeled further down and up the cylinder...remember, air pressure will be the same thru out the whole cylinder....use 90 psi or less.....

Just what ever you do, do not move it back and forth without air...this will damage the bearing surfaces

brent

[Thrud]

Pressure need to be fairly high, the air must be dry and clean or the air bearing will not work. If you make the end bushings of bronze bearing material there is less chance of damaging the spindle if you do not have air pressure. Chrome shafting works well as a spindle because of the finish - you have to make sure what ever material you use does have a smooth surface with no nicks or burrs.

[halfnut]

Our Harig at work has Iron bushings I believe. Home grown rig I built is just steel against hard chrome shaft from a hydralic cylinder, I used my old Sunnen hone and fit it close, less than .001 .

Harig has a bit more clearance, one can get the air to hiss at you if you put enough side load on it. Still not more than .001 clearance I believe.

We use line pressure, 100 - 110 psi.

Poor people have poor ways, I even made my airflow with a R-8 taper, can sharpen anything I can use in my mill that way. Plus I had the collets.

Looked at an old Drill point grinder yesterday, not sure what brand it was, it was painted blue and old. Had most of the fixings for a endmill sharpening machine, just add a tool carrier and an adjustable tool finger and I believe it would work.

[lynnl]

I don't have personal experience, but 'Metal Working', Book 2) has a tool and cutter grinder made by Glenn Wilson that uses an air bearing spindle. (I just happened to be looking at that article last nite.) His specs called for .0015 clearance between spindle and housing, w/about 1/64" annular grooves for the air passages. His air specs were about 5 or 10 PSI.
I had annotated my article to the effect that he (G. Wilson) had subsequently published a correction in either HSM or PIM/Metal Working in (as I recall) OCT/NOV 2000. If you're interested in the contents of that correction, email me and I'll research further.

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