AT1 - AT11 taper tolerances?

[Arthur.Marks]

Is my only option to buy one of the multitudinous, constantly updated and rescinded standards? Why is something as "commonplace" for taper tolerance not in a big compendium book of tolerance references (Machinery's Handbook)?? You would think it would be, but I sure can't find it. A link to further explain: http://www.ctemag.com/aa_pages/2014/...chineTech.html

I am looking for the figures related to both Morse 3 and Jarno 12 tapers. The purpose is to quantify my result (hopefully) using a sine plate.


The plug has already been qualified. It blues up real nice and consistent.


It is without a doubt a #3 Morse Taper; however, a way to put a level of precision to that fact would be welcome.

[Danl]

Did you look at http://www.lyndexnikken.com/blog/ind...dle-toolholder ? Not much out there, for sure.

Dan

Is my only option to buy one of the multitudinous, constantly updated and rescinded standards? Why is something as "commonplace" for taper tolerance not in a big compendium book of tolerance references (Machinery's Handbook)?? You would think it would be, but I sure can't find it. A link to further explain: http://www.ctemag.com/aa_pages/2014/...chineTech.html

I am looking for the figures related to both Morse 3 and Jarno 12 tapers. The purpose is to quantify my result (hopefully) using a sine plate.


The plug has already been qualified. It blues up real nice and consistent.


It is without a doubt a #3 Morse Taper; however, a way to put a level of precision to that fact would be welcome.

[Arthur.Marks]

Danl, yeah, I did find the CAT figures. I am unsure if the angular figures are consistent across all defined tapers. Probably. Machinery's Handbook (27th Ed.) lists a general figure of 0.002" per 12" (included angle?). You may have noticed the given note below the table in my first picture. I may not be able to even measure it anyway with a 5" between rolls sine plate.

[EDIT:] Assuming diameter on the MH tolerance, it works out to within 0.00054" for a 3.25" length taper.

[millwrong]

Please excuse my question;I'm not trying to be obtuse,nor intentionally demonstrate my ignorance, however-to what end? Are you interested in the taper being a standard of some sort? The master to your metrology set? Was your bluing done to a standard,or just a confirmation of the taper type? It's cold, and I'm curious!

[RussZHC]

Only actual reference I can find in an older Machinerys to a taper tolerance is the plus minus .002 but that is in reference to the large end of a taper pin (the way the book has its tables divided I assume it applies only to taper pins).

Awhile ago I mailed Tom Lipton (oxtoolco) a similar question that was rooted in his measurement of a taper (IIRC it was not a standard taper) since, to me, mathematically there was, I thought, a simpler way to approach.
Paraphrasing his response (to lazy to dig it up, and it may not be around at all any more) he had already sent email off to Jacobs more or less asking the same thing...tolerances vis a vis tapers.
Part of the issue, for me anyway, was some vague recollection that really good arbors came with a "datum" line and linear measurements along the axis perpendicular to the datum line were to be used when describing the taper. I can not recall seeing an arbor that actually had a specific datum line around it, so, if true, sort of defeats the idea.

Edit: way back in my Machinerys, it gives several options for dimensioning tapers on drawings, "precision work":

In certain cases where very precise measurements are necessary the taper surface, either internal or external, is specified by giving a diameter at a certain distance from a surface and the slope of the taper

[J Tiers]

Not sure what the question is either.... but a real MT (or other) gage for female taper has a line on it (or a recessed surface) that has to be within a certain distance of the end of the socket in order for the socket to be correct.

Gages for a male taper have an inherent gage line as the end of the gage, but may have a notch cut to provide a protected gaging surface.

http://www.threadcheck.com/cylindrical-taper-gages/

http://www.smitragauges.com/products/gauges/morsetaperG.html

[Arthur.Marks]

Ok, I admit that I did wander from the basic question. The basic, original question is:
What is the technical specification for the "AT" (i.e. AT3) tolerance series?

Interestingly, I just went looking for all those common product listings that cite, "made to AT3 tolerance." I can't find them! Where did they all go? Perhaps everyone abandoned that spec... I remember seeing them touted as a dimensional qualifier for taper tooling I have bought in the past.

[EDIT:] I may not have been clear, but I made that MT3 part. millwrong, the bluing socket is just a step-down sleeve, commercially made, which fits my MT4 milling machine spindle. Regarding the purpose of this item, see the contemporaneous thread Seeking Jarno 12. The male MT3 part calls for no extreme precision. I was just curious how truly close I actually came relative to commercial specifications.

[J Tiers]

Well you needn't worry about it... you show Morse and Jarno, but the AT tolerances ONLY APPLY TO steep tapers

For general info:

http://www.dlindustrial.com/profiles/blogs/steep-tapers-fast-tapers-at3-and-what-it-means

For specific info, you will have to fork-over for the spec itself. And, since the ISO version is "withdrawn", (I think the ASME is also) you may not be able to get it at all from the standards sources. The standards are ASME B5.50-1994 and ISO 1947.

When a standard is "withdrawn" it is "not supported", and the standards outfits no longer deal with it.

[Arthur.Marks]

Ahhh. I erroneously thought it was a general spec' for taper angles. And looking at only steep taper tools, there it is again: AT3 is everywhere. Example 1, 2, 3. Look especially at that last example. I think that is what I was remembering. Its mention next to the Morse Taper end mill holders is almost certainly a catalog error. The Bison-Bial site nor the Toolmex site make any mention of AT3 with Morse Taper tooling.

[Old Hat]

Some missing history here.
Brand new Morse taper tooling today often will not stay wedged in the mating sockets.
Lost it appears is the practice of grinding the tool-shank angles to be (nominal/+nominal)
and grinding the receiver angles to be (nominal/-nominal).
Now they're ground "perfect" which is not perfect. Morse tooling is often stacked.
A drill may be in 2 or 3 sleeves on the way to the spindle.
NOTE: The angles increase from MT1 to MT5.
Minute expansion is / was accounted for.
Further, the grind on both shanks and sockets is now ground to much too fine a finish.
Or specifically, burnished beyond the grind, to much too fine a finish.
We often have to sprinkle emery grit on the brand new shanks,
and slam them home many times repeating this untill they will bite properly.

Morse Taper dimensions (mm)
Morse Taper number Taper A B (max) C (max) D (max) E (max) F G H J K
0 1:19.212 9.045 56.5 59.5 10.5 6 4 1 3 3.9 1° 29' 26"
1 1:20.047 12.065 62 65.5 13.5 8.7 5 1.2 3.5 5.2 1° 25' 43"
2 1:20.020 17.780 75 80 16 13.5 6 1.6 5 6.3 1° 25' 50"
3 1:19.922 23.825 94 99 20 18.5 7 2 5 7.9 1° 26' 16"
4 1:19.254 31.267 117.5 124 24 24.5 8 2.5 6.5 11.9 1° 29' 15"
5 1:19.002 44.399 149.5 156 29 35.7 10 3 6.5 15.9 1° 30' 26"
6 1:19.180 63.348 210 218 40 51 13 4 8 19 1° 29' 36"
7 1:19.231 83.058 285.75 294.1 34.9 - - 19.05 - 19 1° 29' 22"
B Tapers[edit]

MT6 and MT7 are end-mill holders, which may explain the angles no longer increasing nearly incrementally.

[J Tiers]

Here is a link to ISO standards store, showing the standard as "withdrawn".

http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=6671

As for the MT series taper rate increasing, it does NOT.

To begin with, the MT0 is out of sequence, it has a slightly larger taper per foot than the MT4, 0.6246" vs 0.62326".

Starting with the MT1 at 0.59858", they do increase, by very uneven steps. There seems to be no scientific basis for the taper increases, since the size steps are not at all in the same proportion as the taper steps.

The MT2 is just barely larger taper than the MT1, at 0.59941, and the MT3 slightly larger at 0.60235" per foot, but the MT4 jumps up to 0.62326" per foot.

Then there is another oddity, since the MT6 (.62565) and MT7 (.62400) are actually smaller taper rates than the MT5 (.63151)

Size-wise, the small end of the MT2 is 1.5x the diameter of the MT1, but the taper is only 1.0014x larger. However, the MT4 is 1.3x larger than the MT3, a smaller step than from MT1 to MT2, yet the increase of taper is 1.0347x. So for a smaller size ratio between MT3 and MT4 vs MT1 and MT2, the taper increase between them is much larger.

It seems that the legend that the problem was insufficiently accurate measurements may be closer to the truth. It would have made sense to have all of the tapers the same increase per foot, like Jarno, and they are so close as to make no real difference.

Source: 19th ed of Machinery's Handbook

I found no reference to a tolerance, but I do not for a slim moment believe in a tolerance of 0.002 per foot on an MT taper. Anything like that would cause the thing to rattle around like a pencil in a barrel, it wouldn't hold. In an MT3, there would be almost 7 tenths clearance....and worse in larger ones.

There might be a tolerance of 0.0002 per foot, that wouldn't be bad, under a tenth error in most all tapers.

If you have made taper shank tooling, you know how crazy the looseness feels with even a tiny error. And you see the taper doesn't "blue up" at all.

[Old Hat]

Perhaps it has been 'lost' in manufacture, though. I can't speak to that.

In manufacturing = in practice, good enuff for me.
When machining is how one provides funding for groceries and house payments.
In-practice is ALL that matters.

We don't have to even be 100% certain that our conclusions are sound beyond any shadow of any dout.
If a notion stands among a few of us, most of the time, and on varied work. we call it good!

I've been slamming Morse into Morse, for over 40 years. So have my compodreas.
Only recently have we found such a high freguency of Morse popping out of Morse.

And only recently have we noticed that the shanks and sleeves look like they ran the wheel dead
in the manufacture of same. Hence, effectively, the keys to the city have been lost.

The prosecution rests it's case!

[Old Hat]

The prosecution rests it's case!

Almost rests it's case.

Get on a 6" Nomura with a 70 H.P spindle.

Grab a 3" drill with MT5 shank.
Just when you think you can walk off and put a few things away........
.......... the new drill is left in the hole by the new holder.

70 H.P can move allotta steel to unintended places before the Z or W servo's out.
More lost technology at work.

[Arthur.Marks]

Knowledge is good; results are better.

Here we go:


The indicator reading shows 0.0013" error over the length of my ground taper (~ 3.125" on hypotenuse). That error calculates out to 0.0238° which is the same as 0° 1' 28". All figures are included angle. The error is on the + side; it is a steeper taper.

I got the unilateral tolerance the right side of zero. I didn't hit the taper tolerance listed in Machinery's Handbook. Calculating for the same length as my piece, the measurement should be within 0.00052". Mine is more than double that. It does blue up, though, and it does hold fast in my test socket. Make of it what you wish...

[EDIT:] set-up specifics: MT3 included angle is 2.873597559°, 90° V-block, 5" sine plate, gage block stack is 0.3025".

[Old Hat]

I'd call it perfection!
ISO9001 apprOOved.

It's Significantly Ok.

I'm jealous of yer lighting Dude!
You work'n in a Shrine or somethin?

I learned to use the surface gages 180 around.
Fine adjustment is one-handed without let'n go.
And it's better ballanced on crowded inspection plates where
it may be bumped into.
Just a thought!