MT3 V.S. MT2

[Brent H]

So here you go: take a #2 Morse taper dead centre and line it up between centres. You can dial it right in if you use a 4 jaw and rotate it around until you zero in the dead centre. Set your dial indicator up so it can read the taper properly and you want the indicator as close to the centre line of the dead centre as possible.


For the #2 Morse taper look at the chart and it is very close to .6” per foot. Set your taper attachment very close that (you can read the dial on the attachment (top scale) is roughly 6).

Adjust the top and bottom screws (the ones with the Allen head) to achieve a zero reading as you pass the apron back and forth on the Dead Centre. On our taper attachments there are two nuts that need to be loosened in order to swing the attachment back and forth. After that you should be good to go.


When I made your tailstock spindle I made a #2 Morse taper blank, dialled it in on the 4 jaw, mounted your spindle on the taper so it was centred on the taper. I then turned it between centres so it was as bang on as possible.

The #3 is “close” but will not dial into Zero - you will be off a couple thou and only get contact at the neck leaving the tail wagging - LOL

 

[YotaBota]

Why wouldn't the manufacturer mark the scale with MT marks?
BrentH - have you tried or heard of anyone drilling the attachment for a removable pin to locate the MT angle?
That would make it so much easier and you'd get the perfect angle every time.

 

[PeterT]

Another vote for MT3 = 0.60235 in/ft

OK, now I'm confused by this post. Are we talking about machining an MT3 arbor because the lathe taper setup is already established & inserting that into an MT2 socket? The way that would work (in a perfect world) is to also factor the (typically smaller) arbor length. For example MT3 vs MT2 would be (0.60235 - 0.59941) * 4 / 12 = 0.00098". Where 4 represents arbor length & 12 is inches/per foot. So call it 0.001" different at either end rounded up the difference. MT3 male into MT2 hole means arbor will contact MT2 opening & the small end will be slightly loose, 'wag' as Brent says. This is what I was saying before, there actually isn't a lot of taper difference between them. But I would still start from a known (your target MT) & then confirm the setup accordingly or else you are chasing your tail.

Everything Brent shows about taper bar setup is what has been suggested. What I was saying is in the ABSENCE of an MT arbor to replicate or to gain even more taper bar ACCURACY using the same tools & setup methodology, you do the exact same thing with a parallel bar using the table values. Ultimately your dial reads the same slope as handbook over the longest X distance you can accommodate for best accuracy. I made a table showing some setup examples. Hopefully this also demonstrates why doing a setup over a short distance works against you. If you can only measure/read to say 0.001" resolution just as example, best to have that discrepancy occur over the longer distance, because the same 0.001" discrepancy over a shorter distance will have a magnified error effect on the slope angle.

 

[jcdammeyer]

If you don't know the taper you can set up the dial indicator as suggested earlier. But even then ultimately bluing is you friend. For example I had to make a new pulley for my Mill in order to have room for an encoder disk.

I set the original pulley into the 4-Jaw and centered it until the tapered hole no longer had runout. I then used that with the dial indicator to bring the taper attachment in as close as possible.

Next, on a keyed straight shaft I slid on and locked a piece of scrap aluminium casting riser reamed and broached for the key. Now turning between centers I cut the taper until I had about 1" or so tapered. I pulled it off the lathe and with bluing trial fit into the original pulley. I then 'tweaked' the taper attachment and skimmed another pass. This was done a few times until the trial piece fit the taper in the pulley perfectly.. Threaded the end to use the locking nut from the mill and then mounted the mill pulley and with the dial indicator verified no runout..

Next the actual round bar stock, again drilled, bored, reamed and broached for the key. Cut with that taper setting and then again trial fit into the pulley just to make sure. You can see where turning between centers is really handy here. I turned the end for the same pitch thread as the locking nut from the mill. IIRC I think it was 1.25mm.

Then finally the casting blank was chucked in the 4-Jaw drilled bored to minimum size and then with the taper expanded out to match the original pulley. Again bluing was used to verify now against the new arbour which was still on the shaft for turning between centers.

After that a simple exercise to turn the pulley. If I did it again I would make the between centers shaft much larger in diameter to avoid deflection.

So turn the morse taper according to the dial indicator but test it in the socket it's meant to go in with bluing. Even if you initially have to test a piece of scrap aluminium to get the taper set perfect.

 

[Brent H]

@PeterT - my first set up for machining MT tapers was as you suggest. I made a blank the required big diameter, accurately marked off the distance and then adjusted the taper to remove the required material - using an indicator of course.

 

[YYCHM]

So here you go: take a #2 Morse taper dead centre and line it up between centres. You can dial it right in if you use a 4 jaw and rotate it around until you zero in the dead centre. Set your dial indicator up so it can read the taper properly and you want the indicator as close to the centre line of the dead centre as possible.
View attachment 19097

For the #2 Morse taper look at the chart and it is very close to .6” per foot. Set your taper attachment very close that (you can read the dial on the attachment (top scale) is roughly 6).

Adjust the top and bottom screws (the ones with the Allen head) to achieve a zero reading as you pass the apron back and forth on the Dead Centre. On our taper attachments there are two nuts that need to be loosened in order to swing the attachment back and forth. After that you should be good to go.
View attachment 19098View attachment 19099

When I made your tailstock spindle I made a #2 Morse taper blank, dialled it in on the 4 jaw, mounted your spindle on the taper so it was centred on the taper. I then turned it between centres so it was as bang on as possible.

The #3 is “close” but will not dial into Zero - you will be off a couple thou and only get contact at the neck leaving the tail wagging - LOL

Brent, that setup actually occurred to me last night and I started to setup for it until I realized I had to re-attach the taper attachment so I put it off until today. Have to get outdoor stuff this morning as it's a balmy -3C after 3 days of very windy -20C. Guess we get a break today and then it's going back to -20s for a week or more. Should get to it this afternoon some time.

 

[YYCHM]

Another vote for MT3 = 0.60235 in/ft

OK, now I'm confused by this post. Are we talking about machining an MT3 arbor because the lathe taper setup is already established & inserting that into an MT2 socket? The way that would work (in a perfect world) is to also factor the (typically smaller) arbor length. For example MT3 vs MT2 would be (0.60235 - 0.59941) * 4 / 12 = 0.00098". Where 4 represents arbor length & 12 is inches/per foot. So call it 0.001" different at either end rounded up the difference. MT3 male into MT2 hole means arbor will contact MT2 opening & the small end will be slightly loose, 'wag' as Brent says. This is what I was saying before, there actually isn't a lot of taper difference between them. But I would still start from a known (your target MT) & then confirm the setup accordingly or else you are chasing your tail.

Everything Brent shows about taper bar setup is what has been suggested. What I was saying is in the ABSENCE of an MT arbor to replicate or to gain even more taper bar ACCURACY using the same tools & setup methodology, you do the exact same thing with a parallel bar using the table values. Ultimately your dial reads the same slope as handbook over the longest X distance you can accommodate for best accuracy. I made a table showing some setup examples. Hopefully this also demonstrates why doing a setup over a short distance works against you. If you can only measure/read to say 0.001" resolution just as example, best to have that discrepancy occur over the longer distance, because the same 0.001" discrepancy over a shorter distance will have a magnified error effect on the slope angle.

Peter, how this all got started was that I thought I was setup for MT3 and needed a MT2 to make a centering arbor to mount a 4J on my RT. When I looked at the MT2 v.s. MT3 spec I questioned if they were close enough to not bother fooling with. Turned out the MT2 I turned using what I thought was a MT3 setup was out to lunch length wise so I started to question why that would be. After dialing in the taper attachment using a DI over 6" things looked much closer to spec. Now I'm going to confirm my setup against a commercial MT2 taper as per @Brent H 's suggested setup.

 

[YYCHM]

@Brent H , @PeterT - What do you make of this......




From the back end to this point the DI doesn't show any discrepancy. However that's not where the 0.7" location is (the black sharpy line). To get to the 0.7" location the DI shows a 7 thou transition? You can physically see the transition. Dunno..... bad dead center perhaps, it probably came from BB.

UPDATE: I tried a different dead center and it didn't exhibit this behavior. DI didn't show any discrepancy right to the 0.7" location. I don't think I could dial the taper attachment in any better than it is.

 

[PeterT]

Hard to know on that basis alone. Supposedly dead centers are ground on centerless machines so one would assume the tapered shank segment would be a continuous straight surface right out to where it converges to the point section. ie. if you laid teh shank on a flat surface there would be no light shining through down the entire length of the taper. Roll it a bit to new section & repeat. Now if the fatter section outboard of that is a diverges wider for some crazy manufacturing reason & that is mating the socket, then yes, that will be a problem. The light test would show that.

But of you look at the table, it defines the ID of the socket, not the arbor. All of my arbor's extend the same taper line outboard of end of socket. I cant see why yours would be different. i assumed you turned it that way for whatever reason. And of note, you can see MT3 is wildly different ID than MT2, so I wouldn't think second guessing the MT# would ever be an issue on off the shelf macine?

The blue & rub is really the most tell-tale way. If you have 2 same MT# arbors you can trust & they both show the same line rub, then I would think something is up with the socket, a burr or whatever. If one arbor has a line & other doesn't, then something up with that arbor. Also if you have been re-inserting & running an arbor with incorrect taper (where small end is too small), then I wonder if you are just wearing a ring in your arbor for that reason & now what you observing with dial?

I'm not sure what to say. Maybe just get a cheapo dead center & test fit?

LATHE DEAD CENTER MT2 - ALLOY STEEL HARD & GROUND CENTER 2MT - - Amazon.com

LATHE DEAD CENTER MT2 - ALLOY STEEL HARD & GROUND CENTER 2MT - - Amazon.com

www.amazon.com

 

[YYCHM]

Hard to know on that basis alone. Supposedly dead centers are ground on centerless machines so one would assume the tapered shank segment would be a continuous straight surface right out to where it converges to the point section. ie. if you laid teh shank on a flat surface there would be no light shining through down the entire length of the taper. Roll it a bit to new section & repeat. Now if the fatter section outboard of that is a diverges wider for some crazy manufacturing reason & that is mating the socket, then yes, that will be a problem. The light test would show that.

But of you look at the table, it defines the ID of the socket, not the arbor. All of my arbor's extend the same taper line outboard of end of socket. I cant see why yours would be different. i assumed you turned it that way for whatever reason. And of note, you can see MT3 is wildly different ID than MT2, so I wouldn't think second guessing the MT# would ever be an issue on off the shelf macine?

The blue & rub is really the most tell-tale way. If you have 2 same MT# arbors you can trust & they both show the same line rub, then I would think something is up with the socket, a burr or whatever. If one arbor has a line & other doesn't, then something up with that arbor. Also if you have been re-inserting & running an arbor with incorrect taper (where small end is too small), then I wonder if you are just wearing a ring in your arbor for that reason & now what you observing with dial?

I'm not sure what to say. Maybe just get a cheapo dead center & test fit?

LATHE DEAD CENTER MT2 - ALLOY STEEL HARD & GROUND CENTER 2MT - - Amazon.com

LATHE DEAD CENTER MT2 - ALLOY STEEL HARD & GROUND CENTER 2MT - - Amazon.com

www.amazon.com

The dead center I checked came from BB. A second BB dead center measured as expected, zero discrepancy all the way to the 0.7" location.

 

[Brent H]

Hey Craig, make sure you have your dial indicator fixed to a point that moves with the cross feed. I removed my tool post and out the indicator base there.

 

[YYCHM]

Further to this, I checked a BB MT3 and came up with a 3 thou discrepancy. Was expecting something in that order.

And also checked one of my turned MT3 and got a 2 thou discrepancy.

 

[YYCHM]

Hey Craig, make sure you have your dial indicator fixed to a point that moves with the cross feed. I removed my tool post and out the indicator base there.

Really? Do you mean mount it on the compound? What difference would that make?

I mounted it on the extension bracket that ties to the taper shoe.

 

[Dabbler]

For people wanting to be a little more 'sophisto' on tapers, here's a great video:

 

[PeterT]

Never seen a taper measuring mic before. That's cool.