# Morse Taper Slipping between Drill Chuck and Tailstock



## erikmannie (Apr 19, 2020)

I was discussing this issue in an MT3 drill thread, but I don’t want to hijack that thread.

I have a PM1030V with an MT2 tailstock, and I believe that it does not have a female slot for a tang.

I bought an inexpensive 3/4” JT33 to MT2 drill chuck. From the very beginning, I suspected that the manufacturer was not entirely successful in obtaining a proper male MT2 taper. I get problems with slipping at the MT2 interface.

I may solve this problem by buying the 250-105 pictured below. The slot for the tang would prevent any rotation at the MT2 interface, but my drill chuck also has a JT33 interface which hasn’t slipped so far.

I almost always work with steel, and it is entirely possible that I will be using drills up to 1”.  I wonder if that would go smoothly with the MT2 tool post holder pictured below on a 10” swing, 1 HP lathe.


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## erikmannie (Apr 19, 2020)

Methods I use to prevent slippage:
(1) wipe off male Morse taper before inserting in to tailstock,
(2) always start with center drill, very conservative step drilling,
(3) always use cutting fuid,
(4) not getting greedy with cutting (patience),
(5) proper RPM, 
(6) peck drilling, and 
(7) frequently clearing out chips from drill and hole (I use a magnet probe).


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## gradient (Apr 19, 2020)

You could check for proper mating between the male and female MT2 by coating the male part with mark up dye or magic marker and mate them in the usual way. Remove the male part and see if the dye has been removed uniformly.  You may also need to lightly mate them and rotate them a bit.


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## erikmannie (Apr 19, 2020)

Before I got a lathe and mill, I used to have terrible problems drilling steel with a hand drill and drill press.

When I got a job at a steel fabrication shop, my first question to the boss was tips on drilling in steel. He said “go slowly and use plenty of lubricant.”


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## erikmannie (Apr 19, 2020)

gradient said:


> You could check for proper mating between the male and female MT2 by coating the male part with mark up dye or magic marker and mate them in the usual way. Remove the male part and see if the dye has been removed uniformly.  You may also need to lightly mate them and rotate them a bit.



I will do the dye check.

I do like to seat it by hand with a pushing rotation, but I am a little perplexed by the tang.

The male MT2 arbor will rotate in the tailstock, so I am inclined to believe that there is no female slot for a tang. So why do I even bother to align the tang vertically when I install the arbor?

I do find the tang useful for ejection, but I wonder if I should just cut off the tang. It costs me just under an inch of quill travel.

Maybe I should buy a JT33 to MT2 arbor with no tang. The MT2 fit up couldn’t possibly be any worse.

But wouldn’t buying the AXA MT2 tool holder take the tailstock out of the equation, and then I would be good?


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## erikmannie (Apr 19, 2020)

I did buy the 250-105 AXA #2 MT tool post holder for $30. I will let you guys know how it works out. Hopefully the JT33 interface doesn’t slip.

It seems to me that there would be an upper limit on the diameter of drills that can be safely used for drilling steel (either in a tailstock or on a toolpost) in this smaller sized lathe.

Worst case scenario, a huge drill mounted in the toolpost crashes into the work. What is the weak link there?

When I crash a cutting tool, the motor stalls and I either back off or hit the e-stop. I wonder if that situation would damage my compound or cross slide if a huge drill were mounted in the toolpost. Maybe the JT33 interface would be the weak link and slip at that point.


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## pdentrem (Apr 19, 2020)

I would be feeding by hand incase of that possibility and having to back off to add cutting oil. I would likely NOT use the power feed on large diameter drills. Others may do so but not me. 
Pierre


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## Aukai (Apr 19, 2020)

Make sure the quill is far enough out that the arbor seats without the tang hitting the back of the quill. Mine has to be out 1" for the tang to clear, and get a good seat.


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## T Bredehoft (Apr 19, 2020)

The tang was never meant to be a driving device, it is solely for removing the drill from a spindle, (see drill
press and slot in spindle)


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## ErichKeane (Apr 19, 2020)

erikmannie said:


> I will do the dye check.
> 
> I do like to seat it by hand with a pushing rotation, but I am a little perplexed by the tang.
> 
> ...


So, you NEED the tang to get the tool out of the tailstock.  However, they are typically quite long.  I've been considering machining mine down to the bare minimum.  It simply needs to be just barely long enough to touch the back when retracted all the way.  If you retract it to JUST before it pops out and measure how much more  the tailstock can retract, you'll know how much material you can take out!


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## extropic (Apr 19, 2020)

It's my understanding that the tang on a Morse taper shank is intended for ejection only and not intended as an anti-rotation feature. That may seem counterintuitive and I can't site any authoritative publication(s) but, it's what I've read and come to believe. In other words, a *properly mating* Morse taper will successfully resist the torque requirement of the tool.

Regarding your lathe, If you cut the tang off, will your tailstock still eject the shortened shank?

I suspect that either (or both) your tailstock taper or tool shank taper are damaged and not mating properly.
Any ding on the tool shank causes a raised area (around the ding) that will interfere with proper mating.
Both tapers should be kept clean because the slightest sliver or chip will prevent proper mating.
Once a tool shank has been spun in the taper, the source of the problem is imprinted on both parts and needs to be eliminated.

I keep a Morse taper finish reamer to touch-up my tailstock spindle, should it ever become necessary.
I also keep a good quality (vintage unused Jacobs) tool shank to use as a Master Reference for checking the tailstock taper.
Mating the two (with Prussian Blue) verifies, to my satisfaction, that the tailstock spindle taper is inn good shape.
I also keep a cylindrical OD x Morse taper ID adapter as a Master Reference for checking (with Prussian blue) tool shanks.
Mating the adapter (with Prussian blue) with the master reference shank verifies the adapter.

If there are high spots/rings on a tool shank, they must be stoned off. Don't be concerned about any remaining low areas.
Small low areas will not significantly reduce the contact area.
Just cut down the high spots until you get a satisfactory print with the Id Master.


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## erikmannie (Apr 19, 2020)

Thank you for all of the very helpful responses.

I understand that a proper Morse taper is, by itself, able to successfully prevent rotation. I also see that a tang works very nicely to facilitate ejection. So it is a fact that a tang is not designed to help prevent rotation?

Do some tailstock quills have a female slot for a tang? If so, is this a benefit in any way?


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## erikmannie (Apr 19, 2020)

Are any of you guys willing to recount stories of how you had slippage while drilling and then managed to solve the problem? The slippage is very annoying.

Sometimes my drill gets stuck in the work. I believe that this is caused by too high of a feed rate. Am I the only person that has had to remove the work from the lathe, chuck it up in the bench vice and get the drill out with vice grips? That is not a good way to go if you want to maintain concentricity.


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## extropic (Apr 19, 2020)

erikmannie said:


> Are any of you guys willing to recount stories of how you had slippage while drilling and then *managed to solve the problem*? The slippage is very annoying.
> 
> Sometimes my drill gets stuck in the work. I believe that this is caused by too high of a feed rate. Am I the only person that has had to remove the work from the lathe, chuck it up in the bench vice and get the drill out with vice grips? That is not a good way to go if you want to maintain concentricity.



If you collect the bits and follow the procedure that I described in reply #11, I'm sure the Morse taper fit will be cured.

Remove the work from the chuck? Not so far.
Why not just back-off the tailstock and use a wrench on the tang to back the drill out.

So far, to me, your approach to eliminate the slippage seems scattered and non-systematic.
I think you need to take a more systematic approach.
You can't get to the bottom of the problem with a scarred tapers.
I'm sure yours are damaged (based on the problems that you've described).
After you get your tapers in good shape, we can go on to other possible factors such as material, workpiece dimensions, drill condition, drill point geometry, lubricant/coolant, feeds and speeds, etc.


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## ErichKeane (Apr 19, 2020)

On my old lathe, I picked up a MT reamer and re-reamed the taper, but that is because it was pretty rough.  That and clean, correctly tapered tools got rid of my slipping.


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## Dabbler (Apr 22, 2020)

Just a couple of ideas to supplement what is already written above.  

--Using a MT2 - even with a taper tang drill - I would never ever go bigger that about 1/2 or 9/16 of an inch.  There is an upper limit on what a Morse taper (on a lathe) can hold.  If it breaks free, your taper and tool are both going to get damaged. I limit my MT3 drills to .750 - yew they will even sell you a mt2 taper tang drill that is bigger than 9/16, but I'll never use one. I just learned you can buy a 1" drill in MT1 -eek-!

-- always clean your taper -with your finger -  and wipe your male taper, again with you bare hands, before mating anything in the tailstock.  I have lost count of how many damaged tail stocks I have seen due to crud in the taper when seating a tool in the taper.

-- it is quite possible that your male mt2 is incorrectly ground.  The only remedy (unless you have rotary grinding facilities) is to replace it with a properly ground one.  Here's a hint on how to be sure: buy your self a MT2 drill bit.  The use the bluing or magic marker on it to check your tailstock.  If that passes, then the tail stock can be used to check your taper on the tool you want to insert.

--  lastly do you insert your tool very quickly?  I mean 'jamming' the tool into the taper so it seats properly?

If you take my advice on the mt2 drill to check your tailstock, here's one for comparison shopping.  remember buy a REPUTABLE one, not an offshore knockoff.  I've even had a tiny number of MT3 drills made in the USA not being spec - but it is very rare! 



			https://www.mscdirect.com/product/details/01520246


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## Lo-Fi (Apr 22, 2020)

I run a ~13/16" drill in my Myford with an MT2 tailstock just fine with no more than a sharp push to seat it. I rarely drill more than a small pilot to clear the webbs, so load it up heavily every time I use it. Not once have I had it slip. As previously said: the tang is only for ejection, not to stop rotation. Morse tapers were designed at very specific angles to lock well when seated correctly, while still being removable without excessive force. 

I suspect you're probably right that the taper on your drill is not correct. I've only ever had trouble with new tools or damaged old ones. Lots of new budget stuff seems to have "that'll do" baked into it, sadly.


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## Lo-Fi (Apr 22, 2020)

I run a ~13/16" drill in my Myford with an MT2 tailstock just fine with no more than a sharp push to seat it. I rarely drill more than a small pilot to clear the webbs, so load it up heavily every time I use it. Not once have I had it slip. As previously said: the tang is only for ejection, not to stop rotation. Morse tapers were designed at very specific angles to lock well when seated correctly, while still being removable without excessive force.

I suspect you're probably right that the taper on your drill is not correct. I've only ever had trouble with new tools or damaged old ones. Lots of new budget stuff seems to have "that'll do" baked into it, sadly.


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## Janderso (Apr 22, 2020)

Interesting, I assumed all mt had tangs. I know my mt4 tail stock does.
What’s the limit on an mt4?
1” on a mt1? Eeeech.


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## Tozguy (Apr 22, 2020)

Maybe check what KBC is selling to get an idea of the practical limitations in drill size of each MT?


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## stupoty (Apr 22, 2020)

Janderso said:


> Interesting, I assumed all mt had tangs. I know my mt4 tail stock does.
> What’s the limit on an mt4?
> 1” on a mt1? Eeeech.



some one had mentioned a while ago that the tangs are uncommon on lathes , I have no tang slot on my MT3 tail stock.

I tend to tap the end of the drill with a soft hammer to make sure they are seated (not tiny ones)


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## macardoso (Apr 22, 2020)

Maybe I'm the crazy one here, but I've drilled a 1" hole in steel (1/4" starter hole) on my lathe using a silver and deming bit going into an MT2 taper.  I had no slippage at the taper and it cut beautifully. The only issue was the keyless drill chuck got so tight it required a strap wrench to open it up.

If I am going to be cutting hard, I'll seat the taper with a nice whack from a deadblow.


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## SLK001 (Apr 22, 2020)

The tang is NOT for anti-rotation, but is for being able to remove the drill.  You should seat a MT2 device with a smart push into the socket.  Before you do this on your lathe, BE SURE THAT YOUR TAILSTOCK CAN EJECT YOUR DRILL BEFORE YOU SEAT IT!!!  A Morse taper needs to extend beyond the small diameter end to engage the ejecting projection.  If it doesn't, you will have to disassemble your tailstock to remove the drill.


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## Packard V8 (Apr 22, 2020)

Standard range for MT
#1 - up to 1/2"
#2 - 1/2" to 3/4"
#3 - 3/4" to 1"
#4 - 1" to 1-1/2"

That larger than standard drills exist in various MTs is not proof it's good practice to use them.  One may buy 1" round shank drills to use in a 1/2" chuck, but it's not best science.

I have a friend with a decent quality Taiwan lathe who has damaged the holding power of the tailstock by repeatedly drilling oversize holes with a 1/2" chuck in the #2MT.  We're going to have to buy a reamer to clean it up enough to hold as it did when new.

jack vines


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## macardoso (Apr 22, 2020)

Packard V8 said:


> Standard range for MT
> #1 - up to 1/2"
> #2 - 1/2" to 3/4"
> #3 - 3/4" to 1"
> ...



Thanks for sharing that information! Did you have a source you used to find this? I'd like to look up more info.


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## erikmannie (Apr 22, 2020)

Super helpful responses! I do appreciate it.


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## SLK001 (Apr 22, 2020)

macardoso said:


> Thanks for sharing that information! Did you have a source you used to find this? I'd like to look up more info.



I just went to the original source.


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## extropic (Apr 22, 2020)

That's useful information but the source, in the USA, is *ASME B94.11m-1993*. You can purchase a copy here.

*ISO 3291:2016 *is the standard elsewhere. Both specs are probably functionally interchangeable regarding taper shank drills.


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## Dabbler (Apr 22, 2020)

In my experience, on a suboptimal set up like a normal lathe with some wear, the practical values are less.  I'd rather be careful than ruin my tailstock.  Just my view.  As I said, I've seen some ruined tailstocks that needed replacement of the quill or re-reaming to get them to work again.

-Most of my MT#2 drills are in the 1/4 - 3/8 range.  I think I have  a 7/16 one.  My MT#3 drills used to max out at 5/8.  I just acquired a 15/16" MT drill to do some aluminum for a project.


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