MT4 Adapter spun in spindle, how do I clean up the spindle taper?

WobblyHand said:
Measuring the same way you suggested yields a 0.05378"/inch taper. This is a steeper taper than an MT4. y travel = 0.1345, x travel = 2.5000", y/x = 0.05378"/inch taper. This is very close to my earlier micrometer and dowel reading on 123 blocks with the taper vertical method.

I used two 123 blocks. I clamped the first 123 block down (with an aluminum shim to protect it) to the table and aligned to less than a 1/4 of a ten thousandth of an inch over the full 3 inches of the block. Got to love that Interapid DTI! Then layed the taper down on the mill table, and a second 123 block on the table on it's 1" x 3" face. (2 inch face was vertical.) Indicated along 2.5000" of x travel.

The external taper of this MT4 to MT2 taper reducer is not that of an MT4. Tomorrow, I measure the "MT4" dead center I bought.
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I think you have some solid evidence now. A steeper taper would have caused the type of artifact that you observed. The good news is that in all probability your spindle socket is good and after you clean up the rim and get the correct MT4 taper., you should be good to go.
 
To remove any pickup on the hardened internal taper, never use any abrasives. Try using a curved scraper, it will engage with the soft galling and slip over the hardened taper.
 
WobblyHand said:
Cleaned up the spindle with some round stones. At least the rough stuff is gone. Searched for my MT4 dead center, and couldn't find it. :(. I thought I had one when I bought it. Found an "MT4" dead center that I bought. Another never been used tool. Did the smurf thing, tapped the dead center into the spindle and then popped it out. More or less what I expected. Nearly 0 contact. Just the ring around the spindle nose. There was a small amount of contact at the base, but overall total contact maybe 5%. The missing blue in the second picture is not because of contact, it was because I didn't apply the blue to the very end.
View attachment 399775View attachment 399776
From the marks on the spindle and on the morse taper sleeve earlier I suspected that these bits of tooling are off spec. The taper is not MT4, it is steeper than MT4. Looking carefully at the dead center, the external packaging says MT4. On the actual dead center it is marked MS4. Is this some unknown Chinese standard? I can't find any reference to a MS taper. Maybe it stands for morse sleeve? But a dead center is NOT a morse sleeve. Either way, the dead center I have has little contact along the sleeve. Instead, all the forces are concentrated at the very taper edge at the spindle nose.

I will clean up the morse taper sleeve (MT4 to MT2) to do the blue check. Bet it will have similar (nonexistent) contact.

Disappointed in this. Why would someone make a MT that wasn't really a MT? This was nicely ground, can't imagine any meaningful manufacturing economy. Have to think these were (both) rejects, scooped up and resold as compliant.
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Could MS4 refer to the part being a morse taper 4 but shorter, with the "s" refering to the spindle only. This may suggest that the MS4 piece should not be used in the tailstock, as it is too short to eject?
 
Parlo said:
Could MS4 refer to the part being a morse taper 4 but shorter, with the "s" refering to the spindle only. This may suggest that the MS4 piece should not be used in the tailstock, as it is too short to eject?
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MS4 and MT4 are the same, I think China or Europe made the MS designation.
 
Parlo said:
Could MS4 refer to the part being a morse taper 4 but shorter, with the "s" refering to the spindle only. This may suggest that the MS4 piece should not be used in the tailstock, as it is too short to eject?
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My lathe is MT4 for the headstock, and MT3 for the tail stock. Actually, the TS uses a short taper, to the best of my knowledge, never have been able to use a MT3 with a tang. The OEM TS dead center has no tang. Probably yet another example of design to cost.

Mini-lathes also use a short taper for the tail stock. I've had to grind off the tangs of MT2 drills to have them seat in the taper.
 
WobblyHand said:
My lathe is MT4 for the headstock, and MT3 for the tail stock. Actually, the TS uses a short taper, to the best of my knowledge, never have been able to use a MT3 with a tang. The OEM TS dead center has no tang. Probably yet another example of design to cost.

Mini-lathes also use a short taper for the tail stock. I've had to grind off the tangs of MT2 drills to have them seat in the taper.
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I have had to do the same for my 1947 SB9, the tang is for DP applications.
 
Jim F said:
I have had to do the same for my 1947 SB9, the tang is for DP applications.
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The MT4 tailstock on my lathe accepts and locks tangs, so not just for drill presses.

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Navy Chief said:
The MT4 tailstock on my lathe accepts and locks tangs, so not just for drill presses.

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I've never used a lathe that did not accept tangs in the tailstock. Would not be much use otherwise if all the tangs on your tooling had to be removed.
 
eBay vendor is trying to argue with me that I am the first person with this problem... Don't think it is likely that I am the only one to receive a lemon, but hey, anything is possible in eBay land. All I'd like is a good adapter sleeve, ideally with a through hole so I could put in a drawbar if necessary. I will have to fight this out - best case, I get my money back. Worst case, I go source a new one on my own nickel.

The taper sleeve part is off by 0.3mm smaller than the spindle taper at the end of my taper, 0.15mm at half the taper distance. The taper was manufactured wrong and is likely a factory reject.
 
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