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Old 02-26-2020, 04:54 AM
MrCrankyface MrCrankyface is offline
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Default Slipping drill chuck arbor?

I have this recurring issue on my lathe with the drill chuck arbor slipping..
I've tried cleaning both the inside taper of the tailstock and the taper on the drill chuck arbor but it will still slip..

Feels like the problem has gotten worse over time and will now regularly happen even with 1/2" drills with a 1/4" predrill..

Any ideas/tips what I should look for or try to remedy this?

I believe the taper is MK3 if that matters.

Edit: to clarify, the drill bit is secure in the chuck. It's the chuck/arbor that spins in the tailstock.

Last edited by MrCrankyface; 02-26-2020 at 05:53 AM. Reason: Apparently I can't spell.
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Old 02-26-2020, 05:58 AM
bunkclimber bunkclimber is offline
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Default Mk3?

are you meaning Morse Taper 3? -there are reamers for those tapers available to clean then up if wear or scarring has occurred. I have used them in the past with good results.
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Old 02-26-2020, 08:12 AM
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I have a reamer for mt3 and it has been usefull to stop this problem. Check fleabag.
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Old 02-26-2020, 09:03 AM
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A real "Old School" trick is to chalk the taper. It did make extraction a bit more difficult.
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Old 02-26-2020, 09:08 AM
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My tailstock is a MT2 and the drill chuck arbor would slip with 1/2" bits occasionally. Got a MT2 reamer off Banggood and took a very light cut with lots of oil, about one light full turn cut by hand, and now it is holding well.

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Old 02-26-2020, 10:52 AM
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Mr Cranky

Is the chuck slipping on the arbor or is the arbor turning in the tailstock barrel?

I ask because I am not familiar with the MK3 taper you have mentioned. Is it a metric taper or just a typo?

If your having issues with the arbor slipping, there is lots of in the previous posts. Does your arbor automatically eject with the tailstock barrel is fully retracted? That may help with sticking issues. The only other thing I can think of would be to clean the offending parts with alcohol or a degreaser.
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Old 02-26-2020, 10:58 AM
MrCrankyface MrCrankyface is offline
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Yeah, that's my bad, it's apparently only called MK in Swedish and MT in English.
So yes, it's a MT3.
I will see if I can get my hands on one of those reamers and try the other tips meanwhile!

It's the arbor slipping in the tailstock barrel, causing the entire chuck, drill and everything to just rotate with it instead of doing work.

Thanks for all the tips!
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Old 02-26-2020, 12:18 PM
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Default Slipping drill chuck arbor?

Does the end have a rectangle tang that helps eject the chuck when the tail stock is fully retracted? This tang usually helps keep the chuck from turning in my lathe, and I can only put it in a certain way to seat it.

I have heard of people wrapping a fine piece of sandpaper around the chuck tang and lightly turning this in the arbor to help true it up, or mate the two.

Blueing or a black marker can help identify high spots or areas that are not seating correctly.

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Old 02-26-2020, 01:49 PM
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If you're messing with a reamer in the tailstock taper just be aware that it's very easy to run the reamer off centre and lose the tailstock to spindle alignment. Before you run a reamer in I would very carefully check for burrs in the female taper. Low spots don't matter and you're usually better off carefully removing high spots with a fine file so you leave as much of the original taper intact as possible.

Before I did anything I would get some layout dye, blue up the male taper and fit it to the female to see what contact you actually have. That can tell you a lot about the condition of the female taper. In better lathes the tailstocks are heat treated to be slightly harder than the average male taper. This is done to allow for the occasional slip without damaging the female taper. It's much easier to replace a damaged male taper than it is to regrind a female.

Do other tools slip in the tailstock? Can you run a 3/4" morse taper drill into a piece of material without it slipping? If that's the case then the problem is with the drill chuck arbour itself. Before I ever ran a reamer into the tailstock I would seriously consider replacing the arbour...

Measure twice and cut once...or...wait, was that the other way around?
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Old 02-26-2020, 02:26 PM
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I have a Rohm Chuck ($600) that would not stay on the adapter because it was used on a 5 hp gear drive drill press .
I finally got it mounted and running true then a little 7018 solved the problem If the chuck wears out aliottle zip disk time will separate them.
To mount the chuck I clean both sides warm the chuck to about 200 F and chill the arbour to -30 -40 then put them together with a dead blow hammer when they equalize you would think that is good to go and it is but I think that the HP limitation of the system is not very high.
I have an MT3 tailstock on my lathe and have twisted the tang from large
(11/4 inch and up)
What happens is the bit goes through in two places then the last uncut steel pulls the drill forward loosening it in the tail stock and then turns the drill in the tail stock it is all over pretty fast.
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