Drill Chuck Falling Off

I have a drill chuck for my mill, it is a taper connection to the MT3 arbour. The problem is it has started falling off the arbour. It appears to be a good fit. I have tried fixing it on with Loctite 648 which held nicely for a few uses then dropped off again. Has anyone any suggestions apart from launching it over the field behind my workshop? JC

If you're using the chuck to hold milling cutters, you're doomed to failure. The JT doesn't withstand the sideways loading and vibration. It's good for its intended use with twist drills which apply end load.

Ignore this if you aren't using milling cutters in it.

Sounds as if the tapers are not a match, or there is some damage to 1 that prevents a good fit.
In normal use there shouldn't be any such problem as you have.

May I suggest you dismantle and thoroughly clean both tapers and inspect for damage.

Emgee

Edit: As Clive says not good to use with a milling cutter.

Edited By Emgee on 21/11/2018 21:13:11

Try lapping them in.

And dont hit them to make them fit....tapers are designed to be pushed together not forced together by shock loading

Duplex recommended drilling and tapping the male taper for a retaining screw, not possible with some chucks but fine with the ordinary keyed type.

Reversible hand power drills use this idea to prevent the chuck coming off in reverse.

Edited By ega on 21/11/2018 22:33:37

Got an electric welder? That's my usual last resort fix for uncooperative things like chucks that won't stay on the taper of cheapie drill presses and the like, just before the next step of flinging the whole works off into the woods.

Would it shrink on? That is not a suggestion so much as a question

I use a hydraulic press to force them to be friends .

As stated previously it sounds like there may be some damage to the tapers , clean both up and apply either some bearing blue , soot from a candle or draw a few lines along the taper with a permanent marker and put the two tapers together lightly and give them a twist and pull apart , look for where the marker pen or what ever you have used has been rubbed away and ideally it should be over the whole length of the taper . If there is any damage like severe scoring you may have to bin both and start again.

JC there are two standard's for morse taper shanks one jacobs and one din. They look similar but not compatable, the main taper is the same but the smaller taper that fits the chuck is slightly different and not compatible, check with some engineers blue for fit. it must be dry, clean, oil free and a sharp tap on the end of the shank with a copper mallet is all it should need if all is well.

David

As it has 'started' falling off I assume it was OK once?

Take David's suggestion and check the fit, you can use a felt pen if you have no blue.

The fit can be spoilt as it spins free after a job pulls the chuck free.

If it's a B taper you can clean it up with a morse taper reamer. B10 is the small end of MT1 and B16 is the small end of MT2. It does work, I've done it with a B16 fit chuck, just a quick touch of the reamer by hand to remove any bruising.

Any raised burr on the adaptor can be carefully scraped or filed off, just take the minimum of metal away.

Neil

I have been caught being lazy on the mill once.I put a 1/4" or 5/16" cutter in a drill chuck to do a 'quicky'. No. the tapers dont like it and my vice will testify to that.

Use the equipment you have in the way they were designed. quicker in the long run

If the surfaces are now damaged, they will need cleaning up and lapping (as suggested above).

It is a well known fact that tapers are difficult to separate if the outer is warmer than the inner when fitted together. A sort of shrink fitting, I suppose.

As others, they are only good for axial loads.

Given that they apparently used to work/fit together before JC - then the advice about cleaning & checking for damage given above is the best to follow - and I'm assuming that you are not trying to mill with it either.

However, I had this problem a couple of years ago with a small chuck coming off when used in one of my Coronet woodworking lathes. I had it set up to drill 10mm holes into the end of 32" long wooden 'legs' (not easy to do on my drill press) and whilst the MT taper remained in place in the spindle, the chuck kept coming off the body. This had never happened when using it to drill in my metal lathes - possibly because keeping the wood completely true (even though I had a guide setup) as it was pushed forward caused too much friction/grab. As I had about 30+ legs to do - this was a real pain.

The solution was simple - the end of the MT mounting was drilled and tapped (M3 I think) and a cap screw & washer inserted through the chuck jaws and screwed up into the end of the Jacob taper. The chuck then stayed put and this has not been a problem since.

Kinder than welding I would suggest!

Regards,

IanT

Very useful information if you are boring your own female taper.

Can you point to a reference for the B tapers' specification?

Thanks all for the suggestions. I have only used it for drilling.

Cleaned everything up today, marked with permanent marker and gave it a twist. Yes very slight burr that i couldn't feel..

A quick lap using of all things autosoll cleaned it up nicely. Arbour now in freezer and chuck on radiator, hopefully they will shrink fit together nice and tight. JC

Just what I said - the taper is the same as the matching MT which is easy to find online.

The large end of the taper spigot is the number (i.e. 16mm for B16) and large end of the socket is 1mm smaller for B10 and B16.

Neil

This was where I found out, it's actually a publication by Jacobs.

www.cooperhandtools.com.au/PDFs/Jacobs%20Chucks%20Technical-Information.pdf

Very few people seem to be aware of this!

Neil

I went through this with a cheap chuck and arbor. Tried the freezer trick. Ended up buying a decent vertex chuck with integral arbor.

Thank you - that was exactly what I wanted to see. I was unaware of these until recently and am not sure why it was necessary to add to the old-style Jacobs tapers. Presumably, however, I can now finish a new style taper with the appropriate MT reamer.