Keyless chuck adaptor taper fitting

How do you reliably reattach a keyless chuck to its adaptor taper?

It came apart and doesn't firm up using pressure from the quill on a millting machine. I could use a fly-press but wondering if I'm missing something?

Any ideas?

Warm the chuck up with an electric hot air gun, until it's uncomfortable to hold, make sure both surfaces on properly clean, put a block of wood on the drill table, with the Jaws wound all the way back out the way, do this before you start, use the quill handle to press it together, not excessively.

Edit, when I say warm, direct the heat down the inner taper. 

Edited By Pete. on 28/04/2021 17:47:50

First check the tapers mate fully, no burrs or dirt. To fit I always separate the adaptor, place it in the female part and strike it on the wood bench so that the mass of the chuck travels down onto the taper.

Thanks for the ideas.

This has held together for a long while so there shouldn't be any burs.

The best thing I can do is clean the tapers with IPA or acetone and heat the chuck up in the oven to 50-90C. Then bring the two together again.

If that doesn't work it's the freezer for the adaptor too!

Its worth checking the relative lengths of the taper and socket. If they are very close and the end of the socket is closed you can have problems with air entrapment.

Especially if simply pushing the taper in. The socket to taper jion become essentially airtight before things are fully home so the final push compresses the air inside acting against the push not only reducing the holding force but also inducing a sort of thermal pumping effect as the air expands and contracts with temperature changes.

Had one ordinary jacobs chuck & arbor pair that came unshipped on a fairly regular basis. IMy then boss advised drilling through from the socket into the chuck so the air could vent. Its been on there 30 odd years and counting.

Dunno if you can drill a keyless chuck like that.

In my experience rap the taper on the bench so the mass of the chuck pushes it on advocated by Howard works better than an improvised press like a mill or drill feed. But I just bank the end of the tang on a solid block of metal to maximise vibrational forces during seating. Tangs have to be are pretty hard to withstand extractor drifts so burring over is unlikely. Threaded ones j on the end just get banged as is. There is always a clearance above the thread and a steep taper section above the taper so damage is unlikely. It is, or should be a one time job anyway.

Clive

Most small drilling machines have the male taper on the spindle itself, 4 out of 5 I've owned have been anyway, tapping it on a bench would involve removing the spindle from the machine, pushing down no harder than drilling a 12mm hole in steel, I've never had a heat expanded chuck come off.

A bit of heat, as advised should be a permanent remedy. Unfortunately drilling a keyless is not really worth it as the centre is threaded as part of the mechanism and the core diameter is not very big. Ordinary chucks are perfect for drilling.

I first gave everything a good clean. I left the chuck in an oven ~100C and the adaptor (a combination of a MT30 to Morse taper to the chuck taper) in a freezer for a couple of hours.

Held them in pace with a flypress and allowed the temperature to normalise.

I can't see them coming apart very quickly and have just used it successfully.

Many thanks.

15 degree Celsius differential is sufficient to make chuck removal from my lathe rather difficult. I never put a cold Morse Taper in a warm socket.

That's worth bearing in mind.

In this case I was only differentially heating the chuck and its adaptor. Not the Morse to MT30 adaptor.

TBH the chuck - adaptor. taper looked puny in comparison to the Morse taper.

Must admit I've never found it necessary to lower the temp of the male part, on the plus side, Mike probably has his tapers very firmly joined.

I've found one good rap with a large copper-faced hammer does the job.too.

An ordinary hammer and block of hardwood or brass drift should work as well.

Edited By Hopper on 29/04/2021 00:47:21

Clearly. My post was simply to pass on how little the temperature differential needs to be for a very tight interference fit. A sharp tap, to mate the surfaces, is sufficient with a fairly small temperature difference. Less force and with the differential in the ‘wrong direction’ could easily result in a poor grip.

A lot of threads have been posted, in the past, about tight morse tapers and removing stuck tools from sockets. I expect your taper will be less than MTs, so should provide a much tighter grip, once properly joined. Any oil in the joint will likely cause a problem if present. Liquids tend to expand more than solids (less inter-molecular forces due to the distance between them)..

There is, of course, the possibility of mis-matching tapers. I have a 2MT, purchased from ban good, that is simply not an MT taper - so much so that it rattled when fitted in a socket. Rubbish from a rubbish chinese seller. YMMV, of course, but if purchased cheap from China that is a possibility.