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How to keep a chuck from falling off its taper

golash

Aluminum
Joined
May 1, 2005
Location
Northampton Ma
Hi
I just got a new chuck that fits a R8 collet with a taper end. With my drill presses I`ve always had the chuck itself fall off its taper. I`d like to eliminate this problem since I`ll be using this new chuck on my mill | router. I thought about using epoxy on the taper but wonder if there is another solution.
 
Lately it's been suggested that you could warm the chuck (not too hot due to grease) and chill the arbor. Or use locktite. And a machinist friend of mine said that cleaning well and lightly applying talc will make it hold.
 
I think the normal metal on metal tape fit is supposed to be the strongest. Warming the chuck a little and cooling the shank may help get you a few more tenths of interference.
Normaly when I get a new chuck and arbor I turn the jaws into the chuck to hide them, I put the arbor in and slam it straight down on a piece of wood holding onto the shank. Only 1 cheap chinese chuck that came with the mill got it self apart once. I put it back together with a little more force and gave it to a friend.

I did use loctite 609 once on a chuck where I used to work. Thats what the person who had last fixed it did. I guess it hadn't fixed the problem then, but I just went along as it was faster than cleaning the mess that was in there. Loctice 620 may be a better choice if you do go that route.
 
When ever a chuck starts to come off, it is a sure sign that the fit is off.
this can be dirt, or scoring/dents
new chucks and arbors should not have this problem.
drill press chucks subject to side loads are notorious for failing,but as long as you only use the mill for drilling, you should be fine.
rich
 
My experience has been that when your drill chuck falls off its taper adapter, its telling you that you are trying to work it too hard.
That is, your bit is too big, or your hole is too deep.

A new chuck shoud be able to be press fit on the taper, and not come off, under the loads it was designed for.
If you use your 1/2" cheapo chuck to try to drill 1" holes with silver and deming twist drills, thats usually when it comes loose.
 
One way to assess the tapered "fit" is with a Sharpie marker...draw some zigs, zags, or parallel lines down the male taper.

Lightly "grind" the tapers together, and you'll instantly see where contact is being made.

The fit can be tuned with a stone and some careful handwork.
 
you got a problem somewheres if it coming off the taper...cheap arbor, or ding in one of the mating surfaces, etc...
I bought a new LFA chuck and a jacobs arbor not long ago and I only mated them together and a sharp tap with a soft hammer, and it has never come loose
 
As was said tapers can be overloaded until they slip. They will not slip if apropiate drilling thrust is present. If they are assembled clean and with sufficient tension from a shring fit they will stay engaged for the life of the tool.

Here's from a previous post where I described the procedure taught by Jacobs techs in a seminar I once attended a zillion years ago: shrink the chuck on the shank.

Here's how: Clean and deburr the socket and the taper so its grease and oil free. Heat the chuck to 350 degrees F in the oven for 1/2 hour. Have a hammer handy. Take the room temp shank to the oven, open the oven door, grab the chuck with an oven mit, slip the chuck on the shank, and moving swiftly grab the hammer and give the shank a single firm tap home.

Rehearse your moves with the chuck cold. This shrink on installation, according to Jacobs, will give you double the break-away torque of a cold press or hammer installation.

I understand Jacobs has lawyered itself away from this installation scheme fearing if a litigous idiot used it and got a tiny blister Jacobs will wind up enriching tort suit lawyers and rewarding eggregious stupidity.

Do not use epoxy or anerobic locking compounds. The shear strength of an organic bonding agent is but 10% that of a shrink-fitted taper.
 
Are you using this chuck to hold end mills
or router bits?

If yes, then the answer to your question is
simple: it will keep on falling off. Nothing
you can do will stop that from happening.

Jim
 
Two words: Lapping compound.

Unless you are really overdoing it on the chuck (drilling a 2" hole blind with a 20hp machine with a reduced shank bit in a 3/8" chuck...) it should never come off. The harder you push down the tighter it gets. If it's falling off, you most likely have a problem with the fits not matching. Could be a burr but most likely something was not machined properly, or something is worn.

Like another poster mentioned; mark the taper up with a sharpie and lightly twist them together and apart. Using some light valve grinding compound you should be able to get a good match between the surfaces, but keep in mind they will become a matched set and will not be useable with another part unless you relap them. Not a problem usually since most people put on a chuck and keep them on for life
 








 
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