any tricks to keeping a #5 jak taper into a chuck

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while working my small mill today, my 3/4 Jak super chuck keep flying off the taper shaft. How do ya keep them thing on???? took me two days to take the morse taper shaft out of the chuck so i could install a R8 shaft, now i can't keep the Dm thing on......
Reply:put in the freezer for 24 hrs then put back inYou Can't Fix STUPID!!!
Reply:Really???? I'll try it, but I hope the wife don't catch me....
Reply:Put just the arbor in the freezer . . . shrink it.  You can also warm the chuck a little, but make absolutely sure both parts are clean and free of nicks.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:that makes since ....as cold will shrink the steel and heat will expand it...
Reply:I don't think that heating the chuck and cooling the taper shaft is the way to go since it is a taper.  I assume you are installing the chuck with both taper surfaces clean, no burrs, etc.  Put the chuck on the taper shaft and rap it on the end with a wooden block or a dead blow hammer,  that's it.  If it doesn't hold either the chuck or the taper shaft is not machined correctly to mate with the other.Remember that you may want or need to get that taper to release someday."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:What Norite said! Morris tapers are great unions and should only take rap to install or remove. I've only had one come apart in 30 years and it was in a drill press with 1.5 butterfly bit drilling out 2 by 6 vent blocks, lots of chatter!!!Karl
Reply:the chuck is a jacobs super chuck, pretty good quality, the new R8 spindle is (I would guess) made over there (china)  both ends are clean. it might be the quality of the new R8 shaft, ya know china stuff .....
Reply:The Jacobs chuck is the best quality drill chuck I know of.  Here is a page with about everything you need to know about the jacobs chuck and it's mounting.http://www.beautifuliron.com/jacobs.htmI assume the R8 taper on the shaft stays in the mill OK, and the problem is the chuck separating from the other end of the shaft.The Jacobs chuck uses a JT taper to mount onto the shaft, not a "jak" taper, I don't know what that would be.  Are you sure you have the right taper on the shaft to match the chuck?"The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:When the chuck and tapered shaft are apart, draw a heavy line down the taper in a few places using a felt tip marker, then insert the shaft lightly and spin it within the chuck. If the marking is only worn off at one end and not over the whole length, the taper of the shaft might be slightly off. You're supposed to actually use something a little thicker than that black ink, like Prussian Blue (Want the chemical name? ) but the ink should work, in a pinch.BTW, the two should be slightly oiled when assembled; yes I know, seems contrary to your wanting it to hold.....
Reply:Ok, stupid question here:Do you have the RIGHT Jacobs taper.  I have tried to stick with a 6JT for mine so I don't get confused as to which chuck has which taper.  Perhaps your tapers are close but not the same?Just a thought.
Reply:Once a taper fit has slipped, the best way to tighten it up is with a long soak at the river's bottom.
Reply:Here's something nobody asked:You said you were working on your mill.  Are you drilling, or milling?A chuck (or morse) taper will release with significant side loading.  That's one reason drill presses cannot be used as mills.  3 jaw jacobs style chucks are only good for drilling.  You need collets, or endmill holders for milling.As for the "rap" you need to get a jacobs taper to seat.  It takes a little more than a morse taper.  I use a lead hammer, but if you don't have that, you can put a small block of wood between the R8 and your hammer, with the grain oriented in the direction you're hitting.  You'll want to use a hand sledge (2# or so), and it could take a good hit.  Be careful with your fingers if the wood splits (start with a few light taps to see if the wood will hold).
Reply:rlitman has a point, I was milling with the chuck.....It is something to think about, but i can't afford to go out and buy all kinds of goodies right now.....and yes, it is the right taper for the Jacob chuck...I will try the blue stuff (just happen to have some) just to see what i can see. Thanks for the info.......
Reply:If you have a lathe, you could possibly drill and tap the end of the jacobs taper, and drill the center of the chuck and add a keeper screw, to work like a jacobs chuck that mounts on a threaded shaft (like on a drill).  Those screws are often left handed, but with a little loctite it doesn't matter too much.I would say though that you should first try to stop milling with a jacobs chuck.  If the chuck doesn't get thrown, they can throw the cutter because they only hold on three points (and when they do that, you don't want to be around).  I'll work for small and light work, but its just a bad idea.Besides, you have an R8 spindle already.  R8 collets are CHEAP (way less than an R8 jacobs taper).  Cheap, as in only a couple of bucks a piece for used ones in good shape.  Two or three sizes will cover just about all the endmills you'll work with anyway.
Reply:Your right....I checked around and there not that expensive, not at all. so i will get the basic ones. I'm just learning this stuff, lot's to learn here.......I used to think mills and lathes were a piece of cake, but there is a lot to learn if your going to do it right without loosing a finger or two........
Reply:Not sure what kind of stuff you're working with, but 1/2, 3/8, and 1/4 should cover just about any endmill you'll want.  Maybe 1/8" if you're planning on using rotozip bits for odd jobs.Endmill holders offer the ability to lock onto the flat on a cutter, which prevents them from turning in the holder, but they're much more money than collets and I've never had an issue with this.  My mill simply doesn't have the power, and the collets hold so well.Anyway, either is much safer than milling with a drill chuck, and the better holding power (with less stickout) will give you a much better surface finish even with deeper cuts.I think I spent under $50 for my chinese set of R8 collets (must be over a dozen in the set).  No regrets there, as they run at least as true as my chinese mill-drill, but I really don't think I've ever had to use any size I didn't list above.  There are things (like boring attachments and fly cutters) that come with larger sized shanks, but I've always went out of my way to get these with their own R8 shank because even a collet has its limitations; although this does get more expensive in the end).It's not like my lathe collet set, in which they all seem to get used.I keep a rubber mallet and ratchet with a socket that fits the R8 puller, tied to my mill-drill.Loosen the puller, and one whack on it with the mallet, and the endmill falls out.