Jacobs 16n

dlane

dlane

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hi all , have a USA Jacobs 16n super Chuck with a jt3 taper , apparently has spun and has a small scar halfway into the tapper, all the way around, any easy way to clean it up
Thanks
 
Hi Derrick. There is no "easy way." Leave it alone if the rest of the taper is OK and the buggered section is below the surface, just replace the arbor. If the whole thing shows concentric rings from spinning, then the only fix is to regrind the taper, if there is more than a few thou of damage, it may need to be ground to a larger taper, depends on how much room there is in the chuck to seat it deeper:
http://victornet.com/reference/Morse_Jacobs.html
Those are very good chucks, and no longer being made in the USA, so it is probably worth spending some money on it to get it back it top shape. The current new Jacobs branded arbors are Chinese imports, don't waste your money on them. After you get over the sticker shock, buy an Albrecht arbor. They are by far the best.

To do the right thing and have a real professional grind it in so it will be dead nuts accurate will cost money, but again, Those USA Jacobs super chucks are best quality, no longer available new, and worth fixing and taking care of. A half ass repair will leave you with a half ass chuck.
 
Hi Bob ,thanks, it is a nice older super Chuck ,the raised bur is above the taper surface about 1/2 way into taper. Was hopping to find a jt3 taper reamer to knock down the bur can't seem to find one.
Was thinking about a 1/2" - dowel chucked in super Chuck and dowell chucked in lathe 5c collet , and a tool post grinder with stone set to just touch bur to knock it flush with taper . Seems to just be one small bur all the way around ,rest of taper looks good.
 
I would not try any kind of stone or reamer. I would try the shank of a carbide end mill and burnish it. You might want to put it in the lathe. Mount the drill chuck in the chuck. And put the carbide in a handle. Take it slow and work the high spots down. I would not use a HSS tool/object. I would only use carbide and a little oil…Good Luck, Dave.
 
Thanks Dave , and all
Sorry pics are dark
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image.jpeg
 
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To brighten up an area so the pic comes out, try using a flashlight:).
 
Flashlight worked,
image.jpeg
Chips , set up carbide shank in tool toolholder at same angle as taper with chuck in chuck ,
Or just rub high spot With carbide in hand or in toolholder
 
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Chuck it up in the lathe and gently under cut the affected area about .005-.010" deep for about 1/8" wide. Polish the bore to remove any burrs and install your drill chuck.
I've had this to happen to a chuck or two in the past.
 
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