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Old 02-27-2020, 10:35 AM
threepiece threepiece is offline
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Default Slipping Drill Chuck Arbor

I bought a very lightly used Jacobs chuck recently. I can see now after installing it in my machine why it was not used much.

It has an R8 arbor attached that has “Bridgeport” etched on the surface. It is written in cursive like the trade name so I conclude it is the real deal.

When I install it in my Series I Bridgeport it slips. The slipping is occurring between the spindle and the arbor. Aside from lack of thread depth on the draw bar I can’t image what would cause this.

I’m curious to know if anyone has experienced something like this?
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Old 02-27-2020, 11:25 AM
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The draw bar is not bottoming out??
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Old 02-27-2020, 06:40 PM
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Are you sure the slippage is not in the JC taper in the chuck head?
Your Bridgeport has a drive pin that unless it has been removed, prevents the BP arbor from rotating, as it engages the keyway on the arbor.
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Old 02-29-2020, 08:58 AM
Don_S Don_S is offline
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I've had them slip on the JT taper but not the R8 taper yet. I usually get it pretty snug since my drive pin is long gone.

The consensus is that if you are using silver and deming drill bits, you are playing with fire. That's when I have slipped mine. I need to save up for an 18N Jacobs and a good arbor adapter.
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Old 03-01-2020, 12:14 AM
threepiece threepiece is offline
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Quote:
Originally Posted by Ironman View Post
Are you sure the slippage is not in the JC taper in the chuck head?
Apparently I was not. I made a closer observation and discovered the slipping is in fact between the arbor and chuck. I simply expected if the friction hold in the taper was lost the chuck would immediately fall off. I did not consider that the chuck could actually spin without falling off. I still don’t understand how this can happen short of having grooves cut into the surface of the taper. There are no grooves in my taper.
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  #6  
Old 03-01-2020, 12:23 AM
threepiece threepiece is offline
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Quote:
Originally Posted by Don_S View Post
I need to save up for an 18N Jacobs and a good arbor adapter.
Jacobs aren’t what they use to be. Some, perhaps all are made in China. I have had problems with the last three Super Chucks I bought. Two of them are fussy about running true. The 18N I recently bought will not close down completely.
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  #7  
Old 03-01-2020, 12:24 AM
threepiece threepiece is offline
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Quote:
Originally Posted by Ironman View Post
Are you sure the slippage is not in the JC taper in the chuck head?
Apparently I was not. I made a closer observation and discovered the slipping is in fact between the arbor and chuck. I simply expected if the friction hold in the taper was lost the chuck would immediately fall off. I did not consider that the chuck could actually spin without falling off. I still don’t understand how this can happen short of having grooves cut into the surface of the taper. There are no grooves in my taper.
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A technologically advanced society would teach their children how to start a fire by rubbing two sticks together before teaching them how to use a lighter.

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If you are not having fun then you are doing it wrong.
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  #8  
Old 03-01-2020, 09:53 AM
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Quote:
Originally Posted by threepiece View Post
Apparently I was not. I made a closer observation and discovered the slipping is in fact between the arbor and chuck. I simply expected if the friction hold in the taper was lost the chuck would immediately fall off. I did not consider that the chuck could actually spin without falling off. I still don’t understand how this can happen short of having grooves cut into the surface of the taper. There are no grooves in my taper.
Good that you ID'd the problem
As has been suggested, cooling one part and warming another is a way to fasten them together better.
I read on an old engine forum for installing tapered keys to coat them in talcum powder before you hammer them together.
I have dusted the taper with talcum before putting the JT taper into the chuck, and drifting it with a brass hammer. It seems to work.
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  #9  
Old 03-01-2020, 09:56 AM
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Quote:
Originally Posted by threepiece View Post
Jacobs aren’t what they use to be. Some, perhaps all are made in China. I have had problems with the last three Super Chucks I bought. Two of them are fussy about running true. The 18N I recently bought will not close down completely.
I have a $250 dollar import ball bearing chuck, and I sure can't complain about it. Top of the line and when it grips a shank it is not gonna slip.
Of course even US stuff is an import to us, so to be specific, this is from China.
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You got freedom of speech, if you don't say too much.
Aaron Neville.

The virtue is always a cover for the sin. That's the key to understanding the modern left. Whatever they're accusing you of doing, they are doing themselves but more enthusiastically. And that's definitely the story of Justin Trudeau. Tucker Carlson
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  #10  
Old 03-12-2020, 12:08 PM
threepiece threepiece is offline
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It seems the problem was that the arbor was never mated to the chuck. The chuck and arbor look new to me, I guess they really never were used. I went through the process of cleaning the surfaces and smacking them together and they have held together so far.

The deals are out there if you spend some time looking. I bought this new chuck and arbor for $60. Last week I bought a nice four jaw chuck for my new Logan and a large assortment of set screws and cap screws from the same fellow for another $60
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A technologically advanced society would teach their children how to start a fire by rubbing two sticks together before teaching them how to use a lighter.

Aren't energy consumption and computers supposed to make life less stressful?

If you are not having fun then you are doing it wrong.
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