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Something I've been meaning to do

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Phil Pascoe

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for about thirty years. Put drawbars on my Jacobs chucks.
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I had a slight problem - the MT2 arbors are threaded 10mm, which is too large a threaded rod to go through the tailstock. I ordered some helicoil type inserts, but found that a 10mm insert is in fact 12mm - they obviously rate them by the thread size the fits into them, rather than the size they fit in to. I couldn't be bothered to send them back - the P&P probably wasn't worth it, so I ordered a set, thus guaranteeing I'll never need one ever again. :D

The No.32 is a JT2, the No.34 is a JT6. They are easy to pop out - just drill a hole through the bottom of the chuck and put a knockout bar of some description through it. The bottom of the chuck is concave, so the bit drifts to centre. I can't think of the last time I used a Jacobs chuck in the headstock, but I put a longer rod on the smaller chuck just in case. Two washers and wingnuts, job done.
 

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Steliz

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If it took you 30 years to get around to it maybe it didn't need doing. I use my chuck in the headstock fairly often with a little sanding disc to shape 'stuff'.
 

Richard_C

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I've just done the same, only 11 months after I got my lathe. Dead handy to quickly put sanding disc, buffing wheel etc on for little jobs, particularly the buffing wheel because to mount that on the grinder involves much faff with removing wheels and guards.

2 modifications. My hand wheel is deeply dished so made a simple beech spacer so the fastening nut is just within not deep within, and I've got a piece of 9mm mdf c. 12" x 15" screwed to a piece of offcut 2x1 from the scrap bin. That is a snug fit in the gap in the lathe bed so it gives me a little 'table' under the chuck so potions etc. from polishing don't go where they are not wanted.
 

Phil Pascoe

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Steliz":1l4zpaha said:
If it took you 30 years to get around to it maybe it didn't need doing. I use my chuck in the headstock fairly often with a little sanding disc to shape 'stuff'.
I'm more concerned with the tailstock, actually. I found the chucks pulled out when withdrawing the bit, and damaged something when the chuck wobbled.
 

selectortone

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This is what happened to me when an unsecured Jacobs chuck flew out of the headstock of my lathe. It was holding a soft polishing mop which smashed into my safety glasses with a force that felt like a punch from a heavyweight boxer. I was rendered momentarily unconscious. I was lucky; Lord know what damage might have occurred if the chuck was holding something metal and pointy.

Needless to say, I use a drawbar with a headstock mounted Jacobs chuck now.

 

gregmcateer

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"They are easy to pop out - just drill a hole through the bottom of the chuck and put a knockout bar of some description through it. "

That confuses me - I thought a draw bar threaded onto the tapered end of the chuck? So how does a hole in the chuck knock it out? Doesn't the bar need un threading to remove it from the chuck? I must be missing something here. #-o
 

Doug B

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gregmcateer":3h82vwdc said:
"They are easy to pop out - just drill a hole through the bottom of the chuck and put a knockout bar of some description through it. "

That confuses me - I thought a draw bar threaded onto the tapered end of the chuck? So how does a hole in the chuck knock it out? Doesn't the bar need un threading to remove it from the chuck? I must be missing something here. #-o
I read that as how to remove the morse taper part from the chuck which is a friction fit.
By putting the threaded bar into the morse taper you are still only securing the morse taper to the head/tail stock when in use the chuck itself can still come loose from the morse taper, personally I would fix the chuck to the morse taper via a machine screw through the base of the chuck into the taper.
 

Phil Pascoe

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gregmcateer":2edusqur said:
"They are easy to pop out - just drill a hole through the bottom of the chuck and put a knockout bar of some description through it. "

That confuses me - I thought a draw bar threaded onto the tapered end of the chuck? So how does a hole in the chuck knock it out? Doesn't the bar need un threading to remove it from the chuck? I must be missing something here. #-o
No, I meant the original tanged arbor. The bar threads into the new arbor and would need to be unscrewed, but they'll stay there as the chucks aren't used anywhere else.
 

Phil Pascoe

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Doug B":3w2kp943 said:
gregmcateer":3w2kp943 said:
"They are easy to pop out - just drill a hole through the bottom of the chuck and put a knockout bar of some description through it. "

That confuses me - I thought a draw bar threaded onto the tapered end of the chuck? So how does a hole in the chuck knock it out? Doesn't the bar need un threading to remove it from the chuck? I must be missing something here. #-o
I read that as how to remove the morse taper part from the chuck which is a friction fit.
By putting the threaded bar into the morse taper you are still only securing the morse taper to the head/tail stock when in use the chuck itself can still come loose from the morse taper, personally I would fix the chuck to the morse taper via a machine screw through the base of the chuck into the taper.
Certainly, but I suspect a Jacob's taper unlike a Morse taper is designed to stay put. They certainly take a fair clout to knock them out. It would be interesting to know if anyone has ever known a chuck drop off a Jacob's taper.
 

Doug B

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I’ve had Jacobs chucks come off their taper before admittedly on two different pillar drills & not the lathe but it goes to show they can come loose.
 

Doug B

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The chuck off it’s taper, not the chuck & it’s morse taper.
Thinking back I used to have a mortiser that came with an accessory chuck it fitted to the mortiser via a straight shaft, that chuck regularly fell off its taper when in use though to be fair it was usual Chinese Axminster garbage & one of the reasons I bought a Meddings pillar drill.
 

gregmcateer

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Phil,
Cam I jump back in and ask where you got you're threaded tapers?
I like the idea of a draw bar for my chuck, and might not have 30 years left in me!
 
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I'm glad I read this. I don't think I would have been smart enough to know not to just stick the Jacobs chuck directly into the headstock without securing it.
 

Rorschach

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When I did mine I took a bolt that fitted the draw bar thread (can't recall if it was M10 or 3/8"), cut, drilled and tapped that M6 as that was the biggest rod that would go through my headstock, and then made my draw bars from M6 all thread. Works well and very cheap.
 

Phil Pascoe

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Actually there's little point in securing it to the tailstock unless you are prepared to slide the whole tailstock when drilling rather than winding the quill out. :oops: :D
 
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