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I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been toolsandmods.com, but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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Should be able to go out to say 13/16" with a boring bar. Owner of Little Machine Shop used to loan out a 13/16" reamer to ream the spindle bore.
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You can bore the 3 inch 3 jaw out to 0/760 diameter so 3/4 inch stock will pass through John Mattis (retired Mechanical engineer)
I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been , but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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I bored my 3" chuck out to 3/4". I no longer use the chuck very often, as I do most of my work with collets now.? Looks like 13/16" would work, but it looks like you would cut into the heads of the 3 little screws the hold the plastic disk in the back of the chuck.? ----- John
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I too have collets, but I also purchased a 4 inch 3 jaw from little machine shop that I mostle use. Regards, John Mattis (retired mechanical engineer
I bored my 3" chuck out to 3/4". I no longer use the chuck very often, as I do most of my work with collets now.? Looks like 13/16" would work, but it looks like you would cut into the heads of the 3 little screws the hold the plastic disk in the back of the chuck.? ----- John
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What is 13//16? ?I’d guess about 20mm? ? Seems a lot of work for marginal gain. ? Then there are others who complain the mini-lathe is not very stiff. ?It would seem that boring the spindle even a little would not improve the stiffness. ? ?And YES it matters. ?All the cutting force that bends the frame and the bed is transmitted through the spindle.
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On Jun 1, 2024, at 4:12?PM, Doug Pfaff via groups.io <justicekrieger@...> wrote:
Should be able to go out to say 13/16" with a boring bar. Owner of Little Machine Shop used to loan out a 13/16" reamer to ream the spindle bore.
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hi I took mine out to just shy of the screw threads . Pete
I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been toolsandmods.com, but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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I never said that I wanted to bore the spindle.? Someone had misread or misunderstood my post.? My question, same as the thread title, was about the 3-jaw chuck.? If I can bore to 3/4" I'll be tickled some shade of light red.
Mike
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No, I fully understood what you were asking. I mentioned it as an aside. My apologies. Should have been more clear about that.
On Sat, Jun 1, 2024 at 10:16 PM, MikeK via groups.io <upand_at_them@...> wrote: I never said that I wanted to bore the spindle.? Someone had misread or misunderstood my post.? My question, same as the thread title, was about the 3-jaw chuck.? If I can bore to 3/4" I'll be tickled some shade of light red.
Mike
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You can but Hou have take chuck apart and find out how mush
Dave?
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On Sat, Jun 1, 2024 at 03:40 PM, MikeK wrote:
I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been toolsandmods.com, but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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You use 4jaw chuck? I have 5" [125mm] has good size hole. It has 1?" 30mm size 
On Sat, Jun 1, 2024 at 03:40 PM, MikeK wrote:
I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been toolsandmods.com, but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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The bending force is only applied to the distance between the chuck & adjacent bearing - the spindle between the bearings is not subjected to it. Opening the spindle & chuck bore to 13/16" works fine, I did mine years ago, before the LMS loaner reamers disappeared.
Roy
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True.? People have pushed the 7x lathe quite far.? Consider that the Grizzly and PM 10x22/30 lathes have only a 1" spindle bore.? And I definitely want one of those as well.
Mike
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Sounds great.
Most almost same model of chuck 3 or 4 inch?
I will miss fun 4 jaw chuck and bars. It more taking on off chucks it time to do right.?
Dave?
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On Sun, Jun 2, 2024 at 04:51 PM, Roy wrote:
The bending force is only applied to the distance between the chuck & adjacent bearing - the spindle between the bearings is not subjected to it. Opening the spindle & chuck bore to 13/16" works fine, I did mine years ago, before the LMS loaner reamers disappeared.
Roy
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That is a small hole. I can see why you want a bigger hole.? The on the chart for a 3" is only 0.63"? I just a 5" 4 jaw on my lathe it set up for a 4" chuck.? Need backing plate purchased? one from little machine shop.com I purchased the from Amazon.??  Dave?
On Sat, Jun 1, 2024 at 03:40 PM, MikeK wrote:
I seem to remember some years ago someone had increased the through-bore of the standard 3" 3-jaw chuck, but I can't remember where and didn't find anything in my search.? It may have been toolsandmods.com, but that site appears to be defunct now.
I was using the lathe last night and the 5/8" bar stock I was using had trouble sliding through the chuck bore.? It was really tight.? How big can you go without causing issues?? I know the screws holding the back cover on are already close to the bore.
Mike
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By the way, I calculated that boring the spindle to 13/16" reduces the MT3 contact from 3" to 2.5", if that should matter to anyone.? Though I don't suspect many people use the spindle taper for much.? I rarely used my MT3 collets because most of them would get stuck and even using them required removing the motor cover to get the carriage in position.
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I know? 7" and 8" mini lathes have seen? spindle hole just over ?" . I can even find larger
Do some mini lathes have smaller spindle hole?
Dave?
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On Wed, Jun 5, 2024 at 08:17 AM, MikeK wrote:
By the way, I calculated that boring the spindle to 13/16" reduces the MT3 contact from 3" to 2.5", if that should matter to anyone.? Though I don't suspect many people use the spindle taper for much.? I rarely used my MT3 collets because most of them would get stuck and even using them required removing the motor cover to get the carriage in position.
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John Mattis
davesmith1800