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Use of Grub/Set Screws on Chuck?

Keith Flood

Keith Flood

Joined
Nov 17, 2021
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Location
Santa Rosa, CA
I have a 4 jaw chuck that has two grub/set screws that when the chuck is threaded onto spindle the screws bottom out behind the spindle threads and add extra security so the chuck does not come off. Question, should you ALWAYS tighten these when using the chuck or only when you plan to use the lathe in reverse? I am new and started to always use them but also have forgotten to loosen them before trying to remove the chuck. :confused: I have not run my lathe in reverse but there are probably times when I might need to, just have not gotten there yet. Thanks for any thoughts....

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I don'd... maybe sometimes... definitely not always... But I've been known to be forgetful so I keep this old safe magnet (it says "Open" on the other side) handy to remind me I've "Secured" my chuck with a grub screw.
 

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You will hear proponents on both sides of this issue. I never use them because my spindle (26 yr. old lathe) wasn't designed for them. If I used the grub screws it would screw up (pun intended) my spindle. If you mount your chuck with a little snap or lock your spindle and give it a little extra oomph (technical term) with your chuck key (not much needed) you shouldn't have a problem. I use reverse all the time - but, granted, I don't usually turn large pieces.
 
Brian Gustin said:
Me, I'd only use the grub screws if it was gonna be run in reverse, TBH... Unless of course you are turning big heavy pieces that their momentum could spin the chuck off the lathe when you hit the stop switch....
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Thank you all for the replies, all seem reasonable, and being new I did not think of Brian's example with a large heavy piece and hitting the stop switch can only imagine something rolling over the rest and onto my chest as I was turning away to grab something, yikes!
 
I do the same as Mark. I do forget sometimes and had the work/chuck wobble upon restart. Its a function of how quickly your lathe stops and the mass of the work/chuck. Also I reverse the lathe for hollowing and set screws are mandatory for that.

For those worried about spindle thread damage from the set screws, its not a big deal. The damage is easily filed away - spindles are mild steal. An option is to file a flat spot where the set screw will contact (always the same spot for a given chuck). Its a very small amount of thread and does not effect the overall holding capability of the threads.
 
Doug Freeman said:
The damage is easily filed away - spindles are mild steal.
Click to expand...
From Robust: "Spindles are machined from pre-hardened and stress relieved 4140 Chrome Moly alloy steel. The bearing journals are precision ground to within 0.0003".

OneWay Manufacturing: "The spindle is 50 mm (2”) at max dia., 16” long and bored thru 5/8” dia. with a number 2 Morse taper at the inboard. It is made from high alloy steel hardened and ground to precision tolerance of ±0.0003”.
 
Joe Kaufman said:
From Robust: "Spindles are machined from pre-hardened and stress relieved 4140 Chrome Moly alloy steel. The bearing journals are precision ground to within 0.0003".

OneWay Manufacturing: "The spindle is 50 mm (2”) at max dia., 16” long and bored thru 5/8” dia. with a number 2 Morse taper at the inboard. It is made from high alloy steel hardened and ground to precision tolerance of ±0.0003”.
Click to expand...

At least with the "Easy Chuck" and the Robust spindle, the grub screws set behind the spindle threads and so far I am just making the spindle look more used with scuff marks from the grub screws when I forget to loosen them.
 
They were not available on chucks when I got my first one, some 25 or more years ago, and I never depended on them. I would never turn a big piece in the high speed range. This is the only situation I can think of where the piece could unwind when you shut off the lathe. Some sand in reverse, and I did for a while before I went to power sanding. I quickly learned to apply just the right amount of pressure to get the abrasives to cut, but not unwind the chuck. I was sanding at slow speeds also.

robo hippy
 
Joe Kaufman said:
From Robust: "Spindles are machined from pre-hardened and stress relieved 4140 Chrome Moly alloy steel. The bearing journals are precision ground to within 0.0003".

OneWay Manufacturing: "The spindle is 50 mm (2”) at max dia., 16” long and bored thru 5/8” dia. with a number 2 Morse taper at the inboard. It is made from high alloy steel hardened and ground to precision tolerance of ±0.0003”.
Click to expand...

Pre, or unhardened, chrome moly steel is no problem to file. Any other hardened spindles out there besides Oneway? So a diamond file is needed for a Oneway, and being hardened, there wont be much of a mark to worry about.
 
I noticed my Axminster 114 has three of them. I use them every time I turn. I can see where it isn't always necessary. Army SF taught me one thing; Always think it WILL break.
 
Mine are put safely away in a drawer somewhere. Haven't seen them in years!
 
Some Nova chucks use an insert to adapt to various spindle threads. When preparing a new chuck for use I always use a set screw to secure the chuck to the insert adapter, because on several occasions while removing the chuck from the lathe the insert adapter has remained on the spindle.

I use a set screw for larger bowl blanks. It doesn’t take much pressure or weight while sanding to cause a chuck to unthread itself from the spindle, but a light touch is generally OK.
 
Doug Freeman said:
Pre, or unhardened, chrome moly steel is no problem to file. Any other hardened spindles out there besides Oneway? So a diamond file is needed for a Oneway, and being hardened, there wont be much of a mark to worry about.
Click to expand...
I have a Oneway 1640 and it has a dedicated groove behind the threads that the set screw seats into, so no filing necessary. Being new and not wanting to be complacent because of my lack of experience, I made it a habit to use the screws each and every time I add/remove my chucks. Like someone else mentioned - easier this way than forgetting to do it the one time it would really count. Just my $0.02.
 
Like John, my Grizzly G0766 has a grove to accept the set screw. I secure my chuck with 100 mm jaws and do not for the 50 mm jaw chuck (lost the grub}. I guess I have more respect for bad outcomes with bigger bowl blanks.
 
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