# Pin a threaded spindle?



## Ststephen7 (Mar 30, 2018)

I know that even speaking of this will be sacrilege to a lot of people, and I’ll say it anyway… 

Having a chuck that screws on puts limitations on what can be done with the lathe… a lot of operations can be done in reverse, but with a threaded chuck… not so much (I don't know this from experience... just from reading and watching others).

Has anyone ever thought of drilling a hole through either the threaded portion of the spindle, or the non threaded portion behind the threads, and inserting a pin (taper or otherwise) to allow reverse operation?   It could be removed to pass work through the spindle, to remove the chuck, or whenever needed.  I could even envision 2 small screws, with heads shaped to follow the interior of the spindle, to allow the spindle to stay open.

What would be the downsides to doing this? (assuming everything went as planned…).  I'm new to this whole machining world, so there is a lot I don't know yet.
I have a 10" Sheldon, 2 1/4 x 8 threaded spindle.

Thanks,
Steve


----------



## C-Bag (Mar 30, 2018)

I'm a noob too, but pinning a spindle seems to invasive to me. I thought the 3" chuck that came with my lathe had a potentially good solution to me. I've not put it to the test yet, but if nothing else I could replicate it and put another on.

It involves milling a flat, drilling and tapping just the chuck and of course fabbing the little clamp.


----------



## RJSakowski (Mar 30, 2018)

The Grizzly 602 uses two clamps that clamp onto a rebate on the lathe spindle nose.  This has proven effective in preventing loosening of the chuck  when operating in reverse.  The clamps attach to the back plate hub.  It does require that the spindle nose protrude from the headstock housing.



One problem that I would see with your idea is that it locks the mounting of the chuck into a particular orientation. This could be an issue when changing chucks.


----------



## woodchucker (Mar 30, 2018)

I would not pin it.


----------



## magicniner (Mar 30, 2018)

I put a groove in the cylindrical section of the register in my Myford Super 7 and drilled all my chuck back plates for 3 grub screws at 120 degrees to engage the groove and I never had a chuck unscrew when working in reverse


----------



## Jimsehr (Mar 30, 2018)

It’s your machine . And if you want to do it do it. If you use another chuck you can time it’s backplate to the same spot. I like to use collets so I don’t worry about reverse . I have seen it done .


----------



## kd4gij (Mar 30, 2018)

One option is to drill and tap the shoulder and use a soft tip set screw to lock the chuck on.  I haven't had an issue just make sure the chuck is on tight and take light cuts.  When I was working on a larger part with some weight. I made a washer for the chuck and used all thread through the spindle and used lock nuts.


----------



## T Bredehoft (Mar 30, 2018)

C-Bag said:


> It involves milling a flat, drilling and tapping just the chuck and of course fabbing the little clamp.



That's exactly what I did on mine, I put a .100 wide/deep groove in the spindle behind the chuck, put the clamp in there.  It's broken loose once, backed up about 1/8 rev and held. no damage to the part.


----------



## Ststephen7 (Mar 30, 2018)

I don't know that there is space behind the chuck for a groove/rebate... I'll include a pic.  You guys might think differently...  Pretty sure there is a space with no threads for set screws, if that's a thing?

kd4gij... are you saying you used the washer and all thread right through the spindle, maybe like I think of a collet closer, to pull the chuck onto the spindle?


----------



## Ststephen7 (Mar 30, 2018)

magicniner said:


> I put a groove in the cylindrical section of the register in my Myford Super 7 and drilled all my chuck back plates for 3 grub screws at 120 degrees to engage the groove and I never had a chuck unscrew when working in reverse



So... the groove is under the chuck, after/behind the threads?  I could do that I think...


----------



## magicniner (Mar 30, 2018)

Ststephen7 said:


> So... the groove is under the chuck, after/behind the threads?



Yes, under the back plate shoulder, behind the threads.


----------



## benmychree (Mar 30, 2018)

I would not do that ----- !


----------



## kd4gij (Mar 30, 2018)

Ststephen7 said:


> I don't know that there is space behind the chuck for a groove/rebate... I'll include a pic.  You guys might think differently...  Pretty sure there is a space with no threads for set screws, if that's a thing?
> 
> kd4gij... are you saying you used the washer and all thread right through the spindle, maybe like I think of a collet closer, to pull the chuck onto the spindle?
> 
> View attachment 263775




Yes like a collet closer


----------



## kd4gij (Mar 30, 2018)

A soft tip set screw can tighten against the threads with no damage.


----------



## kd4gij (Mar 30, 2018)

My spindle is 1 12-8 tpi the chuck has a 2 1/2" through hole The washer is 1/2" thick drilled and tap for 1/2-13 all thread is in with loc-tite and peened over. the backend gets a washer and double nuts.


----------



## Ststephen7 (Mar 31, 2018)

benmychree said:


> I would not do that ----- !



I'm betting you would not chime in unless you were trying to be helpful, and... to me, simply stating that you would not do it is not that helpful.  Could you state why, what you think might/can/will go wrong?  What experience brings you to guide me towards not putting either a pin in the spindle or a groove for set screws in the spindle?  We can see from the pictures that others have done it.  And you believe I should not, so I am interested in why you think I should not.  I'd like to make a good, informed decision, which is why brought it up here. I will not dismiss your opinion or experience...


----------



## Ststephen7 (Mar 31, 2018)

kd4gij said:


> A soft tip set screw can tighten against the threads with no damage.
> View attachment 263789


So no groove needed?  Just... maybe 3 holes in the chuck, over the threads?  Did you just drill out a set screw and insert a piece of brass?  I like that idea!


----------



## Ststephen7 (Mar 31, 2018)

kd4gij said:


> My spindle is 1 12-8 tpi the chuck has a 2 1/2" through hole The washer is 1/2" thick drilled and tap for 1/2-13 all thread is in with loc-tite and peened over. the backend gets a washer and double nuts.



So I'm picturing a shoulder inside the chuck against which the washer pulls?  I'd really appreciate a picture if you can get one...  Seems as if this is the least invasive idea...


----------



## magicniner (Mar 31, 2018)

benmychree said:


> I would not do that ----- !



_Always with the negative waves Moriarty! _
My suggestion is based on experience of having done it and then run a lathe with the modification for in excess of 10 years without issues, what are you basing your advice on? 

Here's the groove in question - 




Here's the replacement head stock with a native ER40 spindle nose  with a register behind the thread allowing the use of chucks and plates - 




The 3 Jaw and 4 Jaw now only come out on special occasions ;-)


----------



## kd4gij (Mar 31, 2018)

Ststephen7 said:


> So no groove needed?  Just... maybe 3 holes in the chuck, over the threads?  Did you just drill out a set screw and insert a piece of brass?  I like that idea!




 Do you can buy the setscrews. And one set screw will hold it.
https://www.mcmaster.com/#set-screws/=1c7qf2e


----------



## kd4gij (Mar 31, 2018)

I will try to get a picture. My chuck has a 2 1/2 inch through hole. The back plate is 1 1/2-8  internal threads so that leaves a nice shoulder.


----------



## Ststephen7 (Apr 1, 2018)

kd4gij said:


> I will try to get a picture. My chuck has a 2 1/2 inch through hole. The back plate is 1 1/2-8  internal threads so that leaves a nice shoulder.



Perfect!  Thank you so much!


----------



## rwm (Apr 1, 2018)

My first lathe was a Jet 9x20. It had a single set screw in the chuck back plate that bore down on a non-threaded portion of the spindle nose. 
As stated before, the problem with a fixed pin is that the hole will not be in the correct place for all your chucks.
Robert


----------



## Tim9 (Apr 2, 2018)

Here you go Stephen7





This is a two part video of a locking collar and a pin. Just what the doctor ordered. 

Part 2-


----------



## Ststephen7 (Apr 2, 2018)

Tim9 said:


> Here you go Stephen7
> 
> 
> 
> ...



Another great option.  Thank you so much!


----------



## KBeitz (Sep 5, 2018)

If you have room you could bolt half a split collar to the back of your chuck and
The other half would tighten down on the spindle with no damage.


----------



## Downwindtracker2 (Sep 5, 2018)

Rather than mess up threads, use a piece of lead under the set screw. We've used that at work on shafts with more serious stuff hanging off them than chucks.


----------



## Ststephen7 (Sep 6, 2018)

Downwindtracker2 said:


> Rather than mess up threads, use a piece of lead under the set screw. We've used that at work on shafts with more serious stuff hanging off them than chucks.


Both excellent ideas!  I only have about 1/8" between the back of the chuck and the bearing cover, so no split nut.  However... I could use lead under the set screw!  Thank you!!!


----------



## BaronJ (Sep 6, 2018)

Hi Guys,

I have a Myford S7LB which has a screwed on chuck.  In the fifty odd years I've had it, I've never had the chuck even loosen when running in reverse.  I can see and understand the reasons why you would want to secure it and if I were sufficiently concerned then I would only go down the route of drilling the backplate and using a grub screw (set screw) with a brass or lead tip.  Of course you would have to remember to loosen it when you want to remove the chuck.

Now having said all that, the Myford comes supplied with backless narrow body chucks that screw directly onto the lathe spindle.  So that there isn't any way that you could arrange a fastening to secure the chuck.


----------



## Silverbullet (Sep 6, 2018)

I've used a drawl bar set up on mine with a large turned washer in the chuck  behind the jaws yet no contact to the jaws. It rides captured behind the backer mines 2 1/4 -8 threaded. But I made a rod for the spindle so it's bolted to the chuck and the spindle , 3/4 -16 fine threads with a cap and nut to fit and tighten the washer and chuck to the spindle . Only problem is the loss through the spindle work. Most of my left hand cutting was for short items  , it worked with no lathe modification .


----------



## hman (Sep 7, 2018)

Both my lathes (9x20 and 12x24) have threaded spindles.  I've been hesitant to add a setscrew that bears on the spindle threads - any damage would be very hard to repair!  But I've decided I want at least some kind of "insurance," and have added setscrews to each chuck that make light contact with the thread relief area behind the spindle threads.  I don't tighten them, so as not to push the chuck off center.  I still depend on the tightness of the chuck to avoid unscrewing (hasn't happened yet!)  And the setscrew assures that if the chuck does start to unscrew, it won't come off completely.


----------

