Fitting chucks to my lathe

[steamer]

My "NEW" South Bend is in need of chucks!....which I have, but I need to fit them!....I figure others may benefit by the effort, so I'll try to document the way I do it here..

The first thing I need to make is a dummy spindle.   A dummy spindle is a machined bit item that exactly copies the spindle nose of the lathe.  The purpose being to facilitate fitting the female thread and register of a back plate or faceplate being machined.

I'll sketch up something and post as I go as I would bet others have to do this so perhaps a thread would help.

Dave

[steamer]

My South-Bend 9" lathe has a 1 1/2 -8 spindle nose with a 1.512" register diameter.   Now what is that you say?.....well let me explain.

The end of the spindle has a male thread 1.500" in diameter, and with a 8 threads/inch pitch.   This is a once very common spindle nose, and tooling is still readily available for it...but I want something that fits very closely....so we need to pay attention to how this system works...as opposed to perhaps how some might think they work....let me explain...here's a drawing of my spindle..your's may vary...so measure yours and follow along.



With this type of spindle, the chuck is held on with the threads, just like a nut...drawn in tight against a shoulder.   But the threads...contrary to popular belief....DO NOT center the chuck...or at least they shouldn't.    What controls that...is the register diameter...in this case it's 1.512" diameter.

The key to fitting a chuck to this kind of spindle, is to have a close fit on the register diameter, and screwed up tightly and squarely against the shoulder.   A good fit on the threads is fine, but it the fit should have enough clearance to allow the shoulder and register to do their job and not bind against screw or it won't seat tightly against these two surfaces repeat-ably.



Here's a shot of the "Multi-tap" faceplate, on Samantha Bell...(SB)  getting ready to put the 4 jaw back plate on to open the register diameter. 


This 4 jaw was bought on the Bay, and to my happy surprise, the register is 1.495"...so there is some stock to open up the register to fit.  I took the back plate off, and am in the process of mounting it to the face plate for a light boring cut....but first we need a plug gage in the form of a dummy spindle...which I'll get to tomorrow.

Dave

[steamer]

....and you all have a piece of plywood to lay your chuck on...and keep it from dropping on the ways.....right?

[steamer]

And a shot of the new 3 jaw...ready to have a back plate made up ...which is sitting on top...but I still need to measure it and see if it's suitable....I have about 5 of these displaced old back plates...some are useable....some go into the lucky box....



This chuck is an "Adjust true" chuck...and we'll get into that when I take that one on.

Oh and the tool box that sits on the ways...you have one right?....you wouldn't lay your tools on the bare bed ways right?...



Dave

[Don1966]

Interesting Dave, looks to be very educational. My Myford nose is somewhat like yours, but with different dimensions. I will be riding along with you, because I also have a plate to mount on a chuck that will make it a adjustable backplate.

Don

[steamer]

Hey guess what I forgot about!.....Along time ago.like 15 years....I owned an Atlas 10F.   It also had a 1 1/2 -8 spindle nose but with a 1.502 register diameter...I still have the faceplate centering fixture for that....with the dummy spindle.   



I figure I have nothing to lose if I turn up a ring, bond it on the register diameter, and then turn the diameter to the proper diameter for the SB.    The threads seem to fit just fine...so I don't need to change that, and if I do this, I get my centering fixture back for use on Sammy Bell....

Ok then....I turned up a ring on the Logan leaving plenty of meat for further operations later.  The photo's below explain







Once the bond sets, I'll carefully set it up in the Logan, and turn the diameter to match the SB.

Dave

[Tennessee Whiskey]

Good stuff pal, need to make something like this to put Jr's chucks on my rotary table. 3 MT to 1.5x8. No, I didn't know about the register. I'd probably just cut a big relief behind the threads.  I do wish you would use an "I" in Sammi and don't drop the "E" in Belle. It's a Southern thang JR is wanting to know if he can meet Sammi. I tried to explain he may be too old (1939), he said; So. Hey, it's a Southern thang

Yo Redneck,
Eric

[tel]

Dagnabbit Mr Whiskey, I thought you good ol' boys just held 'em on with a bit o' duct tape?

[Tennessee Whiskey]

Sorry Dave. Tel. Duct tape is for my pickup repair and Lou likes it

Whiskey

[steamer]

No worries Eric,

Been busy!....I tried to get away with a bushing...but at .006" thickness....it peeled off at the last cut....so the hell with it...and I roughed out a new one...I'm cutting the threads right now...but the Logan is tooled, and 4 times as powerful...and I want to get it done.....so Logan is doing it now...and making a fine pile of chips too....

Dave

[steamer]

I don't have a suitable back plate for the 3 jaw....so I ordered one from Little Machine Shop....It's threaded but doesn't have the register machined in...very convenient.

So back to making some faceplate straps...and I'll do the whole thing on the SB.

I played with her this evening...     She has the "Large Dial Option"  which is direct reading.... .001 on the dial is .001 on the part..and splitting the mark is a piece of cake with really nice finish....I need to do some more checks regarding squareness. ect

Dave

[steamer]

I got the spindle stub done....


So I mounted up the blank backing plate, and turned the register diameter, and faced off the back ...and recessed it to clear the belt tensioner.


Drilled and tapped 3 holes...and we're in business


I set up the chuck, and dialed in a 1/2 reamer blank..with very little effort, I got .0007" at 3 inches from the chuck jaws..That'll do!

Dave

[steamer]

and she's not clean anymore!.



Dave

[Don1966]

Looking good Dave, that cast iron sure makes a mess doen't it?

Don

[steamer]

Yes sir it did!....but Samantha is all nice and clean now.......

Dave