# Spin Indexer Modification/Improvement (and explanation).



## Ray C (Oct 26, 2013)

Spin indexers like the one shown have a 5C collet spindle in the front, a drawbar in the main cylinder and a hand crank to tighten the drawbar.  They are handy to index things on non-fractional degrees of rotation.  That is, they can be rotated between 0 and 359 degrees but cannot hold an angle of fractional value like 15.1 degrees.  As handy as they are, they're very difficult to tighten the collet  enough to hold a part firmly -much less firmly enough to do light  milling on a small piece. 




This simple modification should help that.  First, make a couple flats and drill some holes in the main cylinder.  Next, sweep the floor and find a couple treasures to make some spanner pins that fit in the holes.




Next, thread the end OD of the draw tube (in this case, I put an 18 TPI thread on there) and make a big nut to fit those threads.  Now you can use a couple crescent wrenches to hold the pins and tighten the big nut.  -That aught to keep those rascal parts from getting pulled out of the collets...




Keep in mind, the existing main cylinder and drawtube are hardened to about RC 35-38C (at least mine were) so, be sure to use the proper cutting tools when doing the mods.  Also, the last time I fired-up the heat treat furnace, I tossed that big nut in there -which happened to be made of a piece of 1045 drops that was hiding behind the leg of the lathe bench.  This way, you wont damage the thread the first time you put some beef behind those crescent wrenches...

Have fun!  -Happy Indexing!


Ray


----------



## Inflight (Oct 26, 2013)

Add a needle thrust bearing in there and you'll have a masterpiece.


----------



## Ray C (Oct 26, 2013)

LOL but, Nah... for the most part, it has very little axial motion because that black retaining ring can be snugged-up against the housing.  I will say though, for an instrument under 50 bucks, this thing is OK in my book.  That main cylinder and hole bored in the casting is dead-on precise.  I've had it for years with a love/hate relationship because you can't get the collets tight and one day I thought:  Duuuh, Gee, Tennessee... Fix the drawbar!

Of course, my method of putting spanner holes and a big nut could be modified as you see fit with any similar solution.

BTW:  A lot of people wonder why these things don't have bolt holes drilled in the base.  Easy answer...  The base is designed to be clamped edge-wise in a vise.  If you had bolt holes, drawing-up on tension would warp the casting and no way in heck would that cylinder spin unimpeded.  The end-to end tolerance is well, well under a half thou.

If anyone wants I'll show how to set the angles on it.


Ray



Inflight said:


> Add a needle thrust bearing in there and you'll have a masterpiece.


----------



## Chuck K (Oct 26, 2013)

Ray, I always thought they didn't have mounting holes because they were designed to be used on a surface grinder.  They don't seem stout enough to use on a milling machine.

Chuck


----------



## Ray C (Oct 26, 2013)

That's a valid reason too.  As for milling, I use it a lot when making bolt heads -which I just had to do for the knurling tool tensioner...  The part does not stick out very far and the cuts are very small and shallow.  It works fine under those conditions.  I also use it when engraving notches on a dial etc which is sometimes done by hand and sometimes with a pointy engraving bit on the mill.  I wouldn't recommend using it for any heavy cuts.   In any event, parts coming loose was always an issue and I think this puts predictability in that variable of the equation.

Ray...




Chuck K said:


> Ray, I always thought they didn't have mounting holes because they were designed to be used on a surface grinder.  They don't seem stout enough to use on a milling machine.
> 
> Chuck


----------



## Ray C (Oct 26, 2013)

Thanks...

I should probably weld those spanner pins to some kind of quickly fashioned handle or wrench.  I just didn't have the time to mess with it too much...


Ray




shawn said:


> It was just last week I had my spin indexer loose its grip on a part, I wasn't pleased but did vow to try and fix the issues. Thanks for your post Ray, I like what you have done.
> 
> Shawn


----------

