Saturday, August 17, 2013

Working in Metal

A knurled knob and lug to stud adapter. Made by ME!
A few weeks ago I bought a metal lathe and milling machine. I've slowly been collecting tools and material to actually accomplish something. Mostly I've been cleaning, oiling adjusting and just getting everything "just right".

One of my latest purchases was this indicator holder, it is held in a regular or quick change tool holder and is designed to attach to a stud on the indicator.  If you look at the fuzzy picture of the indicator you can see one "stud" which is at the right.  But it is way to big to fit into the clamp on the holder.  It does turn out that the stud at the top is the right size but I found that out after I was mostly done.  And I'm not sure I would use it as it is very short.

On the back of the indicator is a "lug" which is this loop thing on the back.  That isn't very helpful by itself.  Of course there are adapters to put a stud into the lug so they can be attached.  I went to my two different indicator holders and pulled out the stud adapter and attached it to the indicator.

Here is the adapter attached to the indicator.  The knurled nut is tightened and that locks the stud in place.
Unfortunately there is a problem with this adapter, it is the wrong size!  It is too big.  It does not fit into the holder.

I did try but the clamp does not fit.  This gives me two choices, make a larger clamp which is primarily a milling operation on steel I don't have or make a new stud adapter.

The first step is to draw a picture and measure everything.  The stud has three parts, the stud, the lip on the stud and the threaded part.  I measure all the parts and then go to figure out what size thread it is.  And it isn't any normal thread.  My gage refused to identify it.  And the size doesn't match anything I have.  Let's think for a moment, oh yeah, I bought this from Grizzly which imports 99% of its stuff which means it must be *metric*.  15+ years ago and 6 moves ago I bought a set of metric taps and dies.  Since that time half the dies have gone missing and all the taps.

I go to double check and it turns out that there is exactly ONE tap remaining... And the gods shine on me it is the right tap for this thread and I have a matching die for it.

On the drawing I have the sizes of the original and then off to the right the range of sizes that the clamp supports.  So now it is time to start the process of making my stud adapter.

I start with the stud piece.  First I put a piece of 1/2" 12L14 steel rod in.  The end is faced and then I use Dykem blue for the first time and mark the location of the shoulder.  With the new tooling it is turned down to size quickly and easily.  To easily.  The first attempt I turned the stud to small and had to cut that part off and throw it away.

2nd try and the stud ends up exactly the right size.  I test it in the clamp and it is a perfect fit.  Yeah!!!!  Now that I've completed the stud I cut it off to length, flip it around face it to length.  The finished surface is protected from the chuck jaws with a piece of 0.005 thick brass shim.  After it is faced I mark the shoulder and turn the threaded section to size.

Done with that I cut the threads with a die.  Unfortunately it is a cheap die and it rips one thread but there is enough left to work.  A few touches of the file and the sharp, finger cutting, edges are broken and it looks finished.   I test with the original knurled knob and it works!  Yeah.

For the next two hours I stare at the knob trying to figure out the order of operations for the knob.  If I cut the small section I won't be able to hold that in the chuck safely and turn the rest of the piece.  In addition I don't have a piece of rod the right size.

The answer finally hits me.  Step one I put a piece of 1" rod in the lathe and mark for a shoulder.  I marked it for 0.750 but I should have made it a bit further.  No real problem

Next I turn the rod to the larger diameter.  0.540 inches.  And I got it right within 0.0005.   Then it is time for a tool I've never used before, the knurling tool.  The wheels of the tool are pressed hard into the metal rod and if it is adjusted correctly it cuts a beautiful knurl.  Of course I adjusted it incorrectly to begin with.  I got it right and was able to cut a knurl.

I now have a knurl but I need to cut the relief.  No problem.  I just turn to size and clean up the shoulder, break the corners.  Then I center drill the piece, drill for tapping.  I should have drilled the clearance hole next but I waited on that.

I tapped the hole and that worked wonderfully!  I know have a 4 ft section of 1 inch rod with a knurl at one end with a hole drilled and threaded.  Out comes the cutting tool and I part off the knob just a little long.

And then my break through... I thread the knob on to the stud, remount the stud with the protective shim and quickly face the knob to size, cutting the screw to length at the same time!  A quick touch up of the corners with a file and the knob is finished!

Last step, take the knob off and touch up the end of the screw with a file to make that edge gentle and finished.

Only about 2 hours to make something that likely would cost me less than $5.00, if I could find it.  Well worth it!

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