Sunday, August 14, 2022

Turning Carbon Steel Was Harder Than I Remembered

No surprise that it is harder to cut than acetal and aluminum.   What I destroyed two carbide tipped Sherline tools discovering: I need to turn carbon steel at a higher speed to get a clean cut.  Otherwise chatter, bad finish and ruined cutting tools.  I was even reduced to putting the carbon steel rod in the mill and cutting across the end.  Even at .5 ipm, the finish end mill left pretty obvious milling marks which I tried to square off in the lathe; by the last piece I discovered I needed more speed than aluminum.  Finally having produced an acceptable finish and square end, the three jaw chuck refused to release its prey.  I have it in the freezer right now.  The step is put the tommy rods in the holes put it on a piece of plywood and mallet it.  Of course it would help to know which direct opens it.  I have the larger three jaw chuck as a model for this.

Make that three carbide tools destroyed.   The last pass finished it off and the uneven finish left by the endmill speeded up the process.  I will never do that again!  Filing the end and some 100# sandpaper at high speed smoothed the ridges enough to get a little smoother and thus lower chatter surface.

The chuck opened after freezing it and carefully examining the somewhat mysterious open procedure.   Looking into the jaws, you turn the ring nearest you counterclockwise to open and the opposite to close.  Putting the chuck with one tommy rod on the plywood case of 7.62mm NATO and using a rubber mallet on the other tommy rod and it popped right open.  I will also never forget the direction to turn the chuck for opening and closing again, until it really matters. 

Another of you smart people informed of a fastener new to me: thumb-nuts.  Put on a screw with a lock washer and you have a thumbscrew.  But I am srill not having any luck finding a 4" long 10-32 screw, I mean except if I buy a hundred on Amazon.

Duh!  Turn down black acetal rod.  It is as black as any finish that I can apply and I can turn it down easily.  It is also self-lubricating when I turn it into the hole.  I am starting with 1/4" rod.  I will thread it to 10-32 and use the thumb-nuts.

I only need about 1" threaded, which is good.  It might be hard to turn that thin a piece of acetal without it bending.

1 comment:

  1. Interestingly I've learned that cutting steel can be accomplished better with a tool steel bit than carbide, and it also runs at a slower speed.

    (Sorry, haven't commented in a long while. For a bit it was broken.)