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View Full Version : Fixed some things this afternoon... and learned something



barts
01-11-2009, 01:08 AM
I'd been unhappy with the carriage stop the previous owner had added to my 15" YMZ lathe; it's a simple rod and block affair which works fine as I have a trav-a-dial on this machine. The problem was the clamping screw is a 1/4" Allen head, so I'd have to use a tool to set the stop so it wouldn't move. I took some 1" cold-rolled rod, drilled and reamed a 3/8" hole, knurled the outside center and cut it off. I broke the corners w/ a file and forced the original Allen head into the 3/8" hole, and silver-soldered it place w/ a propane torch after cleaning it w/ pool acid - HCL. After cleaning the scale off of the part (more acid), I decided to experiment. I'd heard of manganese phosphate coatings, and read somewhere that it took manganese dioxide and phosphoric acid and heat.

Ok... I cut up an expired AA battery and removed the black crunchy bits (crushing the battery helps), which are manganese dioxide. There is some potassium hydroxide in there, so keep it off your fingers, or wash 'em if you don't... I put about 50 ml of Jasco Metal-Prep (phosphoric acid) in a glass jar, and add the black stuff, and put the jar w/ the part inside into a old hot-pot w/ water to act as a water bath. I stuck it outside and fired it up, and let it simmer for 50 minutes or so. After removing the part, I cleaned it off and had a nice, durable gray coating. Oiled up it looks great. This works well, and I like being able to make up the phosphating solution from stuff around the house.

Well, I put the new screw into place, replaced the 3/8" aluminum rod he'd used w/ a piece of 3/8" stainless I had kicking about and presto - now that's a stop! No tools required - a 1" diameter knurl offers plenty of grip.

Next I decided to tackle the carriage lock on the YMZ, which didn't stop the carriage at all, despite my reefing on it... after going over the apron w/ a light for a while, I figured out that the lock just tightens the center of the cast iron plate that prevent the carriage from lifting by running along the underside of the ways. Clearly, the plate wasn't sitting correctly; disassembly showed that the plate was hanging up very slightly on the apron and not pressing against the ways in the center (one sentence - two hours of fiddling). I bolted the plate down to the mill table and indicated it in - first shot was .002 out over the length - I should have bought lottery tickets :D. After gently relieving the offending portions w/ a 3/4" endmill (in a holder!) and reburring, I replaced the part on the lathe - and bingo - it works just fine. In fact, if I tighten the Allen heads at the ends of the carriage really tight, the carriage is much harder to move than before, so I just snug them in place and I have lots of whoa if I need it.

- Bart

Thomas Staubo
01-11-2009, 07:03 PM
What, no pictures!? ;)

It's nice that you could use stuff you already had in the house.
Was the battery alkaline, does it matter if it is or not?

So, is the finish durable, or maybe there's not enough time yet to tell?


.

Paul Alciatore
01-11-2009, 08:10 PM
Boy, I got As and Bs in chemistry but I don't think I would have remembered what was in a battery. Good thinking.

But tell me more about this gray finish. What metals does it work on? Steel obviously, but any others? And what about it's properties regarding rust? Does it prevent rust or do you still have to keep it well oiled? Oh, and does the solution keep or do you (I) have to make it up fresh every time?

I will have to print this thread out.

barts
01-11-2009, 09:09 PM
The finish is supposed to be quite durable - the trade name is "parkerizing".
It's certainly appears and feels quite rugged. It works on steel only...

Either conventional or alkaline cells work; the alkaline cells contains KOH, but otherwise are chemically very similar. An old big dry cell would give you enough manganese dioxide for a long time.

The solution should last a good while, from what gather reading about it. I did some more looking around, and here's a post that references the recipe I used... turns out I should have added more water... next time:

http://www.finishing.com/340/52.shtml

and here's another one; this one add iron which should give mixed iron and manganese phosphate coating:

http://www.surplusrifleforum.com/viewtopic.php?f=80&t=22740&st=0&sk=t&sd=a&sid=10c1422bce545f326ee98c329163646c

http://en.wikipedia.org/wiki/Parkerizing

Have fun w/ this - I had a blast...

- Bart