Tap Troubles

I am making another chandelier consisting of two pieces of fabricated steel that are joined together by four machine screws into blind holes . Since the screw holes had to line up I clamped the two fabbed pieces together, drilled the four holes through both the first piece of metal into the second piece of metal. Then I tapped the blind holes, drilled a slightly large hole in the first piece of metal, and screwed them together. All the holes were aligned just the way I had in mind.

Then I decided I was unhappy with the way the two pieces of metal were lined up. I've commented in an earlier post that one can get away with a lot in art, but less so with design. These pieces of steel were definitely design. Why did I notice the misalignment now and not before I did the fabrication? The truth is that I did notice but I was so focused on getting the piece done I just ignored the flaw thinking it was not that bad.

A half hour of cutting apart, grinding, and welding and I was again ready to join the two pieces. Two holes lined up, two did not. No problem, the welder was right at hand, so I welded the two holes shut, ground them flat, and remarked the new holes in their slightly different location.

In the back of my mind I remembered reading somewhere that weld material was a lot harder than mild steel. The first clue about this memory came when I drilled the new holes and noticed it took longer. The next clue was when I broke a tap in the first hole. Maybe the tap was worn somehow as it was part of a lot of old taps I had purchased at a closed machine shop? No, the final clue was when I broke a second tap in the second hole.

A definition of insanity I read once was doing the same thing over and over again and expecting a different result. I do this all the time on computers. Type something, it does not work. Maybe I miskeyed it, so I type it again. But I only do it twice. My typing is not that bad, and two taps in a row could not be bad either.

I am learning machining by experience. This was a pretty cheap lesson with a price of two taps and an hour or so of rework. Learning how to do it right the first time is a harder lesson to learn.

Sand casting emotions

I am trying to sort out my thoughts about this video on Youtube. First there is amazement because he is doing something in 1 minute and 12 seconds that takes me well over an hour. Take a look, he is filling a mold with green sand, preparing a part that will be cast in the foundry. There is an economy of motion that comes from doing the same thing a zillion times. There is a big stack of molds and when he finishes this one, he will do the next, and the next, and the next.

The filled mold he tosses around weighs 50 to 60 pounds yet he is really hustling. Maybe for the camera but more likely because he gets paid by the piece.

If you do not know any better it looks easy. However if the sand is not just right it falls out or compresses too much. If the sprue is not inserted just right then loose sand winds up in the wrong place and ruins the final piece. When he plonks the final mold down at the end the cavity does not collapse because he has done this so many times the acceptable force is embedded in his muscles.

Sixty times faster than I can do it, sixty times. True, he has a machine to compress the sand, and an air blower for the loose sand whereas I do everything manually. True, everything is set up for efficiency; sand in an overhead compartment so he does not have to shovel it into the mold and the riddle and spruing tool are at hand. This is part of the explanation - but still - the years of repetition and experience are the real difference.

I have done that kind of manual labor in my life but it was a long time ago and I was never as skilled at that job as he is at his. I look at him with admiration and envy although I know he would switch jobs with me in an instant. At the end he looks at the camera as if to say, 'You got that bud'? I have to reply, 'No, I don't think I do and I don't think I ever will.'

75% off

In the never ending project to clean up my shop I completed the cabinets I was building under my workbench. I got a bunch of magnetic catches from eBay. Now what to use for handles? They are pretty expensive and I did not want to take the time to make some.

Thenmy wife and I were in a hardware store and passed a bin filled with cabinet hardware. $2.00 each but 75% off! That is a perfect price for a shop.

Men of Steel

An interesting video of building the San Francisco - Oakland Bay Bridge. From an era when men were men, steel was riveted, and OSHA had yet to be on the scene. Only a few years later Rosie was doing the riveting (and the welding), building Liberty ships at the Kaiser shipyards.

Diacro tooling

Several years ago I bought a Diacro #2 Bender. This is a beautifully made machine for bending steel bar and tube. Put the piece of metal between two pins, apply some leverage, and you have a bend. The Cadillac of benders is the Hossfeld and, IMHO, the Rolls Royce is the Diacro. Of course, if I had a Hossfeld I might reverse the analogy. All of the inexpensive benders on eBay are based on the Hossfeld design because it is much easier to copy.

My Diacro came with a roller nose and no tooling. Easy enough to make some pins but the roller nose is for curves, not sharp bends. Not only do I need a standard nose, I need tons of tooling. Want to bend square or round tube? Want to make sharp 90 degree bends? Want to make spirals? All of these require tooling that, similar to mills and lathes, can easily cost more than the machine.

Over the years I have had the bender, my tooling desire has grown. Finally, with my new mill, I can make it myself. The photo shows my first project, a standard nose which is sitting on the bender. Above it, installed on the handle is the roller nose.

Doing the math, I spent a couple of thousand for a mill that I used to make a tool worth a couple of hundred. Only nine more tools to go before I am even!

Rong Fu Report (RF-45) 4 : Chips at last!

I've been making chips - mild steel and aluminum - and am pretty happy. I can take big cuts in aluminum (1/2 " and 3/4" two flute HSS end mills) and decent cuts in steel (1/2" four flute). The gears make it easy to get the right speed and when I eventually figure out how to set an exact speed using the VFD with the gears it will be even better.

Since my old mill did not have a quill I was stuck with the typically inadequate translated instructions to figure out how to use it. First, the quill lock lever can block turning the quill fine feed wheel. The photo shows the lock lever in a vertical position and you can see if it gets moved any more to the right to the locked position it will run into the fine feed wheel. After a hint from a friend, I discovered the lock lever is on a spring so you can lock it, and then move the lever to another position.

Next I could not engage the fine feed. The coarse quill adjustment is similar to a drill press - three spokes sticking out of a wheel so you can turn it easily. At the center of the wheel is a knob and I turned it all the way out thinking it would disengage the coarse adjustment. After playing around I discovered it had to be turned all the way in, engaging the coarse adjustment with the worm drive of the fine adjustment.

I spent an evening milling a chunk of 3/4" thick steel getting into the rhythm of using the power feed and the quill. What a pleasure!

Rong Fu Report (RF45) - 3: Problems, problems

My old mill had a MT2 taper and the new one was R8 so I purchased a set of import end mill holders. None of them would go all the way into the quill and they appeared to hang up near the end of the groove. Either the groove was too shallow, or the pin inside the mill was too long. I sought out the help of a friend, MM. He had sent me a R8 spec and while the groove appeared pretty shallow it did, in fact, meet the specification.

We needed to tram the mill anyway so we decided to turn the head 90 degrees and take a look. Three large nuts needed to be loosened to rotate the head there was a small pin that prevented me from putting a wrench on the right hand bolt head and the nuts were tightened so much we had to use a rubber mallet on the wrench. The pin and a small nut is just visible above to the right of the large nut in the photo.

"What is this about?" I asked. MM showed no hesitation and unscrewed the little nut and pulled it out. Was it bravery on his part? Nah, just lots of experience working on mills. "It's a taper pin" he said and he carefully put it aside.

We rotated the head and there were two pins that fit inside the R8 groove to guide it. The one in the front was fine and the one in the back stuck out two hundredths. A little filing and every end mill holder in the set fit.

We rotated the mill back to apparent zero and he showed me how to tram it. It took only two tries and MM advised me, "This will never happen again. It always takes five or six tries to get it right." Before the final tightening he inserted the taper pin which fit perfectly. Apparently the Rong Fu folks tram the mill, drill a hole, and then insert a pin - a nice touch. In order to loosed the nuts holding the head in place we had needed to hit the wrench with a dead blow mallet. I think they were tightened so much at the factory so shipping would not change the tram.

Finally I was ready to make chips, but MM looked at the VFD and the motor wiring diagram and told me I had wired it incorrectly. My sequence was a plug to the disconnect, then to the VFD, which was wired to the mill switch. In other words, I was delivering 3 phase power to the switch, and then through the switch to the motor. The issue is electronic components in the switch that would eventually cause problems for the inverter, the motor, or both. In addition I could not use the inverter to change the motor speed in this configuration. The proper way was to connect the inverter directly to the motor.

The following weekend I rewired the VFD directly to the motor and discovered I could now change the motor speed with the inverter. Unfortunately this meant that the nice big red OFF button no longer worked and I had to use a tiny button on the inverter to turn the mill off. I knew there would be times I wanted a nice, big, hand off switch so I wired a large DPDT switch controlling all the power to the mill, and put it in a convenient spot. Eventually I will figure out how to wire the mill switches so they control the inverter.