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Wednesday, 6 April 2011

Sunny Days and UAOs

It's said that a change is as good as a break.  After the five exams last week (Steam Propulsion, Motor Propulsion, Ship Construction, Marine Electrics, Marine Auxiliary Principles) nothing could be more welcome than two weeks of workshop.  

Since Monday, our group have been learning more turning on the lathes, while the other groups do welding, hand fitting or powerplant.  It's been a really enjoyable change, and I've just started the fourth UAO (if you remember, I mentioned our 'UAOs' last year - Useless Arbitrary Objects) since the beginning of the week, so it's going well.  Our first one was a simple stepped shaft, to demonstrate we could turn lengths and diameters accurately, plus facing off.  This had to be done in two stages - the first turning it down to one size, and the next making the diameters smaller again, but keeping the turned lengths the same.  These two stages were just to demonstrate we had the skills necessary.  


Beginning stages

My work plan, clipped to lathe for easy reference while I work

Final Result

For the second workpiece we used the first workpiece and turned it down to make it smaller.  We then added a female thread, a male thread, a taper, chamfers, and knurled it.  For this job we also had to practice mounting it in the four jaw chuck.  Getting the job exactly central in the chuck is crucial, and involves a process which is, I would guess, most similar to leveling a snooker table.  It seems difficult when you don't know how, but with some good explanation, and some precise turns on the chuck key, it all falls into place easily.  I completed this job on Tuesday.

Workpiece in four jaw chuck (DTI used to check workpiece in position correctly)

Drawing plus workpiece

Finished workpiece

After completing this on Tuesday, I began the third workpiece - this involved some new techniques not used before.  We had to use a grooving tool - used to create (you guessed it) grooves in the job.  This involved some logical and careful thinking to get the grooves in the correct place, as the general tolerance for the job was plus or minus 0.2mm - this is actually pretty generous though I think, considering the accuracy.

Turning in motion

Same again, different view

Initial lengths turned

Knurling completed

Knurling close up

Finished workpiece - it's a beauty

I finished this job quite late on today, but did get started on the fourth - the bearing plug and housing.  This is the most difficult job so far I think, probably due to the obvious fact that it is the fourth (!), but mainly the accuracy needed.  We will be creating two different parts: a bearing plug, and a bearing housing.  They need to fit together perfectly.  Hence, it's prudent to make them carefully and accurately.  It's already been a bit hairy so far, as I had to turn metal off the workpiece up to about 1mm away from the chuck (as I had so little material to deal with).  Any further and the chuck would have hit the tool - result: devastation!  However, it is still going well so far.  I'll let you know how that one goes soon.

Today must have been the best day of the year so far, weather wise - a significant change from yesterday's constant wind and rain.  It was amazingly hot, with little wind, and for breaks and lunch we were all able to sit outside on the beach of the Hamble, watching the yachts head in and out.  It made everybody feel fantastic, and due to our restoration of free time in the evening now the exams are over, Chris B, Chris T and I were able to head to The Rising Sun pub on the waterfront for a quick drink after finishing in the workshop.  We had a beer in the sun (it was still really hot even at 5pm) and relaxed for a bit.  It was fantastic, especially as it was one of those spur of the moment decisions to go there.