Having been unwell for a few days, I finally got out into the workshop today. As always I get a little frustrated when kept out of the workshop, and the first session back is usually short, so I decided to have a go at a cam turning job.
I needed to make a turning fixture and bolt, then take a trial cut on a cam blank made before I was unwell. As it turned out I overdid it (no surprise!) because I wanted to complete the trial turning, to see what effect the method of turning made.
I have been using the Home Model Engine Machinist forum for a short while, and recommend it to any model engineer (link on links page www.mikes-models.com) as they are very helpful particularly to new model engineers. One of the forums ideas I like is the team builds they have. This is where a group of people register their interest in building a model engine and then the parts required are split up between those involved.
I registered my interest late but they made room for me and asked if I would be interested in making the cam and a lever arm. I was happy to have a go at the came and may do the lever but felt that it would be better to do the cam first, then if the lever arm wasn't done, I could volunteer again. There are 15 engines being built and 13 members are involved, with one of the engines going to a museum and the second to charity. Although the total engine numbers is a little confusing, as my addition to the team build came late.
So onto the cam task itself. This the first time I have had a go at turning any cam, even just a one lobe one like this build calls for. Therefore I decided that it would be best to make a trial one first then work out a production methodology. The turning of the cam blank was completed with little problems. The half methodology bringing the finished parts to within 0.001" for all three diameters.
Making the turning fixture went smoothly as did the securing bolt. So it was over to the lathe and the first cuts taken. Getting it to the dimension required went slowly, only because I kept checking the diameter to ensure I did not remove more than I should. Once the diameter size was met the plans and methodology called for the top slide to be fixed. I achieved this by clamping but am not sure if this is correct. I will be asking the forum for their comments.
It was then required to the move the cam, by between 5 and 10 degrees and this is where I made a major mistake! However what I was doing is with the aid of a 360 degree protractor, the fixture was turned approximately 5 degrees and then another cut made. So I continued moving the fixture with not the expected outcome. After four or five cuts I decided to recheck the instructions and found where I had gone wrong. It was the cam that needed turning. Obvious in hindsight, but thats as much about my performance level after recovery.
To make the turning of the cam blank easier I thought if I photocopied the protractor and then stuck that onto the fixture, with a mark on the cam blank, it would mean I could measure the 5 degrees succesfully. I must say I was surprised when the photocopies came out on how good they were! Well after doing all of this work I felt I should stop before starting the new cuts. So the position I will be at for tommorow is to be able to start cutting straight away. The cam blank is ruined because of the problems above but there is sufficient metal to be able to find out if the system above works. If it does, then the next stage of finding some production tips will start because there are 15 to make!
Oh how I do enjoy the exercise though!
Some photo's to aid the text above.............................
THE MAIN PARTS - FIXTURE, SECURING BOLT AND CAM BLANK
THE FIRST ELIPITICAL CUTS......
READY TO DO IT PROPERLY THIS TIME! (I HOPE!)
For more information please goto http://www.mikes-models.com