Rebarreling and Home-Shop Machining

This video belongs to the two topics below.  I might as well show the whole unedited verstion as it tells the tale of doing big work on a little machine.  There was also a lot of decision making on how to make this hole.  I have done similar size (3 inch) holes in flat Aluminum 1/2 inch plate.  I took a bimetalic hole saw and cut a disk out.  Now this type of hole saw does not like cutting more than 1/8 inch deep or so.  It just will not clear chips well, but with plenty of force it does the job if you cut from both sides of the plate.  Then I finished the hole up with a boring head.

Because of the angle of the hole, the hole saw will not cut all the way through this 1 inch ABS.  So now the question was to use a large wood cutting Forstner bit undersized and bore to size or just use the 2 inch and hope for a good finish.  Well a good finish was produced boring to full size.  We had to stop once to clearchips.  Had we grabbed that first tail and pulled rapidly this might have been avoided.  The mill spindle stalled once or twice.  I tightened the belt to cure this.  The power feed did not stall and was adequate for milling this plastic.  If not we would have given a hand asist.

Here is the sketch that I made to determine the angles. What I wanted is minimum angles so that the hose sections would clamp well to the throttle bodies and to the inlet runners. I offset the the runner pipes to the right in the diagram 1/4 inch to reduce the angles. The distance from head to TB is 2 inches. I measured in cm the center of the throttle body assembly to the center of each individual throttle bodies. These numbers are at the top of the sketch. I put an arrow where I wanted the short pipes to end up. Then I drew in 2 inch pipes with 1/4 inch walls. I could measure the angles directly from the sketch as raggedy as it is. The offset will be removed by porting the plastic so that there are no steps near the head. At the Throttle bodies the pipes will be ported to make them a little more round and open them up to near 2 inches. The 1.5 inch ID of the pipe can be opened up slightly to match the 42 mm butterfly diameter. More detail on request. The sketch was full size and showed only two of the four throttle body runners. 

John

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