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Harold Hall

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The CES drawings quote a plus tolerance of 0.05mm on one and a similar minus tolerance on the other. This could result in a gap of 0.1mm between two faces if the other two were held together. Because of this, I felt that the lugs, and possibly the table itself, would be called upon to bend if tightened over enthusiastically.

 

To overcome this, I chose to increase the dimension between the two outer lugs by nominally 2mm and similarly decrease the dimension across the two inner lugs. This gave a nominal gap of 4mm which I filled with large washers whose thickness was adjusted to just fill the space, more about that later. The viewer can chooser to adopt this method or go with that on the CES drawings, in either case the methods will be the same.

 

Once more mount the castings vertically and this time machine the outer faces of the lugs, doing this for both castings, Photograph 6. Follow this by machining their inner faces by stepping down the cutter a few millimetres at a time, Photograph 7. This is where I envy workshop owners who have a horizontal machine but as these are very much in the minority in the home workshop. They could of course also machine the outer faces of the lugs, in all a much easier process.

 

Having said above that the machining is at the rough stage, I would suggest that machining the lugs can be final with these operations. In this respect, if you adopt my hinge pin method, full details later, you will need to reduce the width across the outer faces of the base casting so as to keep the head of the screw within the length of the base.

 

However, photograph 7 shows that the result is one having a step at each level that I dropped the cutter to. This though is not due to me traversing the table slightly for each level but due to my tipped cutter cutting slightly deeper at the end nearest the shank than at the outer end. I had initially, before I removed the cutter to measure it, thought this was due to the characteristic that a straight edge tip will cut a convex surface unless the edge is in line with the spindle's axis. That is with no positive or negative rake.

 

If you find this comment surprising see Sk. 1 which shows, albeit exaggerated, that the radius at which the cutter cuts varies along the tip's length. I did also draw out the situation for my cutter, allowing the CAD program to do the mathematics for me, and found that the convex nature of the surface cut would be 0.115mm high. The sketch is of course exaggerated.

Metalworking

Workshop Projects

Tilting angle plate, Adjustable angle plate, Machining
Tilting angle plate, Adjustable angle plate, Machining
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