Friday 7 June 2019

Cover plate for the motor bracket

It's a fairly simple part. Mates with the belt housing cavity on the motor bracket. To avoid the chamfer of the main housing resulting in a silly undercut, I've offset the cover perimeter by the width of the chamfer. 


The top ("inside") of the cover has a step for locating it against the main housing. 


So the top side machining operation involves facing off the surface, contouring the step and chamfering the edges. I've drilled the 2 fixing holes so that I can pick up the coordinates when I flip the part. Always think ahead!






Looks alright, although it's too flimsy to avoid nasty juddering. Rigidity of workholding is only part of the issue. I may also have been a bit ambitious with the depth of cut, so for the visible (exterior) face, I'll have to do better, particularly for the initial facing operation.

Same trick as before, importing the part machined stock as a mesh model. Then a similar face / contour / chamfer process. I've used tabs to hold the part. These can be cut through with decent side cutters and snapped off before cleaning up the face with a fine file.


Ready to go. Note the drilled holes. Obviously it's helpful to correctly identify the correct hole. I don't have any cyanoacrylate adhesive, otherwise the preferred method of holding the plate would have been the John Saunders method (blue paper tape on each part and superglue holding them together). Instead, I had to use double sided tape and hope I could finish the job before the coolant perverted the adhesive.


All done. Still held in place with the tabs and the double sided tape:


You can see that the adhesive has absorbed quite a bit of coolent, as it's gone all cloudy. Sure enough, the plate was barely held on...


Looks good to me. Bracket and cover plate - done!




Next - think about making up the yoke (ballnut bracket)....

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