Here's a basic glimpse into how CAM (computer aided machining) is done. In this picture, the PC has generated a mill toolpath to cut the contours of the parts, then it has centerdrilled the parts, then finally it peck drilled and tapped the holes.

After this, the block of aluminum is flipped over in the vise and a new program is run which basically contours the other side, as it did the top.

 

wow u really got that stuff down pretty good. where do u go to do that?

 

This is done in a program called Mastercam X4. I'm a college student and I have plenty of access to the machines that can do this kind of work, so I thought it would make a good and useful project. The machine that will be doing the cutting is a Haas TM-1 (google it) and the lathe is a TL-1. I've never done a "production" run like this before, so it will be a good learning step. I expect the materials to cost about $7/part, but obviously there's plenty of other labor to do, such as running the bolts through the CNC lathe and pinning the nuts on the end.

And the picture above was done using just arbitrary dimensions -- once the real ones come in from Smitty I'll have to redo the CAM. But also I will be able to figure out which aluminum stock I need to buy, and how much it all will cost.

 

This is what I come up with. All measurements are in 16th of an inch. It's not a perfectly symmetrical piece though. One side comes to more of a point than the other. Does that make sense? Not the side with the mounting holes, but rather the long sides.

a 15/16ths
b 7/16ths
c 26/16ths
d 10/16ths
e 13/16ths
f 6/16ths
g 4/16ths
h 3/16th
i 7/16th
j 6/16th
k 55/16ths

 

Smitty - can't thank you enough. This will leave me with plenty of things to work on over the winter break. I understand what you mean about the long sides -- one I'll keep as a radius and the other I'll put into a point. My guess is that if they are both radiused, they interfere with the engine casting in some way.

 

Actually... are you sure about a-d (especially b)? 7/16" for the overall length of the tensioner seems short.

 

definitely interested, subscribed.

 

I needed more accurate dimensions so I bit the bullet and uninstalled my OEM one. I'm going to keep the outside profile of the original tensioner. It's big, so it will be nice and rigid. I'm going with a 5/16-18 thread to start with, because that's the tap I have. Downside is it will use an english wrench.

I'll try to run 4 of them this weekend, and let you know how they turn out.

 

definitly interesting. looking forward to seeing how they turn out. ill be one of the guinnea pigs for testing, been meaning to get one anyway....

 

sounds good, i'm down to be one of the guinea pigs as well. my cct is completely seized and the rattling is deafening.