Topic: metalworking help please

[eigenvector]

I'm trying to manufacture some connector nuts and am really having some problems drilling the stock.

Have aluminum bar stock, 3/4", and I need to drill a 12.5mm hole in the center.  Finding the center is no problem, that's an easy geometry problem, the problem I am having is clamping it securely enough in the drill press so that it doesn't wobble or more importantly deform while I'm drilling it.  The last thing I want to do is crush the hole because I have to exert so much force to keep a round bar securely mounted.

[calj737]

Chuck it in a lathe, thats the best way. Short of that, you need to create some type of collet to "squeeze" the round stock while in a press. Maybe you have sufficient material that would allow you to flatten two sides so the rod can be held in a vise?

[eigenvector]

I tried grinding, was impressed by how difficult it was to grind aluminum.  Seemed like it wanted to foul the grinder wheel right away. 

Don't have a lathe, well I do - a wood lathe but the collet for that isn't large enough to accommodate 3/4" stock.  That said, a collet is most definitely the solution - just a matter of having one available for a drill press.

Do you think lining the vice with rubber - say from an inner tube, would provide enough friction to hold the stock tight.

[70CB750]

Maybe some custom jaws? 

Could be two pieces of wood with a V-cut in the middle for aluminum.

Lathe is the best, as Cal says or use a lathe chuck under a drill press.

[70CB750]

Something like this:

[calj737]

Are you trying to make an upper motor hangar spacer?

[eigenvector]

No, it's not even for my CB550.  Need to manufacture bolt extenders for the shocks I have for another.  The shocks are aluminum, but they inexplicably used 14x1.25mm threads for the swingarm mounts.  Those threads are impossible to find - so I'm manufacturing my own.  I already have a test piece made - wasn't that difficult, just the hole was off-center.  But it was just a test piece.

Prokop - that's exactly what I need - can't believe I didn't think of that before.  I'll take a run down to a metalworking supply place and see if they have something workable.

[calj737]

So you're basically making an 18mm mounting boss and then going to screw a 14mm bolt into it? And the extension is part the shock will bear on? If so, I question your material choice. Unless the aluminum sleeve is supported all the way thru by a grade steel bolt, and is only to fit within the shock eye...? If so, why internally threaded?

[eigenvector]

Well I'm not worried.  I don't have the time to relate all the details of the project, and I've been a structural engineer long enough to know the materials and what they can take.

I appreciate the help Prokop and Cal.

[Steve F]

Well I'm not worried.  I don't have the time to relate all the details of the project, and I've been a structural engineer long enough to know the materials and what they can take.

I appreciate the help Prokop and Cal.

I see you're in Seattle?  Can you send me a detailed sketch with dimensions of what you're trying to make? Perhaps I can make them for you (as long as it's not a bunch of them, one or two is fine).  I've been a toolmaker most of my life and might be able to help.
Steve F

[eigenvector]

I appreciate the offer Steve.  This is something that I feel like I have to do. 

I actually just finished.  Manufactured a V-block to hold the bar, then drilled it out.  Tapped it and that's that.  The dies haven't come in yet, so I haven't been able to create the bolt yet.  That will be trivial now that I have the V-block.

I don't think I'll be teaching machine shop anytime soon though - at least I didn't burn myself, cut myself, or otherwise put my eye out.

[Steve F]

Well, good to hear you're gaining on the project.  The offer still stands if you want.
Steve F