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ronh72c10 05-04-2005 10:09 AM

DIY Aluminum Hard Line Clamps
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Here's how I made a set of aluminum hard line clamps for my tranny lines. The method is pretty low tech, I needed a drill press and belt sander, but I could see it being done with a regular handheld drill and a file or sanding block. These were made to fit a 5/16" tube but with different washers (more on that later) you can vary the tubing size or overall thickness of the clamp itself.

I imagine alot of people could free hand the profile of these clamps, I have no such skill so I used a little trick to make these in a repeatable fashion. Basically the secret of these is to choose a washer that has an outside diameter that corresponds to the curve of the edges and has an inside diameter that is the same size (or smaller) as the tubing you're using.

For these clamps I used 1/4" washers that had an ouside diameter of a little less than 3/4" and had an actual inner diameter of 5/16". There's no reason to use this exact size, for that matter you could use a bearing or "machinist's filing buttons" for this, the washers were low tech and cheap so I used them.

ronh72c10 05-04-2005 10:10 AM

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I bought some aluminum flat bar 1"x3/8" by about 24" long, it cost about $8. If you don't want as deep a clamp you could certainly go smaller than 1". 3/8" is the critical dimension since it is approximately 1/2 of the 3/4" washer diameter. You don't want to go much thicker than 1/2 the diameter of the washers since you just end up sanding it off and that gets tedious.

Cut two pieces of bar approximately 1-1/2" long, mark a spot centered in the top piece and drill a 7/32" hole (1/4" tap size) through both keeping them clamped down and aligned. Too make it easier to bolt together I tapped the bottom of the clamp for a 1/4" screw. The top was drilled out to 1/4" and then counter sunk enough so the head of the bolt I used was below the surface of the top, I also cut the screw down such that it didn't protrude out the bottom. Dont' forget to deburr all holes so things clamp together tightly.

ronh72c10 05-04-2005 10:10 AM

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Bolt the two pieces tightly together and mark on the side where you'd like the tubing to go through, use the washers as guides for a good location. Clamp the pieces in a vice and drill the holes, aiming for the seam between the two pieces, make sure to start out with a small drill bit and work your way up to the final size. (5/16" in my case) Deburr the holes from either side.

For the first two clamps I made I actually seperated the two pieces and used a file to make a groove to guide the drillbit, I tried one without doing this and it turned out fine, your mileage may vary.

ronh72c10 05-04-2005 10:11 AM

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Using a long bolt (5/16"), place alot of washers on either side of the block and loosely bolt them on, the washers should rotate freely but not have alot of side play in them, use another nut to lock the bolt in place while still making sure that the washers can rotate. I used alot of washers because they tend to be slightly irregular, and using alot tends to average out the shape to a rough circle.

Finally using a belt sander I wore down the edges until the washers started contacting the belt, they keep you from going too far since they rotate and as a result wear alot more slowly than the aluminum. I started out with a 60 grit belt and then finished with a 120 grit belt. You don't necessarily need to use a belt sander, you could use a wide file or flat sanding block, just always go in a direction such that the washers will rotate.

After the shape was pretty much done I took the washers off and knocked down all of the sharp edges.

Polish and you're done. One note on polishing I used a green abrasive, but didn't wear a face shield, by the end of the evening I looked like Herman Munster. :) Use a face shield!

Also I decided to only use the halves to hold the tubing against the frame, but if you use the two pieces together you may have to sand the inner surfaces to clamp the tubing tight.

This should be adaptable for almost any size of tubing, you could also use this technique for more than two tubes. Have fun!

chief bobber 05-04-2005 05:30 PM

First rate work! I think you did a beautiful job of custom fabricating these pieces, but I think you need to take it just a tad further to avoid the reaction between aluminum and the steel. You need to insulate between them some how. Even a coating of some kind will work. Anything to create some kind of barrier between the two metals.
Keep up the good work, KC

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