Author Topic: How to get good fishmouth joints  (Read 5749 times)

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TarheelRick

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How to get good fishmouth joints
« on: March 19, 2018, 09:38:25 AM »
When building roll cages and frames I like to fishmouth the ends of the rods and tubes for a cleaner fit and a better glue joint.  However I have a difficult time getting the fishmouths centered in the ends of the tube (.080 and .100 size).  I also have a difficult time getting each end fishmouthed on the same plane, in other words they are quite often a few degrees off from being parallel with each other.  I use a small round jewelers file for this work.  Does anyone have any ideas on how to get better, more even fishmouths?
When I win the Powerball I will switch to the real ones.

Lefturns75

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Re: How to get good fishmouth joints
« Reply #1 on: March 19, 2018, 11:18:27 AM »
Rick, it may not help you much but I use a round file, maybe a chainsaw file, the same Dia. as the tube I am using.  I lay them both flat on the work surface and move the tube along the file until I get the cut I need.  I check the fit or angle often while doing so.  I mark the tube much the same way you would if doing the real thing.  I hope this makes sense, I don't have a pic.

Olderndirt

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Re: How to get good fishmouth joints
« Reply #2 on: May 30, 2018, 10:51:36 AM »
I don’t use tube for starters, I use rod instead. I cut it with a rotary leather ponch, and clean it up with a round needle file. I give the joint a coat of ProWeld liquid cement, let it sit a few minutes, give it another light coat, and push it together until the softened edges bulge a little to form the welding seam.

  Olderndirt

TarheelRick

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Re: How to get good fishmouth joints
« Reply #3 on: May 31, 2018, 06:55:59 AM »
These are some good tips.  Will give them a try when I get back on the bench.  I especially like the idea of the "double-glue" in order to get a weld seam.  That will definitely come into play when I build the cage and other tubing on my no-fender convertible racer.
When I win the Powerball I will switch to the real ones.

Rich Sipos

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Re: How to get good fishmouth joints
« Reply #4 on: June 01, 2018, 08:04:55 AM »
I to use rod  and also had the issue with the fish mouths not being in the same plane! I tried  taking a piece of wood and filed a grove into it, then file a V notch at the end of the grove and  took a small nail and pushed it into the grove so the rod is a little above the edge of the wood into the V notch. I then fish mouth one end of the rod cut to length then put the rod in the grove , fish mouth against the nail with the cut end a little above the end in the V notch hold the wood with the rod and file the new fish mouth, both ends line up! You will have t6o move the nail for different length bars. Enjoy
 Rich

421sd

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Re: How to get good fishmouth joints
« Reply #5 on: June 03, 2018, 10:32:57 AM »
I use .080 rod. I start by making a center cut on the end (by eye) with a fine blade razor saw. I take the blade out of the handle and use just the blade, so I can control it better. Next I use a very small triangle file to enlarge the saw cut. Then I use a round file, one size smaller than the tubing to finalize the fish mouth. To achieve the weld bead look, I apply Elmers white glue, sparingly around the joint.

Maybe not the best way but it works for me.........
Born in Nashville, Tn. grew up attending races at Nashville Fairgrounds Speedway.