View Full Version : Basic Fishmouth Cutting Tutorial

10-04-2011, 05:59 PM
This basic tutorial will cover cutting a simple 90 degree fishmouth into round and square tubing. A fishmouth is a semi circular cut taken at the end of a tube so that it can be joined to another round tube. In bicycle frame building, it is often necessary to cut several fishmouths into the ends of the steel tubing where the head tube or bottom bracket will be installed.




08-22-2014, 12:48 PM
no video or links?

08-22-2014, 01:01 PM
no video or links?

A lot of tutorials are on the top bar called DYI Tutorials. But I placed the link here for you.

08-22-2014, 07:31 PM
Thanks for bringing that one up DTD. Great tutorial(s).

Although I've seen it before, something important caught my attention, and that is for straight cuts, extreme uber accuracy can be obtained by teaming up the angle grinder loaded with a zip disc, AND a cheap 3"x36" bench sander. Cut the tube about 1/16" in front of the line mark or tape, then sand it to the mark while rotating the tube. That is, feed the tube with the left hand (near the belt), and rotate it with the right hand, which is held slightly behind, for short tubes, and further for long ones.

The tutorials are fantastic, and brilliantly make use of less for more. Kudos to Brad and others who have made AZ a great place.

08-23-2014, 09:05 PM
Thanks for the ideas for cutting fishmouth joints. Let me add another to the mix: The method I prefer is to use a bench grinder with the wheel dressed to a circular arc. Not my idea, I learned it from folks building airplanes.

So if you have a bench grinder and a dressing tool, you might give this a whirl. It's fast.


09-30-2016, 05:20 PM
I bought a set of hole saws from harbor freight to cut the ends of tubing and pipe and this works well so far....I use my drill press..................I see this trick on youtube..............

I bought a harbor freight fountain pump 10.00 and have cutting fluid pumping from a turkey roaster up and onto my spinning holesaw to keep it cool and so it does not lose it's temper and hardness and get dull....

the fluid falls back down into the roaster pan and this seems to work good for me........the tubes are notched really nice this way.......................

04-13-2018, 02:35 AM
will check that out