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miker
01-23-2009, 05:02 PM
Peter wrote in Sir John's thread:

"A trepan is a tool for cutting large discs from sheet metal. Very handy tool and surprisingly accurate I've found. Easy to make."

Here's one: http://www.enuii.org/risley/training...ing_tool_s.jpg

Peter, did you make that tool? If so, what does the "pilot" on the bottom fit into?

Is the cutting tool a long piece of round toolsteel ground on the cutting end?

Do you have a picture of the cutting tool shape?

Is there any problem/trick to getting the top and bottom support arms aligned so that the cutting tool is at 90 to the table?


That looks like a very solid tool!

I didn't want to hijack John's thread. The beauty of this BB is how one thing leads to another! :)

Rgds

Peter.
01-23-2009, 05:14 PM
No I didn't make it (I found that pic with google images), but I did make a quick-and-dirty one to cut a 110mm hole for a filler cap for my bike. It wasn't of the quality of that tool but it did the job. Unfortunately I butchered it for another fitting.

The basics are simple. The spigot in the bottom of the tool fits into a pre-drilled pilot hole in your workpiece and the top in your chuck or quill. For a cutter I simply ground a short parting tool from 1/4 HSS bar and mounted it vertically, held with a grub-screw. Mine didn't had just the one bar but the one in the picture would be much better.

Jim Caudill
01-23-2009, 05:29 PM
I couldn't get the link posted by the OP to work, but I found it anyway. Here's another attempt to show the tool. You will have to scroll down the page until you see the trepanning tool.
http://www.enuii.org/risley/training_school/tool_time.htm
http://www.enuii.org/risley/training_school/Trepanning_tool_s.jpg

Other trepanning tools:
http://i72.photobucket.com/albums/i183/Ferrofab/MVC-009S-1.jpg

miker
01-23-2009, 05:32 PM
Thanks Peter, I have one of the cheap "made in India" ones that sounds like the one you made. It has worked on plastic fairly well but I wouldn't like to push it too hard.

That one in the photo is built like a "Brick Outhouse" :)

I wonder if it would be worth trying to balance it, by putting some sort of sliding arm/arms out the opposite
side? Maybe at slow speeds not necessary?

Rgds

miker
01-23-2009, 05:39 PM
Thanks Jim, that was an interesting site.

I think that "chain wrench" would be illegal here. :)

Rgds

PS Ok thanks for adding the photo of the other trepanning tools. The one on the Left is exactly a more solid version of my bought one.

Now, how was the Square hole made?? :)

Peter.
01-23-2009, 06:37 PM
It's almost identical to the one I made. I drilled a round hole and used square stock with a grub-screw. Not too bad if you keep the cutting bit short.