# Drilling a tank for a horn unit



## the tinker (Nov 21, 2016)

Sometimes we have a tank that never had a horn unit ....and we want one.
I want to put this Murray [ third from left]  back on the road.  Tank is a little rusty as you can see and it never had a horn unit in it. First off I want to get rid of the surface rust in the paint so I will give it a bath in Oxalic Acid for about 20 min.  These wallpaper trays are great for soaking tanks and forks and are inexpensive.to purchase.
After the rust is removed I will drill the holes needed to install the horn.




Next I want to locate locate the holes to fasten an original Delta horn in place. For that you will have to have 
someone allow you to place a hunk of tape on their tank to exactly locate the holes needed to attach your  horn.
 just happen to have this spare tank handy.......



Place a strip of tape aligned on the edge of your tank . Start the tape at the front corner of your tank . 
exactly mark the center of the holes ......


Peel the tape off and place on the other tank in the exact position.


 With a "spring loaded" center punch [  available at Harbor Freight for about 4 bucks] mark your holes.
DO Not use your regular punch with a hammer as YOU WILL dent the tank.

Select the smallest drill bit required for the mounting holes and drill ALL your holes.


Using the smaller hole for a guide next use the larger bit you have selected for the horn button hole. 


Install your horn unit and your tank now has a horn. Done!



For the horns that have the Large horn Button typically on the side of the tank I do it the same way only I hesitate to use that large of a bit on thin sheet metal as it may catch and tear the tank wall.
I "fine tune" the hole to the exact size using the abrasive hole saw pictured on the far right. [ cheap & available at Harbor Freight]  Also a step drill bit can be used but these are not cheap, especially if you may only use it once.$$$$



Pictured at left above is the typical hole saws and spade bits. These bits work well for drilling through the sheet metal on a metal door but should not be used on your precious tank. While drilling through the un backed metal of your tank these bits will "walk" and you will really, really hate yourself.


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## bricycle (Nov 21, 2016)

Nice tutorial!


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## Andrew Gorman (Nov 21, 2016)

I've had good luck using step drills on sheet metal:
http://www.harborfreight.com/catalogsearch/result?q=step+drill


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## abe lugo (Nov 21, 2016)

Great tech post.  A good way to open up a hole to slightly larger is with the dremel diamond 1/4" bit.  It cuts most anything like butter.   Worth the money.  I have used it on many projects.


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## tech549 (Nov 21, 2016)

yes step drills work great ,used them on a colorflow tank worked great.


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## syclesavage (Dec 12, 2016)

Small holes drilled no bigger then 3/16 or less and a hand turned tapered reamer I get me from harbor freight works super in sheet metal making th exact hole diameter you want.


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