Drilling hole thru mast for spreaders

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Drilling hole thru mast for spreaders

Postby s vernon » Tue May 28, 2013 12:14 pm

We all have to drill this hole nice and square if we are making a rig using a teardrop mast. I am wondering how people make sure they get it square and am offering one possible way. I read Rick West's site - EC12.info - on the subject and he said that it is easy for the drill to wander as it starts to go thru the second mast wall.

I am thinking that I can attach a couple of RMD gooseneck fittings to the mast, shim them a bit on one side, lay the mast on the my drill press surface and hold it down, and that should give me a shot at drilling the hole square thru both sides. I will try some practice runs on B rig mast leftovers. For anyone drilling this hole it is a good idea to read what Rick has written.

The mast I am currently working on already has had 2 bad spreader holes drilled in it, one cockeyed vertically and the other radially. Third time's a charm. Glad I backed away from it and gave it some thought. Cockeyed vertically?

Any other suggestions?
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s vernon
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Re: Drilling hole thru mast for spreaders

Postby Chuck Luscomb » Wed May 29, 2013 2:21 am


I use a 2x4 which is about 12" long. I needed something to support the mast and hold it in place 90 degrees to the drill press. So I took the 2x4 and ran it through the table saw a number of times to create a half teardrop mast groove down its length. Once I had a shape I liked and the goldspar mast fit nicely, I took a length of G 10 fiberglass sheet and screwed it to the 2x4 which would insert into the luff grove on the gold spar mast which would further secure the mast in the block and hold it at 90 degrees.

When I drill the spreader holes, I use a .064 OD drill bit which is the OD of the spreader rod I use. When I put the drill bit in the drill press chuck, I choke it up or in other words, i secure the drill bit so that only enough drill bit is exposed to make it through the mast. That way, the drill bit is not as flexible and will not wander when it hits the mast. I also use blue tape to mark the locations on the mast where I want to drill. The tape prevents the drill bit from walking when you start the first hole.

Now, once I have drilled through the mast with the .064 bit, I take a length of rod and stick it through the mast and sight down the mast to see how I did. Usually it is square to the mast and is not lop sided but not always.

So how do I fix it when it is not quite right? I take another drill bit the OD of the spreader tube itself and I drill the hole again being careful to make the necessary corrections to get this hole perfect. Now I check it again with spreader tube to see if it is right. If it is, I take the spreader tube and I stick it in the hole and CA glue a piece in place leaving a hare sticking out on both sides of the mast. When dry, I use a die grinder to trim the excess and get it flush with the sides of the mast. Now my standard spreader tube will fit in the new mast tube and will be nice and straight.

Hope this helps,
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Re: Drilling hole thru mast for spreaders

Postby Bigjake » Thu May 30, 2013 11:12 pm

Here is a method I have used on many occasions:

a. Mark the location of the spreaders on each side of the mast. Measure from the luff slot forward and from the base upward. Using a sharp punch, mark the locations with a light punch.
b. Drill a pilot hole through each location separately using a smaller drill bit than the final hole.
c. Drill a final hole through only one side. With the drill stopped, wiggle the drill bit inside the hole hunting for the opposite pilot hole. You'll know when you find it. Once located, drill the other side. Make sure to place a wooden backing board against the mast when drilling the second hole.
All of the above may be done using a hand drill, no need for jigs or whatever.

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Re: Drilling hole thru mast for spreaders

Postby ohiolyons » Tue Jan 14, 2020 1:02 pm

Put a short screw back in the unused holes. It the screw head is in your way put the screw in with lock-tight and file off the head. The hole is a weak spot because it can distort/collapse. A screw in the hole prevents this.
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