Douglas Suazo

How to bore holes at a 36.6 degree angle...

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I'm baffled!  How do you bore a hole at a perfect 36.4 degrees into into railing posts?  I am installing horizontal balusters on outdoor wooden patio stair of which trying to build.  One rail has 6, 3/4" diameter balusters, 36" length going into treated 4x4 posts.  The bottom posts are already secured in the ground.  The top 4x4 posts - which are laying in the garage - will be bolted to the stringers and have yet to be installed.  I've determined that the angle of my balusters are at 36.4 degrees.  My problem is, how do I bore my 3/4" hole at that strange 36.4 degree angle?  Again, two railing posts are in the ground and two are laying flat in the garage.  How would you approach this?  

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Hi Tom, thank you so much for your quick reply.  I was thinking of making a guide block.  My question is, if a total of 24 holes have to be bored, how will the bore drill bit affect the block?  Wont the bit cut into the block guide hole (due to an imperfect handheld drill angle), distorting the hole, in turn, creating an incorrect angled hole?  Tom, I greatly appreciate you.  - Doug

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Drill bits aren’t great at cutting along the length of the bit. They can, but it takes a bit of effort. If you use a harder wood you probably won’t have any trouble. If you just have pine, you could make a couple or few guide blocks at the same time and then switch to a new one every so often. The longer (taller) the guide block is, the less likely the bit will distort the hole. 

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25 minutes ago, Douglas Suazo said:

Wont the bit cut into the block guide hole (due to an imperfect handheld drill angle), distorting the hole, in turn, creating an incorrect angled hole?  Tom, I greatly appreciate you.  - Doug

Read Tom’s carefully again. You might need a block to keep your big from skipping. This depends on the style of drill bit you choose. He, however, referenced a sight block alongside the angle you need, not a block you drill through. 

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A somewhat more cumbersome, but dead accurate method, would be to use a bench top drill press, tilting the table to the necessary angle in relation to the bit, and clamping the table against the back of the post. This usage emulates a magnetic base drill used for steel fabrication, or a chain-clamp drill used in pipeline work. A lot of trouble for your application, but if you want perfectly repeatable angled holes, it will do the trick.

Of course, you'll need help to hold the tool in place until it is clamped.

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The block will just be an eyeball reference-no hole in it, just a simple triangle.  Spade bits are good for starting such holes.  If the corners catch before the center can establish a good center hole, I regrind the bit.

After a good starting hole, almost any bit the right size will work, if it's long enough.   I'd avoid any self-feeding bit because they're too hard to stop where you want.  I've even used two drills, one with the good starting bit in it, and the other to finish the hole, so you don't have to keep switching bits.

With a few guide blocks made, in case you screw up one, a tape flag on the drill bit will let you know when to stop pushing on the bit when it gets to the guide block as a reference.

I have one rig that works like a little drill press, with two rods that it slides on, and a base sort of like a router base.   I haven't used it in probably over 35 years, and forget what it's called, but there are similar things on the market if you aren't confident in your eyeballing it ability.

For the holes that don't have to be drilled in place, I'd use a drill press.  Otherwise, it's not a job that requires  tenth of a degree accuracy.

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I find that drilling a small diameter pilot hole first is easier to keep straight when using a guide block as Tom suggested. The pilot hole guides the center point of a spade or forstner bit, making it less prone to wander.

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Thank you, everyone.  I used a drill press on the two "loose" 4x4 post and set the table and the proper angle.  The holes look pretty good but I'll know for sure later.  However, I'm still stuck on the lower posts, which are already secured in the ground.  I am now using a 13/16 bore bit.  Actually I have two - one is a speed bore and the other Forstner.  GRagatz...I looked into those "drill mates" and learned that they only go to up to 45 degree angles so I do not believe that device will work.  Nonetheless, thank you.  I'm made two jig blocks.  While I was able to capture the proper angle, I'm at the mercy of their shank length - please see pics.  I feel I'm on the verge of making it work but... still at a loss!  Thank you...everyone!

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Does the hole go all the way through? Unless ot does, and requires a tolerance somewhat out of character for the materials, you don't need the angle blocks to physically guide the bit. Just place them to use as 'sight lines', and use your eyes to align the bit with the block.

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Looks good to me!

The bottom end of those stringers look a little scary to me.  I would sister some reinforcement beside them.

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7 hours ago, Tom King said:

Looks good to me!

The bottom end of those stringers look a little scary to me.  I would sister some reinforcement beside them.

@Tom King just out of curiosity, why do you say that about the bottom end of the stringers? Because the bottom edge does not continue the full length? 

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Look at how the grain runs, and the only support is at the end.  Grain in the stringer, from the inside of the support 4x exits the surface before the next riser.  It would probably be okay for some length of time, but what is that length of time?  I always try to give support back towards the heal of stringers, as well as the outer end.

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