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Drill press alignment confusion

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Forum topic by PeteMoss posted 08-06-2014 01:19 AM 617 views 0 times favorited 12 replies Add to Favorites Watch
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PeteMoss

207 posts in 2122 days


08-06-2014 01:19 AM

Topic tags/keywords: drill press angle problem

Hey guys,

I have a question about my drill press that I can’t believe I am having so much trouble with. I have a square piece of wood 12” X 12”. I have laid out two holes on it near the center offset by about 2 inches. I want to drill those holes on a 5 degree angle relative to one dimension (length we’ll call it).

I had thought that I could simply angle my drill press table to 5 degrees and drill the holes. The problem that I am running into is that if I angle the table to 5 degrees, then the piece of wood still needs to be clamped to the table so that it is dead parallel to the edge of the piece. In other words, since the table can be rotated 360 degrees, I have no guarantee that the 5 degree hole will line up pointing in the direction / in line with the edge of the piece.

I am having a hard time trying to figure out how to align the table to make sure that it is perfectly straight or at 0 degrees (rotationally) prior to setting the angle. Can anyone help me with this setup.

Thanks

-- "Never measure......cut as many times as necessary." - PeteMoss


12 replies so far

View shampeon's profile

shampeon

1376 posts in 835 days


#1 posted 08-06-2014 01:35 AM

If you’ve got a digital angle finder, or an iPhone, you can use it to set the position of the table to 0 degrees on both axes before putting the piece on it. Then you set the y angle of the table, verify it with the angle finder/iPhone, and finally put the piece on, and do a final verification of the angle before clamping it down.

The iPhone has a Compass app that doubles as an angle finder.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

View Beatnik's profile

Beatnik

33 posts in 53 days


#2 posted 08-06-2014 02:04 AM

I might be misunderstanding completely, but if you make sure the bit is directly on center with the hole on the table (could use a larger bit to be more exact) it should be right if the table and chuck are accurate to each other. When you tilt the table it should be right ?

You could add a fence parallel with the table so you can slide the piece to hit your mark. If you mark a line parallel across the work piece your bit should hit center on the line when the table is tilted both left and right.

View mantwi's profile

mantwi

312 posts in 548 days


#3 posted 08-06-2014 04:08 AM

Clamp a fence to the table to establish the distance from the edge of the board to the center of the hole. Then drill a hole in a sample piece that is also clamped down with the table tilted to the desired angle. Measuring from the center or either end of the hole depending on your preference cut the sample end to the desired length then put it back on the table and lower the bit into the hole. Clamp it back to the table and attach a stop block to the fence at the end of the board, this will give you repeatable duplicate holes without having to resort to higher math to do it. It’s difficult to hit the hoped for center of a large (I’m assuming your talking forstner bit) hole accurately and using this set up will eliminate the trial and error aspect of finding a solution. Since the hole will no longer be round but a parabolic radius it will be longer than it is wide, how much depends on the angle of approach. If your a glutton for punishment here’s a link to the math involved in solving the problem, just reading it made my head hurt.
http://math.stackexchange.com/questions/279457/how-to-find-focal-radius-in-parabola

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Yonak

274 posts in 173 days


#4 posted 08-06-2014 04:16 AM

If you cut a support piece (or two strips, say) that is at 5° and put your piece on it, lined up with one edge, then it doesn’t matter how your piece is oriented on the table as long as it is beneath the drill. In other words, line your piece up on the ramp piece instead of on the drill press table.

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JoeinGa

3229 posts in 659 days


#5 posted 08-06-2014 11:38 AM

The ramp idea sounds like a simple solution (because I dont have a cell phone ,,, large audible GASP from the audience! )

And I’d like to ask mantwi … Are you related to Sheldon Cooper (of the Big Bang Theory) ? Because I honestly read your answer 3 times and for the life of me I cant seem to follow it :-)

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View PeteMoss's profile

PeteMoss

207 posts in 2122 days


#6 posted 08-06-2014 02:33 PM

Hey guys. Thank you all for your comments and advice. Life would have been much easier if Grizzly would have but some markers on the table and the arm that holds it to indicate when the table was rotated to its square on position.

Thinking about it, I do believe that I could use my Wixey digital angle gauge to determine when the angled table edge is pointing to its most vertical position.

In the end though I think Yonak’s idea to just incline the work rather than the table makes a ton of sense. That way it doesn’t make any difference what the work/table is doing rotationally.

Thanks again.

-- "Never measure......cut as many times as necessary." - PeteMoss

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timbertailor

533 posts in 76 days


#7 posted 08-06-2014 02:37 PM

Just clamp a straight edge to the table that your work can rest against when the the table is turned at an angle.

-- Brad, Texas, https://www.youtube.com/user/tonkatoytruck/feed

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MrRon

2830 posts in 1895 days


#8 posted 08-07-2014 03:10 PM

Mantwi, The hole will not be elliptical. It is still a round hole.

View mantwi's profile

mantwi

312 posts in 548 days


#9 posted 08-07-2014 11:00 PM

MrRon: any hole not drilled square to the surface will be an ellipse. At 5 degrees it may not be very pronounced but it will not be round. I was wrong to call it a parabola because a parabola is half of an ellipse. The only reason I know this is because I ran into the problem about 30 years ago when I was building a house that had an elliptical radius in the porch ceiling that continued into the house. I had the task of building the radius into the 12/12 pitch roof so the ceiling line matched. As much as I hate it I had to study the math. Any radius that is at an angle other than 90 degrees is an ellipse and if you will google “conic section” you will see how it works.

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Grandpa

3129 posts in 1327 days


#10 posted 08-07-2014 11:56 PM

mantwi, a drill cannot make an elliptical hole….only round. The opening at the surface is elliptical but only when you change the angle of the surface back to level. IF the board is at a 5 deg angle then the side of the drill will strike the board first and this give the illusion of an elliptical hole. A machine going round and round with a fixed quill in the drill will only make round holes. Think about this a minute and you will see it. When the change the surface of the board or whatever you are drilling into from 5 deg. to level it will appear to be elliptical but that is surface only. IF you can get your eye on the centerline you will see a round hole.

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mantwi

312 posts in 548 days


#11 posted 08-08-2014 02:42 PM

Grandpa: Obviously a round bit will cut a round hole but that isn’t what I was talking about. The question at the beginning of the thread was how to find the center of a hole that is drilled at an angle other than 90 degrees to the surface and at the surface the hole will be elliptical. How much is a matter of how great the angle is. You and I are saying the same thing here. I am talking about the appearance of the hole at the surface. Once it gets beyond there the angle of approach has no effect and the hole will be round.

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Grandpa

3129 posts in 1327 days


#12 posted 08-08-2014 03:33 PM

I worked in the engineering section for a large manufacturer. We never and I mean never dimensioned anything to a centerline of a hole because you can’t find it. If you can’t place your finger on it, it doesn’t exist. It is imaginary and you can’t find it. It is possible to put a mandrel in that hole and find a center of the mandrel in some cases. You can find the edge of the hole so work from there. That is positive.

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