Horizontal Boring: Getting the holes centered in the edges of boards

pennview · Post by **pennview** » Mon May 09, 2011 10:24 am

If you place a piece of masking tape on the surface of the saw table and then add a center mark on it where the center of the bit enters the stock, you can then use this mark to align your stock for hole spacing, rather than trying to center a bit on your marks on the stock. It might take a couple of tries to get that mark on the tape in exactly the right spot, but when you do it's quick and easy to get get good alignment for your dowel pins.

One way to get this centering mark on the tape is to use a large bit (the bigger the better to prevent the bit from flexing or drifting off course) and bore a hole in the edge of your stock (this doesn't have to be the stock you're using -- you could use something like a 1" bit drilling into a piece of 2x4). Now use a square to transfer the edges of the hole down to the tape and then use a divider or compass to find the center point between those two marks. You can then install your dowel-sized bit and drill your stock precisely.

pennview · Post by **pennview** » Mon May 09, 2011 10:24 am

If you place a piece of masking tape on the surface of the saw table and then add a center mark on it where the center of the bit enters the stock, you can then use this mark to align your stock for hole spacing, rather than trying to center a bit on your marks on the stock. It might take a couple of tries to get that mark on the tape in exactly the right spot, but when you do it's quick and easy to get get good alignment for your dowel pins.

One way to get this centering mark on the tape is to use a large bit (the bigger the better to prevent the bit from flexing or drifting off course) and bore a hole in the edge of your stock (this doesn't have to be the stock you're using -- you could use something like a 1" bit drilling into a piece of 2x4). Now use a square to transfer the edges of the hole down to the tape and then use a divider or compass to find the center point between those two marks. You can then install your dowel-sized bit and drill your stock precisely.

pennview · Post by **pennview** » Mon May 09, 2011 10:25 am

If you place a piece of masking tape on the surface of the saw table and then add a center mark on it where the center of the bit enters the stock, you can then use this mark to align your stock for hole spacing, rather than trying to center a bit on your marks on the stock. It might take a couple of tries to get that mark on the tape in exactly the right spot, but when you do it's quick and easy to get get good alignment for your dowel pins.

One way to get this centering mark on the tape is to use a large bit (the bigger the better to prevent the bit from drifting off course) and bore a hole in the edge of your stock (this doesn't have to be the stock you're using). Now use a square to transfer the edges of the hole down to the tape and then use a divider or compass to find the center point between those two marks. You can then install your dowel-sized bit and drill your stock precisely.

JPG · Post by **JPG** » Mon May 09, 2011 11:03 am

algale wrote:Flex, twist. Call it what you will. But the table does have some slop in it when it is just supported on its posts/trunions.

And how does that contribute to the vertical positioning of the horizontally bored holes?

Maybe your tables are too large!:D

I just have not experienced vertical error due to table post movement.

algale · Post by **algale** » Mon May 09, 2011 11:47 am

pennview wrote:If you place a piece of masking tape on the surface of the saw table and then add a center mark on it where the center of the bit enters the stock, you can then use this mark to align your stock for hole spacing, rather than trying to center a bit on your marks on the stock. It might take a couple of tries to get that mark on the tape in exactly the right spot, but when you do it's quick and easy to get get good alignment for your dowel pins.

One way to get this centering mark on the tape is to use a large bit (the bigger the better to prevent the bit from flexing or drifting off course) and bore a hole in the edge of your stock (this doesn't have to be the stock you're using -- you could use something like a 1" bit drilling into a piece of 2x4). Now use a square to transfer the edges of the hole down to the tape and then use a divider or compass to find the center point between those two marks. You can then install your dowel-sized bit and drill your stock precisely.

Great tip, thanks!

algale · Post by **algale** » Mon May 09, 2011 11:50 am

JPG40504 wrote:And how does that contribute to the vertical positioning of the horizontally bored holes?

Maybe your tables are too large!:D

I just have not experienced vertical error due to table post movement.

I'm not certain that the flex/twist did contribute to the vertical misalignment in the horizontally bored holes. I only know that when I connected the main table to an extension table with the extension tubes, I got a much better result in terms of alignment. Could be a coincidence. On the other hand, I imagine it wouldn't take very much flex/twist in the table to deflect the drill bit very, very slightly.

JPG · Post by **JPG** » Mon May 09, 2011 2:08 pm

algale wrote:I'm not certain that the flex/twist did contribute to the vertical misalignment in the horizontally bored holes. I only know that when I connected the main table to an extension table with the extension tubes, I got a much better result in terms of alignment. Could be a coincidence. On the other hand, I imagine it wouldn't take very much flex/twist in the table to deflect the drill bit very, very slightly.

Maybe I have been boring 'sloppy holes' and letting the clamps align the surface. Lately I have used biscuits instead.

dusty · Post by **dusty** » Mon May 09, 2011 3:16 pm

algale wrote:I'm not certain that the flex/twist did contribute to the vertical misalignment in the horizontally bored holes. I only know that when I connected the main table to an extension table with the extension tubes, I got a much better result in terms of alignment. Could be a coincidence. On the other hand, I imagine it wouldn't take very much flex/twist in the table to deflect the drill bit very, very slightly.

It moves and that is all it has to do to effect alignment. How this movement might effect alignment is impossible to predict but all you have to do is push a little here or there, while the Mark V is set up either in horizontal or vertical mode, and watch the table. It is not rock solid.

As a Mark V owner, you must be aware of this and take the appropriate precautions.

Tieing the extension table into configurations is the most effective way I know...along with telescopic legs now and then.