Hole Drilling

[Rita B.]

So much to learn and when things crop up, this is my go to place for answers.  From time to time in a project or house hold repair, I have been required to drill a hole.   I am aware that there are hole saws, spade/butterfly bits and forstner bits.  How do you choose which type to use and what are the differences between them?

[Ken Darga]

When drilling a blind hole, it is necessary to lift the drill bit often, to allow the shavings/chips, and the like, to be removed from the material---whether in soft or hard materials.

[Ken Darga]

Forstner bits are intended to drill flat bottom holes.

They can also be used to drill "thru holes" in wood.

Place a "backer board", or the like, behind the work-piece, to avoid tear-out on the work-piece back side.

Lift the drill bit out often, to allow the removal of the wood chips.

[Ken Darga]

"Brad-point" drill bits, are intended for drilling into wood and soft material, like plastics---

it features a small point at the drill bit tip.

The brad-point acts like a center punch mark, when one starts to drill a hole.

Press the drill point tip into the work-piece, to make the center punch mark, before proceeding with the drilling operation.

[Ken Darga]

Hole-saws

The tool needs to be lifted out of the drilled hole, so allow removal of the sawdust/wood chips.

When drilling a hole, such as in a door to install a door lock mechanism, drill a small 1/8" dia pilot hole thru the door, before proceeding with the hole saw. 

The pilot bit in the hole saw will follow the smaller pilot hole, and make for a straighter drilled hole.

NOTE:  For accurate placement of a drilled hole, use a combination square, or the like, to make accurate markings on the work-piece, before proceeding.

[Rita B.]

Thanks for the tips Ken.   Will be ready to use the hole saw tomorrow on my piece.   Great idea for marking location and using the backer board to help avoid tear out.   One of those things where I only get one shot at the given piece.

[Jay Boutwell]

Rita, backer boards do not always work and that is why if You can drill from both sides that is the method to use to insure a clean splinter or tear out surface .  Like I indicated in the post I wrote, watch for the start of the penetration of the drill bit coming through and then use that dimple or small hose to locate the bit for the second cut.   If you can use a backer board then that means that you should be able to drill from both sides.  Keeping the complete rim of the bit on the surface you are boring at the start will insure that you arrive at a straight bored hole.  If boring a door blank most of the time the saw is not as deep as the material you are boring so you will need to reverse the side anyway.  It also keeps the amount of friction of the bit down as the bit is not having to travel far in material that is already cut.  It will also allow you a better extraction of the core as the first part you drilled before moving to the opposite side will be cut free of the surface and therefore will remain sticking out the hole saw.  It is then a matter of grabbing onto the piece with something like a pair of channel locks and twisting it in a counter clock rotation and it will twist free of the pilot bit.
 
Rita B. said:

Thanks for the tips Ken.   Will be ready to use the hole saw tomorrow on my piece.   Great idea for marking location and using the backer board to help avoid tear out.   One of those things where I only get one shot at the given piece.

[Jay Boutwell]

  The easiest way is to use two screws that are longer than the thickness of the core and holding the hole saw so that it is the core is facing you and equally drive them into the core until the screws bottoms out on the top of the how saw.  This will actually push the core out of the saw.  often if you use the slots on the saw you will distort the saw and it will not bore as nice the next time you use it.  That is why I use the two screws and have for years
 
Ken Darga said:

Rita,

Thanks for your reply.

It's difficult to remove the wood "slug" from some of the hole saws.

The type/style with a slot in the side wall, is to aide in the removal of the slug.

Rita B. said:

Thanks for the tips Ken.   Will be ready to use the hole saw tomorrow on my piece.   Great idea for marking location and using the backer board to help avoid tear out.   One of those things where I only get one shot at the given piece.

[Rita B.]

I appreciate all the tips more than you know.   Jay,  I think Ken was referring to using a backer board in the event I needed to use a Forstner bit for a thru hole.    Knowing what the slots in the hole saw are designed for is knowledge in itself of the design of the tool.  I had no idea.     What I have done thus far working with wood has been a lot of trial and error.   It is great to have a reference of the best way to achieve a given task.

[Ken Darga]

PS

Alternate method:

Drill a small pilot hole thru the work-piece.

Then proceed to drill the larger hole---

drill halfway thru one side and

drill thru the opposite-side.

Ken Darga said:

Forstner bits are intended to drill flat bottom holes.

They can also be used to drill "thru holes" in wood.

Place a "backer board", or the like, behind the work-piece, to avoid tear-out on the work-piece back side.

Lift the drill bit out often, to allow the removal of the wood chips.

[Ken Darga]

Spade Bits

Sometimes referred to as "speed-bore bits".

This type drill bit is more suited for drilling rough-cut holes in construction lumber material,

such as when routing conduit and piping.

Tear-out often occurs---a smooth hole is not achieved.

When drilling thicker stock, drill a thru-hole with a small dia bit, and drill the desired hole from both sides.

Extensions can be used to drill deep holes or to reach a longer distance.

This type bit is also available in a "stub" version.

They are useful when drilling between studs, or the like, and drilling shallow depth holes.

A newer style spade bit features a "threaded drill point lead end".

This style can be referred to as "self-feeding", because of the threaded point.

Exercise caution with this bit---if the bit locks-up in the material, when using a power drill,

it could cause injury to your wrist or arms.

Some of the larger bits in a large heavy-duty drill, when locked up, could break your wrist or arms.

[Jay Boutwell]

I understand that but what I am trying to make clear is that a backer board is fine however it you want to insure that you have a tear free hole bore from both sides.  This applies to any thing of which bores a hole.  from a hole saw to a simple bit they all will have a tendency to tear out the hole  as they exit the back of the material.  Backer boards require you to have them tight against the material and that means clamping tight against the material being bored.  It is not always a method where you can apply a backer board but can still bore from both sides.  For example boring a hole in a desk top that is already applied to the desk ore boring a hole in the back of a cabinet panel.  How are you going to hold a backer board on the panel of under the desk top?   This is what I am referring to. I guess after doing this professionally for the amount of time that I have, experience has taught me a few things. 

I appreciate all the tips more than you know.   Jay,  I think Ken was referring to using a backer board in the event I needed to use a Forstner bit for a thru hole.    Knowing what the slots in the hole saw are designed for is knowledge in itself of the design of the tool.  I had no idea.     What I have done thus far working with wood has been a lot of trial and error.   It is great to have a reference of the best way to achieve a given task.

[Ken Darga]

Jay,

Thanks for the tip.

I'll have to give the "two screw" method a try.

I generally use the heavy-duty style hole saw, that features angled slots on the side walls---

and use a prick- punch to pry out the slug.  The hole saw body also features small holes in the top area, that allows a tool to push/punch-out the slug.

Jay Boutwell said:

  The easiest way is to use two screws that are longer than the thickness of the core.../p>