I am building an outside shed, using large timbers and lag screws of two
sizes, 3/8 inch and some 1/2 inch. In some places, I want to
counter-sink the lag screws. I want to see if I am on the right track.

For the 3/8 inch lag screws, I plan to use a 1/4 auger drill bit for a
pilot hole. Would that be the right size ? To countersink the head of
the screw, I plan to use a 1 inch spade drill bit.


For the 1/2 inch screws, I plan to use a 3/8 auger drill bit for the pilot
hole. Again, is this the ideal size ? To countersink the screw head, I
would use a 1 1/2 inch spade drill bit.

I will be using washers, so the countersunk holes must accomodate the size
of the washers.



Summary of Questions:

1. Am I planning the correct pilot hole sizes ?

2. For drilling through 6 inch timbers, what type of drill bits are better,
the auger type, or spade ?

3. Is the use of the spade bit the correct type of bit for the
countersinking ?



I know these are rather "green" questions, but I learn from this group.

Thanks !!

--James--

In a previous post James wrote...
Summary of Questions:

1. Am I planning the correct pilot hole sizes ?


The pilot hole should be no more than 60% of the lag shank.

For 3/8" (0.375") this works out to 0.225", or 7/32".

2. For drilling through 6 inch timbers, what type of drill bits are better,
the auger type, or spade ?

Either one works, but you will get a cleaner hole with an auger type bit.

3. Is the use of the spade bit the correct type of bit for the
countersinking ?

Again, you can use either one, but the hole will be cleaner with an auger
type bit. You might even consider using a 1-inch hole saw to cut a
groove and then use your spade bit to clean out the hole.

The countersink hole should be just slightly larger in diameter than the
washer under the head of the lag -- you are using washers aren't you?

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

"Bob Morrison" wrote in message
k.net...
In a previous post James wrote...
Summary of Questions:

1. Am I planning the correct pilot hole sizes ?


The pilot hole should be no more than 60% of the lag shank.

For 3/8" (0.375") this works out to 0.225", or 7/32".

2. For drilling through 6 inch timbers, what type of drill bits are
better,
the auger type, or spade ?

Either one works, but you will get a cleaner hole with an auger type bit.

3. Is the use of the spade bit the correct type of bit for the
countersinking ?

Again, you can use either one, but the hole will be cleaner with an auger
type bit. You might even consider using a 1-inch hole saw to cut a
groove and then use your spade bit to clean out the hole.

The countersink hole should be just slightly larger in diameter than the
washer under the head of the lag -- you are using washers aren't you?


Make sure you do the counter-sunk holes first. Once you make the pilot holes
it'll be too big for either a spade or auger tip and make a VERY sloppy
hole, of centered as well. If it were me I'd use a forstner (some call em
forsner's) bit for the counter-sunk followed by an auger for the pilot.

James wrote:
I am building an outside shed, using large timbers and lag screws of two
sizes, 3/8 inch and some 1/2 inch. In some places, I want to
counter-sink the lag screws. I want to see if I am on the right track.

For the 3/8 inch lag screws, I plan to use a 1/4 auger drill bit for a
pilot hole. Would that be the right size ? To countersink the head of
the screw, I plan to use a 1 inch spade drill bit.


For the 1/2 inch screws, I plan to use a 3/8 auger drill bit for the pilot
hole. Again, is this the ideal size ? To countersink the screw head, I
would use a 1 1/2 inch spade drill bit.

I will be using washers, so the countersunk holes must accomodate the size
of the washers.



Summary of Questions:

1. Am I planning the correct pilot hole sizes ?

2. For drilling through 6 inch timbers, what type of drill bits are better,
the auger type, or spade ?

3. Is the use of the spade bit the correct type of bit for the
countersinking ?



I know these are rather "green" questions, but I learn from this group.

Thanks !!

--James--

The holes you are suggesting are just a little too big. The pilot hole
size should be a function of the wood species as well. That said,
since you're most likely building with a softwood I would cheat
sligthly smaller.

I usually measure the root diameter of lag & go just slightly smaller
(in softwoods) . This way, I get a lttle bit of compression of the
wood & it makes for a nice tght assembly. Hardwoods I go the other
way; esp oak!

I want to have as much thread as possiblw w/o danger of splitting the
wood or breaking the lag.


A slight 'nit' about the OP's teminology........

a countersink is a tapered feature desinged to accept the tapered head
of a flat head bolt or screw.......... usually 82 deg or 100 deg or
other

the feature the OP is creating; a flat bottomed hole is actually
refered to as a counterbore

cheers
Bob

In a previous post Bobk207 wrote...
The holes you are suggesting are just a little too big. The pilot hole
size should be a function of the wood species as well. That said,
since you're most likely building with a softwood I would cheat
sligthly smaller.


Bob K is correct. Here's a quote from the National Design Specification
for Wood Construction regarding the holes for Lag Screws:

"(a) The clearance hole for the shank shall have the same diameter as the
shank and the depth of penetration as the length of unthreaded shank."

(b) The lead hole for the threaded portion shall have a diameter equal to
65% to 85% of the shank diameter in wood with G 0.60, 60% to 75% in wood
with 0.50=G=0.60, and 40% to 70% in wood with G=0.50 (see Table
11.3.2A) and a length to at least the length of the threaded portion. The
larger percentile in each range shall apply to lag screws of greater
diameters."

So it seems you will need 3 drills: one for the pilot hole, one for the
shank hole, and one for the counterbore. You don't say what kind of wood
you are using, but Douglas-Fir had a "G" of 0.50 and Hem-Fir has a "G" of
0.43. The typical pressure treated timbers are Hem-Fir, but look for a
grade mark to be sure.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Save yourself a lot of time, money, and aggravation.
Use these:
http://www.fastenmaster.com

Using an impact driver with these fasteners makes it very easy on the
wrists. I would suggest getting the basic structure connected using
this type of fastener. Then if you want the regular lagscrew and
washer, those can be added once everything is square, level and plumb.
I use an electric impact wrench with lagscrews.

On Fri, 30 Jun 2006 14:29:07 -0400, "James"
wrote:



I am building an outside shed, using large timbers and lag screws of two
sizes, 3/8 inch and some 1/2 inch. In some places, I want to
counter-sink the lag screws. I want to see if I am on the right track.

For the 3/8 inch lag screws, I plan to use a 1/4 auger drill bit for a
pilot hole. Would that be the right size ? To countersink the head of
the screw, I plan to use a 1 inch spade drill bit.


For the 1/2 inch screws, I plan to use a 3/8 auger drill bit for the pilot
hole. Again, is this the ideal size ? To countersink the screw head, I
would use a 1 1/2 inch spade drill bit.

I will be using washers, so the countersunk holes must accomodate the size
of the washers.



Summary of Questions:

1. Am I planning the correct pilot hole sizes ?

2. For drilling through 6 inch timbers, what type of drill bits are better,
the auger type, or spade ?

3. Is the use of the spade bit the correct type of bit for the
countersinking ?



I know these are rather "green" questions, but I learn from this group.

Thanks !!

--James--

Save yourself a lot of time, money, and aggravation.
Use these:
http://www.fastenmaster.com

Thanks Bob for the good info !! You recommend 7/32 bit for the 3/8 lag
screw. I have a 1/4 inch bit, which is only 1/32 of an inch larger.
From your notes, I guess whether this would be too marginal depends on the
species of wood. It will be pressured treated, and I "guess" it is
Southern Yellow Pine. (My materials are in another location right now, 500
miles away) Either way, would the 1/32 likely make much of a difference
?

IF I am correct about the Yellow Pine species, what bit would you guess
would be acceptable for the 1/2 inch lag screws ? Would the 3/8 inch
bit be too big??

What is the difference between a forester (sp) bit and a "wood boring" bit
?

Thanks again guys !!!


--James--

I agree with Brian. I used a 1 1/4 forstner bit to drill counter sink holes
in 6X timbers that I used for my shed foundation. Make sure you drill the
counter-sink holes first. If not it is really difficult to keep a large
forstner bit centered with a hand drill. Use flat washers under the screw
head.
I used the same size washer as the hole drilled. Made a nice looking job and
tightened down tight without any crushing of the wood fibers with the large
washers
CC


"Brian V" wrote in message
. ..

"Bob Morrison" wrote in message
k.net...
In a previous post James wrote...
Summary of Questions:

1. Am I planning the correct pilot hole sizes ?


The pilot hole should be no more than 60% of the lag shank.

For 3/8" (0.375") this works out to 0.225", or 7/32".

2. For drilling through 6 inch timbers, what type of drill bits are
better,
the auger type, or spade ?

Either one works, but you will get a cleaner hole with an auger type bit.

3. Is the use of the spade bit the correct type of bit for the
countersinking ?

Again, you can use either one, but the hole will be cleaner with an auger
type bit. You might even consider using a 1-inch hole saw to cut a
groove and then use your spade bit to clean out the hole.

The countersink hole should be just slightly larger in diameter than the
washer under the head of the lag -- you are using washers aren't you?


Make sure you do the counter-sunk holes first. Once you make the pilot
holes it'll be too big for either a spade or auger tip and make a VERY
sloppy hole, of centered as well. If it were me I'd use a forstner (some
call em forsner's) bit for the counter-sunk followed by an auger for the
pilot.

Bob Morrison wrote:

So it seems you will need 3 drills: one for the pilot hole, one for the
shank hole, and one for the counterbore.


But, not in that order!
I used to have a job making timber children's playground equipment, and
counterboring was standard procedure. The holes were further plugged
with plastic caps.
Drilling the hole before the counterbore I found is not good, pilot or
no pilot. Unless of course you have some fancy guided counterboring
drill (unecessary).
Counterbore first, then drill for the bolt.

Some grease injected into the bolt holes sure makes bolts go in
easier.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Bob Morrison" wrote in message
k.net...
In a previous post Bobk207 wrote...
The holes you are suggesting are just a little too big. The pilot
hole
size should be a function of the wood species as well. That said,
since you're most likely building with a softwood I would cheat
sligthly smaller.


Bob K is correct. Here's a quote from the National Design
Specification
for Wood Construction regarding the holes for Lag Screws:

"(a) The clearance hole for the shank shall have the same diameter as
the
shank and the depth of penetration as the length of unthreaded shank."

(b) The lead hole for the threaded portion shall have a diameter equal
to
65% to 85% of the shank diameter in wood with G 0.60, 60% to 75% in
wood
with 0.50=G=0.60, and 40% to 70% in wood with G=0.50 (see Table
11.3.2A) and a length to at least the length of the threaded portion.
The
larger percentile in each range shall apply to lag screws of greater
diameters."

So it seems you will need 3 drills: one for the pilot hole, one for
the
shank hole, and one for the counterbore. You don't say what kind of
wood
you are using, but Douglas-Fir had a "G" of 0.50 and Hem-Fir has a "G"
of
0.43. The typical pressure treated timbers are Hem-Fir, but look for
a
grade mark to be sure.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

I've used socket tips on a power drill. But not yet tried an impact
wrench. Might try that some time.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"IBM5081" wrote in message
oups.com...
Save yourself a lot of time, money, and aggravation.
Use these:
http://www.fastenmaster.com

Using an impact driver with these fasteners makes it very easy on the
wrists. I would suggest getting the basic structure connected using
this type of fastener. Then if you want the regular lagscrew and
washer, those can be added once everything is square, level and plumb.
I use an electric impact wrench with lagscrews.

Do it backwards and save you some unneeded engineering aspects. Bore the
larger hole 1/4" bigger than the intended washer first. Make yourself a
countersink jig to maintain the same depth. Then drill the smaller hole to
run the lag bolt in. I'd go with a 1/4" bit for the 3/8 bolt, and 5/16" for
the 1/2" bolt. You don't need a particular bit type to make the hole, just
be sure its long enough. You might clamp the timbers in place while
drilling.
--
Jonny
"James" wrote in message
. ..


I am building an outside shed, using large timbers and lag screws of two
sizes, 3/8 inch and some 1/2 inch. In some places, I want to
counter-sink the lag screws. I want to see if I am on the right track.

For the 3/8 inch lag screws, I plan to use a 1/4 auger drill bit for a
pilot hole. Would that be the right size ? To countersink the head of
the screw, I plan to use a 1 inch spade drill bit.


For the 1/2 inch screws, I plan to use a 3/8 auger drill bit for the pilot
hole. Again, is this the ideal size ? To countersink the screw head, I
would use a 1 1/2 inch spade drill bit.

I will be using washers, so the countersunk holes must accomodate the size
of the washers.



Summary of Questions:

1. Am I planning the correct pilot hole sizes ?

2. For drilling through 6 inch timbers, what type of drill bits are
better,
the auger type, or spade ?

3. Is the use of the spade bit the correct type of bit for the
countersinking ?



I know these are rather "green" questions, but I learn from this group.

Thanks !!

--James--

On Fri, 30 Jun 2006 20:08:15 -0400, "James"
wrote:

Thanks Bob for the good info !! You recommend 7/32 bit for the 3/8 lag
screw. I have a 1/4 inch bit, which is only 1/32 of an inch larger.
From your notes, I guess whether this would be too marginal depends on the
species of wood. It will be pressured treated, and I "guess" it is

If it is pressure treated, I think you have to use some sort of mask
when drilling. I know you do when sawing. Arsenic, poison, lungs.


I may be missing something, but you know the coutersink hole is
supposed to be in the top piece of wood, and the pilot hole is
supposed to be in the other piece of wood.

You need another drill yet, bigger than the pilot drill, to drill
through the top, the first piece of wood. There is no point in trying
to force yourself all the way through two pieces of wood.

MM has made a good point. Yes, I do know that the countersunk hole is
the top piece. And, I have also wondered if I should "force screw" the
lag through the first piece, or just drill a hole big enough to allow it to
"slip" through, and then allow the 2nd piece of wood to do the holding.


Maybe that is what one poster meant when he said I would need THREE bits.
One pilot, one "shank" and one for the countersink. I didn't pick up on
that when I first read it.

Do all of you concur, that the screw can go in rather loosely on the top
piece, and the tight fit should only be on the second piece ??

You guys are very helpful , and full of experience. I appreciate the tips a
lot, and I will use them.


--James--

-----------------------------------------------------------------

MM said:


I may be missing something, but you know the countersink hole is
supposed to be in the top piece of wood, and the pilot hole is
supposed to be in the other piece of wood.

You need another drill yet, bigger than the pilot drill, to drill
through the top, the first piece of wood. There is no point in trying
to force yourself all the way through two pieces of wood.

"James" wrote in message

Do all of you concur, that the screw can go in rather loosely on the top
piece, and the tight fit should only be on the second piece ??

You guys are very helpful , and full of experience. I appreciate the tips
a
lot, and I will use them.


Yes. Often, a washer under the head is used.

James wrote:

MM has made a good point. Yes, I do know that the countersunk hole is
the top piece. And, I have also wondered if I should "force screw" the
lag through the first piece, or just drill a hole big enough to allow it
to
"slip" through, and then allow the 2nd piece of wood to do the holding.


Maybe that is what one poster meant when he said I would need THREE
bits.
One pilot, one "shank" and one for the countersink. I didn't pick up on
that when I first read it.

Do all of you concur, that the screw can go in rather loosely on the top
piece, and the tight fit should only be on the second piece ??

You guys are very helpful , and full of experience. I appreciate the tips
a lot, and I will use them.

You want the shank to be a tight fit, otherwise you don't get the full load
bearing capacity.

A "Forstner" bit http://www.woodcraft.com/family.aspx?familyid=8311 cuts a
flat bottomed hole. A spade bit will also do that particular job, the
Forstner is a bit neater, but more difficult to use hand-held. An auger
bit will also do for the countersink but they're relatively hard to find
and expensive.

--James--

-----------------------------------------------------------------

MM said:


I may be missing something, but you know the countersink hole is
supposed to be in the top piece of wood, and the pilot hole is
supposed to be in the other piece of wood.

You need another drill yet, bigger than the pilot drill, to drill
through the top, the first piece of wood. There is no point in trying
to force yourself all the way through two pieces of wood.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

No one has mentioned one key item about your project. Since you said that
the timbers are pressure treated I would assume they are the newer type that
requires either hot dipped galvanized or stainless fasteners. I would also
use the same material for the washers. The new pressure treated lumber eats
regular metal fast. In my area most PT lumber is some type of pine from the
south east part of the states. Running the screw threads on a bar of soap or
wax ( beeswax the best) works very well for installing the screws also.



"Jonny" wrote in message
k.net...
Do it backwards and save you some unneeded engineering aspects. Bore the
larger hole 1/4" bigger than the intended washer first. Make yourself a
countersink jig to maintain the same depth. Then drill the smaller hole
to run the lag bolt in. I'd go with a 1/4" bit for the 3/8 bolt, and
5/16" for the 1/2" bolt. You don't need a particular bit type to make the
hole, just be sure its long enough. You might clamp the timbers in place
while drilling.
--
Jonny
"James" wrote in message
. ..


I am building an outside shed, using large timbers and lag screws of two
sizes, 3/8 inch and some 1/2 inch. In some places, I want to
counter-sink the lag screws. I want to see if I am on the right track.

For the 3/8 inch lag screws, I plan to use a 1/4 auger drill bit for a
pilot hole. Would that be the right size ? To countersink the head of
the screw, I plan to use a 1 inch spade drill bit.


For the 1/2 inch screws, I plan to use a 3/8 auger drill bit for the
pilot
hole. Again, is this the ideal size ? To countersink the screw head, I
would use a 1 1/2 inch spade drill bit.

I will be using washers, so the countersunk holes must accomodate the
size
of the washers.



Summary of Questions:

1. Am I planning the correct pilot hole sizes ?

2. For drilling through 6 inch timbers, what type of drill bits are
better,
the auger type, or spade ?

3. Is the use of the spade bit the correct type of bit for the
countersinking ?



I know these are rather "green" questions, but I learn from this group.

Thanks !!

--James--

Yes, I am going to use hot dipped galvanized lagscrews and washers.

Thanks !!

--James--

In article ,
"Stormin Mormon" wrote:

Some grease injected into the bolt holes sure makes bolts go in
easier.

Liquid Ivory soap works great

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Reports are that soap attracts moisture so metal will rust faster and
wax is preferred lube.

On Sat, 01 Jul 2006 20:19:18 GMT, Nick Hull
wrote:

In article ,
"Stormin Mormon" wrote:

Some grease injected into the bolt holes sure makes bolts go in
easier.

Liquid Ivory soap works great

While I doubt that, we are talking about lag bolts, right? A
skift of rust will just make them hold better and in wood they may
rust out in 150 years instead of 152 years.

wrote in message

Reports are that soap attracts moisture so metal will
rust faster and wax is preferred lube.

According to Glenn :
While I doubt that, we are talking about lag bolts, right? A
skift of rust will just make them hold better and in wood they may
rust out in 150 years instead of 152 years.

You'd be surprised how quickly fasteners can corrode out in
PT lumber if not chosen correctly. Eg: on the deck I was
repairing on the weekend, some #10 screws lasted less than
3 years.

Double-dipped galvanized or stainless is the way to go.

If you're using ordinary galvanized, a wax coating might make
quite a bit of difference.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.

Whatever they are now using to PT lumber will corrode a regular nail or
screw within a few years.
You MUST use double dipped galvanized or Stainless steel fasteners or you
will have a mess in a few years.
Because people didn't know this when the new PT lumber came out, there are
many decks built with the wrong fasteners which will nedd major repairs.



According to Glenn :
While I doubt that, we are talking about lag bolts, right? A
skift of rust will just make them hold better and in wood they may
rust out in 150 years instead of 152 years.

You'd be surprised how quickly fasteners can corrode out in
PT lumber if not chosen correctly. Eg: on the deck I was
repairing on the weekend, some #10 screws lasted less than
3 years.

Double-dipped galvanized or stainless is the way to go.

If you're using ordinary galvanized, a wax coating might make
quite a bit of difference.

--
JerryD(upstateNY)