Home Depot 1/4" Lag Screw

Page 2 of 8  
wrote:

I measured a 1/4", just one, and its root measured .186-.187 top to bottom. I don't imagine lags are a precision item, tho.
And one of the links someone posted gives the pilot as 3/16 in softwood, 7/32 in hard! It also mentioned grease or vegeteable oil as a lube, but cautioned against soap.
1/4 lags are fragile, tho. I'd use 5/16 on anything semi-substantial.
--
EA

>
> The next natural drill size is .187, or 3/16".
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 12/16/2009 01:13 PM, Tom Watson wrote:

For optimum strength in solid wood you actually want to drill the pilot hole smaller than the root diameter. Specifically between 0.7 and 0.9 times the root diameter, depending on the density of the wood in question--softwood gets a smaller hole.
Chris
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 16 Dec 2009 13:25:08 -0600, Chris Friesen

Where does that come from?
Regards,
Tom Watson http://home.comcast.net/~tjwatson1 /
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Watson wrote:

...
Long lore, at least...
I don't have a direct URL; I'd expect you'd find the information in some of the US Forest Products Laboratory technical publications. It was something I was taught way back in one of first HS ag-ed classes is first I recall it personally, anyway...don't recall if it was taught as a specific ratio, only "tubafores get smaller, rr-ties get bigger" was the gist of it. :)
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I don't see the point. The pilot hole sizes quoted work for nails where compression determines strength but I don't see any benefit in having a pilot hole of less than the root diameter of a threaded fastener.
Regards,
Tom Watson http://home.comcast.net/~tjwatson1 /
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Watson wrote:

...
The point is to have a larger pilot-hole in softer woods than hardwood to minimize the effort of installation but to ensure a full bite which can be marginal if use a full root diameter for pilot, particularly in softwoods that tend often to "crumble".
No claim made (at least by me) that there's any _precise_ ratio other than the aforementioned bigger/smaller based on the material.
I'd still wager there is some information at US FPL but I've not taken time to search for it.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hmmm....
Seems like it would be the opposite, the softer wood requiring a smaller pilot hole for more compression in surrounding wood to "ensure" a solid bite in a wood that tends to "crumble".
nb
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
notbob wrote:

Mea culpa...yes, that was inadvertent swap of the intent I didn't catch... :( sorry.
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
dpb wrote:

It's in "Wood As An Engineering Material", Page 7-11. What they say is:
"For low-density softwoods, such as the cedars and white pines, 40% to 70% of the shank diameter; for Douglas-fir and Southern Pine, 60% to 75%; and for dense hardwoods, such as oaks, 65% to 85%. The smaller percentage in each range applies to lag screws of the smaller diameters and the larger percentage to lag screws of larger diameters."
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
J. Clarke wrote:

Excellent reference, J. Thank you for posting that, it is very much appreciated!
The lag bolt which snapped off had an average shank diameter of 0.182". Sixty percent of this value is 0.1092, while seventy five percent of this value is 0.1365, which puts a pilot bit of 1/8" right in the middle.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 17 Dec 2009 11:19:09 -0800, "Jon Danniken"

What do you mean by "shank diameter"?
Machinery's Handbook lists the "body" or "shoulder" diameter of a 1/4" lag bolt as between .237" and .260". This is the area that is not threaded.
The "root diameter" is listed as .173". This is the diameter of the remaining cylinder after the threads are formed.
(American National Standard Square Lag Screws - ANSI/ASME B18.2.1-1996)
Regards,
Tom Watson http://home.comcast.net/~tjwatson1 /
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Watson wrote:

Thanks Tom, I should have said the root diameter.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

BUT Jon,,,,,, While it is a kewl reference that agrees with what you were using as a pilot hole, how did that work out for you?
The information could be out dated for readily available fasteners today. If might be a new publication using old data.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Leon wrote:

It works out great, Leon, once I purchased lag bolts that weren't from the bulk bin at Home Depot. The bolts are currently holding up a home-made welded bracket, which in turn is holding up my bathroom sink.
The sink itself weighs maybe 20 or 30 pounds, so I tested the bracket by holding myself up with it, and it didn't budge.
Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Leon wrote:

The numbers are based on maximizing holding power, not making a crap fastener survive being driven. They state the assumptions, which are 35,000 PSI yield and 77,000 PSI UTS, slightly higher than required for a Grade 1 bolt.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
J. Clarke wrote:

...
...
Indeed...thanks for saving me the effort... :)
Now if I just hadn't made the swap of sense in the relative sizes... :(
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I wonder if that material was written in modern years or 30 plus. I see lag screw failures galore.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Leon wrote:

Are you saying that the properties of wood have changed so radically in the last 30 years that lag screws hold differently in them now? Because the recommendations are not about allowing you to use crap screws without breaking them while driving, they are about sticking wood together so it stays stuck.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well yes actually. Wood with wider growth rings as oppose to narrower more compact gowth rings, which were more available many years back, may yield different results today.
Because the

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Leon wrote:

Won't that be reflected in the density though?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.