# Local machinists: I need a 10' straightedge.



## steelheart (Jul 7, 2019)

I need a 10' straightedge that I can use to determine that a concrete floor is within spec for laying porcelain tile, that is, it is flat to within 1/8 inch over 10' when measuring from the high spots:

_“the maximum allowable variation is no more than 1/8” in 10’ (3 mm in 3 m) and no more than 1/16” in 2’ (1.6 mm in 0.6 m) from the required plane, when measured from the high points in the surface.”_

I'm based in Reston, Virginia, USA. Of course, I'll be willing to pay for your services. This is something I'll need to have within 2 weeks.

Thanks!

Stephen


----------



## RJSakowski (Jul 7, 2019)

I use a length of 3" Aluminum channel for a straight edge for jobs like yours.  It's available from heavy hardware suppliers.  The AA profile has straight walled flanges.  I just finished laying a patio using a 12' length.


----------



## Barncat (Jul 7, 2019)

Can you just pull a string tight across it and measure? Or a laser.


----------



## Timwalker (Jul 7, 2019)

With that loose of a tolerance, I think it would be worth looking into whether an aluminum extrusion would fit your needs.  Would probably be worlds cheaper than having a 10 foot straight edge machined.


----------



## Latinrascalrg1 (Jul 7, 2019)

Is this some kinda super special environment for some reason or is this just a basic home improvement project?


----------



## Cadillac (Jul 7, 2019)

You can buy a 8’ level from just about any big box store that should be plenty good for a tile job. 
I’ve laid hundreds of square feet of tile and really never worried about if the subfloor was level or not to a 1/8”. If the floor isn’t sound and wavey then that’s another story. Tiles 12x12 and under can take deviation like that. Larger ones not so much. Butter the back of the tiles and do you typical notch trowel should be good. Thinking of it I wonder how many floors are that level?


----------



## Cadillac STS (Jul 7, 2019)

I was at Lowe’s today and they sell a 6 foot ruler/straight edge. Could buy two of those and clamp them together.  And with the inch marks you can measure your variance more easily.


----------



## whitmore (Jul 7, 2019)

steelheart said:


> I need a 10' straightedge that I can use to determine that a concrete floor is within spec for laying porcelain tile



That's an easy job for a laser; a ten foot stick would be hard to haul, store, or handle, but a little laser-and-mirrors item
can come out of the box, sit on the floor, and broadcast a flat sheet of light; drop a yardstick to the floor at any point,
and read off the deviation from that.

"Rotary laser levels" often have a float, or plumb bob, built in (these are self-leveling), so they will ONLY measure level-and-flat, not  flat-and-sloped, 
If slope is OK, it'll take some close reading of the instructions (or maybe a very dumb model).  Mathematically, you could
identify the slope direction and use a grid aligned to it for a quick check of flat, but that's a tad tedious.

The old-fashioned way, is a handheld sight level, maybe with a monopod, and an assistant holding a stadia stick; I remember using those, but
haven't played with the rotary laser gizmos.   It might be worthwhile renting one before shelling out the cash (they're
expensive, but so are good levels).


----------



## lordbeezer (Jul 7, 2019)

This is a great site..don't care what questions someone asks there's a bunch of really smart people that take time to answer..not common in today's world


----------



## JimDawson (Jul 7, 2019)

I'm surprised that nobody has mentioned leveling compound.  Just poor it on and presto, instant flat floor for tile. At least that's the way I understand it.


----------



## Cadillac STS (Jul 7, 2019)

If you are willing to pay for the service why not call your local tile installing place and see if they will send someone out to tell you if you are ok and what to do if not. Ask the professionals. 

Could also ask for an estimate for them to install it just so you know the price to do it. Probably same cost or more than the tile itself but you never know.


----------



## steelheart (Jul 7, 2019)

Latinrascalrg1 said:


> Is this some kinda super special environment for some reason or is this just a basic home improvement project?



This is just for remodeling my basement. Nothing super special.



Barncat said:


> Can you just pull a string tight across it and measure? Or a laser.



I could. I think I'll try this first as it's cheap enough to use a chalk line to find the major problem spots first.



RJSakowski said:


> I use a length of 3" Aluminum channel for a straight edge for jobs like yours.  It's available from heavy hardware suppliers.  The AA profile has straight walled flanges.  I just finished laying a patio using a 12' length.



Thanks for this suggestion! I'll call around and see where I can find this locally.



Cadillac STS said:


> I was at Lowe’s today and they sell a 6 foot ruler/straight edge. Could buy two of those and clamp them together.  And with the inch marks you can measure your variance more easily.


If I did this, wouldn't the weight of the clamp cause flexing/sagging in the middle?



Cadillac said:


> You can buy a 8’ level from just about any big box store that should be plenty good for a tile job.
> I’ve laid hundreds of square feet of tile and really never worried about if the subfloor was level or not to a 1/8”. If the floor isn’t sound and wavey then that’s another story. Tiles 12x12 and under can take deviation like that. Larger ones not so much. Butter the back of the tiles and do you typical notch trowel should be good. Thinking of it I wonder how many floors are that level?



My tiles will be 12x24, so I am a little more concerned than I would be if they were 12x12.



JimDawson said:


> I'm surprised that nobody has mentioned leveling compound.  Just poor it on and presto, instant flat floor for tile. At least that's the way I understand it.



Only catch is that leveling compound is quite pricy for using across my entire basement level. I'd like to only deal with the problem spots if possible.



lordbeezer said:


> This is a great site..don't care what questions someone asks there's a bunch of really smart people that take time to answer..not common in today's world


Agreed! This is my first post here and I'm pleasantly surprised at how many useful and helpful answers I got within the span of a few hours!


----------



## steelheart (Jul 7, 2019)

Based on what I'm reading, it looks like having a 10' straightedge machined is not really practical and that there are other alternatives that I should (and will) try first. Thank you everyone for your responses! I'll post back here with a picture of my finished floor when I'm done (hoping by the end of this month).


----------



## Cadillac STS (Jul 8, 2019)

"If I did this, wouldn't the weight of the clamp cause flexing/sagging in the middle?"

I have some 2 inch clamps and was thinking of those which I don't think would be a problem.  Otherwise you could temporarily clamp them and drill two 1/4 inch holes in the 1/4 inch aluminum they are made of and put in two nuts and bolts.

Tiling is something that is not that difficult and really rewarding to do yourself.

Great site indeed.


----------



## ELHEAD (Jul 8, 2019)

Stephen, I did wood floors for more than 30 years. We used 4" wide MDF baseboard  for our long straight edges. Plenty accurate for floor work
Dave


----------



## Illinoyance (Jul 8, 2019)

My Dad made one many years ago.  I believe it was a 1x8.  He tapered the ends to about 3".  He planed the bottom until it was true, using a taut string as a reference.


----------



## kb58 (Jul 8, 2019)

I don't get that level specification. I mean, if it's for a floor, who cares if it's not perfectly flat. 1/4" (or even 1/2") over 10 feet wouldn't be noticeable. Am I wrong?


----------



## francist (Jul 8, 2019)

I'm thinking the idea is to avoid humps or dips in the surface that could lead to pressure points and subsequent cracking of a large tile. Level is likely not the consideration as much as flatness is. Not so much of a concern with small tiles that will conform, but with large ones I can see wanting a pretty flat substrate.

-frank


----------



## RJSakowski (Jul 8, 2019)

francist said:


> I'm thinking the idea is to avoid humps or dips in the surface that could lead to pressure points and subsequent cracking of a large tile. Level is likely not the consideration as much as flatness is. Not so much of a concern with small tiles that will conform, but with large ones I can see wanting a pretty flat substrate.
> 
> -frank


I agree with what Frank said.  Most important are the high spots as localized lows can be easily compensated for with additional cement.  High spots, on the other hand, could cause insufficient cement or a pivot point which could result in breaking a tile.

A short straight edge would be sufficient to locate and address these issues.  A 4 ft. level should work for this purpose. High spots can be ground down with a masonry wheel in an angle grinder ot a cold chisel and hammer.  

I have a rotating laser level and it is great for establishing levels around a perimeter but it would be tedious trying to high localized highs and lows.  If the floor is fairly level overall, a quick preliminary check would be to run some water with a small amount of detergent as a wetting agent on it.  high and low spots will quickly be spotted.  Once spotted, mark the areas with markers for any needed corrections.


----------



## ezduzit (Jul 8, 2019)

RJSakowski said:


> I use a length of 3" Aluminum channel for a straight edge...



Channel is an unbalanced shape. I would choose a balanced shape such as I-beam or rectangular tube.


----------



## RJSakowski (Jul 8, 2019)

ezduzit said:


> Channel is an unbalanced shape. I would choose a balanced shape such as I-beam or rectangular tube.


This is true but there is no load on the extrusion.  I have used the 3" channel for more than twenty years and have found it to be flat in use.  I use it as a "C" rather than a "U".  If I were picking a form to make the tool, I beam would be my choice.   I happened to have the channel so I used it. What the I beam form does is stiffen the beam in right angles to the web.  It tends to make the beam resistant to twisting.   Structural channel is just one side of the I beam.


----------



## ezduzit (Jul 8, 2019)

RJSakowski said:


> ...there is no load on the extrusion.  I have used the 3" channel for more than twenty years and have found it to be flat in use.  I use it as a "C" rather than a "U".  If I ...



Not true. The "beam" will bend just from its own weight. So, if straightness is important, channel is a poor choice. 
I understand that you used it because you already had it.


----------



## Latinrascalrg1 (Jul 8, 2019)

Ive never used this product but i can see this being very helpful to a noob tile installer.  It wont resolve those problem high/ low spots but this product should do a good job with keeping each tile level to its neighbor. Add in the "+ spacers" separately to control spacing between and your good to go.






						iRookie 100pc Reusable Tile Leveler Spacers with Special Wrench - Tile Leveling System for Floor and Wall Construction -T Shape Levelling Shim Flooring Alignment Leveller -Tile Positioning Tools Set - - Amazon.com
					

iRookie 100pc Reusable Tile Leveler Spacers with Special Wrench - Tile Leveling System for Floor and Wall Construction -T Shape Levelling Shim Flooring Alignment Leveller -Tile Positioning Tools Set - - Amazon.com



					www.amazon.com


----------



## RJSakowski (Jul 8, 2019)

ezduzit said:


> Not true. The "beam" will bend just from its own weight. So, if straightness is important, channel is a poor choice.
> I understand that you used it because you already had it.


Since the cross section of a piece of channel is one half a piece of I beam, the bending due to the weight of the beam will be the same.  Yes there is bending due to gravity's effect  but for construction purposes, it is negligible.  By actual measurement around .005" over 8 ft.  The contractors that I know work to +/- 1/8".


----------



## ezduzit (Jul 8, 2019)

RJSakowski said:


> Since the cross section of a piece of channel is one half a piece of I beam, the bending due to the weight of the beam will be the same...



Simply untrue. The I-beam is a much more efficient shape for beam loading, which is still the case for supporting its own weight. This is why the I-beam and I-joist are chosen for supporting spans in construction.

The amount of bending in a 10-foot channel can be measured in 1/16'ths of an inch. It is very easy to check this for yourself by supporting one at its ends and sighting down it.


----------



## Cadillac (Jul 8, 2019)

Having more info helps with a solution. For any tile job expecially a virgin concrete floor I would use a 16” wide scraper on a pole a scrape the entire surface. It will show high spots, find nails,screws, anything that might be a problem. Same style of scraper used to lift laminate tiles and glued carpet. 
 With a 12x24 tile your in the larger size notch probably 1/2x1/2 or larger. Back buttering the tile and a large notch gives you a ton of wiggle room to float the floor level. Using a 2’ level tile to tile keeping you flush and level. Don’t need much more than that other than some patience. Look into adding a latex bonding agent to mix in the mortar for helping adhesion to the concrete. Good luck.


----------



## T Bredehoft (Jul 8, 2019)

ezduzit said:


> It is very easy to check this for yourself by supporting one at its ends and sighting down it.



While the above is true, the use to which it will be put, determining variation in a floor, won't suspend it by the ends, but by many points across the floor. I'm sure an 8 foot 3" sq tube would work.


----------



## ezduzit (Jul 8, 2019)

T Bredehoft said:


> While the above is true, the use to which it will be put, determining variation in a floor, won't suspend it by the ends, but by many points across the floor. I'm sure an 8 foot 3" sq tube would work.



A square tube would be much better than a channel, as it is a balanced shape. A straight line would touch on only 2 points. A flat plane would touch on just 3 points. Because of sag, the channel would touch on possibly a few more.


----------



## francist (Jul 8, 2019)

Off on a bit of a tangent here, but what else is new....

RJ mentioned in one of his posts about using a laser level on a grid to measure the relative flatness of a floor. And also that it would probably be a tiresome process. I actually did just that a few years ago, and yes, it was laborious!

I wanted to get a topographical map, as it were, of a fairly large section of floor (40' X 75' roughly) that had a questionable support member. We wanted to be able to document whether the member was continuing to deflect, and if so where. So I came up with this system using exactly what RJ mentioned: a laser level and means of measuring from level line to individual points on a half-metre grid. These points were plotted into an Excel spreadsheet and I had my topo map of the floor.

Well it kind of worked but kind of didn't. The laser line is actually pretty thick, so if you're going for 1/8" tolerance that's maybe doable, but finer than that and you're guessing. And of course my level, although it was a pretty decent one, was not a razu  rotating kind. But it many ways as it often is, figuring the "how to" is often the most fun anyway.

I took the level and made a kinematic mount for it out of MDF. To let it rotate smoothly, I used part of a scrapped magnetic drive out of I'm not sure what anymore, but it was super smooth and very tight. Attachment to the rotating platform was accomplished with three rare earth magnets so I could easily assemble and disassemble the setup.












For the measuring part, a similar base of MDF held an aluminum scale at vertical and tensioned with a screw so that the scale could always be zeroed at a given point. Once the scale was zeroed to the laser line, I just moved the base around to the various points on my grid and any deviation would show as the line being higher or lower than my "zero" mark. 

Then I painted them both banana yellow, yay!

I took a number of measurement sets this way and yes it was interesting but ultimately not one hundred percent viable. Our more reliable surveys were done using an optical level and stadia rod, land surveyor style. But it was a lot of fun in the making, that's for sure.

Now back to your regular scheduled programming.....

-frank


----------



## RJSakowski (Jul 8, 2019)

ezduzit said:


> Simply untrue. The I-beam is a much more efficient shape for beam loading, which is still the case for supporting its own weight. This is why the I-beam and I-joist are chosen for supporting spans in construction.
> 
> The amount of bending in a 10-foot channel can be measured in 1/16'ths of an inch. It is very easy to check this for yourself by supporting one at its ends and sighting down it.


I cantilevered my 8' beam from a single point which should cause almost 10x the deflection of a beam suspended from two points and could see no measurable deflection by eye, by laser, and with a straight edge.


----------



## astjp2 (Jul 8, 2019)

Way overthinking this, just have a piece of .050+ aluminum sheetmetal sheared to 3-6" wide, it will be accurate to .010 or better, cost will be about $40.


----------



## tq60 (Jul 8, 2019)

Just buy a sheer if plywood and cut it in half, 8 x 2 now.

Factory edge will be dead straight.

Get a couple 2x4 and drywall screws to allow stacking and you can make it longer.

Sent from my SAMSUNG-SM-G930A using Tapatalk


----------



## RJSakowski (Jul 9, 2019)

astjp2 said:


> Way overthinking this, just have a piece of .050+ aluminum sheetmetal sheared to 3-6" wide, it will be accurate to .010 or better, cost will be about $40.


I often use a 12" x 60" sheet of aluminum as a straight edge when doing layout.  It works great as a cutting guide for drywall.  The problem with sheet metal is it bows easily.  Then, if it is not held perfectly vertical and it is bowed, the edge isn't straight any more.  It could be improved by sandwiching it between two pieces of 1x4 to stiffen it though.


----------



## Cooter Brown (Jul 9, 2019)

buy a piece of Starrett Ground flat stock from McMasterCarr....


----------



## whitmore (Jul 9, 2019)

ezduzit said:


> Channel is an unbalanced shape. I would choose a balanced shape such as I-beam or rectangular tube.


Perhaps a section of Unistrut/superstrut channel would be good; the ten-foot length is available, it has been
cold-worked, so should hold a straight  (if it didn't get munged in shipment).   I'd check (sight down a length)  the stock
at the local hardware emporium, you might get a pristine item with straight edges for not much outlay of cash.


----------



## astjp2 (Jul 9, 2019)

simple 90 degree bend will stiffen it up too


RJSakowski said:


> I often use a 12" x 60" sheet of aluminum as a straight edge when doing layout.  It works great as a cutting guide for drywall.  The problem with sheet metal is it bows easily.  Then, if it is not held perfectly vertical and it is bowed, the edge isn't straight any more.  It could be improved by sandwiching it between two pieces of 1x4 to stiffen it though.


----------



## Cadillac (Jul 9, 2019)

Cooter Brown said:


> buy a piece of Starrett Ground flat stock from McMasterCarr....



 Hate to see that bill! 10’ pieces of ground flat stock from starrett. I would want to scratch or get it dirty.


----------



## Cooter Brown (Jul 9, 2019)

Here is a 6' straight edge for $80 lol








						McMaster-Carr
					

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




					www.mcmaster.com


----------



## Cadillac (Jul 9, 2019)

Cooter Brown said:


> Here is a 6' straight edge for $80 lol
> 
> 
> 
> ...


Yeah that would do I suppose but who’d wanna handle that. 1/4x1”-6’ would be as flimsy as twizzler hanging from my mouth. You’d need at least 3” to be sturdy still would whip. My wife has a carpet binding biz and uses straight edges a lot. Hers are all 1/4” x3”from 4’-12’ all commercial bought. Precise enough for carpet but a pain to handle the large ones. As expected if not vertical with two hands on em they bow to either direction.


----------



## Toolmaker51 (Jul 14, 2019)

My focus is still on the straightedge more than the floor; you''ll have a tough [$$$] time finding a shop with a 10'+ plus mill, planer, or surface grinder. I'd go craigslist for a 8' plate level. A decent bar or extrusion isn't bad, just calculate rough Airy points. Your floor will never realize the difference.





						Airy points - Wikipedia
					






					en.wikipedia.org


----------



## .LMS. (Jul 15, 2019)

I have one of these that I use as a reference edge for milling long boards.   It's heavy, but it does the trick.









						Straight Edge 102" | The Pinske Edge | Solid Surface Fabrication Tools & Supplies
					

Specializing in high quality, solid surface solutions for commercial & residential customers. We also carry high performing tools and supplies for purchase.




					pinske-edge.com


----------

