Site Measuring Joists - Web Thickness

[EngDM]

Hey all,

Just wondering if anyone has a solution to finding a web thickness of a hollow round bar member. I want to perhaps bring a drill and put a small hole, but what tool could measure thicknesses off that? My callipers would require quite the substatial hole.

There is an old joist type up in Canada where the OD is the same but the thicknesses vary throughout. As of late we have just been using the minimum size and reinforcing heavy, but I'd like to find a more economical solution.

 

[Retrograde]

You can get ultrasonic thickness testers. My company has one and it works reasonably well.

Thickness Testers

www.starrett.com

 

[skeletron]

Drill a hole. Then take some 22ga or 20ga wire or similar. You can get some at the craft store, or the site might have some kicking around from tying rebar or other bundles. Then crimp the wire into an L, hook the end over the thickness, mark it with your fingernail or whatever. Measure the wire distance with calipers. This will give you a "best guess" for the lowest dollar in a pinch.

 

[hawkaz]

We use an Ultrasound tester also.

 

[XR250]

Drill a hole. Then take some 22ga or 20ga wire or similar. You can get some at the craft store, or the site might have some kicking around from tying rebar or other bundles. Then crimp the wire into an L, hook the end over the thickness, mark it with your fingernail or whatever. Measure the wire distance with calipers. This will give you a "best guess" for the lowest dollar in a pinch.

Buggering on the interior surface of the hole can make this inaccurate.

 

[skeletron]

Buggering on the interior surface of the hole can make this inaccurate.

Very true. But it's an option vs. assuming a minimum thickness vs. buying a $1500 USD machine. Buddy needs to do the cost benefit analysis.

 

[EngDM]

I have decided to proceed with hitting the member with a tuning fork and using my finely tuned ears to determine the resonance, and from that, the thickness.

/s

 

[Harbringer80]

There is an inexpensive tool for this. Drill a hole, and use a hi-lo gauge to accurately measure the thickness. If you are concerned about the burr inside the hole affecting your measurement use a deburring tool (in red below) before measuring. I've done this multiple times.

 

[EngDM]

There is an inexpensive tool for this. Drill a hole, and use a hi-lo gauge to accurately measure the thickness. If you are concerned about the burr inside the hole affecting your measurement use a deburring tool (in red below) before measuring. I've done this multiple times.
View attachment 7655View attachment 7656View attachment 7657

How big of a hole does this thing need?

 

[gte447f]

How big of a hole does this thing need?

I was curious, so I just watched a video on the manufacturer's website. I'm still not sure exactly what size hole is required, but pretty big. Definitely not a pinhole. Looks to be about 1-4"-1/2", Neat tool though. It looks like it's actually intended to measure various aspects of pipe fit-up when welding sections of pipe together.

 

[DanKile]

You could use a wire or the depth gauge of calipers through a small hole to measure from the outside at the hole to the inside opposite to the hole. Then subtract off the outside diameter to get the thickness.

 

[Harbringer80]

Obviously it's not going to be a pinhole but you can offset the ends when you insert it. If you are careful you might be able to make a 1/4" diameter hole work. Though a 1/2" hole is plenty. We keep a box of these metal plugs for when we need to drill. If you want something completely non-destructive you are going to need to pay more. Or drill a pinhole with a bent wire and get a very approximate result.

 

[Retrograde]

But it's an option vs. assuming a minimum thickness vs. buying a $1500 USD machine. Buddy needs to do the cost benefit analysis.

You can get ones that are significantly cheaper than $1500. I have seen some for under $200. Check out Amazon.

 

[Harbringer80]

You can get ones that are significantly cheaper than $1500. I have seen some for under $200. Check out Amazon.

When I last checked out the cheaper ones (couple of years ago) I thought they were not accurate enough for me for hot rolled steel and even the expensive ones were not accurate enough if I need to measure cold formed.

 

[EngDM]

You can get ones that are significantly cheaper than $1500. I have seen some for under $200. Check out Amazon.

I'll have to take a look. There's a couple that have pretty low minimum thicknesses, but with it being Amazon I am just a bit weary, can't say whether that is justified or not.

 

[bones206]

I got one of the cheap Amazon ultrasonic gauges a couple years ago. Tried to measure the thickness of a tube steel column supporting 6 stories, and each measurement I took varied by more than 50%. Haven’t used it since because I just don’t trust it.

 

[BridgeSmith]

Since it's round, you could drill a small hole, insert a straight wire to the opposite side and subtract from the OD.

 

[EngDM]

Since it's round, you could drill a small hole, insert a straight wire to the opposite side and subtract from the OD.

I think this is what DanKile suggested above. This is quite an easy an inexpensive fix. If the owners permit me to drill through the joists a bit then this will work. I will look into a cheaper (but still reliable) thickness scanner too.

I got one of the cheap Amazon ultrasonic gauges a couple years ago. Tried to measure the thickness of a tube steel column supporting 6 stories, and each measurement I took varied by more than 50%. Haven’t used it since because I just don’t trust it.

Which one, so I can avoid it?

 

[bones206]

It's collecting dust somewhere at the office. I'll try to remember to check next time I go in. But it was in the $150 range and I think all those Amazon ones are more or less the same.

 

[BridgeSmith]

I think this is what DanKile suggested above.

Oh, you're right. I missed that. Sorry DanKile; didn't mean to try to steal your thunder.