10mm vs 3/8" hanger

Quick question:

Will a 10mm hanger work with a 3/8" bolt or is 3/8" hanger my only option for a 3/8" bolt

ClimbBaja wrote:

Yes, a 10mm hanger will physically fit on a 3/8" bolt.  3/8" = 9.525mm  I don't see any problem with that at all. 

Just don't apply that thinking to drill bit diameters and bolt sizes! No mismatching of bolts and holes allowed. Those tolerances are critical with mechanical anchors.

Yes, I know the 10mm will fit on the bolt but I'm wondering if the difference in size could potentially cause issues. For example, I could see this potentially causing the hanger to spin. I understand this isn't an issue functionally, but I know that many climbers aren't aware of this and that I may get complaints if the hanger spins. However, if I'm wrong and it won't cause the hanger to spin then obviously that isn't an issue. I guess what I'm asking is what issues, safety related or not, could potentially arise from using a different sized bolt hanger combo.

Full disclosure:

I can buy hangers for cheaper but only those of the european variety and I would like to use them with the 3/8" bolts I typically use. I'm trying to save a buck (actually quite a few bucks) by getting the euro hangers but before I commit to this decision I want to make sure that the difference in size won't come back to bite me in the ass. 

The fixture hole on literally every single hanger placed on a 3/8" diameter bolt is 10mm. Fixe, metolius, petzl, climbtech and such only use metric sizing in their manufacturing process. All those hangers you see marketed for 3/8" bolts are really made with 10mm holes. The real issues come from inexperienced developers using incorrect hardware for the rock type and local environment, and poorly placed hardware. If you are concerned about spinners use a lock washer in between the nut and hanger and make sure you use a torque wrench to tighten the bolt to what ever the manufacturer recomends (usually 25-30 ft/lbs for 3/8" wedge anchors).  

C. Williams wrote:

The fixture hole on literally every single hanger placed on a 3/8" diameter bolt is 10mm. Fixe, metolius, petzl, climbtech and such only use metric sizing in their manufacturing process. All those hangers you see marketed for 3/8" bolts are really made with 10mm holes. The real issues come from inexperienced developers using incorrect hardware for the rock type and local environment, and poorly placed hardware. If you are concerned about spinners use a lock washer in between the nut and hanger and make sure you use a torque wrench to tighten the bolt to what ever the manufacturer recomends (usually 25-30 ft/lbs for 3/8" wedge anchors).  

Cool, thanks. This is the info I needed.

Ny-locks are great on studs too as cheap anti spinner insurance

ClimbBaja wrote:

 Torque specs for a 3/8" stainless steel wedge anchor never exceed 25 ft. lbs.  20 ft. lbs. is typical. Torque values for stainless steel are significantly lower than for carbon steel bolts. And I hope no one is so cheap that they are placing carbon steel wedge anchors.

Hilti "Kwik Bolt" KB3, 3/8" SS wedge anchor = 20 ft. lbs. per the Hilti website. https://www.hilti.com/medias/sys_master/documents/h7a/9233453875230/Technical_information_ASSET_DOC_LOC_1543385.pdf

Powers "Power-Stud", 3/8" SS wedge anchor = 20 ft. lbs. per the Powers website. http://www.powers.com/pdfs/mechanical/07424MGSS.pdf

I hate to be pedantic here, but the technical documents you posted for the power studs clearly states 28 ft/lbs for the 304 and 316 grade anchors. I have been using Simpson wedge-all anchors and they torque to 30ft/lbs. https://embed.widencdn.net/pdf/plus/ssttoolbox/hvn6qpw1xx/C-A-2016-Wedge-All-designinfo.pdf?u=nytqc5

If you were referring to the torque values for stainless 5-piece bolts then you are correct as those values are significantly lower than the plated steel version. 3/8" torque to 12ft/lbs and 1/2" to 25 ft/lbs if I remember correctly. Regardless, I feel it is important to carefully read and understand the technical literature for what ever anchor the developer chooses before they begin drilling holes.

ClimbBaja wrote:

Just don't apply that thinking to drill bit diameters and bolt sizes! No mismatching of bolts and holes allowed. Those tolerances are critical with mechanical anchors.

The Powers Power Bolt (AKA 5-piece) is rated to be used in either a 3/8" or 10mm hole.  It even says that on the outer sleeve of the bolt.  We have bench tested it with a load cell and the pull out strength in either size hole exceeds manufacturers spec.

Other makes/types of bolts might require tighter tolerances.

Bruce Hildenbrand wrote:

The Powers Power Bolt (AKA 5-piece) is rated to be used in either a 3/8" or 10mm hole.  

It doesent appear so. After reading this I sent an email to Powers Engineering and they responded back saying that the bolt is only approved for use in holes drilled with ANSI 3/8" bits. I also looked through the technical manual and the installation manual and neither appear to say that 10mm is an appropriate size. Both manuals say to install the bolts in 3/8" holes using ANSI certified 3/8" SDS or carbine masonry drill bits. I dont know why Power's put 10mm on the side of the sleeve, but I dont think it's meant to mean it's approved for use in a 10mm hole since they are saying it's not and the installation guide says the same thing.

Even so, it's not smart to use a hole larger than the bolt is intended to be installed in. Mechanical bolts in general have tight tolerances and even a difference of less than 1mm can drastically influence the holding power of the bolt. Your tests might have shown that the bolt doesn’t pull in the larger hole, but certainly you couldent have tested every type of rock and in every situation, and in this situation dynamic loads could produce a much different outcome than static pull testing. Awhile back I tested the Fixe Triplex bolts in 1/2" holes, which is only 0.7mm larger than rated, and the holding power dropped from 25kN+ to less than 6kN in tension and those are sleeve style bolts. I even used a 10mm hanger so I wasent pulling on the flange and I installed the samples in extremely hard rock.

20 kN wrote:

After reading this I sent an email to Powers Engineering and they responded back saying that the bolt is only approved for use in holes drilled with ANSI 3/8" bits. I also looked through the technical manual and the installation manual and neither appear to say that 10mm is an appropriate size. Both manuals say to install the bolts in 3/8" holes using ANSI certified 3/8" SDS or carbine masonry drill bits.

I don't work in the industry, but a quick glance suggests the applicable ANSI standard for carbide masonry bits is B212.15, which specifies 0.390” and 0.398” as the min and max diameters for a 3/8" bit.  Which in real units is 9.9 - 10.1 mm, indicating that the 3/8" label is just a nominal size and not the actual physical size.

Jeremy B. wrote:

I don't work in the industry, but a quick glance suggests the applicable ANSI standard for carbide masonry bits is B212.15, which specifies 0.390” and 0.398” as the min and max diameters for a 3/8" bit.  Which in real units is 9.9 - 10.1 mm, indicating that the 3/8" label is just a nominal size and not the actual physical size.

Masonry bits are a nominal size to take fixings which are also nominally sized (the sizes are governed by an industry standards organisation in Germany which is why quality bits have a funny symbol on the shank like a wavy oval). Hand -held rotary hammers produce an out-of round hole (called a Reuleaux polygon) which is normally triangular. If you take a 10mm drill bit it measures 10.6mm across the tips and the hole will measure the same diameter BUT it is impossible to fit a 10mm bar into it as it is actually triangular with curved sides, for this reason the relevant fastening will have a diameter of 9.8mm. As the system is designed around this it is normally of no consequence since the two parts are made to be compatible..

There are special bits (normally three fluted) which reduce the problem for special applications like sleeve bolts, the ones I know of are called Deltagon bits from Miyanaga but there are probably others around. 

ClimbBaja wrote:

C. Williams,

You're right about the Powers torque spec of 28 ft. lbs. (normal-weight concrete). I missed that; lower on the same page is a chart showing 20 ft. lbs. for structural lightweight concrete.

ITW Red Head "Trubolt" wedge anchor, 3/8" SS = 25 ft. lbs. https://www.itwredhead.com/Portals/0/Documents/2017%20Catalog/Trubolt%20Wedge%20Anchors.pdf?ver=2017-03-23-150439-603

The Pocket Ref, Glover 3rd edition shows standard dry torque for 18-8 SS (aka: 304 SS) 3/8" - 16 bolts = 19.37 ft.lbs. ;  316 SS = 20.30 ft. lbs. 

Another chart shows suggested maximum torque values around 20 ft.lbs. http://www.engineersedge.com/torque_table_sae.htm

It's interesting that at least one manufacturer of wedge anchors is exceeding that by 50%. 

There´s loads of confusion about the torque values especially for wedge-bolts. For these (and other types) the given torque values are those which achieve the rated pull-out value for the product.

The maximum recommended torque values given in engineering handbooks are NOT related to the failure point of the bolt, they are the maximum practible clamping pressure before the two surfaces (the threads) start to gall together (they seize up) which is why they are given as dry torques. All commercially available fasteners are pre-treated to reduce galling which is a particular problem with stainless steel and you can generally go at least double the recommended torque before failure is likely.

Wedge bolts are designed (or are supposed to be) so that the small "ears" that engage in the rock shear off before the bolt actually breaks and both the bolt and the clip spin, I´ve tested a number of different manufacturers bolts and they all turn into spinners before the bolt breaks, for the standard Euro 10mm stainless bolt this occurs at around 92Nm (68ft lbs) which is below the failure point  of the bolt itself and around double the recommended torque.

C. Williams wrote:

The fixture hole on literally every single hanger placed on a 3/8" diameter bolt is 10mm. Fixe, metolius, petzl, climbtech and such only use metric sizing in their manufacturing process. All those hangers you see marketed for 3/8" bolts are really made with 10mm holes. The real issues come from inexperienced developers using incorrect hardware for the rock type and local environment, and poorly placed hardware. If you are concerned about spinners use a lock washer in between the nut and hanger and make sure you use a torque wrench to tighten the bolt to what ever the manufacturer recomends (usually 25-30 ft/lbs for 3/8" wedge anchors).  

C. Williams is right, everything made these days is actually a 10mm hole. You can find true 3/8" size holes only on very old hangers such as old SMC and Leeper hangers. Stainless SMC hangers from the 1980s in the 3/8" size will fit a 3/8" stud bolt, but the sleeve of a 3/8" 5-piece is just slightly too big to fit (so I assume the sleeve on the 5-piece is just a tiny bit larger than 3/8", either that or the hole is just slightly smaller than 3/8").

The one exception with newer hangers is that sometimes powder-coated camouflaged hangers can have thick coatings that reduce the hole size a little bit. But it's usually possible to force the bolt through.