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Rock Climbing Micro Nuts - A Comparison

 

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Micro Nuts Comparison

 

Broken Micro WiresThe table below gives a comprison of micro nut strengths using data from both silver soldered and swaged nuts.

Small soldered nuts are generally stronger than the equivalent size of swaged nut because you can get a wider diameter wire into the head of the nut, not because soldering creates a stronger join or because it removes a tight bend as the wire goes around the top of the nut. This advantage decreases as the head size increases.

Thus use a 2.00mm wire and you can get circa 4-5kN out of a nut, but if you can use a 2.5mm wire you can get 7 - 8kN.

This is where the IMPS/Brass Offsets/RP's win in sizes 1+ 2 - on an IMP/RP size 2 you can get a 2.00mm wire in a miniscule head and achieve 5kn. A swaged nut of the same size (Wallnut 0) has to use 1.5mm wire and the strength drops to 2+kN.

However jump up slightly in head size and you can get 2.00mm wire into a swaged head. The Wallnut 0.5 uses 2.00mm wire and is only very slightly wider than a IMP/RP 2 and is conservatively rated at 4kN. In a real world situation it is as/almost as strong as an IMP/RP 2

On IMPS/Brass Offsets/RP size 3 the advantage is further decreased because you can't get a 2.5mm wire into the base of the head, but on the Wallnut 0.75 the head is now big enough to take a 2.50mm wire when swaged and also has plenty of metal to stop it pulling through placements. Thus the Wallnut 0.75 (same width as a IMP/RP 3) going forward will use 2.50mm wire and be conservatively rated 6kN - stronger than an IMP/RP 3.

It also needs to be remembered that the swaged micro nuts (i.e. DMM Micro Wallnuts) offer greater, surface contact which is an important consideration as a common mechanism for failure in real life is the nut pulling through the placement. Once again the devil is in the detail - using a tougher 7075 aluminium alloy nut as on the DMM Micro Wallnuts gives extra holding power compared to a softer 6000 series alloy.

Add to this the fact that standard steel wire as used on swaged nuts generally has a higher tensile strength than the stainless steel wire that must be used on soldered nuts.

On the other side of the coin IMPs/RPs and Brass Offsets will fit where the wider swaged alloy nuts won't go....

Each nut has its own strengths and weaknesses and the key thing is to understand them.

There is no perfect micro wire although an IMP/RP 2 comes pretty close; but a micro wire rack that includes IMP/RPs 2, 3 and 4, Brass Offsets 2, 3 and 4 plus Micro Wallnuts 0.5 and 0.75 is a really good starting point.

There are more climbing articles on the Climbing Tips & Advice page.

Model
wire diameter (mm)
width of nut (mm)
depth of nut  (mm)
kN - marked rating
Comment
DMM Peenut 5
2.50
13.9
9.6
8.0
BD Swedge 6
2.90
10.5
8.9
8.0
DMM Peenut 4
2.50
13.4
8.8
8.0
RP 5
2.50
11.4
8.7
8.2
High - most likely a mean or max reading
DMM IMP 5
2.50
10.5
8.0
7.0
A 3 sigma rating
DMM Wallnut 2
3.45
15.6
8.2
9.0
Very strong for its size
RP 4
2.50
9.3
8.0
8.2
High - most likely a mean or max reading
DMM IMP 4
2.50
9.3
8.0
7.0
A 3 sigma rating
BD Swedge 5
2.50
9.6
7.5
6.0
A low rating - it should be stronger
DMM Peenut 3
2.00
12.8
7.4
5.0
DMM Wallnut 1
2.50
14.0
6.6
7.0 + 4.0
Again very strong for its size
DMM Peenut 2
2.00
11.8
6.4
5.0
RP 3
2.00
8.0
6.2
5.5
High - most likely a mean or max reading
DMM IMP 3
2.00
8.0
6.2
5.0
Good
DMM MW 0.75
2.50
12.8
6.0
6.0
Very Good
BD Swedge 4
2.50
8.6
6.0
6.0
Good
DMM Peenut 1
2.00
11.6
5.7
4.0
BD Swedge 3
2.00
7.5
5.2
5.0
Very Good
DMM MW 0.5
2.00
11.6
5.2
4.0
BD Mini 2
1.65
10.7
4.8
2.0
DMM MW 0
1.50
10.7
4.6
2.0
BD Swedge 2
1.75
6.6
4.4
3.0
RP 2
2.00
6.6
4.4
5.5
Awesome
DMM IMP 2
2.00
6.8
5.0
5.5
Awesome
BD Mini 1
1.65
9.0
4.1
2.0
DMM MW 00
1.50
9.6
4.0
2.0
DMM IMP 1
1.00
5.3
3.6
4.0
Very Good
RP 1
1.00
5.3
3.6
3.6
BD Swedge 1
1.30
5.0
3.2
2.0

 

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