Stainless Expansion Bolt with Fixed Hanger

Cost: approx. $10 each with hanger

Expansion bolts are easy to place, strong and readily available. Mechanical bolts work by either expanding of compressing - gripping the rock by pressing against the wall of the bolt hole. The pressing action creates friction between the anchor and the rock; for the bolt to pull out, the applied load has to overpower this coefficient of friction.

Expansion bolts are expensive as a unit as you have to purchase a commercial hanger on top of the expensive bolt. If you are only placing a few bolts then expansion anchors are the best place to start as the cost outlay for tools is very small compared to glue in anchors.

• Pro: You can use them immediately after placing
  
• Pro: Almost ‘fool proof’ to place
  
• Pro: Less tools to buy
  
• Pro: Hanger is replaceable
  
• Pro : Likely to show signs of working loose if in marginal placement
  
• Con: Bolt and hanger deforms after repeated falls
  
• Con: Hanger can be stolen and bolt tampered with
  
• Con: Bolt can loosen
  
• Con: Rust can occur when two grades of stainless (i.e. bolt & hanger) are forced together

Recommended brands/models for medium to hard rock

Ramset 12mmx75mm SS Hex-Head Dynabolt DP12075HSS
Powers Flush Head Sleeve 12mm SS FHS1275SS
Powers Power-Bolt Anchor 12mm SS RBHM1370SS
Fixe 12mmx75mm Triplex SS Expansion
Hilti 12mmx102mm SS HSL-G-R

Recommended brands/models for hard rock (granite)

Ramset 10mmx65mm SS Trubolt T10065SS
Powers Through Bolt 10mmx50mm SBA1050SS

Glue in Ring Bolt

Cost: approx. $5 excluding glue

Glue in rings are the strongest and most hard wearing of all the bolt types. They are complex to place however and involve quite a bit of expensive equipment to place. For a ring with a rod diameter of 10mm - a 12mm hole must be drilled and a large notch to recess the ring must be drilled. They must be recessed to stop the ring twisting out of the hole. You can only use injection gun glue with rings as the capsules never have enough glue to fill the notch. Most ring bolts placed in Australia are homemade. If you can weld and bend stainless steel then you could consider making your own.

Before use it is important to prepare the ringbolt so it achieves maximum bond with the glue. Wash the entire ring with soapy water to remove any grease. This removes any residual chemicals left over in the manufacture of stainless steel. Brush the entire surface of the bolt with a wire brush or rounded file. This creates a rough surface which the glue will bond to. If the ring has less than four surface notches then it is recommended to add some extras using an angle grinder or hand file. The notches stop the ring from turning in the hole and breaking the glue bond.

• Pro: Eye fits multiple carabiners and can be lowered off from
  
• Pro: Bolt cannot be stolen or tampered with
  
• Pro: Good in soft rock
  
• Con: Messy to install and takes up to 24 hours before you can use it
  
• Con: Hard to replace
  
• Con: Tools are expensive (caulking gun)
  
• Con: Likely to pull out without warning if placed incorrectly

Recommended brands/models

The Rebolting Fund (NSW)
Fixe ringbolt

Glue in U-Bolt

Cost: approx. $3 excluding glue

U Bolts are by far the cheapest of the bolt solutions if you are bolting steep rock. They are moderately easy to make at home - using 10mm bent stainless steel bar. The biggest problem is their high visibility and the requirement to drill two holes per bolt. One of the biggest advantages is that they usually require light hammering to get them into the two holes which means they stay in the rock when the glue is drying - which is great when bolting roofs. You can only use injection gun glue with U bolts as you cannot spin the bolt into the capsule. U bolts have been known to fail in very soft rock because of the close distance between the two legs.

Before use it is important to prepare the U Bolt so it achieves maximum bond with the glue. Wash the entire U with soapy water to remove any grease. This removes any residual chemicals left over in the manufacture of stainless steel. Brush the entire surface of the bolt with a wire brush or rounded file. This creates a rough surface which the glue will bond to. If the U has less than four surface notches then it is recommended to add some extras using an angle grinder or hand file.

• Pro: Eye fits multiple carabiners and can be lowered off from
  
• Pro: Cheap to make – no welding required
  
• Pro: Stays in overhangs when drying
  
• Pro: Bolt cannot be stolen or tampered with
  
• Con: Hard to install and takes up to 24 hours before you can use it
  
• Con: Hard to replace
  
• Con: Tools expensive (caulking gun)
  
• Con: High visibility
  
• Con: Likely to pull out without warning if placed incorrectly

Recommended brands/models

Fixe SS Glue In 3.5 014-B

Glue in Machine Bolt

Cost: approx. $2 excluding glue

These look like the Aussie classic bash-in 'carrot' but are instead held in by glue. They are very low in visibility and easy to place when using capsules. Buy 10mmx100mm (approx. - imperial measurements is fine). Make sure the bolt head is large enough that hangers won't slip off. Depending on the manufacturer of the bolt the head diameter changes greatly. I always bring a range of keyhole hanger brands in to the bolt shop to test them all before buying. It is better to buy bigger - as you can file the head down a little if they are not perfect.

After purchasing you must do some manual work to the bolt to make it bond with the glue. Firstly 'roughen' up the smooth section of the bolt shaft with a wire brush/file. Then make small 'notches' in the shaft with an angle grinder about 1/10 of the diameter of the bolt. Make lots of these - but steer clear of the top 2 cm of the bolt or so. This will create 'pockets' for the glue to hold the bolt in when there is no thread. Create a chisel end on the bolt so it can break and mix the glue correctly in capsules. The chisel end also stops the bolt rotating in the hole. Wash the entire bolt with soapy water to remove any grease. Full design specs of glue in machine bolt are here.

• Pro: Cheapest
  
• Pro: Cleaner when using glue capsules
  
• Pro: Low visibility
  
• Pro: Easier to replace than ring/U (unscrew)
  
• Pro: Bolt cannot be stolen or tampered with
  
• Con: Cannot be used on overhangs without hanger
  
• Con: Hard to install and takes up to 24 hours before you can use it
  
• Con: Likely to pull out without warning if placed incorrectly

Recommended brands/models

Stainless Steel 10mm x 90mm Machine Bolt

Glue Capsules

Cost: approx. $4 excluding bolt

Capsules are a quick no-mess solution to install glue-in machine bolts and studs. Never use them to install ring bolts as they do not contain enough glue to fill the recessed eye of the bolt. Capsules contain two parts of glue in a glass or plastic casing which is broken and mixed together by 'drilling' the bolt into the capsule. You must use a hammer drill to install them or they will not mix correctly. A hex head socket adapter which fits SDS drills needs to be used. Hilti makes a commercial version of this that costs around $30. Glue capsules will expire after a set time. Do not use capsules that you do not know the history of.

Glue in anchors transmit the load of the anchor over a wider area of rock than expansion bolts ever can. This means that the load is spread over the entire area that the glue bolds with the rock. This is turn means that the anchor is more reliable in general because it is usually impossible to visually identify internal rock fault lines.

Recommended brands/models

Ramset M10 Chemset Spin
Hilti M10 HVU
Powers Chem-Stud KEM10

Injection Glue

Cost: approx. $2 excluding bolt

If you are placing ring bolts and U bolts then you must use an injection glue system. Most bolt manufacturers produce high quality glue which is deposited using a brand specific caulking gun. The two parts of the glue are mixed through a nozzle and the end result is perfect mixed glue which dries in a few hours. If you are placing a lot of bolts then a glue system is certainly a cost effective method. It is very messy and requires diligent attention to detail and quality control. The easiest way to make an obvious, messy and bad bolt is to try and place rings without practicing first! Of all the systems this one requires reading in detail the manufacturers installation guidelines.

Glue in anchors transmit the load of the anchor over a wider area of rock than expansion bolts ever can. This means that the load is spread over the entire area that the glue bolds with the rock. This is turn means that the anchor is more reliable in general because it is usually impossible to visually identify internal rock fault lines.

Recommended brands/models

Ramset Chemset Injection 801
Ramset Chemset Injection 101
Hilti HIT-HY 150
Powers Power-fast Epoxy
Powers Acrylic-100
Powers KF2