This is the first batch of U-bolts I've made.
Spec for solid sandstone or equivalent:
- 9.52mm or 10mm diameter stainless
- 70-80mm embedment
- 60mm ground and notched
- 9.52mm diameter 304 stainless steel. They sell it in 4m lengths and the guys at Midway Metals at Yatala appear to be the cheapest in Brisbane by far at $15.60 +GST per length (thanks for the tip Mikl). The Sydney guys use SAS Sales. Use 316 stainless for seaside areas.
- A bench grinder
- A sturdy bench vice (I'm up to my third - they break!)
- 500-600mm of sturdy water pipe 20mm diameter
- An angle grinder or (better) a circular saw with a metal cutting disc (the blades are swappable, remove the wood cutting blade and buy a cutting disc for a few dollars). If you're making lots, the best and safest option is a drop saw (i.e. a cutoff saw). You can get these for under $100 at Bunnings.
- Ear plugs
- Ear muffs (yes, as well)
- Face mask covering nose and mouth
- Jeans
- Shoes
- Eye protection (crucial - I had a flaming bit of metal hit them yesterday)
- Cut into 220mm lengths with saw
- Remove burred ends with bench grinder
- Grind surface 60mm both ends
- Notch the ground area thoroughly, but not too deeply towards the centre
- Place roughly 70mm length into vice and commence bending with pipe
- Very soft rock is rock that is able to be reamed out when you're using your hole cleaning brush to clean the hole. You'll sometimes see this with very soft sandstone. In this case, you need to use longer bolts, and more glue. Go for U-bolts with legs that have an embedment of at least 100mm each. Any longer than 180mm is probably overkill.
- In softer rock like sandstone, polyester glue like Ramset 101 is okay, but a better option (and crucial in hard rock due to smooth-sided holes) is epoxy based glue like Ramset 801 or Powers PowerFast PRO. PowerFast PRO is the best glue I've ever seen as it has no odour, and lasts for three years.
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