Atlas Copco have a range of such machines, I've used them on more than one site, used for production drilling of blast holes, up to 5 m, either in an air cor or RC format. There are various bit sizes available; depending on required spec. Modern trend I think is to sample blast holes for GC, rather than a separate drilling program.

Probably one of the best track mounted rigs I have used - in mining environment for grade control sampling was the Atlas Copco ROC L8 blast hole drill rig (which can be retro-fitted with the Metzke and Sandvik RC sampling system with cone splitter).

The benefit of this system is that if rigs are needed for blast hole (percussion drilling) the RC configuration can be removed (and re attached for RC Grade control when needed.).

As we were blasting / mining 5m benches (2.5m flitches), and the ore body was dipping approx 60 deg, we would generally drill 24m (20m vertical - or 4 benches in advance), in some instances would drill 36m if we could not gain access in future campaigns. Did not go much further as we didn't want to downhole survey the holes (the hammer does tend to affect the hole trace on longer holes).

From memory we were drilling 108mm diameter (4 inch bit), I remember penetration rate was good (can't remember metres / shift), the rock type was ultramafic / felsic material.

We use a Schramm T450 rig. The holes are angled 60 degrees; depths usually target 4 benches (approx 50m) with a 5 1/2" hole. This is a dedicated grade control rig that when possible also drills piezometers and water wells.

We have a Progradex sampling system and a blowdown valve for wet drilling rod changes to keep the samples dry. Our drill rate is currently hitting 200-240m per day in sediments and lavas.

I have had experience with the ROC L8. They are not much bigger than the normal top hammer blast hole rigs so they are quite easy to manoeuvre around. In summary - they are very good. There are numerous companies in Western Australia that have these now.

The hole diameters we were using was 130mm, and were drilling angled holes to 46 m - that is about 40 vertical metres. Hole deviation was checked by EMS and generally was less than 2-3 degrees. Penetration rates for reasonably hard material (fresh dolerite) were around 130m/shift.

As above, have used ROC L8's fitted with progradex rotary cone splitters 4 inch 6m rods fitted with 5 1/2 bit. Drilling consisted of 20m holes at 65deg to cover 18m bench mined in 3m flitches. Samples collected on 2m intervals generally ranged from 6-10kg depending on material type. In primary, drilled 8-10 holes in 11hr shift and in oxide up to 16 holes. These rigs can be fitted with carousels to hold the rods so for shallow grade control ideal. Again the ability to convert from RC to blasthole meant they could be used by both geology and production. Use air core as well in wet clays that worked fairly well too.

Here's my 2 cents worth: There are numerous drills and sampling systems available, as indicated by others in this thread. Atlas Copco makes several suitable rigs, as do other companies.

The question on hole diameter and depth should be answered in consideration of the block model and rate of production planned for the open pit mine plan, and also on the size of the benches, and mining plan (ROM vs. crushed ore). The depth should be 0.5 to 1.0 meter greater than the planned mining bench height, and usually this is determined by the size of the blocks used for the mine model to calculate resource/reserve determinations. The distance between holes should take into consideration the effective blast characteristics of the ground and the continuity of mineralization determined from the original exploration drilling.

If selective mining is to be employed, smaller benches and smaller blocks would argue for 3.5 to 5 m depth and 2.5 to 5 meter spacing between holes with 4-inch bits. Larger production with larger benches - where the mine plan is to take the entire block to ore or waste, would require deeper holes with wider spacing, and larger bits (providing for more explosives capacity). Six meter- to 20 meter benches would be appropriate, depending on mine plan.

Daily rates of drill production relate to several factors including how hard the ground is, how altered the rocks are, how far apart and how big the holes are. 200 meters per shift, per drill is a good number to use for budgeting, and then adjust it according to actual production or historical experience. 

How does the Progradex perform when sampling in damp conditions when drilling clays?

Generally pretty good! The trick for us was to switch from RC using a hammer (standard system) to air core bit. Then for the rotary cone splitter set the dropbox gates to stay open continuously, so the sample falls continuously to prevent bridging inside the dropbox. This worked well and duplicates sampling and twin drillholes confirmed the method was viable. A lot depends on the driller and the rate of drilling. With the setup the driller could see the sample reject falling through the base of the sampling system and if it stopped while drilling could stop rods pull back and work the hole till sample return was re-established.