[Coral-List] Underwater drills & their care: a summary

[Vaidas Kirsys]

Dear Coral-Listers,
Thanks ever so much for all the info. Since a lot of you actually asked to share what people replied to me, I did a quick summary of things I learned. But... before you immerse yourself into brilliant tips on drills & drill tender-loving-care, please note that one question remains unanswered: Is it okay to run a drill which is made for 90psi (6bar) from a normal dive regulator ~120 psi (8-9bar) ? If you had any experiences, pleas indicate if you adjusted the 1st stage  to lower intermediate pressure or just ran it at higher than recommended pressure?
Now here is the summary:
General agreement is that lifetime of drills is limited at sea (G.Challenger, A.Ross). Most agree that any brand is okay (D,Deis, J.Carilli, B.Bourke, D.Barshis, A.Ross), few said that more expensive drills seem to last longer (J.Carilli). B. Bourke suggested to just buy whatever is cheap and available - two or three at a time, and replace when broken.
Care of the drill after dive is key. Most suggestions included running it in freshwater, and C.Hunter recommended flushing with pneumatic tool oil between uses to prevent freezing up (disconnect the hose, depress trigger, and pour in oil; reconnect to blow oil out==kind of messy, so I use the same towel to wrap around the drill each time).
Particularly good advise seems to be storing in a bucket of food oil/mineral oil (D.Deis), or vegetable oil (B.Bourke, D.Barshis). Barshis reported using all different kinds of oil (pnuematic tool oil, grease, etc.), but finally settling on just plain vegetable oil from the grocery store, reporting that they have been able to use the same $50 drill for many years by following the procedure below (Thanks D.Barshis!):
1. Use drill on a dive
2. As soon after the dive as possible run the drill in a bucket of freshwater
3. Store the drill completely submerged (over the handle and connection as well) in a small bucket of vegetable oil (canola, mix, really any cooking oil should do).
4. Rinse drill with freshwater and dish soap right before the next dive
5. Repeat.
NOTE: as soon as you forget to rinse in freshwater and/or let it dry out in the air instead of storing in oil it will rust. If you're on the boat you can always transport the drill back to shore submerged in the freshwater bucket until you can put it in the oil. Any drill bits /hole saws should also be stored in oil .
J. Carilli, D. Bureau, Heiss and a few others suggested to take drills apart after each dive and clean all the pieces (WD40), then marine lube to re-grease all the pieces before putting it back together.
 D. Barshis aviced that other important considerations are to get the right connectors (some scuba shops will have access to 1/4in npt quick disconnect fittings).
Most people seem to run their tools off of a standard scuba regulator hooked up to a separate  tank. Intermediate pressure of most regulators needs to be adjusted to be within the range of your drill (~90-100psi (6bar)) (D.Barshis), as the intermediate pressure of regulators is normally quite a bit higher (8-9bar). However below is an interesting excerpt from Heiss et all 1993
 “A commercially available RODCRAFT 4200-pneumatic drill was selected on the basis of its size and technical characteristics. It works at a speed of 2000 rpm with an air consumption of 220 l/min under full power Although the operating pressure is 0.6 MPa (6 bar,  manufacturer's information), we operated the drill at a pressure of 8-9 bar which is the pressure supplied by an ordinary first stage regulator for Scuba-diving. We used in the first year a SCUBAPRO Mark II first stage. We later improved the system by using a balanced first stage (SCUBAPRO Mark X) in order to have a better air supply in water depths greater than 10m. The air came from 15 l dive tanks, pressurized to 200 bar, which provides an air capacity of 3000 l. The connection between tank and drill was a standard industrial pressure hose of 2 m” length”

So question remains - is it okay to use drills at higher than 90psi ?

Finally below are some models of drills used by Coral Listers :

Ingersoll-Rand 7803, Kobalt 3/8" reversible, Husky 3/8 in. Reversible Drill, Metabo Bohrmaschine BM 310 Druckluft , Chicago Pneumatic (brand) model CP 0009 A (or Part Number T022083), RODCRAFT 4200-pneumatic drill
A.Ross suggested that a hydraulic system (rather than pneumatic), makes holes much faster (holes take seconds rather than minutes (...lots of minutes)).

Hope this is of use to you all working on field coral reef research.

Once we get our drill we will be posting our stories of success and failures on our project website at http://lines.lankanfushi.com .

Cheers
Vaidas

Vaidotas Kirsys
Marine Biologist & Environmental Officer
Gili Lankanfushi Maldives

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