* First-quarter revenue drops 27 pct to $839.3 mln
* Earnings $0.48/share vs $1.33 a year earlier
* Bookings fall 16 pct to $860.5 mln
March 6 (Reuters) - Joy Global Inc reported a two-thirds drop in quarterly profit due to lower demand for mining equipment in the middle of a coal glut, but the company said maintenance revenue was rising as miners can no longer delay work on old equipment.
The company joins Caterpillar Inc, the world's largest mining and construction equipment maker, in warning about weak investment by customers.
"While the economic outlook is improving and should provide some demand catalyst, commodity oversupply and a depressed pricing environment are straining miner cash flows and slowing capital expenditures," Joy Global Chief Executive Ted Doheny said in a statement on Thursday.
Over the past year, top U.S. coal miners such as Peabody Energy Corp, Alpha Natural Resources Inc and Arch Coal Inc have cut expenditure on mining equipment such as longwall shearers, giant shovels and draglines.
However, Joy Global raised the low end of its 2014 profit forecast range as it cuts costs and as miners booked in equipment for long-delayed maintenance.
The company reported a 3.7 percent rise in service bookings in the first quarter ended Jan. 31 - the first quarterly increase in more than a year. Maintenance made up 71 percent of bookings in the quarter.
Jefferies & Co analyst Stephen Volkmann said that the mining industry might be hitting a bottom, but any pick up would likely come only in 2015 or 2016.
Joy Global's bookings fell 16 percent to $860.5 million in the quarter. Coal miners account for about two-thirds of the company's revenue.
Joy Global, which also supplies miners of copper, iron ore and other minerals, kept its forecast for 2014 sales of $3.6 billion-$3.8 billion but raised the lower end of its profit forecast range by 10 cents to $3.10.
Analysts on average were expecting earnings of $3.29 per share on revenue of $3.72 billion, according to Thomson Reuters I/B/E/S.
Product development, selling and administrative costs fell 2.7 percent to $153 million in the first quarter ended Jan. 31.
Net income fell to $48.9 million, or 48 cents per share, in the quarter from $142.1 million, or $1.33 per share, a year earlier.
Excluding items, Joy Global earned 49 cents per share, but missed the average analysts' estimate of 64 cents.
Revenue fell 27 percent to $839.3 million but was above the $835.4 million analysts expected.
Joy Global's shares were up 0.2 percent at $55.95 in premarket trading. They have declined about 10 percent in the past 12 months, compared with a 26 percent rise in the Dow Jones U.S. Industrials index.