I usually start from current offer (search engine), for numbers and sturdiness MAKITA 2013, DEWALT 2014, MAKITA 2017 and MAKITA 2018 guides allowed me to spot the metal gear versions. My enthusiasm was cooled down with a few “How to replace” Youtube videos showing many Makita with so called “metal gears” having a plastic -R-ing gear (red below) so not 100% metal gear for best possible life time. Finally, as rotating in water isn’t as difficult as in a solid material like steel or concrete that creates a lot of wear on planet gears, the problem is now to determine/find/(modify?) the reduction gear to suit the propeller we have or ask to guys like @Flying_Rodeo to design us a propeller according to the reduction gear that offers the best quality/price ratio. If many people are interested, ity’s a win-win if the produced quantities are high.
According to you @MaB , what would be a good potential candidate ?
@Antonbit : 50USD for a genuine model is quite good. In the 2017 guide above the Makita DHP484 Brushless 18v is described as a general duty so the beginning of sturdiness (inferior to Heavy Duty range 458 and 481 see below)
The brushless DHP484 is the newer general duty option from Makita. The gear housing is upgraded to all aluminium giving it a distinctive sturdier look whilst making it the lightest drill in our comparison. A brushless motor and metal gears mean the DHP 484 will outlast lesser options. Slightly reduced torque numbers are the price paid for a smaller, longer-lasting machine. The DHP 484 is the perfect choice for tradesmen who tackle a variety of daily challenges and require a long-lasting, reliable, robust option.
In the guides they say:
DHP or DDF it doesnt matter in terms of drill performance. The only difference is DHP = hammer action, DDF = no hammer action.
Meaning that non-hammer (Makita DDF) drill gearbox must be favoured as they are more simple and hopefully more compact and cheaper.
Same process with Hilti and the other professional brands. Could be a long search. But if we can be at least 5 persons looking in different directions…
DHP 458 gearbox : 56 USD on aliexpress for a 88mN torque is well above our needs but can it cope with the 3500 rpm we need ?
Spoiled for choice on AliExpress : 22 genuine gearbox models from 25 to 67 USD all with nylon outer housing make me think that the first one you find in a junk will provide plenty of information.