Makita Cordless Drill (M651D)

A large part of the cost of a cordless drill system are in its batteries, so when this Makita cordless drill wore out its NiCad batteries, it made more sense to get a modern lithium-ion powered drill system to replace this one. Retiring it to the teardown workbench. I tackled the charger first, because I didn’t think there was much point holding on to a NiCad/NiMH battery charger when lithium chemistries have taken over. Next up is the drill itself, which is an interesting comparison to an even older cordless drill taken apart at SGVHAK a few years ago.

The drill itself still works fine. As a powerful motor and gearbox combination with a torque-limiting clutch, I think it’ll still be useful for something, so this is only a partial and nondestructive teardown in order to leave it in working condition. Thanks to excellent work by Makita designers and engineers, this turned out to be extremely easy.

One element of this ease is how this drill was held together by machine screws. Not self-tapping plastic screws, which are cheaper and easier to assemble but weaken every time they are removed and reinstalled. And those machine screws go into captive hex nuts, not heat-set inserts. Together, it means this drill can be disassembled and reassembled repeatedly without weakening. Nice!

After I removed all of the fasteners, I pried the two blue plastic halves apart. As I did so, all internal components fell out. It was startling at the time, but then I was happy to realize that it meant all internals are easily accessible and nondestructively so. Major subsystems fit together without any adhesives or additional fasteners.

I see the planetary gearbox has provision for fasteners to hold it onto the motor, but that provision was not used. It was not necessary: the drill enclosure held them against each other well enough for the drill to function. Speaking of that planetary gearbox, I see a few screws for further disassembly and decided against it. I wanted to keep the gearbox in running order, and I didn’t want the mess of lubricants all over my workbench. Someday I might take it apart to see internal implementation of high/low gear shift and the torque-limiting clutch, but not today.

Control of motor speed and direction is handled by a completely integrated unit. It has solder points for battery terminals on one end, and motor terminals on the other. It exposes two mechanical controls: one for direction, and the trigger for speed. Printed on the side is:

defond
DGT-1225A
25A 14.4VDC

I found the website for Defond and its “Power Tools” division that specializes in making such devices for other companies. I found no listing for DGT-1225A or a catalog at all, implying each product is a custom unit designed and built for a customer like Makita. More useful to me are the ratings printed on the side: up to 25 amps and 14.4V DC. This gives me the power envelope I must keep in mind if I want to incorporate this motor and gearbox into future projects. If I want to put them under a microcontroller’s programmatic control, I’ll need to use motor drivers capable of handling 14.4V * 25A = 360 Watts. Or perhaps I can rig up a different set of batteries?

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