For many applications, a 12 volt impact driver has more than enough power.  I have sold power tools and fasteners for over 25 years.  I have seen a lot of really good cordless tools and some, well, not so good.  My Bosch 12 volt impact driver is by far my most used cordless tool.  Read on and see why I highly recommend this tool.  Now I am not saying the others aren’t good, it’s just that this is what I own and what we use in assembly work at our office.  There are situations where an 18 volt impact (or 20 volt) may be better for you. First let’s look at the 12 volt.

Most of the time that I grab for my little impact it’s for assembly work. I can think of three recent projects that I used the tool on this last fall that was much easier because of it. I assembled a smoker, a grill and bench work in my garage. All three of these projects came with bags of hardware that I could tighten by hand easy enough but with the impact it was super-fast. Typically I just hand tighten all the hardware and then come back and “zip” it up with my impactor. It’s so effortless! I would have to say for myself, the speed of my little 12 volt Bosch is my favorite feature. Not only does it have more torque than a drill but it installs and tightens screws and fasteners faster and with less stripping. Removing stuck bolts and screws is also easier with the impact. Most of what I am assembling has smaller machine as well as drywall and cabinet screws. We do some production work at our office on a routine basis and the little 12 volt Bosch really shines. It’s lightweight and has incredible run time.

Most of what I am assembling has smaller machine screws and construction type screws.  I use a lot of ¼-20 screws and smaller as well as drywall and cabinet screws. If you are getting into bigger lag bolts and tap bolts, you may want a bigger impact.  For instance if you are installing lag bolts larger than ¼”, I would say lean towards the 18 volt.  Even ¼” lags in wet treated lumber my start to tax a 12 volt impact.  I recently built a small pier system to place my new garden shed on.  I was using larger construction type and connector screws and really the 18 volt impact was much faster.  The run time was also better as the tool didn’t have to struggle as much to set the fasteners.  The tool is a bit heavier than the 12 volt but still with the lithium batteries not that bad at all.  Note that some companies are offering a 20 volt impact driver.  I would still hold these in the same class as the 18 volt impact driver.  If you are Bosch fan, click here for info on my favorite 18V impact driver the Bosch GDX18V EC.

One thing that may influence your choice between a 12 volt or 18 volt impact driver may come down to something as simple as what you have on hand for batteries.  Most of the major tool manufacturers offer bare tools so if you have an 18 volt Milwaukee set up now, you may just want to add the bare impact.  I bought my Bosch 12 volt impact in a combo kit with a drill.  The batteries also fit my cordless Dremel.  I have 18 volt tools and so just grabbing a bare Bosch 18 volt was the way to go.