I recently posted about a new Milwaukee M18 Fuel cordless rotary hammer, and a reader had a great question. The new rotary hammer has a 1-1/4″ drilling capacity, but what does that really mean?
Simply put, SDS Plus and SDS Max rotary hammers are often advertised with a maximum drilling capacity specification.
In other words, a rotary hammer that’s advertised as being a 1-1/4″ SDS Plus rotary hammer should be capable of drilling holes in masonry materials up to 1-1/4″ in diameter.
That sounds simple, right? But, that’s a rotary hammer’s maximum drilling capacity. How should you interpret it?
SDS Plus vs SDS Max?
Compact, mid-sized, and even many larger cordless rotary hammers feature SDS Plus chucks, which fit SDS Plus-shank masonry drill bits and accessories.
When stepping up to higher capacity rotary hammers, you will find tools with larger SDS Max chucks that only fit SDS Max masonry drill bits and accessories.
I wanted to better understand the implications of different SDS Plus and Max rotary hammers sizes.
So, I reached out to Milwaukee Tool with some questions. My questions are edited here for brevity, and I added line breaks to the answers for easier readability.
Thank you very much to AJ Johnson, Product Manager at Milwaukee Tool, for the thorough explanations!
With an SDS Plus or Max rotary hammer, what does the drilling capacity specification mean?
Rotary hammers are typically named for their maximum drilling diameter capacity. For example, a 1” Hammer is recommended to be used for drilling holes no larger than 1”. Maximum capacity of hammers is not their optimal drilling capacity.
Typically, a hammer’s optimal drilling diameter is around half of its max capacity. For instance, a 1” hammer’s optimal drilling diameter is usually around ½”. The optimal drilling range will be a couple of sizes up and down from its optimal diameter. (Optimal range of 1” hammer is around 5/16” – 5/8”).
Okay, this makes perfect sense!
Let’s say that the most weight you can lift is 100 pounds. Will it be easy? Controllable? Comfortable? Of course not! What about 50 pounds? That’s going to be much less of a struggle.
It makes sense for the same to be true for rotary hammers, especially given that masonry materials and drilling depths might vary in different projects or applications.
Half its max capacity and a little higher or lower seems like a good rule of thumb.
What hole diameters and drilling depths will users typically select different rotary hammer sizes for?
Users should choose a rotary hammer by understanding their most common drilling diameter, their maximum drilling diameter, what orientation they will be drilling mostly (downward, horizontally in a wall, vertically up in a ceiling), and if they will be doing chipping/how much.
Users should choose a hammer that is optimal for their most consistent drilling diameters and has a maximum capacity greater than or equal to the largest holes the user will drill.
Users should consider the orientation they will use the hammer because they may want to choose a lighter, less performing hammer if using the tool upward or in situations where weight can be cumbersome.
This all seems straightforward, and seems especially useful for newer users.
Milwaukee provided us with a handy SDS rotary hammer selection chart. (As the Q&A took place some time ago, the chart does not include the latest model.)
Looking at the chart, each SDS Plus and SDS Max rotary hammer has an “optimal use” drilling size range, an “occasional use” range, and a range for which they are not recommended.
There is overlap in the “optimal use” ranges between models. For instance, if you will frequently be drilling 3/8″ holes, you will be well-served by selecting a more compact or mid-size tool. A heavier duty rotary hammer can accomplish the same job as well, albeit with more weight.
Or, if you will be frequently drilling many 5/8″ holes, you might be better served with a higher capacity rotary hammer, such as 1″ and up.
The optimal drilling range expands a bit for heavier duty models, and you can still use them to their maximum drilling capacity.
As with most cordless power tools, it’s good to have extra available power for when you need it. You can use a rotary hammer at its maximum drilling capacity, but it’s best to consider what size of holes you will be drilling most frequently, and size-up accordingly.
How do drilling specs correspond to chipping performance?
Finally, not all rotary hammers offer chipping, so if a user wants chipping they need to make sure the tool has that capability and the necessary impact energy for the applications they will do.
Is there anything else that you could add to help users perfectly understand rotary hammer drilling capacity specs?
Keep in mind that different rotary hammers even in the same class can be better at different sized holes. For example, one 1″ hammer might be best at drilling 3/8″ while another is best for 1/2″ etc.
In general, though, hammers in the same class have similar optimal drilling ranges. Following these guidelines will ensure a user gets a product that performs well and has the life that they should expect out of the tool.
Thank you to AJ Johnson and Milwaukee Tool for the helpful insights and explanations!
Do you have any questions or your own recommendations to add?