A good thing about cordless rotohammers is that they seem to have standardized on SDS (Plus or Max) fittings. Our first batch of corded tools (like the Porter Cable 616) had hex drive – but smaller in size than our pneumatics. Then we moved to spline drive and finally to SDS.)

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.

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.

I came here to answer this question! Snap, maybe. But definitely melt. My guys kept melting 5/32 and 3/16 bits with a 1″ roto hammer.

Perhaps the minimum relates to the striking force and/or torque delivered by the tool. A big rotohammer might be more likely to snap a 5/32 bit.

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.

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.)

Sds definition drillsizes

I had never heard the guideline of common usage being 1/2 of max capacity but it makes perfect sense and holds true to my experience. Having stood on a ladder while running a 2.5″ hollow core bit through a wall a couple times I will say that having a not too oversized of drill can make a huge difference. That is even more “fun”than using a holehawg or superhawg with a good sized selfeed bit from a ladder.

Great post! I recently took a side job for a sign company. I will have to drill approximately 400 3/16” holes in concrete to install metal brackets per day. Using Tapcon 1/4” X 1 1/4” fasteners.

In the past, some manufacturers would provide 2 different hole size ratings – one for sold-core bits and one for hollow core (sort of the masonry equivalent of a hole saw) bits. This may have been confusing for some newbies – but could be useful info. For demolition hammers – manufacturers often provide impact energy ratings in Joules. We found that some of these ratings were akin to HP ratings on some saws – where they were subject to interpretation and perhaps more sales-pitch than precision data.

I agree with Milwaukee’s statement that the ideal drilling capacity of a rotary hammer is approximately one-half of its rated size. I’ve always found that to be a solid rule of thumb.

The low side in some ways is more critical. You can suffer through getting a large hole done with a small SDS in many situations.

I think the other important factor is to consider where you’re working and the weight of the machine. If you had to drill a bunch of half-inch holes in the floor using a big 1.5″ capacity machine would work fine since you don’t have to lift it. If anything the weight helps you drill. On the other hand using a big heavy drill like that for wall or overhead applications when you don’t need the capacity? That gets tiring real fast.

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.

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?

You could go larger, but why? If you’re only drilling for 1/4″ Tapcons, any rotary hammer should do. M18 Fuel 5/8″ will likely give you the best performance without compromises or undue fatigue.

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.

Hammer drills are really best for small bits, 1/4 or 3/8″ or less. You can do larger ones occasionally, but even with the highest end brushless drills I’ve found drilling 1/2″ holes to be excruciatingly slow.

I forgot to say thank you for reporting the info in the post. I got so excited with my question that I forgot why I started the comment in the first place. Thank you.

Compact, mid-sized, and even many larger cordless rotary hammers feature SDS Plus chucks, which fit SDS Plus-shank masonry drill bits and accessories.

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.

SDSMaxDrill

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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.

Question is what Milwaukee M18 SDS drill size is best. I want a cordless workhorse but don’t want to buy it to oversized. Thinking the 1” is too big. I have Milwaukee batteries.

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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.

Stuart. Great reference point post. This certainly mirrors my (and our) experience over the years. And I imagine nearly everyone who’s actually used these kind of tools. And except for the occasional heavier rental or borrowed tool we still prefer our Bosch corded and 18V Core models.

Two things: I wonder why these tools have a MINIMUM recommended hole size. Would a rotary hammer have trouble drilling a SMALL hole? Why?

AreSDSandSDSPlus interchangeable

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.

Additionally, at some point, an oversized tool is actually slower since they hit harder but with lower frequency and spin more slowly. Not to mention fatigue due to a heavy tool, and rapid battery depletion.

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.

I think I “knew” this before but is really nice to have it confirmed by a manufacture. I don’t own a sds and I don’t need one. I have a compact hammer drill and I almost never use the hammer function. I bought it in case I needed to drill a hole for a tapcon sometime. It works for that but it is slow. A followup question to your source: what size holes do they recommend for their regular hammer drills? I am sure it will all be for occasional use. I am looking to buy another drill for daily use and trying to decide if my occasional use is worth upgrading the hammer function as well. A chart like the sds tools above would go a long way in helping me decide which drill is a good fit for my use case.

Sds definition drillbit

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Now this is the kind of communication we want from manufacturers. Clear, specific, and without sales-speak! Milwaukee must have a lot of respect for you and your readers, Stuart!

I would agree. I would bet HO batteries will over heat similar to other m18 HO tools.. on the 1-3/4 sds max roto hammer.

SDSPlusDrill

You see the same two-rating system for magnetic base drills. One rating for twist drills, the other for rotabroach style cutters. I’ve seen stud-and-joist drills advertise different capacities for hole saw vs. auger vs. self-feed bit as well.

SDSvsSDSPlus

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.

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”).

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.

The optimal drilling range expands a bit for heavier duty models, and you can still use them to their maximum drilling capacity.

Buy one, try it for a day or two, and determine whether it’s the best fit for your needs. A 1″ can do the job too, but unless you specifically need the extra power or chipping feature, a compact rotary hammer will be a lot easier on your arms.

This is a great article/Post. It can potentially save you money and prevent frustration. I wish vocational/technical schools went into this kind of details (when related to the trade being taught).

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.

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.

I have a DCH273, it is rated at 1 inch. For anything smaller than 3/8″ it goes like the proverbial hot knife through butter. At around 1/2″-5/8″ it’s competent. It will certainly do 3/4 and 1″ but not very fast. For my purposes this is great but if I found myself having to drill 3/4″ or 1″ holes often I’d be looking at an SDS-Max machine rated at 1.5″ or up.

Yes it does. Here I use TS (Tensile Strength as asynonym for Ultimate Strength; YS for Yield Strength.

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.

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.

What isSDSPlus

Sds definition drillvs hammerdrill

Lastly, we could probably use higher resolution on that chart. It’s a little difficult to read, even when expanded to 175%.

I’m honestly a bit curious about it myself. I have experienced issues with very small bits in a large rotohammer but it was only with the extremely small sizes. Back at my old university job I’d often have to mount things to the wall in our lab building, which was concrete block construction. I would typically borrow a hammer drill from the departmental tool crib and would use tapcon fasteners, sometimes wedge anchors if something had to be attached to the floor. I was used to doing the work with an older corded Bosch roto hammer, I don’t recall the model or the rating but it was a mid-size unit at best, probably 3/4 to 1 inch rated, it did the job fine. At some point that tool disappeared and the powers that be replaced it with the top-of-the-line Milwaukee SDS Max model, a much much larger tool. It was tricky to use it for the tapcons, it seemed like the bits would flex sideways under the hammering and would end up making an oversize hole. But once the bits got to about 3/8 inch or so I noticed no issues with using the bigger tool, except that it was just extra weight to lug around.

Jul 19, 2021 — Metric Drive Size Chart ; 8.5 mm. 0.3347. 8.5 ; 8.6 mm. 0.3386. 8.6 ; 8.7 mm. 0.3425. 8.7 ; 8.8 mm. 0.3465. 8.8.

Yeah, this is the kind of thing you really only learn on the job these days, by watching which tools people leave on the trucks unless they really need them.

Trying to make small hole with a large SDS is nearly impossible in my experience. The whole just blows out too big or you snap the bit.

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