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Model # P421

Internet # 100519983

Store SKU # 152332

ONE+ 18-Volt 4-1/2 in. Angle Grinder (Tool-Only)

This item has been discontinued.
The Home Depot no longer carries this specific product.

$39.97 /each
  • Over 50 great ONE+™ tools work with the same 18V battery platform
  • Any 18V ONE+™ blue or green tool works with any 18V ONE+™ battery
  • Up to 6,500 RPMs enable fast and precise work




Model # P421

Internet # 100519983

Store SKU # 152332

The Ryobi 18-Volt ONE+ 4-1/2 in. Angle Grinder offers cordless convenience and the power of 6500 RPM for fast and precise work. This tool offers a host of user-friendly features, such as onboard wrench storage, a comfortable overmolded grip and a 3-position side handle to help reduce fatigue. It also has an intuitive trigger switch.

California residents: see  Proposition 65 information

Info & Guides

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Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
Wheel Diameter (in.) 
4.5 in 
Amperage (amps) 
Arbor Size 
5/8 x 11 UNC 
Batteries Included 
Battery Amp Hours 
Battery Power Type 
Lithium Ion 
Battery Size 
Lithium Ion 
Charger Included 
Color Family 
Cordless Tool Type 
Angle Grinder 
Maximum Speed (rpm) 
Number of Batteries Included 
Power Tool Features 
Adjustable Handle Position,Grinding Wheel Included,No Tool Wheel Change,Spindle Lock,Variable Speed 
Power Tool Product Type 
Product Weight (lb.) 
6.18 lb 
Tools Product Type 
Power Tool 
Variable Speed 
Voltage (volts) 
Warranty / Certifications
Certifications and Listings 
1-UL Listed 
Manufacturer Warranty 
3 Year Limited Warranty 


Rated 4.3 out of 5 by 123 reviewers.
Rated 4.0 out of 5.0 by Handy grinder I have used this grinder to sharpen my lawnmower blade wihout removing it from the lawnmower and it did a good job. I have also installed a steel cut off blade to cut through metal closet door hardware and it worked great. December 26, 2008
Rated 4.0 out of 5.0 by Good tool for smaller jobs I have been using this tool to open up some cracks in my garage floor in order to fill them and resurface the floor. The tool is great and does its job with a decent diamond blade. However you NEED to buy the high capacity battery for it or else you only get about 5-10 minutes of real working time. Good tool, but chews up battery quick. For bigger jobs a corded tool is better, or dish out the cash for a high capacity battery. May 7, 2014
Rated 4.0 out of 5.0 by Works well for ordinary use Some reviewers have had problems with this 4 1/2" angle grinder, including one man in the store who had just returned one that never worked. My experience is different, though. I had to reduce the size of some t-bar metal fence posts and this tool worked well. I used it for about 45 minutes (and drained the 4ah battery) with no signs of problems. The handle remained cool, the job was completed, and only a battery recharge was needed. This is not an industrial angle grinder, but for home, hobby, or as an alternative when electricity or compressed air is not available, it does the job at a slightly slower pace but gets the job done. No regrets at all. April 27, 2015
Rated 5.0 out of 5.0 by High quality and unexpensive RYOBI cordless tools get proffesional work done I have been doing commercial HVAC since mid 2010 and I have used this grinder ever since. The grinder is not as fast as my corded Dewalt. But, in reality, no cordless grinder is going to be as fast as a corded one (regardless of brand name). However, this cordless RYOBI grinder gets the job done. It's supposed to be a DO-IT-YOURSELFER tool, but as a professional HVAC installer, I have used this grinder for professional uses. I have built ductwork in new hospitals, schools, apartment buildings, and super stores (a couple WALMARTS). I would recommend this Ryobi grinder (and any other Ryobi cordless tool) to DO-IT-YOURSELFERS and professionals as well. January 28, 2014
Rated 4.0 out of 5.0 by A Solid Cordless Tool I bought this grinder to use with a diamond masonry blade to score flagstone so that I could cut to shape for a path. Upon reading the manual after receiving it, the manual specifically says not to use flat blades (diamond masonry blades are flat) or any blades designed to use to carve wood (one of the other uses I have planned for it). It also says not to use the tool for cutting off -- grinding, sanding or wire brushing only. Basically, you are only supposed to use depressed center blades similar to the one provided in the box. After looking at the way the retaining flange works, It seemed to be designed to be used with flat blades by simply inverting the flange which perfectly centered the Ridgid 4" diamond masonry blade so I decided to proceed. The only problem that I had was that it was possible to overload the tool which caused it to stop (not sure if it was the battery or tool causing this) but otherwise it seemed to work just fine. I certainly never felt like it was dangerous to use it this way. I knew that it was less powerful and had a much lower RPM and HP than the corded versions available but cordless convenience made this a good trade off for what I intend to use this for, especially for the price. If I didn't already have the One+ batteries, the price would obviously not be very good. I gave it only 4 stars because the HD listing said nothing about the blade limitations but maybe all of the Ryobi grinders list this limitation. So make sure that you read the online manual if you plan to use it for anything other that grinding. I love the way the spanner fits into the handle so that you always know where it is and the blade guard was well designed to make it easy to adjust for different angles. For what it is (a lower power cordless angle grinder), it worked perfectly and I would buy it again. While I didn't drain a battery by the end of the day, I also didn't use it continuously like you might when grinding or sanding a large project so you'll want multiple large LiON batteries if that is your intended use. May 8, 2015
Rated 5.0 out of 5.0 by Great grinder. Little bit of a battery hog. I love this grinder. It's a 5/8 spindle 11UNC. So it's easy to find wheels for. It only takes type 27, and not flat wheels, so make sure you get the right type. But slap a battery in this sucker and it's off to the races. Battery life is as to be expected..about 10 minutes on a compact lithium ion battery. I have 3, so I can get some solid work done while charging one. I'll be looking at a couple 4ah in the future. Overall, great grinder. Comfortable. Good balance. My hands never got tired. Has the fit and finish to last a good long time, and enough beans to knock down a weld. May 18, 2015
Rated 5.0 out of 5.0 by Plenty of power. Solid. Working on my family members truck exhaust system. Some bolts wouldnt come off. Of course. Grabbed this and ground them off. Also used it with a cutting wheel to get the old brackets off. Went right thru them, no problem. And, no cord to tangle in brackets, etc. Was a pleasure to use. Well made, plenty of power, lots of different handle angles available in case 1 wont do it. Good buy. June 2, 2015
Rated 5.0 out of 5.0 by Excellent Tool This tool, along with all other Ryobi 18V tools, works really great. Straitghy out of the box, it was ready to preform. It cut the grout lines in my foyer very quickly and I've used it on a few metal cuts as well. One word of caution: this tool only takes cutting wheels that have a curved design. It will not accept the flat cutting wheels. November 11, 2015
  • 2015-11-30 T11:47:41.235-06:00
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