How Reamers Work - Haas Automation Tip of the Day

This table is covered with all different styles of reamers, each serving a different purpose. And if you've ever owned a pocket knife like this one, you've had a reamer on you this entire time. We're gonna show you which tool to use in which circumstance and how to make perfect, precise holes each and every time in this Haas Tip of the Day. Here are all of the edges that are meant to cut on this end mill. Now, chucking reamers are quite different though. They are meant to be held perfectly in line with our spindles, and they feed directly into a preexisting hole. This enlarges the hole, cleaning it up and making it more precise. Now, here are all the cutting edges on this chucking reamer. That's it. These small chamfers on our chucking reamers are doing all of the work. The end of this tool cannot cut. And the outer edges, our circular margin, should not be doing any cutting either. Now, this circular land should just help guide the tool through our part, using the already reamed section of the hole as a drill bushing of sorts to aid in alignment. This isn't how all reamers work though. There are countless types of reamers out there, but for this video, we'll be splitting things up into just two categories, hand reamers and chucking reamers. These reamers are not interchangeable though. The main difference between them is number one, how they are held. And number two, how they cut. A reamer is just any tool that is meant to take an existing hole and make it bigger. Now, my pocket knife has a reamer on it. It is meant to be held by hand and the entire side of the tool, the entire flute, is meant to cut. One of the easiest ways to spot a hand reamer is to take a look at its shank. If the reamer has a square interface on the end, it's a hand reamer and not a machine reamer. Have you tried to use one of these adjustable hand reamers in your CNC? If you have, let us know in the comments. Now, they can be great for fabrication work, but they will chatter and die if used in your CNC. Not that I've tried it recently. Now, this T-handled tapered hand reamer is also meant to cut along its edges to make a hole bigger. It's a hand tool. No one's gonna try and put one of these tools in a CNC machine, but these tools fit and we might try. Don't do it though. There are much better options. This style of hand reamer is literally just referred to as a hand reamer. Now, these tools have an extended chamfer in front for easier alignment and material removal when hand reaming. Again, we are not gonna use these reamers in a CNC machine. We have much better, more precise options available to us. For machine use, we're gonna go with chucking reamers, but we gotta ask ourselves, do we even know what the word chucking means? No. In this context, we're talking about chucking as in a chuck. In a machine shop, a chuck is anything designed to hold something on center with radial symmetry. For parts, we have three jaw chucks and collet chucks of all kinds. Now, these hold our parts on center. Vises aren't chucks because they do not center our parts in all directions equally. We have chucks to hold our tools as well. ER collet chucks, milling chucks, hydraulic chucks, drill chucks. An end mill holder isn't a chuck because the set screw holds from only one side. No radial symmetry. A chucking reamer is just a reamer that is precisely held in a machine, in a chuck, and fed axially in and out of our part. Now, in a machine shop, when we say reamer or ream for short, we're talking about a chucking reamer. Now, we can check how well-centered our reams are with the help of an indicator or a tool presetter. If our reamer wobbles in our holder at all, if it has excessive runout, it will cut the hole oversize. And also, running a reamer dry or with a low coolant concentration will affect our hole size and our surface finish. It's important that we use plenty of good, rich coolant when reaming. This is why we use reamers in the first place, when we need holes with perfect finishes, great cylindricities, and need them made fast. Dowel pin holes are a great example where we might use a reamer to create press-fit, interference, or slip-fit holes. Machinists often use a stack of coins to illustrate what can go wrong when creating holes, especially with a drill. Even if a hole is fairly round, good circularity, it might not be straight. A drill can walk. A drill can give us great circularity, but it could stagger the hole where a pin might not fit perfectly. For a perfect hole with great cylindricity, let's say for a dowel pin, we should go with a ream. Reamers give us a precision that we can both see and hear. I love that, I can do that all day. The reamer is important, but just as important is the drill that we run before we ream. Reamers will follow the pre-drilled hole, so we need to start with a nice quality drill, and the size of our pre-drilled hole is critical. This brings us to our 3% rule of thumb. We want a 3% stock allowance left after drilling for our reamer to remove. If we try and take off too much material with our reamers, those cutting chamfers at the tip of our tool will become overworked, and our hole finish will suffer. And if we leave too little material for our ream, the tool may just rub instead of cutting cleanly, and our tool will heat up and wear out. Too much allowance, too little, just right. 2% to 5% diameter stock allowance, depending upon the material. And we have all of this information on the website for our reamers, for both the drill size and how fast to run them. On the programming side of things, for the best hole finishes, we'll wanna use a G85 can cycle that feeds in and feeds out. This is gonna give us great surface finishes. Now, I know that a lot of us might use a G81 cycle, where the tool feeds in and rapids out. And I do this myself on occasion, it can save some cycle time. But it often leaves swirl marks on the inside of our holes. So it's not the best for our surface finish, even though it's a little bit faster. No matter which way we go with a G85 or a G81, use a G85, we will not want to ever run a reamer backwards. Keep going clockwise, otherwise we can run into problems. If I only had one reamer to choose, it would be a carbide straight flute chucking reamer. Long lasting and they work on both blind and through holes. As we run larger hole diameters, great big reamers, we may start looking at high speed steel or maybe carbide tipped chucking reamers to keep the cost of the tool down. What makes these spiral fluted reamers unique is the way they spread the tool load around the entire inside diameter of the hole, making them really stable during interrupted cuts. We'll see them used when reaming holes with key ways or on parts that have cross drilled holes in them. Now, these left hand spiral reamers are still right hand cutting using an M3 clockwise spindle command. And they do a good job of forcing the chips forward in the hole, which is why they are only used on through holes and never on blind holes. Right hand spiral reamers do a good job of pulling the chips out of blind holes. But chucking reamers aren't creating a ton of chips in the first place. Remember, we're only shaving off 3% of the hole's diameter. So don't get stuck on this. The next time you have a tight tolerance hole, try using a chucking reamer. Be sure to choose the right pre-drill, use lots of coolant and make some money. Well, thanks for letting us be a part of your success and for watching this Haas Tip of the Day. Well, if you're still here, I just wanted to show you one tool on the table that did not belong. This is not a reamer. This is an awl. And some people confuse them. So awls are meant for punching holes in things, leather, plastic, what have you. This is a scratch awl. It's meant for marking our materials. And that's it. This is meant for punching holes, while reamers are meant for making existing holes larger. That's it, see you guys.