13 practical machining projects for students and beginners make it from metal
One thing that I found out after the program, though, is that the chess pieces and keychains were quickly lost, but the tools I made are still in my box and used daily 12 years later. When youre able to use great tools that you made yourself, it adds a definite element of pride to your work.
Ive compiled a list of practical projects for up-and-coming machinists to hone their skills. Theyre not decorative pieces, like turners cubes or random widgets. All of them are tools that youll likely use every week, if not every day.
For each one, Ill go over the BOM, the equipment needed, and give you the drawings. Most of them are ones that Ive made myself, and some of them are the upgraded versions to make them more useful as tools.
This tool is exactly what youll need to pull 1/2 dowels from tight holes. To make it last longer, theres a replaceable 1/4-20 set screw thats used to hold on to the dowel. Mines in perfect shape still, aside from a few scuffs and dings, and I use it daily.
Personally, I like making tools out of stainless where possible, since theyll last longer than I will. If the budget is tight or selection is limited, though, you can just as easily use steel or aluminum.
I modified the design of the one I made over a decade ago based on things I wasnt crazy about. For example, this one has flats on the handle. I always found it annoying that with a fully round handle, you couldnt keep the hammer straight by feel you had to look at it. Now thats fixed.
To mill the flats, I wait until the hammer is finished and assembled. Then I stick it in a milling vise, dial in the hammer head, and mill one side and add the chamfer. Then I flip it, using the underside as a register for the second flat and chamfer.
I also drilled a hole in the bottom of the handle. I use it to fit allen keys, so I can use the hammer as a small cheater bar. Its saved my knuckles a few times. You can make it shallower or deeper to get a hammer balance that suits you.
I adjusted the balance between the head and the handle to something I find more comfortable for the light tapping that this type of hammer is more typically used for. Some people like to have one end brass and one end aluminum, although I prefer two brass inserts thats the end I always use anyway. And, since brass is significantly heavier than aluminum, I find that it feels better.
This is a good project to get familiar with taper cutting on the lathe. For cutting the self-holding tapers for the inserts, I usually lock the compound rest at the angle and use a single setup to cut both the male and female tapers. If you get a smooth surface, that taper will hold forever. Either the taper attachment or the offset tailstock method can be used for the handle.
This one is good for more advanced students. Traditionally, this has been a project for tool and die makers. The skills that are targeted are job planning with grind allowance and order of operations. Machines used are mills, heat treating ovens, grinders, and lathes.
The vise is definitely an involved project, but one thats well made is a work of art. For an extra challenge, try CNC engraving the name of the student in the vise body prior to heat treat and try to make the letters appear even after grinding.
I strongly prefer to make this out of A2, since its stable and air-quenched, which means that the vise will be nice and clean. Some schools choose to use 4140, but it can be pretty demotivating when a student rough machines the part, and then has to do it again because it cracked in the oil quench.
I went light on this drawing. Lots of schools have it slathered with GD&T. Personally, I love it, since it helps ensure a working part at the end of the day. If you want to add the GD&T requirements on this drawing, youll usually find this part covered in perpendicularity and parallelism callouts of 0.0003everywhere. Use your discretion with what your students can reasonably measure.
This one is actually really uncommon to see as a school project, but its definitely a handy tool to have. Whether youre checking against the standard or trying to measure an awkward little part to 0.0002, a mic stand is worth having around.
Overall this project will help the beginner learn basic things like slotting on a mill and threading on a lathe. There are lots of non-critical features that are purely cosmetic, but there are a handful that just need to be done right for this thing to work smoothly.
This is the simpler of the two depth attachments. Its a very basic project to get familiar with mills and lathes. Youll get to do some threading on the lathe and learn how to make a clean undercut. You can also use it as an opportunity to grind some HSS cutting tools for threading and undercutting.
This project gives you a bit of experience on both a mill and a lathe. Specific skills to hone are how to maintain perpendicularity, turning and threading small parts, and how to do a bolt circle (although its just cosmetic).
This is a really simple little job, but it does require precision. Whats kind of cool about this is that for marking student projects, you can just have a plate drilled with holes in known locations, then compare what you get on the calipers.
Since theres so little material needed, this is a nice and cheap project for an entire classroom to work on. The bottom of the slot is aligned with the center of the taper, so the idea is that you should be able to keep your calipers set as they are instead of needing to rezero for basic measurements.
Overall, you get to try out working with a collet on the lathe (ideally) and being able to very accurately aligning and cutting a slot on a shaft. Youll also get to try tapping some really small 4-40 holes.
This project will hone the skills of job planning, milling, heat treating, and grinding. If you choose to make the clamps using a band saw, theres also the opportunity to practice layouts and some bench work.
If youre teaching a course on machining, it might be cool to start on the clamps early on, and then later on make the vee blocks as a separate project. That way the students can be challenged at their skill level for both aspects of the project.
Heres how they work: When you loosen them and push them against the workpiece, the jaw is moved off the countersunk hole centerline. When you tighten them, the flat head screw tries to force the jaw back into alignment to it can properly seat. The result is clamping force.
If you want to have some clearance under the part for drilling through, try putting the clamps on a 45-degree angle so only a small part of the base is supporting the part. For thicker workpieces, they can be used very similarly to a standard toe clamp.
By alternating a pattern of counterbored threaded holes, you can use a socket head cap screw with a large undercut to bolt these 123 blocks together. The best thing about it is that the bolt heads are competely inside the blocks, so there is zero interference as youre making a creative setup.
Now, keep in mind that these bolts arent terribly strong. They wont be competing with a hold-down clamp with a 1/2 stud and handling heavy machining. But theyre really handy when you want to use these block in a machine setup and dont want them to move between cycles. Or if you need to stabilize a part in a way that gravity doesnt agree with. Or if you need a creative inspection fixture. You get the idea.
Fair warning: these take a little longer to make than the more traditional (and less useful) 123 blocks. But its time well spent. Theyll be the envy of everyone in the shop and theyre just really cool. Thats why I call them 123 SuperBlocks.
Most people make the sets of 123 blocks match ground in pairs. Id really recommend making at least a set of 4 of this kind. Id even do 6 if possible. Since theyre so stackable, the more you have the better.
Personally I like to use A2 for jobs like this since its an air quench and very stable. I used O1 when I was in school and it worked OK but not great. Its more prone to cracking, especially around sharp corners and threads, so a few guys had to start over. That said, itll work if thats all you can afford.
You might also want to make sure that youre using an oversized tap (H11) instead of a more common H3 or H5, especially if youre using O1. It tends to shrink and warp a little bit when heat treated, so you might not be able to use the threads otherwise.
This is a tool that can help you keep your tap straight over a plate or a shaft. It has holes drilled to accommodate taps from #6 to 1/2. The drawings specify mild steel, but you can use tool steel and heat treat it if you want it to last longer. If thats the case, 4140 will work perfectly fine.
Even though this is a simple milling job, its a good opportunity to practice precision. The holes need to be aligned to the vee on the bottom. This can be an excellent exercise demonstrating how to precisely locate a vee using a pin and a depth mic to measure. You can use this to check both how it aligns to the outside edges as well as check the depth.
This is a good job for practicing how to align a vise. If youre doing it on a CNC, there are also a bunch of drills to load up, so theres some repetitive practice. The really nice thing about this is that its a handy tool and practical project that needs hardly any material.
This one is another classic. I made mine in a CNC course in college. One thing I didnt like about the set I made, though, is that they were really limited on the amount of travel you could get out of them.
If you program them on the CNC, then you can get a really nice set. Technically the bare minimum that would be useful is 3 units, but Id recommend making more than that. It seems that Im always using about 6 at a time.
If you make a set of 6, make two riser blocks for each screw jack. If you run these on a CNC lathe, you should be able to do each piece in one operation. The only exception is that you might want to flip the screw, so it has a nice, smooth finish everywhere.
This is a good project for learning CNC lathes, and it also gives a great opportunity to wrap your head around clearances and unilateral tolerances. You can feel what the difference is between a slip fit of 0.005 and 0.015.
I put those in as bar lengths with a little extra to grip on to near the end of the run. This is because usually this is a CNC job, so cutting them all up into individual pieces will just end up wasting material and taking longer.
Realistically, the most common approach to bending a piece of metal when you dont have easy access to a proper brake is to shove it in a vise and wail on it with a hammer. This just makes that happen a little more professionally.
Its got magnets that help it to just snap on to any steel vise. This is a tool that can give you accurate and clean bends in a very basic shop. The die is in three sections, so you can remove and adjust as needed if youre working on smaller pieces.
The tool itself is pretty easy to make and mostly just teaches you not to put a workpiece in the milling vise the wrong way. Whats interesting about it though is that its a nice, very basic introduction to tool and die. This can be a way of learning some of the fundamental terminology and principles of sheet metal forming.
Since this probably isnt something thats going to see a ton of daily use, most guys just make it out of mild steel. If you want something that will last a really long time, make it out of 4140 instead and heat treat it.
Theres definitely nothing wrong with many of the more trinket style of projects that are common in many machining programs. You can get very focused in the operations to hone really specific skills.
The nice thing about making tools, though, is that theres a lot of pride that goes into the workmanship, and the fact that you might very well still have them in your toolbox after ten or twenty years.
I've been working in manufacturing and repair for the past 14 years. My specialty is machining. I've managed a machine shop with multiaxis CNC machines for aerospace and medical prototyping and contract manufacturing. I also have done a lot of welding/fabrication, along with special processes. Now I run a consulting company to help others solve manufacturing problems.
If you're not used to it, stainless steel can be absolutely brutal for drilling. You might end up burning through bits faster than you can load them. But if you know how to do it properly, it really...
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tech talk: hammer mills and the attrition zone
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Traditional hammer mills work on the principle that most materials will crush, shatter, or pulverize upon impact. Material is fed into the mills chamber through the feed chute, and struck by ganged hammers, which are attached to a shaft that rotates at high speed inside the mills grinding chamber. The material is crushed or shattered by a combination of repeated hammer impacts, collisions with the walls of the grinding chamber, and particle on particle impact. The initial impact of the slow-moving particles against the high tip speed of the hammers produces the most significant size reduction. As the particles begin to reach the tip speed of the hammers, less reduction occurs because the energy transfer drops as the velocity differential levels out. Perforated metal screens or bar grates covering the discharge opening of the mill retain coarse material for further grinding until the particle size and approach angles are aligned, allowing properly sized materials to pass as finished product.
By contrast, dual-stage hammer mills are designed specifically to maximize space and efficiency by producing the finest possible end-product in just one pass. Dual stage mills feature two independently driven hammer mills stacked one over the other.
In a dual-stage hammer mill, there are really three phases of size reduction, due to what is known as the attrition zone. The attrition zone is the area created between the top rotor and bottom rotor of a dual stage hammer mill. Materials pass through the initial mill and screen arrangement and are then directed toward the secondary mill chamber. Before reaching the second rotor, particle-to-particle impact in the attrition zone creates additional opportunities for size reduction, in an area with principles similar to a jet mill. The turbulence created by the opposing rotors, and continuous stream of particles creates high impact forces; serving two purposes:
In many situations, depending on materials and processing goals, materials are processed through a single stage mill, they are then screened and fed back into the mill for a second pass and additional processing. With this arrangement, a much larger mill may be required as it must process the virgin feed and the additional recirculating load of oversized particles.
It is important to note that multiple passes through a single-stage mill does not necessarily produce the same finished result as a single pass through a dual stage mill. Hammer mills are typically designed to have a short dwell time, meaning material is fed into, and evacuates the mill quickly; allowing material to be processed efficiently. By recycling pre-milled materials through the same screen over multiple passes, that material will not see the same impact forces as they will tend to pass through the screen quickly, already having been sized to clear the screen. Adding the second mill, with a smaller screen size, allows for a longer dwell time within the mill. Since the pre-milled product still must be reduced before passing the secondary sizing screen, material is suspended briefly so that a continuous feed rate will keep the attrition zone fully occupied with both coarse materials from above and finer particles working below.
Energy transferred from particle to particle impact, at very high speeds, produces the increased gradation at a finer particle range. This gradation is outlined in the table below. More size reduction occurs as significant energy is exchanged from the repeated collisions between particles and hammers, until the material finally passes through the secondary screen at the desired particle size.
There are many variables in milling efficiency with fine particle size. A major factor is the screen selection for the top and bottom mills. Again, depending on the material properties, mills are equipped with bar grates or perforated screens; any combination can be employed. In cases where material is bulky, a bar grate may be selected for the initial milling to allow for higher wear resistance and durability against heavier materials. While the secondary mill will use a perforated screen with small bore diameter for finer finished particles. Screen size is the most influential factor relating to particle size, as the material must clear the screen.
Another variable is the rotor speed, as described in this article, the imposing force of the hammer to particle is what provides the size reduction. On a dual-stage mill, each mill is driven independently, such that they may rotate with the same tip speed, or the bottom mill may run at higher speed for fine grinding if outfitted by a variable frequency drive. This allows the user to fine tune the process and have more control over particle size distribution.
Finally, hammer style and size will contribute to the efficiency. The rotor can be assembled with many hammer configurations, selecting the right hammer configuration at the right tip-speed will produce the necessary impact force to correspond to the material being reduced without being knocked back during contact with the material.
Particularly, when dealing with fine grinding applications, air assist is another critical factor. Aspiration air is often employed to assist in efficiently drawing material through the milling chamber with the proper dwell time. Not only does the aspiration help produce more product uniformity, but also controls heat build-up and nuisance dust around the mill. By having dual stage processing contained in a streamlined system, the air path is simplified and prevents the need for multiple conveying steps with dust collection for a given system. Properly sizing the air system is critical, since the air flow through the mill must be carefully sized to capture only the ultra-fine dust, not to draw the material through the mill without allowing for the proper dwell time through each milling stage.
design and fabrication of hammer mill mechanical project
The hammer mill is an impact mill employing a high speed rotating disc, to which are fixed a number of hammer bars which are swung outwards by centrifugal force. Material is fed in, either at the top or at the Centre, and it is thrown out centrifugally and crushed by being beaten between the hammer bars, or against breaker plates fixed around the periphery of the cylindrical casing.
Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.
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