How much use do you get out of a belt/disc sander, bench grinder, and portable grinder?

We are about to order some things to help our team be successful moving forward (most of my posts have been related to this). In planning for this, I have been pouring over the incredible Spectrum docs, the Frist 1000, and the first 10000 dollars teams should spend. Our team has some grant money for this, but not 10000 dollars. We are going to be making a super pit, and purchasing some things, however, we are at a point where we will need to make some concessions.

So, my question is, for teams that have all three, how important is it to have a bench grinder, portable grinder, and a belt/disc sander combo?

We currently have an orbital sander. We use 8020 for a majority of our structure but have some incredible mentors who help us by making custom machined parts that we also use.

Given that, info. Is it worth it to have all three ( It really is not about the money, but more about workbench space)?

If not, where would you prioritize for the three?

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I’d say our portable grinder is used the least. We are fortunate enough to have a parent/sponsor weld our chassis components for us. Sometimes the welds, while done quite well, get in the way of something the students what to fit to the chassis. So the portable grinder comes out for that. Otherwise it sits on a shelf.

The bench grinder with a brush wheel and the belt sander get used a LOT during prototyping. Parts getting cut quickly are a little off so they need to be sanded square. Then there are burs on the ends of the bars that can be quickly removed with the brush wheel.

The actual grinder wheel doesn’t get used as much since aluminum tends to gum it up. And the disc sander on the side of our belt sander combo pretty much never gets used… but it’s really small.

Not sure which of these you’re considering for the super pit, or just your shop. Be mindful of rules at events concerning allowed power tools before making any big purchases.

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For FRC purposes we use our belt/ disc sander the most by far. We have this little guy

Every part off the CNC gets some sanding so it isn’t too sharp.
In general, in the manufacturing classes I teach we use a 4in Milwaukee angle grinder with a flap disc sander far more than anything else.

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I use a small bench grinder to sharpen HSS cutting tools that I use in my 1946 South Bend lathe…but never have had a need for one building robots at school…

Like any other equipment, how often you’ll use it, depends on what other equipment you have, and what materials and techniques you use to build robots. Those are questions that only you can answer.

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I’m with those here telling you to ditch the bench grinder. There’s basically nothing it can do for you that the belt/disc sander can’t, but the reverse is not true. That makes the sander the better choice for a stationary tool for the role. The portable (i.e., angle) grinder is too useful not to have. There will be plenty of times that you need to smooth/round things or cut things on the robot, where disassembly may not be an option, and that’s where the angle grinder comes in. Our team has found these two tools to be indispensable.

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That, and a clogged wheel is prone to overheating and expansion issues which can result in a sudden and spontaneous deconstruction of the wheel.

We use our 24" disc sander in the schools woodshop to do a lot of touch up work on rough cut items. We have a belt sander as well but it is used much less frequently. The small belt/disc combos are used less often too. The disc provides a very large flat surface for squaring hand cut items quickly and most parts we make will at least make one stop at the sander. It does add a whole new safety program to add because the bigger the machine the more aggressive they become.

When using a sander for steel parts be sure to clean it out before as the sparks will ignite sawdust or plastic pretty quickly.

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Like @snoman, we have a similar machine (only a belt though, no disk… otherwise identical). It gets used a lot - it saves a lot of time on those sharp edges. You can clean up an edge faster than it takes to find the file, usually!

As for the grinder… we have a floor grinder that gets occasional use, almost always by mentors. It’s really not a critical piece of equipment for us.

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For 1712’s use cases:

Belt/disc sander - Used fairly frequently during build season. So much so that we actually replaced ours about 2 years ago since the previous Delta one we had was dying (we had it for about 10 years, with a notable decline in performance over several years). We ended up picking up one of these, and have been happy with its performance so far. We use it for deburring, removing small overcuts on aluminum and polycarb, and shaping polycarb and wood.

Bench grinder - Occasional usage. Mostly for cleaning up cuts on a steel shaft or bolts. We used this a lot more when we used a lot more steel shafts, back before the proliferation of 6061-T6 aluminum hex shaft for FRC. Still a useful tool to have, even if we only use it sparsely.

Portable angle grinder - I cannot remember the last time we used this in our shop at home. Sometimes sees usage at competitions when we need to make a cut in a hurry.

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re: angle grinder. I’ve had students spend 30 minutes cutting away at something with a Dremel that an angle grinder could do in seconds. Sometimes it’s the perfect tool to grind or cut something to size in an awkward spot. The cheap one at Lowes will work just fine, should be $30 or so. Buy a cutting disc too if it doesn’t come with one. I’d rather have one than not for the low price point.

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Replace one of the stock aluminum oxide grinding wheels on your bench grinder with a silicon carbide one. Use the aluminum oxide grinding wheel only on metals that make sparks (like steel) and the silicon carbide one for only on metals that don’t make sparks (like aluminum, brass, etc).

A good silicon carbide grinding wheel is really effective at deburring the sharp edges of cut aluminum parts.

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I use angle grinders a lot at home, but I work on cars and stuff, doing steel fabrication. Very few teams have built their robots from steel (yes, we’re one team that has)(and the underwater robot in my avatar has a steel chassis, which had some angle grinder action during construction, and later modification)

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A Scotch Brite wheel like this on a grinder works very well for smoothing aluminum edges. It leaves a smoother surface than a sander. It’s slightly flexible so curved edges are maintained.

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We make almost no use of any kind of grinder. Pretty much any custom part was made on the CNC, lathe, or mill. If something doesn’t fit that’s a design and/or manufacturing error that should be investigated, corrected and a new part made. On rare occasions we’ll make some fine adjustments with a hand file.

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I’ll second the Scotch Brite wheels. Been using those in machine shops for decades with great success.
After they’re worn to a too small a diameter, you can still use them free hand with a drill motor. etc.

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High grit flap discs are also wonderful on an angle grinder in the right hands. They can remove material quickly or neatly polish the base material with a delicate touch

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It is important to remember that not every team has access to CNC equipment. We are just now moving into the world of manual machines after 10 years of being comfortably competitive with only hand tools, a basic metal shop focused on steel, and a woodshop. Our only reliable CNC machine is a plasma table that is used to rough out geometry to get finished by hand.

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Thank you all for replies. We are a small team with an even smaller space. Our “shop” is a classroom, but we need to completely clean up most nights (save for weekends). Our storage space is limited too, but we need to put everything in storage each night. So, we are building a small (~4 foot) super pit style workbench to help with small off-season projects and are considering creating one leg of an 8 foot section super pit (hopefully with an aluminum frame) for the full robot fabrication days.

We are aware of pit limitations as far as both tool-usage and space go. However, the idea is that anything we can build that would streamline our inventory, organization, and portability for an event will maximize our time in the shop (so prohibited event tools will still need a space to live during build season).

We also have no direct CNC, mill, or lathe capability. The two aforementioned mentors can do some, but we cannot do any of it in-house.

These responses are helpful. Though we work almost entirely in aluminum, based on these responses, I am leaning toward the angle grinder and sander combo.

Thanks again.

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I feel for you, as we’ve been there as a team in the recent past. Until this year (and our move into our new school building) we were housed in an old supply closet for a “shop” space, where we just barely had room for a small band saw and a sander as stationary tools. Most of our work was done in a classroom (mine, actually) and had to be cleaned up every day. We have a much better space now (a real dedicated shop of a reasonable size, thanks to a very supportive administration and the fact that there’s actually space available in the new building) and are moving into the realm of large stationary tools, including a large MIG welder and an Omio CNC machine. It will be a very new experience for the team.

Your idea of using pit workbenches is pretty smart and should help out a good bit. We never managed anything like that, since we’d never have been able to fit them into the closet with the shelves full of robot parts, etc.

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Good point. None the less, even with simple tools you can usually get close enough that a good set of hand files will get you where you want to be. And they’re a lot harder for students to injure themselves with or accidentally ruin a part.

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We haven’t had an injury on our disc sander in 10 years. Each tool requires safety training and instruction on proper use.

I would be curious how long it would take for a student with a hand file to clean up a piece of 1/4 aluminum plate that has a rough bevel from the plasma cutter though…

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