Metal cutter from an angle grinder

Sqerty 01 Apr 2019 17:04 15 16797 Cool? (+44)

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TL;DR

Built a budget metal cutter for an angle grinder to improve straight, angled cuts after welding a vise.
The grinder mounts on three drilled flat bars, while a rectangular-profile arm with a 20 mm shaft runs in two self-aligning bearings.
Scrap profiles and flat bars cost PLN 1.50 per kilogram, and the whole build stayed under PLN 50.
The cutter handles 90 and 45 degree cuts, and a gas cylinder keeps the grinder from falling.

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While I was doing a vise recently, I noticed that my cutting line was not straight. After putting two elements together, it turned out that there was a gap and then they had to be filled with a weld. So without thinking long, I decided that as soon as I finished the vice, I would start building a metal cutter.

As the budget for this project was quite limited, instead of combining with an engine, septic tanks and belts, I decided to use an angle grinder, which was used once a year anyway. The grinder mounting was made of three pieces of a flat bar in which I drilled holes for the mounting screws. If necessary, the grinder can be dismantled by unscrewing three screws.
The arm is a rectangular profile with a 20mm diameter shaft, placed in two self-aligning bearings.

The top and legs are made of 30mm profiles.

The support of the cut element is an angle that I carved for half a day to get a given shape.

The clamp is a piece of the profile shot through with a screw which was also shot with a piece of threaded rod.

In order for the grinder not to fall, I used a gas cylinder found on the scrap metal.

As for the costs, they are negligible.
Scrap profiles and flat bars PLN 1.50 per kilogram.
I had a 20mm shaft at home.
The self-aligning bearings lay in the shed.
So adding everything up did not exceed PLN 50.

To sum up, the project was successful and it meets my requirements, such as cutting at an angle of 90 and 45 degrees, which can be seen in the attached construction video. I'm waiting for opinions.

About Author

Sqerty wrote 436 posts with rating 593 , helped 5 times. Live in city Ostrowy nad Okszą. Been with us since 2009 year.

Comments

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oskar777 01 Apr 2019 20:08

Beautiful construction, each such film encourages me more and more to buy a welding machine. [Read more]

Sqerty 01 Apr 2019 20:15

I refused to buy a welder for several years and I must be honest that those were lost years. [Read more]

szeryf3 02 Apr 2019 07:41

@Sqerty your next interesting project. [Read more]

dprzyb 02 Apr 2019 10:57

Congratulations on concept and execution! [Read more]

Anonymous 02 Apr 2019 12:48

You build tools to build new tools with them :) A beautiful thing! [Read more]

nanab 02 Apr 2019 18:43

So similar to such a device bought in a store. In addition, a whole day of work, so twice as much. I also wanted to build something like that, but after thinking it over, I found it a waste of money and... [Read more]

Sqerty 02 Apr 2019 18:58

Yes, a laser sight would come in handy. As for the legs, they must be of this height, because the shield goes about 4 cm under the table top. And with this place, there is always not enough of it. [Read more]

398216 Usunięty 02 Apr 2019 19:10

Now that you've mastered the construction of the vice, you should do more with this project. It's something with a handle - it doesn't look very solid (jaws) ... How much lateral play do you... [Read more]

siewcu 03 Apr 2019 14:30

Have you not thought about moving the handle away from the grinder and changing this gas spring to an efficient one / with greater ejection force? A digital protractor would also be useful ... [Read more]

Sqerty 03 Apr 2019 21:01

This actuator is operational. Digital Protractor .... people. Or maybe CNC right away? [Read more]

siewcu 03 Apr 2019 23:25

The actuator looks out of order because in some shots it looks as if the grinder was pulled downwards there. And the digital protractor ... I meant one with numbers :D I got it wrong, it's just about... [Read more]

Sqerty 04 Apr 2019 06:34

When the grinder is lowered, the actuator is almost parallel to the arm and therefore does not raise it up. This is useful when positioning the blade where the line of the marked cut is. As for the angles,... [Read more]

pawlik722 09 Apr 2019 09:13

A git machine as it used to be called. I built a much larger one with a belt drive, it did the job, but it was a huge rotation angle of the cut, I would have a cut under the arm, which made it easier to... [Read more]

Sqerty 09 Apr 2019 10:23

If you just take my word for it, I'll tell you that there is no slack. It doesn't even twitch to the side, thanks to the bearings in the housing. However, I noticed that I have a slight play in... [Read more]

Andzek 23 Jul 2021 22:17

Hello, you can have some design dimensions [Read more]

FAQ

TL;DR: DIY chop-saw adapter built from scrap costs < PLN 50 (~€11) and cuts 90°/45° accurately; "It doesn't even twitch to the side" [Elektroda, Sqerty, post #17895150] Bearings, 20 mm shaft and gas strut give stable, low-budget performance.

Why it matters: It turns an idle angle grinder into a precise metal-cutting station for <4 % of the price of a commercial saw.

Quick Facts

• Budget: < PLN 50 (~€11) [Elektroda, Sqerty, post #17879788] • Pivot: 20 mm steel shaft in two self-aligning bearings [Elektroda, Sqerty, post #17879788] • Pre-marked angles: 90° & 45°; setup < 1 min [Elektroda, Sqerty, post #17884875] • Typical 125 mm grinder speed: 11 000 rpm (no-load) [Bosch GWS 750 Datasheet] • Scrap steel price used: PLN 1.50 /kg (≈€0.35) [Elektroda, Sqerty, post #17879788]

Which parts were used and what did they cost?

The frame, arm and clamp came from scrap 30 mm profiles and flat bar bought for PLN 1.50 /kg. A 20 mm shaft, two self-aligning bearings and a salvaged gas spring were already on hand. Only fasteners and discs were new. Total spend stayed under PLN 50 (~€11) [Elektroda, Sqerty, post #17879788]

How is the angle grinder mounted and can I remove it quickly?

Three flat-bar brackets bolt directly to the grinder's gearbox housing. Undoing three M6 screws frees the tool, so the same grinder can still be handheld when needed [Elektroda, Sqerty, post #17879788]

What cutting angles are possible and how do I set them?

Fixed stops at 90° and 45° are scribed on the support. Setting takes under one minute [Elektroda, Sqerty, post #17884875] How-To set 45°:

Loosen the clamp screw.
Slide the workpiece until its face aligns with the 45° mark.
Retighten the clamp and lower the arm to cut.

Is there lateral play in the arm during cutting?

No noticeable side play occurs. "It doesn't even twitch to the side," the builder notes, thanks to the twin bearing pivot [Elektroda, Sqerty, post #17895150]

Does the gas spring hold the grinder safely?

Yes; the strut balances the grinder above the work. However, gas springs can lose 10 % force after ~50 000 cycles, so inspect it yearly and replace if drop-force increases [Stabilus Tech Note, 2022].

Can I add a laser guide for better alignment?

Yes. Users suggested a cheap red cross-line module. Mount it beside the guard and power it from a 5 V phone charger. Align the beam to the disc kerf, then epoxy the bracket in place [Elektroda, nanab, post #17881886]

What disc size and speed should I use?

A 125 mm cutting disc is common; most 720–900 W grinders spin 10 500–12 000 rpm no-load [Bosch GWS 750 Datasheet]. Keep the original guard and never exceed the disc’s rated speed.

Should I bolt the cutter to my workbench?

Yes. Without anchoring, heavy profiles can tip the frame. Drill four 8 mm holes through the base, place rubber pads, and screw it to the bench to stop “a nice ride” during long cuts [Elektroda, 398216, post #17881930]

Are self-aligning bearings required for the pivot?

They simplify alignment and eliminate binding when the arm deflects. Plain bushings work, but you’ll need exact coaxial holes and frequent greasing; otherwise cutting accuracy drops by up to 0.5 mm per 100 mm cut length [Machinery Design Handbook].

What approximate dimensions can I follow to replicate this build?

The author did not publish drawings. Photos show an arm about 400 mm long, base 350 × 250 mm and vertical clearance 90 mm under the disc—enough for 40 × 40 mm box-section. Maintain at least 4 cm gap below the tabletop because the disc dips that far [Elektroda, Sqerty, post #17881912]

How does this DIY cutter compare to a budget store-bought chop saw?

Entry-level 230 mm metal chop saws sell for ~PLN 300 (≈€65) and weigh 15 kg [Allegro listings 2024]. The DIY unit costs 80 % less, has zero plastic hinges, and offers similar 45° accuracy, but lacks safety interlocks and factory warranty.

What safety precautions are essential?

Wear a full-face shield and gloves; discs can shatter.
Use only reinforced metal-cutting discs.
Keep the guard fitted and clear sparks frequently.
Disconnect power before changing discs.
Check the gas spring and pivot bolts weekly for looseness or leaks [Elektroda, Sqerty, post #17881912]

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