Nut Splitter DIY




Introduction: Nut Splitter DIY

Sometimes nuts are too much seized on screw or head is so much damaged or too much stuck from rust and they cannot be unscrewed with conventional tools.
With this simple tool, just put the nut you want to loosen

into the hole of the Nut Splitter Tool

and screw the bolt until the nut breaks.

If needing to be save the bolt in some cases,

then do not over tighten to prevent damage to the threads under the nut.

All materials and dimensions are available at the time line.

Nut Splitter also is known as Nut Cutter or Nut Cracker.

This size of Nut Splitter is suitable for breaking M6-M8-M10 & M12 nuts.

For bigger size nuts is needed a bigger size tool.

Step 1: Tools & Materials

Remember Safety First.

Welding Cutting and Grinding Tools are Dangerous!

Do it at your own Risk!

Use Always the Suitable Protective Equipment.

  • Tools

Angle Grinder

Cutting disk 1mm for cuts & 3mm for the griinding of chisel

Flap Disk Grinding Wheel

Drill Press

Drill bits ø4-5-8-10-12mm



Files flat-square-round-half round

Center punch

Taps set M6

Tap handle

Welding machine

Electrodes 6013 2.5mm

Welding Mask

Welding gloves

  • Materials

M24 Nut 1pcs

Rod ø19x45mm 1pcs (ø20mm is acceptable too)

Bolt M6x6mm 1pcs

Bolt MF12x1.25x50mm 1pcs

Nuts MF12x1.25 2pcs

Ball bearing ø8mm 1pcs

A piece 25mm cut off from the tail of an HSS ø10mm drill bit.

A piece ø10x12mm HS for the making of the ball bearing nest (you can cut a piece from a hard steel M10 bolt)

Step 2: Main Piece

For the main piece I used a M24 nut and a piece of Rod ø19x45mm

At the center of one of the six sides that constitute the nut, make an ø8mm hole using at first ø4mm and then ø8mm drill bit.

Using a square 8mm file and then a flat file make a channel about 11mm width.

File the threads of the M24 nut using a round and then a half round file so the M12 nut can be fitted correctly.

M12 nut can fit at ø22mm hole.

Cut a piece 45mm from an ø19mm rod using angle grinder with 1mm cutting disk.

For this cut I used a piece of angle-iron (L shape) with a length stop at 45mm distance from the right edge

and make the cut, sliding the disk at the angle-iron edge, rotating the rod simultaneously.

Using my home made Circle Center Finder Tool find the center of rod and make an ø8mm hole using at first an ø4mm and then ø8mm drill bit.

Using a set of M8 bolt/nut assembly the two pieces to see if they fit correctly.

Increase the hole at the two pieces at ø10mm.

Assembly the two pieces using this time a set of M10 bolt/nut.

The bolt's diameter is very critical; don't use the M8 bolt from the previous step.

With the two pieces assembled tight with the bolt/nut, make a groove all around and then weld.

Let it cool remove the M10 bolt/nut and then smoothen the weld.

With a flat file make two seats at shaft so to can be fitting a Num-17 wrench.

On one of the narrow sides drill an ø5mm hole, perpendicular to the imaginable axis of the tool.

Using a M6 set taps cut the M6 threads.

Increase the ø10mm hole at the shaft to ø12mm,

the depth of drilling must be only 26mm.

You can use a paper tape at the drill bit as depth guide (see photo).

Step 3: Pressing Bolt

For Pressing Bolt I have choose

a Fine Thread Bolt


I haven’t a long nut so decided to wed two nuts together making a longer nut for best performance.

I covered the threads with paper tape and oiling the vise to protect from splatters.

It doesn't matter if the paper-tape will be burn; the threads will be still stay clean from splatters.

Place the main piece with the bolt and the welded long nut at the vise and weld the nut onto the main piece, using again paper tape for protection.

After that a little grinding at the two welds and then weld a second pass.

Step 4: Chisel & Ball Bearing Nest

The Chisel

For the chisel I decided to use a piece 25mm which I cut from the tail of an HSS ø10mm drill bit.

Don’t worry the drill bit is still to be workable 100%

now is 25mm shorter; but this isn't a so big deal.

For this cut I used the same jig with the (L shape) angle iron as at the Main Piece step.

At the grinding process, I had used a sponge with water at regular basis to avoid the overheating.

For the last hand fine sharpening, I have used a piece from a broken fine grindstone with water.

Chisel guide

Place the chisel at the vise (as at the photo) and using a file, make a flat guide place.

The Ball Bearing Nest

For the ball bearing nest I have use a piece ø10x12mm of hard steel

(you can cut a piece of a hard steel bolt M10).

The Jig

I haven't a lathe but using this jig (see photo) the job can do as well.

The two chucks are Concentric and the down one can't rotate.

For the centering of the two chucks I have use an axle ø12mm.

All pieces are secured/bolted at the drill press base.

Place the ø10x12mm piece at the lower chuck

and using ø4 & ø8mm drill bits at the upper chuck

make a hole ø8mm with 4mm depth (the half of ball's diameter).


Assembly the cutting unit at the main piece using Graphite Grease as follows

Chisel - Ball Nest - Ball Bearing - Bolt.

Adjust the chisel's worm screw so as to can't turn left/right but not over tighten so to be move freely in/out.

Step 5: First Tests

From the first test the spliter works just fine without any problem or glitch.

Can splitting / cracking / cutting or bending the nut; when our needs are to save the bolt for any reason.

You can see it in action on my YouTube video.

Nut Splitter DIY

  • All comments are welcome
  • Thanks for your reading.
  • Good Luck if you try it.
  • Never say I can't do it.
  • Necessity is the mother of invention.

kess: -

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    3 years ago on Step 5

    Nice. Very complicated and involves hard work but it might just be worth it.



    Reply 3 years ago

    Hi Seth,
    It isn’t a so complicated build as you think and yes at some circumstances it is a very
    helpful tool.
    Perhaps the harder work it was the dimensioning of the plan but not the build by itself.
    If you decide to give a try to make it; then you will see that is an easy and quick build.


    3 years ago

    Great job!
    As you are making this yourself, you have one more option if you want to split open a nut without damaging the bolt:
    Make a 2nd chisel, this one blunt.
    Use the first chisel to cut trough the nut, (almost) as far as the threads of the bolt.
    Then use the blunt chisel to pry the nut open without touching the threads.


    Reply 3 years ago

    Thanks alot!


    3 years ago

    Pro tip for step 4: if your camera is struggling to focus on a small object/angle, put your hand close to the object or at the same distance from the lens, focus on it, remove the hand, then take a picture. This works if you're using a DSLR or some phone apps.


    Reply 3 years ago

    Thanks for your tip.


    3 years ago

    That's neat! Thanks for posting this up. My mind does debate making one when purchase price isn't that high, but I understand the desire to make it, and you did a good job. I share similar thoughts but just lack the motivation and energy these days!


    Reply 3 years ago

    Thanks a lot.

    All tools can't do the job, especially the cheap tools, the better for you is to try and built one, isn't a so difficult build.
    A good quality nut splitter tool is expensive when if you don't need to used it at daily basis. But as we say at my country; "The cheap tool at the end is more expensive than the expensive tool” (because has be paid twice).



    3 years ago on Step 5

    Poli Kali doulia mpravo


    Reply 3 years ago

    Ευχαριστώ Πολύ!


    3 years ago

    Really well done!


    Reply 3 years ago

    Thanks a lot!