Power Hacksaw

[Vyacheslav.Nevolya]

I will add information about the motor. This is a German Grunhain with 240 watt with a built-in gearbox.

[old_toolmaker]

Vyacheslav Nevolya,

Nice Job!!! I always wanted a small power hacksaw.

[old_toolmaker]

Vyacheslav Nevolya,

Does this saw lift the blade out of the cut on the reverse stroke?

[Jon]

Congratulations Vyacheslav.Nevolya - your Power Hacksaw is the Homemade Tool of the Week!

Excellent work. This is our first winning power hacksaw, and it's also a well-documented and comprehensive example of a good build.

Some nice tools from this week:

Harbor Freight Hydraulic Press Improvements by dudley.toolwright
Caliper Modification by Eloy Workshop
Chainsaw Blower Attachment by Made in Garage
Collet Key by petertha
Bandsaw Roll Around Wheel Brake by rgsparber
Tactical Pen by KraftSmith
Saw Sharpening Vise by Philip Davies
Bench Vise by diyfixman
Dial Indicator Mount by tonyfoale
Electrolysis Setup by mariost
Welders Accessory Stand by Canobi
Texturing Hammer by Dimitris.Polychronis
Sonic Cleaner by Al8236


Vyacheslav.Nevolya - We've added your tool entry to our All Homemade Tool of the Week winners post, and you'll be receiving a $25 online gift card, in your choice of Amazon, PayPal, or bitcoin. Please PM me your current email address and award choice and I'll get it sent over right away.

More importantly, this is your 10th Homemade Tool of the Week win! I've just added the golden wrench-on-pedestal graphic to the awards showcase in your postbit, visible underneath your avatar.

You join these two other 10-time winners: rossbotics and mklotz. Congratulations again and good job

Here are all 10 of your Homemade Tool of the Week winning tools:

Metalworking Lathe by Vyacheslav.Nevolya

tags: lathe, gears, motor

Belt Grinder by Vyacheslav.Nevolya

tags: belt grinder, motor

Walk Behind Tractor by Vyacheslav.Nevolya

tags: tractor, farm tools, gears, motor

Tracked Mini Dumper by Vyacheslav.Nevolya

tags: farm tools

Tractor Crane by Vyacheslav.Nevolya

tags: crane, hydraulic, tractor

Mini Lathe by Vyacheslav.Nevolya

tags: lathe, chuck, motor

C Clamp by Vyacheslav.Nevolya

tags: C-clamp

Milling Machine by Vyacheslav.Nevolya

tags: mill

Universal Cutter Grinder by Vyacheslav.Nevolya

tags: grinder, cutter

Power Hacksaw by Vyacheslav.Nevolya

tags: hacksaw, motor

[Vyacheslav.Nevolya]

Vyacheslav Nevolya,

Does this saw lift the blade out of the cut on the reverse stroke?

The blade does not rise when the reverse movement is, and it constantly presses the weight.

[old_toolmaker]

Vyacheslav.Nevolya

Thank for the information. That is a great little saw!

[Gergemall]

Bravo . It looks very sturdy! Thank you.

[old_toolmaker]

That sure does look like a solid machine. I would like to build one for my shop.

[tonyfoale]

The blade does not rise when the reverse movement is, and it constantly presses the weight.

Vyacheslav Nevolya,

Nice job, it is the best power hacksaw using handsaw blades that I have seen.
However, I think that with a simple modification its performance could be significantly improved. This sketch shows the basics.

The modification consists of raising the link mounting point on the sliding assembly and lengthening the link to suit. Alternatively you could lower the motor and crank, or both. Lowering the motor is probably a lot more work and not so simple .

Click for full size

On the sketch.
The hatched block represents the sliding assembly, the rest is obvious showing the crank in two positions, approximately half way through each stroke.
On the right of the sketch are some force diagrams assuming an anti-clockwise rotation of the crank. I have no idea which way yours rotates.
In the original case we can see that the tension force in A can be resolved into Fxa a horizontal force pulling the blade back AND Fya which is a vertical force pulling the blade downwards. All good.
Looking at the forces in case B we see that Fxb pushes the blade forward on the return stroke BUT Fyb is pushing the blade down. Which is not good. This causes increased blade wear, it takes more energy to move the blade and so heating is increased for no benefit.

The lower sketch shows the situation after raising the mounting point. In the A case the forces are as in the unmodified case except that the vertical force on the blade is increased. As long as this is not too severe it is a good thing as it will cut better. Looking at case B we can see that the situation has reversed itself. The vertical force Fyb is now upward, that is; relieving some of the downward weight force, this is a welcome change. So raising the link mounting point is beneficial on both strokes.

This was for anti-clockwise crank rotation. Clockwise rotation reverses everything. The purpose of the link in A and B positions is also reversed. A is now the return stroke and B is the cutting stroke, so the forces Fa and Fb are reversed. In the original case instead of the blade being pulled down more on the cutting stroke it will be subject to a lifting force acting against the weight force. Not good.