Shear Luck?

[Mel Ristau]

I've been cutting light gauge metal sheet with a 24” DI-ACRO O’NEIL-Irwin shear for about 30 years. Cuts are no longer clean. The shear has been used a few times a year to cut .03 aluminum. Can't afford to have it professionally sharpened. Is there advice/info here on how to go about tuning/adjusting? Thanks!

https://www.dropbox.com/scl/fi/zsumq...1scneb2d2&dl=0

[crystallographic]

Originally Posted by Mel Ristau

I've been cutting light gauge metal sheet with a 24” DI-ACRO O’NEIL-Irwin shear for about 30 years. Cuts are no longer clean. The shear has been used a few times a year to cut .03 aluminum. Can't afford to have it professionally sharpened. Is there advice/info here on how to go about tuning/adjusting? Thanks!

https://www.dropbox.com/scl/fi/zsumq...1scneb2d2&dl=0

Knife shears have a "pinch" tolerance and cutting angles.
Where the blades bypass one another wear occurs.
With this size I would try a diamond "stone" making flat passes on the bypass surfaces - w/ light oil, and cleaning the surface and stone every so often.
After the faces clean up I would take a look at the narrow faces. -
-- Oh- just reminded myself that some blades have two cutting faces, so flipping blades may be good - IF not done prior?

[Bad Bob]

I sharpened the blades on my 52” stomp shear using (carefully!) a 4” angle grinder, then a 8” long water stone to polish the grinder marks out. That was over 35 years ago. It still will cut thin stainless without bending over the blade.

[skintkarter]

What everybody else has said, but also pay close attention to the gap or lack thereof between the blades as they pass one another. I have an insurance client who is also a knife sharpener and he schooled me that there should be bugger all clearance and to just keep adjusting the lower blade towards the upper blade until the shear will cut a sheet of copy paper cleanly. Tighten everything up and walk away. Has worked well on my 4' old thing and it cuts everything from 22g galv to smaller bits of 2.0mm 5005

[crystallographic]

Originally Posted by skintkarter

What everybody else has said, but also pay close attention to the gap or lack thereof between the blades as they pass one another. I have an insurance client who is also a knife sharpener and he schooled me that there should be bugger all clearance and to just keep adjusting the lower blade towards the upper blade until the shear will cut a sheet of copy paper cleanly. Tighten everything up and walk away. Has worked well on my 4' old thing and it cuts everything from 22g galv to smaller bits of 2.0mm 5005

Agreed - "clearance" can sometimes be heard as a whisper when the blades close without cutting any material.

(ps, I set my Pullmax cutters to cut thin paper, as the factory recommends.)

[bobadame]

Most shear blades can be flipped over to expose a new edge. Yours may have this feature. The bottom blades are often perfectly square with 4 cutting edges. The top blade might have a rake angle so only 2 cutting edges, If not, there was a sharp shop here in Fort Collins that would grind blades for $.50/inch. I don't know if they are still around but certainly someone in Denver.
Edit: By the way, I'm also in Fort Collins and I'd be glad to help you adjust your shear. I used to do that sort of thing years ago.

[Mel Ristau]

Thanks All
With your suggestions, it sounds like getting it back in shape is possible.
Fairly mechanically inclined but experience probably best route with this.
Will see what Bobadame thinks.

[Marc Bourget]

I believe my Pexto manual gives adjustment info, but I was unable to find a "How to adjust my Pexto shear" on YouTube.


Hint, hint, Bob!

[Jaroslav]

Mel, if you are going to sharpen knives professionally, you need to sharpen them on the flat side. I have serviced a lot of scissors. Many users have ruined the blades in their scissors by sharpening them on the narrow side.
If the knives are sharpened on the wider side, it is possible to turn them 4 times. Mostly it is set for 2 human lives. If you sharpen the knives on the narrow side, you have to underlay them with pads. They are lower than the table after regrinding. Tightening screws are damaged in the same way. They tighten the knife diagonally.
I measure the clearance on the knives to 0.05 mm. It's a more complicated process.
At the same time, it is necessary to define the clearance in the machine guidance. The clearance between the knives is the final adjustment.
I have set up many machines in very poor condition to run like they did when they were young. I always kept my hand on my forehead and couldn't understand how anyone could resharpen knives on the narrower side. He was probably the one who was lazy to think and was not willing to understand the basic idea.

[bobadame]

Originally Posted by Jaroslav

Mel, if you are going to sharpen knives professionally, you need to sharpen them on the flat side. I have serviced a lot of scissors. Many users have ruined the blades in their scissors by sharpening them on the narrow side.
If the knives are sharpened on the wider side, it is possible to turn them 4 times. Mostly it is set for 2 human lives. If you sharpen the knives on the narrow side, you have to underlay them with pads. They are lower than the table after regrinding. Tightening screws are damaged in the same way. They tighten the knife diagonally.
I measure the clearance on the knives to 0.05 mm. It's a more complicated process.
At the same time, it is necessary to define the clearance in the machine guidance. The clearance between the knives is the final adjustment.
I have set up many machines in very poor condition to run like they did when they were young. I always kept my hand on my forehead and couldn't understand how anyone could resharpen knives on the narrower side. He was probably the one who was lazy to think and was not willing to understand the basic idea.

This model Di-acro is different. The only possible adjustment is the height of the bottom blade which is done with leveling screws under the blade. Clearance between the blades is machined in at the factory. Everything being made within a tolerance then I suppose the blades are selectively assembled to the machine. I believe this machine has 4 useable edges top and bottom. Like you said, should last a couple of lifetimes. After that the blades can be sharpened on the thin edgeand last another couple of lifetimes.