Shear Luck?

[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.

[Mel Ristau]

Mel Ristau
9704207421
8001 Country Farms Court, Fort Collins, 89528

[bobadame]

Follow up on this shear. Neat little machine. Each blade had 4 cutting edges and they had never been flipped or rotated so we did that. The machine was designed to cut a maximum thickness of .060", 1.5mm so clearance from the factory was set at .008". We found a shim behind the top blade which set that clearance. Most of Mel's work is in aluminum less than half that thickness so we added a layer of clear packing tape behind the bottom blade to decrease the clearance another frog hair, give or take. Tested with a .012 thick piece of 6061 and both machine and Mel were happy. Cool design, if it can't be adjusted it come out of adjustment.

[Jaroslav]

It is a pleasure to read good reports from such a distance about the correct approach to machine repair. Now it's for 2 more lives.
And other edges will be dulled in 200 years. Then it will be necessary to grind.
Maybe in 200 years there will be other animals here...

[Brzeczyszczykiewicz]

If there are animals, remember to always sharpen your tools. Otherwise we will never be able to get out of the cage.

[Mel Ristau]

Great guy that Bob!
Monday I tried to edit/update post #11 above but it has not been revised. However, Bob’s description of what we found is best.
One question though…. Years ago, might Di-acro have offered a range of shim thicknesses appropriate for various material thicknesses?

https://www.dropbox.com/scl/fo/4bd98...o4jiqpzh0&dl=0