Best Angle to Sharpen a Hook

[friquant]

I'd like to sharpen the hook on my Singer 144W103 in order to reduce skipped stitches. 

With the needle guard removed, the hook is barely close enough to graze the needle. But it's not the tip of the hook that strikes the needle. About 2mm back from the hook tip---that's the part of the hook that actually strikes the needle. I don't know if that means the hook is simply dull, or if it has been improperly sharpened in the past. When sharpening scissors, for example, the going strategy is to only grind on one face of the blade.

So what are the rules of thumb for sharpening a hook? File one side, or both? What angle to use?

Here are photos of the hook

 

 

[TonyV]

I may be wrong (I have limited experience on machines), but I don't think sharpening the hook is common practice.  I would think that the hook/needle interaction is more a matter of timing.

Perhaps someone more knowledgeable will chime in.

[friquant]

15 minutes ago, TonyV said:

I don't think sharpening the hook is common practice.  I would think that the hook/needle interaction is more a matter of timing.

Considering that I couldn't find much for references, I agree that sharpening a hook is uncommon. I'm satisfied with the hook-to-needle timing, and I want a sharp hook with useful angles. So here we go...

Here's the before photo, so you can see how rounded the tip of this hook is. Also note that the hook tip is positioned directly above the center of the hook in this photo, so you can imagine the arc swung by the hook as it intercepts the thread/needle.

 

[friquant]

Here is the after photo:

I can see now that the camera is not looking directly down the hook axis. Oh well..at least the before and after shots got the same treatment 🤷‍♂️

I faced the inside and outside edges of the hook using a diamond sharpening stone. Stone is 25x75x6 millimeters, on a 320mm stick of oak.

 

[MikeRock]

How does it work after sharpening?

 

[friquant]

1 hour ago, MikeRock said:

How does it work after sharpening?

I did get the hook back in the machine, but it's not adjusted yet. I need to bend the hook's needle guard so it doesn't protrude out so far, now that the hook has been filed. I have not figured out a good way to adjust needle guards. I've seen people use a screwdriver as a pry bar, pressing against the machine head. I've done that in the past, but it felt clunky. Not finding something good to press against today, so may need a custom tool.

 

Or maybe pry against the feed dog support 🤷‍♂️

[friquant]

5 hours ago, MikeRock said:

How does it work after sharpening?

So far so good!

Here is an example of the type of stitching that would make it skip like crazy before. That is, stitching a puffy thing with the puff mostly on the opposite side from the hook. (I suspect this is in part because there is some play in the rock bar bushings.) But it nailed every stitch this time