Feedscrew Knife Jumping

[woot92]

Hey Folks!

Fairly new here to the society, but I’ve been embossing for about year now. I now have two presto 6n’s, but I’ve run into an issue that I thought I had resolved and wanted to see if I could get some better insight into what’s going on here.

So at some point, the knife to the feedscrew started to hop once or twice when cutting, typically a little more than halfway into a 12” cut, and then once again close to the center. Now this was happening during earlier days when I didn’t know as much, so I had tried adjusting the brass piece that lifts the carriage and therefore feed knife. Kept adjusting and adjusting, and eventually could get it to work but with the feed knob up pretty high, which I learned is bad for the knife.

Eventually, with the help of Piaptk, we sharpened the feed knife with a dremel, and after a few tested positions got it to work. But then maybe the next day I started getting hops occasionally. I’ve found that there was not much meat left on the knife blade, so luckily he had a good one that we replaced it with. Even with the replaced knife blade however, I found that I had to ride the feed knob a little high as opposed to being flush like it should be, but I was getting no jumps, so I figured if it works, it works.

Cut to now, I’ve started to get jumps towards the center, but it doesn’t happen all the time and it only happens after embossing a 12” from start to finish. Even if I try running the feedscrew from the outer edge to inner, I get no jumps.

There’s no noticeable burrs that I can see, and I tried resharpening the blade but still have the same problem. I also found that the knife jumps more on lower lpi feedscrews.

Wondering if anyone has any insight on this?

[andyburnout]

Hey Woot92!
I had a similar issue once where the feed screw would slip off the pin which the pin would then slide around the feed screw and pop back into place. During this time the knife would lift slightly.
Could it be that your disc is slipping slightly between the flange and the platter and for a moment stopping the advancement of the carriage?

Have you tried swapping parts from each machine?

[woot92]

Hey Andy,

So I think I actually may have finally solved it after much headache, fingers crossed.

I swapped the knives in each lathe with each other and found that the problem was actually with the lathe itself, so then when trying to keep the feed knob flush, I noticed the knife was not making full contact with the feedscrew. So I unscrewed the two screws on the overhead handle that connects to the main gear in there, and essentially jimmyed it a little so that the knife made full contact and would crank in without problem, and then retightened.

Everything seems to be in working order now so that may have done it!