NEED HELP WITH USE OF SKIVING MACHINE

[Morse]

I recently purchased a NP/4 skiving machine and I need an answer to a problem. When skiving 4 sides the last skive tears out the first corner. I assume someone knows the answer.  What is the procedure? Is it the way I have adjusted it?  Would appreciate some advise.

[Matt S]

First action when my skiver doesn't do what I expect is to give the knife a quick sharpen and deburr. That tends to solve a lot of minor issues, because the leather is less likely to dive under or climb over the knife. Then I check that the foot locking pin is still secure, the foot angle screw hasn't walked out, and that C-shaped spring that applies bias against the front of the presser foot is still providing enough pressure, and make sure that there's no waste hung up in or around the knife.

I'm no expert but I've found that reducing the foot pressure on the last corner (by unlocking the presser lever just a smidge as it comes up) and pulling the work away from the machine just a little as it feeds the last corner helps when skiving all around something with corners. This prevents the first/last corner from getting smooshed down under the edge of the knife by the presser foot.

Generally, reduced foot pressure makes tearing less likely too, which usually requires a freshly sharpened and deburred knife, and 'just right" setting of the knife distance, feed wheel height and feed wheel spring pressure. Leather is less likely to tear and more likely to behave predictably with a freshly sharpened and deburred knife. I leave my machine setup for maximum knife revs and slowest feed, which gives me best results but your mileage may vary.

Oh and sharpen and deburr your knife frequently.

Did I mention to sharpen and deburr your knife?



What thickness and type of leather are you skiving?

[Annie977]

We have the same machine and definitely had the same problem - to the point where we stopped using it on any leather that was expensive or important. Wrecked A LOT of things we don't even want to talk about. We finally just decided to blunder through and figure it out by making every finite adjustment the machine has available until it stopped doing that. We found the angle of the stone to be our biggest culprit.

I also heavily second the sharpen/deburr advice above.

If you want to take some pics from the left side of the machine (where you can see the blade/stone/everything) - use a light - you should be able to see if stone angle is part of the issue.

If you're skivving really thick...do it in more than one go.

[RockyAussie]

8 hours ago, Morse said:

I recently purchased a NP/4 skiving machine and I need an answer to a problem. When skiving 4 sides the last skive tears out the first corner. I assume someone knows the answer.  What is the procedure? Is it the way I have adjusted it?  Would appreciate some advise.

If you would care to post a few pictures of how you have it set up may help. What I would try for now is to put the feed stone onto a softer spring pressure with the notch adjuster at the back. Also assuming you have the bell well and truly sharpened, move the bell back away (to the right) 1/2mm and try that. The tighter the bell is to the top guide the more the guide is likely to force the leather down as it slides through. If it still does it move it back a little more. The softer feed stone pressure helps to stop the sudden jump down as it slides through as well. Having a separate motor to keep the bell running at full speed  all the time allows the feed to go as slow as you want while maintaining the best cutting speed (flat out) at the same time. Check a couple of my videos and you may see what I mean. The Fortuna there allows the bell speed to always run fast whilst allowing a slow feed at the same time.https://www.youtube.com/watch?v=3mRlsetzIJg

Knowing what thickness and temper of leather you are having trouble with would help to know as well.

[Morse]

On 6/4/2020 at 4:15 PM, RockyAussie said:

If you would care to post a few pictures of how you have it set up may help. What I would try for now is to put the feed stone onto a softer spring pressure with the notch adjuster at the back. Also assuming you have the bell well and truly sharpened, move the bell back away (to the right) 1/2mm and try that. The tighter the bell is to the top guide the more the guide is likely to force the leather down as it slides through. If it still does it move it back a little more. The softer feed stone pressure helps to stop the sudden jump down as it slides through as well. Having a separate motor to keep the bell running at full speed  all the time allows the feed to go as slow as you want while maintaining the best cutting speed (flat out) at the same time. Check a couple of my videos and you may see what I mean. The Fortuna there allows the bell speed to always run fast whilst allowing a slow feed at the same time.https://www.youtube.com/watch?v=3mRlsetzIJg

Knowing what thickness and temper of leather you are having trouble with would help to know as well.

Dear Mr. Rocky,  On June 4, you answered a question I posted on Leatherworker.net.  I am a relatively new member and am not good at finding my way around the site.  I hope this gets to you I appreciate your response and will try what you have suggested. I did call Leather Machine Co. on the problem and they had a very simple suggestion which I tried and it essentially worked. The said that as your reach the fourth and already skived corner lift the final edge up as your reach it.  When I bought the machine it came with 3 pressure feet. I have no idea what each does.  In any event, thank you so much for your assistance and I will experiment with your suggestions.  santafesam3@gmail.com 

[RockyAussie]

Glad to hear you have found a solution that works for the problem. Thanks also for letting us know.

[Rahere]

Look at Japanese waterstones for sharpening - you can get ridiculously fine grits. They were developed to spare scarce carbon steel edges, and are half of the secret of samurai blades.

Just dunk the stone in water, no oil, and look after the paste building on the surface. Once you've ground the pitch, these are a lot less likely to muss witg it than oilstones are. An 800 grade for roughing out, 1500-2000 for polish - no need for rouge.