Bell Skiver technique question

[chuckgaudette]

Not sure if this question should go in the machinery section or technique. If I cut a 1 foot square of 2mm leather and skive a half inch along one side it will come out as I intended. Then if I turn the leather to skive the opposite side with the exact same settings the second side may barely skive at all. does this have something to do with the grain of the leather? If so, how do I correct this without readjusting the skiving depth for each side?

Thanks 

[Matt S]

Hi Chuck,

I'm a relative newbie to the bell skiver myself, having bought mine only this month. However I've learned that they can be fussy things and that even a tiny variation in thickness or stiffness, that you might find in a single piece of leather, can make the difference between a good skive and barely any skive -- or a jam.

Do you have a way to accurately measure the thickness of the leather around your piece? I use a pocket vernier caliper. You may find that there's a very small variation between the thickness on one side and the other.

What sort of leather is it you are skiving? I find that softer leathers can be less forgiving. If it's something with a heavily corrected top surface it may be difficult to see the variations in the grain of they leather which, as you allude, can change the stiffness of the leather and affect how it skives.

[gigi]

I am not sure if I understood correctly: you skive one side of the square (for example from 2 mm to 1.6 mm  final thickness) and flip over the leather  (flesh side up) and want to skive the back of the same square-side (for example from 1.6 to 1.2 mm)? parallel skive or angled (beveled)?

Edited August 17, 2018 by gigi

[chuckgaudette]

4 hours ago, Matt S said:

Hi Chuck,

I'm a relative newbie to the bell skiver myself, having bought mine only this month. However I've learned that they can be fussy things and that even a tiny variation in thickness or stiffness, that you might find in a single piece of leather, can make the difference between a good skive and barely any skive -- or a jam.

Do you have a way to accurately measure the thickness of the leather around your piece? I use a pocket vernier caliper. You may find that there's a very small variation between the thickness on one side and the other.

What sort of leather is it you are skiving? I find that softer leathers can be less forgiving. If it's something with a heavily corrected top surface it may be difficult to see the variations in the grain of they leather which, as you allude, can change the stiffness of the leather and affect how it skives.

Matt, I'm skiving fairly thin soft leather used mostly for handbags. Its typically embossed and dyed and maybe 1.5 - 2 mm and I like to take it down to around 1 mm. I do have a digital thickness gauge I can use. 

Gigi, Yes I am skiving both the left and right side of one piece so when I rotate it I get a different result through the bell skiver. Once I get it adjusted to where I want it on one side, I rotate the piece and get a different result on the other side.  

[gigi]

Anything matters with thin leathers:  most important - Is the knife sharp enough?  Is the presser foot polished and has good geometry? 

Adjusting the tension for the driving wheel might help: softer tension for softer leathers.

I don't think is necessary to adjust the pressure-foot height for each side (unless you don't mind small variations in thickness for each skived side). 

[Matt S]

6 hours ago, chuckgaudette said:

Matt, I'm skiving fairly thin soft leather used mostly for handbags. Its typically embossed and dyed and maybe 1.5 - 2 mm and I like to take it down to around 1 mm. I do have a digital thickness gauge I can use. 

Gigi, Yes I am skiving both the left and right side of one piece so when I rotate it I get a different result through the bell skiver. Once I get it adjusted to where I want it on one side, I rotate the piece and get a different result on the other side.  

What does your digital thickness gauge tell you about this piece of leather? If we call the first skived edge A (the one that went fine) and the second skived edge (the one that didn't go very well) B, what is the full thickness of the leather immediately behind each skive and on each skive?

What part of the hide is the piece of leather from? Squashy bits like belly could vary a lot. Heavily embossed leathers, like are often seen in handbags, often camouflage these grain variations until you start working them.

What shape of skive are you going for -- tapered, flat... tapered skives can vary a surprising amount if the leather isn't brought up to the guide exactly the same each time.

As Gigi mentioned, try sharpening and deburring your knife. The guy I bought my skiver off said that solves a lot of "odd" behaviours that can crop up. Bit like putting a fresh needle in your sewing machine I guess.

As I said I'm pretty new to bell skivers. Most of my experience is with fairly firm chrome tans so I don't know how applicable these thoughts are.

[chuckgaudette]

Here is an example. This is both ends of an 8 " strip skived with the exact same settings. It is a embossed leather and closer to the belly area. The blade was just sharpened. The one on the left had an original thickness of about .97mm and it skived down to .95mm. On the right (the opposite end) it was originally .95mm and it skived down to .23 mm. 

[Matt S]

Well that's weird.

That looks like some real squashy and spongy belly, which is most likely related to your issue. Does the same thing happen in firmer leather from the same hide? I wonder if you have so much gap between the feed wheel, the knife and the presser foot that it's able to compress against the presser foot and ride over the knif, then spring back again once it's free of the skiver machine. 

What adjustments would/do you have to make to the machine to successfully skive the 'difficult' bit of leather? And if you put the 'easy' bit of leather through the machine on these settings what happens?

Possibly related, but that's a very heavy skive from 0.95 to 0.23mm. Looks like you've gone too deep and are breaking through the 'valleys' of the embossing. Might need to raise the presser foot up a little bit, and the feed wheel if it then doesn't grip.