Help a guy out with his new skiving machine!

[YinTx]

6 hours ago, RockyAussie said:

The only disadvantage I can think is that the vacuum may need to be off when sharpening the bell blade in case any sparks could be picked up.

I'll try to get you some measurements if I can.  It would seem to be a pretty simple thing to make it retractable?  Would hate to have a spark fly into a pile of leather powder and set off a fire 2 hours later... Or perhaps a spark arrestor but I'd think it might be more difficult to implement.

YinTx

[YinTx]

The only disadvantage I can think is that the vacuum may need to be off when sharpening the bell blade in case any sparks could be picked up.

I'll try to get you some measurements if I can.  It would seem to be a pretty simple thing to make it retractable?  Would hate to have a spark fly into a pile of leather powder and set off a fire 2 hours later... Or perhaps a spark arrestor but I'd think it might be more difficult to implement.

I had some success yesterday.  First, here is the bad:  leather goes through without skiving at all, then at the end, bites in and takes out a chunk.  You can see where the blade went along without removing anything, then at the end, cuts in.

 

So, I got to thinking sometimes it's the simple things that are the solution.  This was simple:

On 8/3/2019 at 4:22 AM, alexitbe said:

Could there be a burr left after grinding which just needs removing?

Alex

So, even though I had tried a couple of times already, I went at it again.  This time I really dug in there with the ceramic rod on the inside of the bell to make sure I wasn't being too delicate in the past.  Viola, all of a sudden it acted like a whole new machine!   Here is the result, I was able to skive very fast, the feedwheel pulled the leather in without any assistance or needing to place it under the foot before lowering the foot.  The only issue I have right now is where it takes a chunk out at the end when the skive overlaps.  Do I need to reduce the feedwheel tension/pressure to alleviate this?

YinTx

[alexitbe]

haha.... Lucky guess! But since I started skiving  by hand I have come to realise how important removing the burr is...

 

[YinTx]

@RockyAussie, here are some dimensions for you on the Cobra NP-4.  Let me know if there is another you need...

 

bottom opening side 1

bottom opening side 2

opening radius

table thickness

dimension from base of machine to bell bottom (note that divisions in this photo only are in 1/12's of an inch, not 1/8's or 1/16's)

dimension of a "shop vac" hose

 

YinTx

[RockyAussie]

Thanks YinTx. I need this measurement from the bell edge (the sharp edge ) to the inside frame as shown here below.

[YinTx]

Oh snap.  I knew I missed one.  Next time I'm there I'll see if I can get it.

YinTx 

[YinTx]

There was a much older thread on LW showing this video.  Judging by the "lines" on the skived section of my leather, my blade may still be a bit dull.  Might be time to get a better stone for it.  Anyone comment on the techniques used here?

 

[RockyAussie]

1 hour ago, YinTx said:

Judging by the "lines" on the skived section of my leather, my blade may still be a bit dull.  Might be time to get a better stone for it.

Your blade may have started of sharp but those lines are from where the blade has picked up very small sometimes large chips out of it. I mentioned earlier about stropping the blade and I say it again. Once the blade is sharp some leathers can knock the edge about within a few inches and some wont hurt it at all. Once the blade is sharpened and stropped it will hold the edge for many times longer. To strop you find a decent behaving leather preferably about 2mm thick and feed it through very very slow even stopping it sometimes. This seems to smooth the edge of the sharp blade a little and you can hear the noticeably quieter sound as the leather feeds through. Choppy lines will often lead to the chopping out holes so as soon as you see them stop and resharpen. I do not strop every time as sometimes through a long run I will let the stone lightly touch for a few seconds and continue on. This does not seem to hurt the stropped edge much. If it feels or sounds rough it will need to be sharpened and stropped. I will look at the video above more as I have not seen it previously but at a quick glance I noted around 18 minute mark where leather shavings went all over the top. No extractor. I notice the noise difference on the FAV when he skives against my Fav and when it sounds like that I know it needs stropping. 

P.S. Hole chops in crocodile are expensive mistakes and may be why I am very attuned to the problem.

[alexitbe]

With regard to stropping the blade: do you add any polishing compound to the leather or is the leather enough...?  If I were stropping a skiving knife I would use sole veg ant leather to strop on... Would you use 2mm veg tan here or a chrome leather?

 

Thanks

Alex

Edited August 9, 2019 by alexitbe

[mikesc]

Just a thought, but it might be better to use the internal diametre of the "shop hose" rather than the outside diametre , make it a "push on" rather than a "push in"..( like car hoses, always "push on" ) On a "push in "design the small "step" where the opening of the "shop hose" would be might cause some "build up", however small, I would imagine you'd want to be avoiding potential "build up" spots.

Interesting thread..even for those of us who do not have skivers. :)

[YinTx]

16 hours ago, RockyAussie said:

To strop you find a decent behaving leather preferably about 2mm thick

I did run some leather through before I did the good leather, but I guess I should have asked for clarity.  What characteristics would define a decent behaving leather? 

I should be able to get your dimensions later this evening.

YinTx

[YinTx]

@RockyAussie, I think this is the dimension you are looking for.

YinTx

 

[RockyAussie]

Thanks YinTx. That sort of looks like 1 1/4" plus whatever the width is of that ruler. I think you need to hold the square the other way around. I would expect to see something about 2 1/2" . Does your skiver hinge back ? Would it be hard to put the back of the square against the frame as I have done above with the measurements shown next to the edge?

[RockyAussie]

18 hours ago, alexitbe said:

With regard to stropping the blade: do you add any polishing compound to the leather or is the leather enough...?  If I were stropping a skiving knife I would use sole veg ant leather to strop on... Would you use 2mm veg tan here or a chrome leather?

 

Thanks

Alex

 

6 hours ago, YinTx said:

I did run some leather through before I did the good leather, but I guess I should have asked for clarity.  What characteristics would define a decent behaving leather? 

I should be able to get your dimensions later this evening.

YinTx

Most leathers are fine but some are really bad. I tend to use a 2mm chrome tan that I use for my dress belt backs but that's because I have plenty of scrap of it. I have never used any polishing compound with it so I can't say how that would go or how to use it. If a leather feels scratchy when you feed it in while doing normal skiving then that would not be a decent behaving leather. They tend to chip out your blade early.

[YinTx]

22 minutes ago, RockyAussie said:

Thanks YinTx. That sort of looks like 1 1/4" plus whatever the width is of that ruler. I think you need to hold the square the other way around. I would expect to see something about 2 1/2" . Does your skiver hinge back ? Would it be hard to put the back of the square against the frame as I have done above with the measurements shown next to the edge?

It is a framing square, the one side is 1," so if you read the inside dimension, you will have to add the 1," so yes, 2 1/4" total.  The skiver does hinge back, I did that for the previous measurements.  Not necessary for this one, I try to avoid it since I have to remove screws from the base to remove the drive belt to allow it to hinge (as far as I know), and one of them has already stripped out the wood.  

YinTx

[YinTx]

Bah.  Tried sharpening again, stropping, it's worse.  Worked better yesterday.  I wouldn't think there would be skill in applying a stone on these things, but apparently there is.  Will order a smoother stone Monday.  

YinTx

[RockyAussie]

3 hours ago, YinTx said:

Bah.  Tried sharpening again, stropping, it's worse.  Worked better yesterday.  I wouldn't think there would be skill in applying a stone on these things, but apparently there is.  Will order a smoother stone Monday.  

YinTx

Warning...the smooth stones do not grip as much and on the stiffer leathers it will not feed through well. On garment type leathers they can be good if you are going to be doing that a lot. DO NOT use the stone on the stick inside the bell too much as if you overdo it on an angle it will be worse than ever. The leather will dive in and down and holes aplenty. Are you trying out some different leathers to see how they perform? Not having seen a video yet on how the machine is performing it is still a wild guessing game as to what could be the problem.Your top foot may be not tapered/angled well or smooth as needed or many other things that can come into play. What is the brand name on the back of the bell? Does the skiving go smooth and ripple free at all on any edges for a while?

[alexitbe]

Here are measurements for a Fortuna DRP... Its very old so may not be relevent... But I think many of the skivers are based on this old model so maybe it helps

 

Edited August 10, 2019 by alexitbe

[RockyAussie]

Thanks @alexitbe That is a good picture. Looks like that one has been out of action for a while. I have been trying to get some measurements of a Cowboy from the dealer over here but no luck as yet. I was hoping to be able to get enough measurements of different machines to make up a universal type suction funnel affair but so far the interest looks pretty poor and not worth the effort. I suppose if you haven't used one with a vacuum it is hard know the difference it makes. On yours for what it is worth I think the guard over the bell has been rubbing on the bell and there is an cam adjustment knob on that cover to stop that. The bell is a bit far back I suspect which is why the blade angle looks overly acute. The sharpening stone has junk in it to be dressed out before and sharpening is done. I hope that is of help and again thank you for the picture measurements.

Brian

[alexitbe]

It was no problem to do, I am happy to help if I can...  Its a shame that interest is so low...

Thanks for the advice on the skiver. Your are right, it has not been used in a very long and I have never used one personally... It is something I will work on after I fixed my Pfaff 193-5 shoemaking machine... The skiver is for shoemaking too, but everything is taking so long to find and then repair...Oneday, I will have a workshop that works..

Enjoy what remains of the weekend.

ALex

[Scoutmom103]

I'm very interested in this thread and the suction funnel.   I'm scheduled to pick up a Fortschritt (Has 2136 with Germany on a Tag, could be a inventory tag)  in Mid January.  It's being stored in a warehouse until I am traveling a couple of hours from the warehouse, so I can't get any measurements at this time.  I will have to remove the skiver from the worktable to fit it in my Outback so I'll be able to get lots of measurements once I get it home.  

You do amazing work with the ways you come up with solutions to problems and ways to improve production and use of machines and processes.  Thank you for being so willing to share and utilize those skills for others.

 

Edited August 11, 2019 by Scoutmom103
Not enough coffee yet this morning.

[RockyAussie]

13 hours ago, Scoutmom103 said:

I'm very interested in this thread and the suction funnel.   I'm scheduled to pick up a Fortschritt (Has 2136 with Germany on a Tag, could be a inventory tag)  in Mid January.  It's being stored in a warehouse until I am traveling a couple of hours from the warehouse, so I can't get any measurements at this time.  I will have to remove the skiver from the worktable to fit it in my Outback so I'll be able to get lots of measurements once I get it home.  

You do amazing work with the ways you come up with solutions to problems and ways to improve production and use of machines and processes.  Thank you for being so willing to share and utilize those skills for others.

 

Sounds good. Do you have any pictures of it? As you are taking it off a table I am wondering if it is presently set up with suction? @Constabulary gives a little history on this brand in this earlier post and @David Bruce has one and likes it.

 

[Scoutmom103]

I only have a few pics and they aren't great.   From what I can see, it probably doesn't have suction.    Thanks for the link to the post.  

[YinTx]

Update:  So I've had more success with the machine, following more diligent sharpening and a bit less aggressive deburring on the inside.  I imagine it will only get better as I do things like put in a smoother sharpening stone, add vacuum, roller foot, practice, etc.  Thank you all for helping me learn to use this thing better!

Learned a really cool thing, and that is the type of foot you have installed affects the type of skive you get, beyond just adjusting the angle of the foot!  Now I have to decide which feet to spend $$ on... 

Here is a photo of the recent skive, not perfect, but no holes blown out, and the thickness I wanted, on 5 oz veg tan even.

YinTx

[RockyAussie]

Congratulations @YinTx it looks like you are getting there. That is pretty good for that wide a skive I think.. On the spring pressure adjustment on the left at the side it varies how easily or hard the feed wheel drops down when the leather goes in. Try turning 1/4 off anticlockwise and test then try some more. You will find an ideal point for a given thickness and hardness and will help avoid them holes and generally go through smoother.

I just did a check back and saw that some of these Chinese machines don't have a fine adjustment knob on the end of the spring pressure adjuster. They may only have the lift it out and stretch or release type of lever with slots. I don't know what yours has yet so I will have to check.

Edited August 26, 2019 by RockyAussie
mistake maybe.