Grinding diagnosis/troubleshooting requested

[Greg Obach]

had a similar problem.... fixed it by wearing a work boot on my right foot... brought my grind on one side abit higher... ... bob nextdoor told me that makes sense cause all the country music and foot stampin on my right foot made it on the flat side.. innit the way it is


tip is alway the hard part.. just takes some practice... by the way..sweet little blade you have


G :thumbup:

 

[Jack O'Neill]

drives you nuts , don't it PJ ? I believe your question has been answered even by yourself . Strong side/weak side . Angle of holding blade etc. . Will and Nathan got that one .
I only have 2 things to say , get use to it because it will probably happen more offend than not . One poster wrote once the easiest part of knife making was the mistakes , the hardest part is fixing or correcting them .
Now Greg's post might sound like a shot at humor , but , all human beings have one arm shorter than the other and one leg shorter also , unless you go to a chiropactor daily . It changes the way you hold things and stand .
Just my 2 cents of something .

 

[allenr]

Paul,

I have exactly the same issue with my Sears 2x42. My plunges look identical, i.e. the right side is more curved than the left. Since I'm new at this I just figured I didn't know what I was doing. So, I built a jig that would hold the blank at the desired angle, extend the grinder table, and even used some small pieces of carbide for a "file guide" type arrangement. Oh, and I have a ceramic platen. The problem still exists.

What I have observed is that when grinding on the left side the belt moves to the right just a bit after a little pressure is applied. I'm not sure if this is an inherent tracking problem, a belt problem, or my less than spectacular technique. I'm going to try some different belts to see if that changes anything.

Allen

 

[Will Leavitt]

Allen if there's room on the idler wheel put a line of tape in the center of it to increase the "crown" of the idler wheel. Just a couple layers of masking tape can work wonders.

 

[efleming]

The problem with the bevel is all about pressure. Direct pressure right where you need it... back off where you don't need it.

This is MUCH easier to dial in if you grind off the toolrest like I do and use a push-stick. Come to my shop, and I'll show you how

Keep it up Paul.... you're doing awesome! :thumbup:

Hello Paul,

I've ground my blades for a few years now with no tool rest, completely free hand. It took a lot of time and practice to get grind lines to match up evenly.

A few weeks back I had the pleasure to spend two days in Mike Vagnino's shop. While there he showed me the technique of grinding off a tool rest as Nick points out above. Using the tool rest technique along with a push stick makes it much easier to get near perfect grinds with a fantastic amount of control. This control even lets you fix mistakes rather easily as well. It's all about placement of pressure.

1++ for using a tool rest and push stick while grinding.

Eric

 

[allenr]

Allen if there's room on the idler wheel put a line of tape in the center of it to increase the "crown" of the idler wheel. Just a couple layers of masking tape can work wonders.

Will,

Thanks for the tip. I'm headed to the shop to give it a try.

Allen

 

[NickWheeler]

Thanks for the back-up Eric. I ground totally free-hand for something like 5 or 6 years which included LOTS of double hollow ground daggers. I'm pretty sure I thought a tool rest was cheating back then like many do now.

Then I went to Mike's.

Tim Hancock showed Mike the method of grinding with a tool rest. Mike showed me.

I gave up on it for a while, because there were problems that were just making it more of a hassle for me.

Then I covered my long tool rest with thin micarta to reduce drag, and built some push-sticks with bearings. Fancy push-sticks...but not ideal.

Made some push-sticks out of UHMW and went to Mike's to try them out. We decided that was the cat's meow.

It's still very easy to totally F up a blade with a tool rest, but it takes out a lot of variables. I gave Erin a quick lesson on doing it this way, and the first blades he ground on his KMG looked better than a lot of guys' blades that have been at this for years.

But y'all can crucify me for cheating if 'ya must.

 

[Will Leavitt]

Noooo if it makes my grinding more precise and improves my fit and finish then I'll at least try it out. I don't want to get into the whole "cheating" thing.

 

[allenr]

Allen if there's room on the idler wheel put a line of tape in the center of it to increase the "crown" of the idler wheel. Just a couple layers of masking tape can work wonders.

Will,

I gave this a try. Two layers of tape, 1/8" wide, down the center of the idler helped. The belt stays put much better than it did. I obviously didn't get the tape aligned straight since I induced a bit of side to side wobble, but that can be corrected. The idler has precious little crown to it, so no wonder the tracking wasn't the best. There was also a bit of side to side wobble before I put the tape on, which tells me that the idler crown was far from being true to begin with. Guess a guy gets what he pays for. A better grinder would be nice, but I need to get a few knives under my belt before contemplating making that expenditure.

Thanks again for the tip.

Allen

 

[dustfurn]

Made some push-sticks out of UHMW and went to Mike's to try them out. We decided that was the cat's meow.

What is UHMW? Can anyone post pics of their push-sticks? Also, does anyone have a push-stick grinding tutorial?

Thanks for the Advice.

Dustin

 

[Trace Rinaldi]

Paul- It's looking really good!

There are many things that can throw off your grinds.

One thing to watch, is if your platen it set up so that the belt is running in line with it. Make sure the belt is backed evenly.

Watch belt drift. Lots of guys put a radius on their platen edges. I used to, but ended up finding I have better control with square edges and just drifting the belt off the edge a little. I only drift it over about 1/16" AT MOST.

That's just me.

The problem with the bevel is all about pressure. Direct pressure right where you need it... back off where you don't need it.

This is MUCH easier to dial in if you grind off the toolrest like I do and use a push-stick. Come to my shop, and I'll show you how

Keep it up Paul.... you're doing awesome! :thumbup:

+1 Nick.. I agree with all that.. The part about direct pressure where its needed is the key to good grinding IMHO.. I dont use a push stick though, I just burn my thumbs up..
BTW I think that blade looks pretty good.:thumbup:

 

[NickWheeler]

UHMW is a thermoplastic polymer...Ultra High Molecular Weight plastic.



It's a "high tech" plastic that is VERY slick. My introduction to it was Hewes Craft Boats. My uncle drove a delivery truck for them, and instead of using rollers on their boat trailers, they used UHMW because the boats would slide on it better than rollers.

I don't think there are any tutorials on grinding this way.

The reason I've never done one, is because Tim Hancock and Mike Vagnino both make part of their living by teaching students. Part of the reason to go to guys like that, is they can show you techniques like this that aren't readily available anywhere else.

Since both men are my friends and people I respect, I felt like I'd be cutting into their family's income if I showed processes that they have developed.

Call me old fashioned, but it is what it is. I've showed a few guys here in my shop.

Folks get mad about others "holding secrets" but if one were to look at my history around here and the couple dozen "tag along threads" I've done, they'd realize that the grinding thing is sure not about secrecy, it's out of respect for my two friends.

 

[Greg Obach]

Nick... i want to be a cheater too ! if that means having great grinds...

if theres a chance you could do a small tutorial on it... :thumbup:




argh... sorry ... i posted too late on this.... don't worry about it ...i understand the circumstance

 

[efleming]

What is UHMW? Can anyone post pics of their push-sticks? Also, does anyone have a push-stick grinding tutorial?

Thanks for the Advice.

Dustin

Hello Dustin,

UHMW = Ultra-High Molecular Weight - It's a very low friction plastic.

I got my 4" X 24" X 3/8" sheet at my local Rockler Woodworking store. Here is a web link --> http://www.rockler.com/product.cfm?page=1580&cookietest=1

Search for part number 67934

You mount a layer of UHMW to your tool rest using two sided tape. My tool rest is a piece of aluminum stock ~18" X 3" X 1/2" with a 1/2" notch in the middle of the rest that allows the surface to sit a little past the grinding belt. This allows you to drag your blade across the platen or wheel, with very little surface friction, while applying pressure to the blade with a push stick. As Nick has found, just a piece of UHMW works VERY well for a push stick.

Eric

 

[efleming]

Posted the same time. Nick, you are too fast!

 

[PIndelicato]

I ground another blade this morning, trying to keep in mind everyone's comments, and my own theory about grinding the tip to proper thickness. I think I may be onto the problem with the tip issue, looking at the results from today's blade. It's better, but on both sides rises up at the end. As I get out towards the tip, I sort of tighten up and I'm not sure what to do. In my head, it seems if you apply more pressure and/or pull the butt out to thin the tip, then the grind will have to go higher/deeper....yes, no???

The top grind lines are not PERFECT, but I think between some more practice and some hand sanding that will get better. Unfortunately I did not take pics of the first blade fresh from the grinder to do an exact comparison (the first blade had been mostly hand sanded to 320x for HT, the 2nd one is fresh of the grinder with a 400x belt.)

I used an unsharpened pencil as a makeshift push stick on these two, experimenting with both the eraser end and the flat wood end. I think slick is the way to go, so I'm going to have to figure out where to get some of that UHMW polymer.

I just 'kissed' the flat above the grind towards the end with the 400x belt being sloppy, but I think you can still make out the grind line. It should sand right out.

Thanks again for everyone's input!

 

[PIndelicato]

had a similar problem.... fixed it by wearing a work boot on my right foot... brought my grind on one side abit higher... ... bob nextdoor told me that makes sense cause all the country music and foot stampin on my right foot made it on the flat side.. innit the way it is


tip is alway the hard part.. just takes some practice... by the way..sweet little blade you have


G :thumbup:

I think my legs are the same length but I do have terrible posture! Anyway, since I'm using a work rest, I think that variable has been eliminated. Thanks for your input and the nice words!

drives you nuts , don't it PJ ? I believe your question has been answered even by yourself . Strong side/weak side . Angle of holding blade etc. . Will and Nathan got that one .
I only have 2 things to say , get use to it because it will probably happen more offend than not . One poster wrote once the easiest part of knife making was the mistakes , the hardest part is fixing or correcting them .
Now Greg's post might sound like a shot at humor , but , all human beings have one arm shorter than the other and one leg shorter also , unless you go to a chiropactor daily . It changes the way you hold things and stand .
Just my 2 cents of something .

Thanks ONeill, I'm sure the frustration will grow but at this point I'm thrilled to just feel like I can make a decent grind without crossing my fingers, eyes, toes, and saying a prayer to Craftsman every time I approach the belt!

Paul,

I have exactly the same issue with my Sears 2x42. My plunges look identical, i.e. the right side is more curved than the left. Since I'm new at this I just figured I didn't know what I was doing. So, I built a jig that would hold the blank at the desired angle, extend the grinder table, and even used some small pieces of carbide for a "file guide" type arrangement. Oh, and I have a ceramic platen. The problem still exists.

What I have observed is that when grinding on the left side the belt moves to the right just a bit after a little pressure is applied. I'm not sure if this is an inherent tracking problem, a belt problem, or my less than spectacular technique. I'm going to try some different belts to see if that changes anything.

Allen

Hi Allen, now that you mention it I think I have seen the same belt effect on my machine. I have tried a file guide on a couple of previous blades but didn't this time around. This may help explain any differences between the plunges. I will have to try Will's trick of taping the wheel as well.

 

[Will Leavitt]

I had tape on the idler wheel of my Burr King until a maker that I talked to pointed out I could adjust the idler wheel side to side I was like huh? ohhhhh yeahhhh I'm stupid.

Oh yeah.... looking really good there Paul. :thumbup:

I'm going to cobble a work rest together and burn some steel up!!!! Nick, I don't blame you a bit about the sharing issue, if it was an "open source" thing then share, if it's something that 2 guys use to feed their families then let them feed their families.

 

[J-siah]

Here is a useful tip:

While grinding with your strong hand, pay close attention to how you're holding the blade with your strong hand and supporting it with your weak hand. Study what you're doing. Then when you switch to the other side take note how you're holding the blade. I'll bet it isn't the same. You need to force yourself to hold the blade and support it the exact same way for both sides. And I will bet your problem is coming from the way you support the blade.

I will second this. I started doing this and it made a huge difference.

 

[PIndelicato]

I had tape on the idler wheel of my Burr King until a maker that I talked to pointed out I could adjust the idler wheel side to side I was like huh? ohhhhh yeahhhh I'm stupid.

Oh yeah.... looking really good there Paul. :thumbup:

I'm going to cobble a work rest together and burn some steel up!!!! Nick, I don't blame you a bit about the sharing issue, if it was an "open source" thing then share, if it's something that 2 guys use to feed their families then let them feed their families.

Thanks Will! Give it a try, I think it works great.

I will second this. I started doing this and it made a huge difference.

I thought about this, but once I got started it faded into the background somewhat with everything else to think about. I will make a more concerted effort the next time to really focus on this.