Blade Grinding and Stropping


prov163

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I'm reorganizing my shop and planning to set up a dedicated sharpening station.  I have learned that the more consistent I am with sharpening the more I enjoy my shop time and better my final result.  I have a couple of questions:

I know that being able to repair damaged blades or grind new bevel angles is important.  I have a Porter Cable 2.5 A, 3450 rpm, 6" grinder I bought on sale a couple of years ago but never really used.  Will this work for grinding blades to prepare for honing?  I understand that heat is a serious issue.  From what I've read, slow speed grinders are extremely popular.  Are they really worth the investment?  If so, what are you guys using and what is a reasonable price to pay?

I'm also thinking of having a stropping setup.  In your experience, how beneficial is stropping?  Leather is easy to get but what is your favorite compound and why?  What's the stropping procedure you recommend?

Any good videos/articles on the above you know about would be appreciated!

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Asking about sharpening is like whacking a hornets nest. After almost 50 years of making sawdust, I am of the opinion that every technique I have heard of works well if you understand it's strengths and weaknesses. You are right about heat from your grinder. Keep a container of water next to your grinder and use it often. A slow speed grinder does not build heat as quickly, but you can still take the temper out of a tool with it if not used carefully. I do a lot of carving in the winter cause I can do that in the house. I touch up my blades with a hard white washita when I start then use a strop every 10 to 15 minutes to keep the edge. I use a piece of leather from an old purse my wife was going to throw out. If you can't talk her out of one, check the thrift stores. Doesn't seem to matter if you use the smooth or rough side of the leather. For hand carving, I have never noticed much difference in compounds as long as you avoid the "Lapping" compounds. They use an abrasive and will scratch, not polish. Just remember you are trying to achieve a mirror polish on both sides of the cutting edge. Have fun and practice.

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One tip on the grinder question. Don't underestimate a belt sander as an option for re-shaping a damaged blade. It's faster, and doesn't seem to build up as much heat. You can get the whole bevel in one go too, as opposed to sliding back and forth on the grinder. The only thing I've ever done with my 6" grinder is ruin blades, but a 220 belt on the sander straightened out a couple old Stanley irons for me.

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Scott, I know that any discussion of sharpening, or pallet wood, will start a furor, but I was hoping these narrow questions would avoid the "what's the best way to sharpen" arguments.  I have a couple of Stanley beater chisels I'll play with on the grinder.  Thanks for sharing your wisdom of 50 years in the shop :)

Bon Pacific, I had never thought of using a sander.  Hmmm.  I'll have to play with that idea.

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If you turn the steel color you've gone to far to fast with the grinder.  Even a belt sander clamped in a vice may be a better option than a high speed grinder. 

I like diamond lapidary paste on my strops.  I found some on amazon for pretty cheap. 

I strop varying amounts based on what I'm doing at the time, usually about 10-30 strokes on my coarsest strop.  If I really want to polish an edge I go through all 4 of my strops ending at 100k grit (I bought that paste because I figured I could always go coarser but not necessarily finer when adding pastes later on).  IMO stropping is the difference between sharp and scary sharp.  I strop my knives to the finer grits just for the appearance.  I like seeing the look on peoples face when they borrow a knife and see that mirror polished edge looking back at them. 

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14 minutes ago, Scott Meggison said:

I have had good results with belt sanders also. Good suggestion.
Diamond Lapidary Paste? I may have to try some. I have always used the sticks of jewelers rouge, but I am always looking for better ways of doing something. 

It's the stuff they use to polish rocks, it's great.  Way better IMO than different color rouges.  https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=diamond+lapidary+paste

A little bit goes a long ways too.  I've had my same 4 tubes for a few years now, seldom reapply any to the strops.  If you put too much at once it will build up on the blade.

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15 hours ago, Scott Meggison said:

wtnhighlander: I like the inside out belt idea. Good use for a worn out belt.

xxdabroxx: Just out looking at diamond lap paste at amazon. They have grits from 400-200,000. What range of grits do you use?

 

I have a few from 1200 grit to 100,000 grit.  I generally use only the 1200 for wood tools unless I have some really angry wood I'm dealing with, I can't remember what the next step up I use is.  I'll try and remember and grab a picture of the ones I have.  I bought the 100k grit because I figured I could always go with a coarser grit later but couldn't necessarily go finer later. 

 

Found some old pictures I had. 

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Level of polish I got on a Mora knife. 

UtEuB8pVMFYf7hIZcwLu2TP-0c-8GAuP6yYkl-Qx

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I've not had any trouble with burning steel on my (adjustable) high speed porter cable bench grinder, but I switched out the wheels for green Norton 3x wheels.  I think the slow speed might be more necessary if you're using them to sharpen, as well, but if you're just grinding then anything will work so long as you're careful about losing temper. 

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On 1/15/2017 at 5:22 AM, prov163 said:

 I have a Porter Cable 2.5 A, 3450 rpm, 6" grinder I bought on sale a couple of years ago but never really used.  Will this work for grinding blades to prepare for honing?  I understand that heat is a serious issue.  

Matt Cremona had a good tip on one of his videos on sharpening - keep dipping the blade in water to cool it while grinding, also keep a bead of water on the end of the blade while grinding - when it starts to boil/dissapear re-dip it. So long as you then follow up with a good hand-sharpen you should be good; the bladesmith in the below vid takes that approach when he has to actually re-grind rather than just sharpen. Actually at 16:19 in you can see the power of stropping - ridiculously sharp knife that's been used for 6 months & only been stropped...and it's not got a fine bevel angle on it...

https://youtu.be/33DM8Q63vM0

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  • 2 weeks later...

On your trip in May, if you end up driving back down I85 to get home, I'm about halfway between 85 and 95 right at the Va./N.C. line, or 20 to 25 minutes from either.  If you stop by here on your way back, I can put your hands on what is available for sharpening to show you how to use it.

I have everything available that's not too hard to get to, except for one of those 20" sandstone wheels.  I have one of those, but it's still in the wooden crate that it came in when I bought it new in the early '70s.  I can show you how to not burn an edge with a regular, friable grinder, and what a CBN wheel does.

I started sharpening edges in 1959 with a cheap, manmade honing stone, moved to Arkansas stones and used them until the early '90s.  I've been through what's available with water stones, and now have the most efficient dedicated setup for their use there is, or at least will have it set up by the time you get here with the sink I recently bought off of Craigslist.

I can let you use any kind of plane or chisel that is set up, ready to go, and as sharp as possible, so you can see what the benefit of the goal is.  I use this stuff for what I do for a living, and have for 43 years now.

I also have a broadcast quality HD video camera, so maybe we can put your Wife to work with the camera, and you will have something for show and tell.

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