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Flattening plane blade back.

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Forum topic by hiswillus posted 445 days ago 1143 views 0 times favorited 29 replies Add to Favorites Watch
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hiswillus

70 posts in 551 days


445 days ago

Topic tags/keywords: question

Fellow woodworkers,

I desperately need someones help! Someone with the insight to see what I’m doing wrong.

I can’t even begin to try and explain all the methods and variations I’ve tried to get a flat back on my plane blades, so I won’t even begin to cover them all. I’ve tried different blades, different surfaces, different media always ending with the same result pictured below. I can tip it forward a bit (ruler trick) and get most of the cutting edge, but still miss the corners. What on earth can I be missing. I’ve sanded and grided for acumulated days trying to get this down (as I know how importaint a sharp blade is) to no avail.

Oh I pray someone has the insite to have a clue what I’m doing wrong here. Any help would put me in a debt of gratitude.

Thanks,

Jeff


29 replies so far

View chrisstef's profile

chrisstef

10431 posts in 1609 days


#1 posted 445 days ago

Jeff – have you tried marking the back of the blade with a sharpie to make sure that you are missing those corners. It looks like you have a little hollow on the back of that iron but I cant really tell. Also you only need to flatten a little bit of the iron so id concentrate on that 1” at the edge. Could it be that your pushing down really hard on the center of the iron and causing a bit of flex?

What grit are you using?

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

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JustJoe

1554 posts in 641 days


#2 posted 445 days ago

Others may disagree with me, but in my never-humble opinion:
The back right behind the edge needs to be flat so you can form the bevel on the front, and so that you have a flat place to put the chipbreaker and get a good fit so no shavings can jam in between it and the blade. All that other space from about 1/4” from the blade all the way back to the slot is just wasted time if you’re trying to flatten it. I use a stone or sandpaper and only work the 1/2” or so at the tip of the blade. Once I’ve got that first 1/4-1/2” flat, I’m done with it.
If you can’t get the corners flat then the blade might have been abused or over-cambered (my term, I claim copyright) You might have to grind back 1/16 to get to a flat enough area, but that should be a rare occurence.

The ruler trick is good for blades that have pitting on the back – bevel on the front and the slight back bevel means the cutting tip is from clean unpitted metal in the middle. If the back’s not pitted, there’s no need to back-bevel.

-- This Ad Space For Sale! Your Ad Here! Reach a targeted audience! Affordable Rates, easy financing! Contact an ad represenative today at JustJoe's Advertising Consortium.

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Dan

3543 posts in 1483 days


#3 posted 445 days ago

If you start flattening with a lower grit sand paper… say 80 or 120 grit, you should be able to get the back of that iron flat rather quickly. Once it is flat then you work up the grits until it is polished. I think you just need to spend some more time on it and put a little more pressure at the center of the iron.

-- Dan - "Collector of Hand Planes"

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hiswillus

70 posts in 551 days


#4 posted 445 days ago

Yea, weather you like your whole back flat (OCD) or just the end I can’t get either. If the blade was “over-chambered” (all copyrights respected by the owner) wouldn’t it be unlikely that I get this problem on multiple blades? I get up to about 240 grit and it is a perfectly scratched surface, but seems no matter how long I grind on 320 and then on to a 1000 grit water stone I loose it somewhere in there. Maybe that’s to big of a jump, but I figured most people do it with 3 steps or something don’t they. I figured a fine diamond stone direct to the 1000 grit should have done the trick. So dan you can see I’ve seemed to have gotten it flat all the way up to 320 and still loose it somewhere so I don’t know what the deal is.

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chrisstef

10431 posts in 1609 days


#5 posted 445 days ago

Looking a bit closer at your scratch marks are you moving the iron back and forth the long way? If so it could be causing your corners to dig it ever so slightly.

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

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hiswillus

70 posts in 551 days


#6 posted 445 days ago

chrisstef I thought that as well was likely the problem! It seems the larger scratches are on the outside, but this is highly likely the problem as I remember once switching grits and suing 2 fingers to “third” the blade and remember at my first check I actually had two scratch patterns where my fingers where. Couldn’t believe that I cold apply that much pressure in that short of a distance and have that problem :/

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hiswillus

70 posts in 551 days


#7 posted 445 days ago

chrisstef I usually alternate directions every grit to make sure I have covered the whole surface completely.

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bondogaposis

2446 posts in 954 days


#8 posted 445 days ago

You need to start w/ a coarser grit and do most of your honing at that grit until it is flat, then and only then start moving up the grits. I begin w/ 220 grit diamond stone. If you are using sandpaper use 220 or even 150 to flatten, they will cut much faster than 320 and give you the results you are looking for w/ much less effort.

-- Bondo Gaposis

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chrisstef

10431 posts in 1609 days


#9 posted 445 days ago

Sharpie the back of the iron closest to the cutting edge on the back and try running it the other way on the sandpaper or stone so that the bevel is 90* to your sharpening surface instead of head on. (I hope im making sense).

Id stick with one direction and using a magic marker on the back to make sure you’re getting flat personally. I hope we got ya figured out here brother.

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

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hiswillus

70 posts in 551 days


#10 posted 445 days ago

I began with a 600 grit diamond stone and moved up the grits and seemed to keep the flat until I reached 320, so that shouldn’t be the problem bondagaposis…

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hiswillus

70 posts in 551 days


#11 posted 445 days ago

In other words push and pull parallel to my sanding media vs. perpendicular pushing and pulling right chrisstef?

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chrisstef

10431 posts in 1609 days


#12 posted 445 days ago

Excuse my rudimentary designs here but lets pretend my notepad is your stone and the chip breaker isn’t on your iron .. Follow the arrows.

Hand position also not accurate, I was just keeping it from falling off my desk.

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

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hiswillus

70 posts in 551 days


#13 posted 445 days ago

I’ll go give it another go. Thank you all so much for your input as I’m desperate to use my first properly flattned plane blade. I’m sure it’s going to make a world of difference. I especially appreciate your persistence in helping chrisstef :)

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chrisstef

10431 posts in 1609 days


#14 posted 445 days ago

Not a problem brother, im actually quite astonished that I might have actually figured something out.

Keep up posted as to your progress Jeff.

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

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hiswillus

70 posts in 551 days


#15 posted 445 days ago

Ok, clearly moving in the right direction here. I think I was applying entirely to much pressure here. I attempted to keep even steady moderate pressure focussing more on the end. However even when removing pressure in the middle and only applying pressure on each corner I still miss the corners. I think I’m going back it up a few grits and try my luck. I’m going to give it a brake though as there is blood allover my keyboard from my finger tip being sanded off :/

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