Hand Plane Blades: How straight is straight enough?

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Forum topic by Kent posted 04-29-2016 04:55 PM 929 views 0 times favorited 22 replies Add to Favorites Watch
View Kent's profile


129 posts in 1403 days

04-29-2016 04:55 PM

Topic tags/keywords: question refurbishing

I was recently using my old Stanley #5 for the first time. I had already done some lapping and fettering to get it working better, but I didn’t go overboard for fear of hurting its value. Since then, I’ve been reading a lot more about planes, and I realise that this plane has much more value as a user than as a collectable. Good, that’s what I want.

Anyways, the mouth of this plane started jamming with very fine chips. My investigation showed that the Sweetheart iron that was installed in this plane (a type 16?) was quite bent and twisted. I swapped out the iron and the plane started to work well without clogging.

By using my metal bench vise as a press, I was able to get most of the really bad bends and twists out, but this iron still isn’t “perfectly flat”. Okay, it’s not even close. I checked it on my granite block after straightening and I can still slip a .015” (!) feeler gauge between the iron and the granite. I checked out the flatness of both my granite block and my flattest anvil. The granite was flatter than I can measure, but the anvil was at least .020” out of flat.

So how do I straighten this blade, and how straight is straight enough? Do I also need to flatten my anvil?

-- .

22 replies so far

View OSU55's profile


1233 posts in 1596 days

#1 posted 04-29-2016 09:43 PM

Not sure how to flatten the blade. The chips jamming in the mouth was probably due to chips getting under the chip breaker. The chip breaker has to mate flat with the blade – no gaps. The blade is probably scrap.

View Ocelot's profile


1544 posts in 2245 days

#2 posted 04-29-2016 10:05 PM

The entire blade does not have to be flat, only the first 1/4” or so where the chipbreaker meets it. That much can be flattened on your surface plate with sandpaper or on a diamond plate.


View Kent's profile


129 posts in 1403 days

#3 posted 04-29-2016 10:42 PM

OSU55 and Paul, you’re entirely correct about where the chips are getting stuck. The iron has already been flattened for the first 1/4”, but the chip breaker still does not fit tightly against the blade because the entire blade is bent and twisted that badly. The chip breaker is working fine with the replacement blade; it just isn’t strong and heavy enough to pull enough of the twist out of the blade to make it fit tightly.

I have made the situation better with the judicious use of force on the twisted blade; I just haven’t been able to get enough of the twist out of it for the chip breaker to fit correctly.

-- .

View TheFridge's profile


6681 posts in 1093 days

#4 posted 04-29-2016 11:46 PM

I sometimes use a 1/2” dowel hit with hammer to help straighten spots of an iron.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View jdmaher's profile


400 posts in 2186 days

#5 posted 04-30-2016 12:19 AM

If it’s just a user, why not just buy a replacement blade?

-- Jim Maher, Illinois

View Ripthorn's profile


1433 posts in 2592 days

#6 posted 04-30-2016 12:27 AM

I would just toss the blade. An inexpensive replacement from HD can be had for $3-5 and those work relatively well. I have one in my #4 and it takes whispy thin shavings.

-- Brian T. - Exact science is not an exact science

View Don W's profile

Don W

18252 posts in 2174 days

#7 posted 04-30-2016 11:03 AM

Some pictures would help. Are you sure it’s not a problem with the chip breaker?

-- - Collecting is an investment in the past, and the future.

View rwe2156's profile


2423 posts in 1087 days

#8 posted 04-30-2016 12:18 PM

The only way to flatten hardened steel is heat it to kill the temper. Then retemper if you’ve managed to get it flat.
If you can flatten a plane blade without doing that I would question the quality of the steel.

I would get a new blade. I recommend Hock or Veritas. I wouldn’t buy a used one.

-- Everything is a prototype thats why its one of a kind!!

View OSU55's profile


1233 posts in 1596 days

#9 posted 04-30-2016 02:09 PM

Try this link 2” double iron for $3.50. It’s best to buy several if you can use them to spread the shipping cost.

View Kent's profile


129 posts in 1403 days

#10 posted 04-30-2016 02:42 PM


When the chips are jamming in the breaker, they only ever jam on the right side (when viewed from the flat/breaker side of the iron). I did the sharpee trick and tried reflattening the blade quickly this morning using 120 grit sandpaper on granite and a course diamond plate (220?). Neither wanted to take the surface down quickly, but they revealed a definate hump just about 3/16” back from the cutting edge.

Just before this flattening, I checked the clearance (gaps) in the breaker, and I got about .004” on both sides. This does not make sense to me; equal gaps but clogging only on one side?

The chips breaker fits well on another blade, with less than .0015” gap, my thinnest feeler gauge. Nice shavings can be made with that other blade.


Where exactly would I be hitting this blade? I’m guess somewhat centred on the high spot in the above photo?


Forgive me if I seem to be missing something obvious here, but just investigating this, doing that small amount of flattening, trying to get a good photo, and then writing up this entry have stressed both my brain and my vision to their limit for the day. I will need to let them recover for a day or two before I can get back in the shop to do any more.

-- .

View Ripthorn's profile


1433 posts in 2592 days

#11 posted 04-30-2016 03:03 PM

The only way to flatten hardened steel is heat it to kill the temper. Then retemper if you ve managed to get it flat.
If you can flatten a plane blade without doing that I would question the quality of the steel.

I would get a new blade. I recommend Hock or Veritas. I wouldn t buy a used one.

- rwe2156

This is not entirely true. Think of how hand saw blades can be hand tensioned by hammering them. Even though the steel is hard, it still has some give. Hitting it in the right spots will create internal tensions that can straighten it out to a degree. A hand plane iron is usually at about 60-62 HRC, which still has some give to it, regardless of the quality of the steel.

-- Brian T. - Exact science is not an exact science

View Richard H's profile

Richard H

489 posts in 1287 days

#12 posted 04-30-2016 03:13 PM

How flat does a plane iron need to be? If it’s not flat it won’t seat against the frog securely and when you push it into a piece of wood it will flex and chatter. I have run into a few twisted irons in my time and I just swapped them out for ones that where already flat. Spare irons shouldn’t be that hard to find be it antiques or new replacement brands. It also has to be flat enough that there are no gaps between the chip breaker and the iron or you will get shavings wedged between the two.

View bandit571's profile


16424 posts in 2290 days

#13 posted 04-30-2016 05:51 PM

Depends on which way the “bends” go.

Might see what happens when the chipbreaker is attached to the iron.

Might also check the chipbreaker for flatness, as well. Have had to tap more than a few cb’s back into flat. I check then by laying them flat on a flat surface. First one face, then the other. I try to rock the cb to test where it may be bent at. Sometimes, they are bent right in the middle with the curved side up. I will then flip it over, use a punch and the hammer, and a few whacks right into the highest spot. Flip it back over, and recheck. Some take a few tries, some don’t. THEN I can mate the cb to the iron. I look to get a knife edge where the chipbreaker will sit on the iron. That way, when the two are tightened together, the edge will deform just enough to seal any small gaps. I also polish the curved part of the chipbreaker so chips have a smooth path up and away.

Do NOT place the iron in the vise and then use your hands to “pull it back into straight…..irons will snap

-- A Planer? I'M the planer, this is what I use

View Kent's profile


129 posts in 1403 days

#14 posted 05-02-2016 06:38 PM


Thanks for the reply. I can rock both the iron and the blade on my flat surface (granite), and I can measure the height of the corner that doesn’t touch it at rest. I’ve even managed to take some of the really bad bends out of the blade using the techniques that you describe. I did use the vise for that, too, although only as a sort of a press; it helped with one gnarly ~5 degree bend in the tail of the iron.

Here’s what’s stopping me from continuing to straighten the blade now:
  1. I don’t want to use the granite as an anvil
  2. the top of my flattest anvil is about .030” out of flat
  3. my eyes (vision) are really very, very bad right now; I’m recovering from a very serious contusion. The iron is about .020” out of flat at the one corner and possibly more in the middle, but I just cannot see (or feel) where the bends and high spots are. I can see light between the blade and a straight edge, but my resolution is so low that I can’t see where the two touch. When I know where to hit (see the picture above), I can get the blade straight enough (see below).
  4. as mentioned, I can measure the gaps at the corners with a feeler gauge. When I put the iron and the chip breaker together, the gap between them is BIGGER than the sum of the gaps. “Does not compute”.

How can I straighten it when I don’t know where to hit? Are there any other techniques (like a hydraulic press) that I could use?


Thanks for the link. I have some other irons and am currently using 1 pair in the #5, but because that looked to me to be an awesome price, I went to check the link out. That site should be a case study about failed customer service. Here’s why:
  • they were out of stock of everything I tried to find (blades, caps and irons for #4 & #5 planes)
  • they refered me to SERVICE NET, where they had the parts. But Service Net’s FAQs say that they won’t ship them to me; I’m Canadian, eh!
  • The Service Net FAQs then send me to 2helpU so that I can find my local Stanley service centre.
  • 2helpU will only let you select your country by tunnelling down through the appropriate continent, then selecting your country. Apparently, Canada isn’t in North America! In fact, according to 2helpU, it isn’t on any continent.
  • There is no way to contact 2helpU

Stanley, are you listening? It’s faster and easier for me to physically get to Lee Valley from here (6 miles away) than to find your service centre online (right in front of me).

-- .

View Ripthorn's profile


1433 posts in 2592 days

#15 posted 05-02-2016 10:16 PM

If you have a machinist style bench vise, you can put in a small piece of round rod or similar at the crown of the bend and then begin to slowly tighten. Once it looks like you have over travelled a little bit, loosen and check, as it will spring back some.

-- Brian T. - Exact science is not an exact science

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