Blades and Frogs

[Ray Selinger]

As I'm tuning up a couple of planes, I noticed something.One of the first mentioned tune-ups is flattening the frog face . I use a file, but I've done a fair bit of filing in my work. OK,fine. But what about the blade. Nobody seems to mention the flatness of the blade. I'm using the word blade, but cutter or iron, depending apon country or manufacturer usage. That is the other half of the mating. On the old blades I'm working on, the word flat can't be used in the same room as them. One is a laminated Stanley and the other a Anchor brand, so both were worth the effort.After some careful hammering, I resorted to using to using a dial indicator mag base and a 6x48 sander. Tricky but doable. Thanks Derick Cohen (sp). It's just something else to think about.

[Robert Engel]

I would think the cap iron lever will take out any minor discrepancy in blade flatness.

[Ray Selinger]

I don't think so, Robert. If you fully tighten the screw on the cap iron, the blade will arch,even that 99 cent rule you picked up at the store counter will show the gap. My expertise isn't planes, rather it's setting up machinery. The Stay-Set lever cap of the Record/Clifford or the hinged one of MillersFall would help.My usual answer would be the thicker Vertas blade and cap iron but at $100 for a $12 planes, Canadian $,it's pricey. I'm not sure if there is an answer here.

[Patrick Chase]

The dirty little secret here is that most planes (including premium ones from people like LN and LV) have gaps between the iron and the frog when tightened, and work perfectly well. As you say, the fact that the lever cap only applies pressure at two points along the blade makes gaps in between nearly inevitable. As you also point out the manner in which the cap-iron attaches to the blade adds to this, because preload that holds the cap iron in place also bends the middle of the blade (along the lengthwise axis) away from the frog. In the absence of any lever cap load in the middle that basically guarantees a gap even if everything starts out perfectly flat.

Basically every plane I own has a gap, though most are quite small and only detectable with effort. I suspect the same is true of many people who claim to have flattened everything for "perfect registration". They just aren't using the right methods to detect small gaps.

This is one of those things where you can drive yourself nuts trying to flatten everything in sight, and not get any real improvement in performance. What really matters is that the blade is bedded well directly behind the edge, where the leading edge of the lever cap applies pressure. Are you seeing a specific problem that leads you to suspect inadequate bedding? If not I'd suggest not worrying about it.

One other remark: LV actually manufactures the datum surface on the adjuster (the round pad that the blade rests upon, directly below the tightening screw) very slightly slightly proud of the flog. Even if the blade/cap-iron assembly were perfectly flat when assembled (it isn't, see above) the blade would still contact at the base of the frog and at the adjuster. All of the precisely machined "registration surface" in between is for show.

[Bill White]

I just wonder how exactly we NEED to be.
Is there an "excessive" factor that is used?
I just keep my planes tuned to work, and don't bother about .002 shavings.
Not tryin' to be a bummer, just a realist.
Bill

[Patrick Chase]

I would think the cap iron lever will take out any minor discrepancy in blade flatness.

As Ray points out, the opposite is true. The Cap iron is effectively a spring that "pushes down" on the iron at its ends and "pulls up" at the attachment screw (where "up" and "down" are as installed in the plane). The attachment screw is smack in the middle of the frog, in between the lever cap's two interface points, so the cap iron pulls the middle of the blade away from the frog.

As Ray says, all you need to do to disprove the "large mating area myth" is to actually take a straightedge to an assembled double iron.

[Patrick Chase]

I just wonder how exactly we NEED to be.

In my experience you need to have good mating at the base of the frog, close to the edge. If you don't have that then you will be susceptible to chatter.

I suspect that the reason LV machines the rear mating surface (at the adjuster) very slightly proud of the frog is to add some tolerance, such that even if the iron is slightly concave-up most of the lever cap's pressure will still be applied at the base of the frog. It's a simple matter of optimizing functional importance over mythology.



Is there an "excessive" factor that is used?
I just keep my planes tuned to work, and don't bother about .002 shavings.

Yes, there is an "excessive" factor.

As I said previously almost all of my bench planes have at least some gap over middle/upper part of the frog. I can get 1/2 mil shavings out of any of them with a well-prepared iron, and I don't experience chatter.

[Patrick Chase]

One other thought: The lever cap can only apply so much normal force before Bad Things (tm) happen, for example you lose the ability to adjust the plane or you strip the screw.

That being the case, registration of blade<->frog becomes a zero-sum game. If the blade is pressed against the frog in the middle then there will be less pressure at both ends ("both" because the overall pressure distribution must be centered about the screw).

Given that reality, I question whether it's even desirable to have the blade in contact with the frog along its full length, as opposed to having the normal forces distributed more towards the cutting edge. LV's design choice looks increasingly sensible as I think about this more deeply.

[Jim Koepke]

Didn't Millers Falls have a lever cap with three point contact?

Not sure if it improved performance or just sounded good in advertising.

I have adjusted many a cap iron to do less warping of the blades. The cap iron being softer than the blade will give a little more and still supply good contact at the chip breaker's edge.

jtk

[steven c newman]

Maybe just need a Millers Falls type lever cap?

IF the blade is bowed a bit so that when installed, the bow flattens out. Seen way too many "curved" irons come through the shop. The "bow" would flatten out, when the lever cap is installed.

Just food for thought......

BTW: what IS this "gap" you be talking about? Haven't seen any around here......

[Patrick Chase]

Didn't Millers Falls have a lever cap with three point contact?
Not sure if it improved performance or just sounded good in advertising.

I'm going to go out on a limb and guess that the fact that nobody bothered to copy that design when the patent ran out (c. 1946) is telling us something. It seems to me that it's just wasting normal force where it's not needed, except for marketing purposes of course.



I have adjusted many a cap iron to do less warping of the blades. The cap iron being softer than the blade will give a little more and still supply good contact at the chip breaker's edge.


You can make a blade bend further away from the middle of the frog that way by increasing the cap-iron's preload, though only to a point as the cap iron is quite weak relative to the blade. You can't go the other way without decreasing the cap iron's preload, and that causes other problems such as jammed shavings at the blade to cap-iron interface.

[steven c newman]

Have quite a few Millers Falls planes. Never had an issue. Why nobody copied it? Cost, pure and simple. Stanley was too busy cutting costs then.
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Then again....YMMV

[Patrick Chase]

Have quite a few Millers Falls planes. Never had an issue. Why nobody copied it? Cost, pure and simple. Stanley was too busy cutting costs then.

What about the modern makers?

[Glen Canaday]

It was copied. Pope in Australia post-war (definitely) and I believe Record as well, but don't quote me on that.

As far as why no one in the US copied it, well...

[steven c newman]

They are too busy making Stanley knock-offs.....unless you count Clifton. Might cost too much to make one out of Bronze?

[Jim Koepke]

You can make a blade bend further away from the middle of the frog that way by increasing the cap-iron's preload, though only to a point as the cap iron is quite weak relative to the blade. You can't go the other way without decreasing the cap iron's preload, and that causes other problems such as jammed shavings at the blade to cap-iron interface.

I must be lucky in finding the sweet spot of cap iron tension.

Here is something of mine from before David Weaver posted about setting the chip breaker:

http://www.sawmillcreek.org/showthread.php?114373-Fettling-A-Plane-from-Junker-to-Jointer

Scroll down to post #27 & #28, Chips Ahoy or is that a Cap Iron?, for a little bit about cap iron tuning.

jtk

[bridger berdel]

I'm sure that someone somewhere has mated a stayset cap iron with a Miller's falls lever cap. Seems like that would be about the max you could do in the "total bedding" arena. I doubt it would make a whole lot of difference in the performance of the plane but it might make for a nice solid "feel".

[Rob Lee]

(snip)
Given that reality, I question whether it's even desirable to have the blade in contact with the frog along its full length, as opposed to having the normal forces distributed more towards the cutting edge. LV's design choice looks increasingly sensible as I think about this more deeply.

Hi Patrick -

Our planes are designed with a line of contact along the mouth, and a locus (more than just a point) of contact on top of the adjuster. The blade "bed" (or frog, if the plane has a frog) is machined to ensure clearance.

We think trying to get two surfaces to mate perfectly is a mug's game.... and have gone for predictable, repeatable, and controllable geometry.

Just as a three legged stool is stable, the line and point approach ensures we have contact where we want it.

Cheers -

Rob

[Ray Selinger]

What Rob Lee didn't mention is with the Vertas replacement blade and cap iron, you have a pretty healthy chunk of steel.Bowing shouldn't be a question.

[Patrick Chase]

What Rob Lee didn't mention is with the Vertas replacement blade and cap iron, you have a pretty healthy chunk of steel.Bowing shouldn't be a question.

IMO it isn't really a problem with Stanley blades either. Those designers knew what they were doing way back when, and sized the blades adequately.

As I said earlier, this is one of those things that you shouldn't even look at unless you have a specific problem that you're trying to fix. If you know anything about metrology then you will *always* be able to find a gap somewhere, and you will chase your tail endlessly and quite possibly make matters worse
if you try to fix it. I think that's what Rob meant when he referred to "a mug's game".


As I said in another post, I think that from a functional perspective you want the pressure at the iron<->frog interface distributed toward the cutting edge of the blade. If you strive for "perfect mating" in the middle then you will necessarily sacrifice some pressure at the ends, and that may hurt you.

[steven c newman]

Gaps? What gaps? This is a Millers Falls No. 11 I have been using on the latest project..
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Do you see any gap? As with 99.9% of the rest of my planes in the shop. Have had a few come through....that something else was causing the "gap"...like a badly fitted lateral lever sticking up too far, or not sitting in the slot that was made for it.

[Ray Selinger]

Steven if you pull off that nice lever-cap, lift the cap-iron/ blade out and put the edge of a 6" rule on the blade of the cap-iron/blade, you'll see the gap. It doesn't even have to be a good 6" rule. Does it matter? that's a different story.

[Patrick Chase]

Steven if you pull off that nice lever-cap, lift the cap-iron/ blade out and put the edge of a 6" rule on the blade of the cap-iron/blade, you'll see the gap. It doesn't even have to be a good 6" rule. Does it matter? that's a different story.

Steven showed us a Millers Falls for a reason - it has a 3-point lever cap, which means that the straightedge check isn't conclusive.

In any case you can't diagnose gaps in an assembly as complicated as a plane from a picture or any other form of direct visual inspection. Apply an extremely thin coat of marking grease (something like Prussian Blue) on the underside of the blade, install it, and see where you (don't) get transfer. I guarantee that you will be shocked at the percentage of the area that's actually in contact, even with an MF lever cap. Even that is a conservative way of measuring since the marking fluid won't be zero thickness. There are more involved ways of detecting smaller gaps, but this will do for now.

Note also that gaps are unlike horse shoes or hand grenades: Close doesn't count.

[Stewie Simpson]

Mr Bailey was a fairly switched on guy. He realized that a metal bed is much more susceptible to chatter than a wooden bed, and the best way to address that issue was to use a thinner blade that would allow the cap iron to add additional tension. We are of course talking about a period where a 4 point contact was considered ideal. The use of a thicker blade is a fairly contentious approach if its aim is to reduce chatter. The use of a 3 point approach as Mr Lee mentioned makes for perfect sense. As a side issue, theirs a very good reason that tapered irons for a wooden bed have a slight concavity to their underside.

[steven c newman]

Anyone is free to come to the Dungeon Shop and verify the lack of gap. I also used a lot of Stanley planes....which are also gap-free.

So, come on over, bring whatever you need to test the lack of a gap.

[Patrick Chase]

Mr Bailey was a fairly switched on guy. He realized that a metal bed is much more susceptible to chatter than a wooden bed, and the best way to address that issue was to use a thinner blade that would allow the cap iron to add additional tension. We are of course talking about a period where a 4 point contact was considered ideal. The use of a thicker is a fairly contentious approach if its aim is to reduce chatter. The use of a 3 point approach as Mr Lee mentioned makes for perfect sense. As a side issue, theirs a very good reason that tapered irons for a wooden bed have a slight concavity to their underside.

Lee Valley uses a two-area approach - a linear patch across the leading edge of the frog, and a "locus" (Rob's term) that's roughly semicircular at the adjuster.

In any case we finally agree on something: That approach is basically ideal. Everything in between doesn't matter so much.

[steven c newman]

Hmmm, I am not from Lee valley. Went back down to take a picture or three of the Stanley planes...
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Stanley #5
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Stanley #6c,T-10
346469
Stanley, Made in England #4


All lay on the frog with no gaps.......IF you take the cutters out of the plane, they will curve a bit. Curve is on the frog side of the irons, away from the chipbreaker. Yet, when I place them back on the plane...no gaps. Either it is "magic" or the frog has been fettle correctly. I can not even slip a piece of paper between the frog and the iron.
346471
Close up of the #6c's frog.

Magic?

[Kees Heiden]

Once upon a time I did a little test with an old Stanley that appeared to have no gap between frog and blade. I took a very thin piece of paper and put it under the blade, sticking out on one side. Then I installed the blade assembly and fiddled with the lever cap screw until the piece of paper was clamped just so I couldn't move it. Then I took a very heavy shaving and while I took the shaving I could easilly pull out the piece of paper.

This shows that allthough the fit might look tight, the blade bends enough under planing pressure to create a gap nonetheless.

[Ray Selinger]

So it's worth while filing the frog face, not to get a full contact rather so the machining mistakes (Stanley and their machining of green castings) don't interfere with the contact at the bottom.

I think,for a while in the '80s, Lee Valley sold an English made plane with a hinged lever cap under their Lee Valley name.

[Patrick Chase]

So it's worth while filing the frog face, not to get a full contact rather so the machining mistakes (Stanley and their machining of green castings) don't interfere with the contact at the bottom.

Yeah, if you have a plane wherein the blade doesn't bed at the bottom then IMO that's worthy of intervention. I'd still say to rely on performance rather than on inspection to determine how much work is necessary though.

[Stewie Simpson]

If your Stanley plane has the original blade its likely not an issue because the thinner blade should allow the lever cap to generate a small amount of concavity over the frog surface. If you have changed from the original Stanley blade to a thicker version being offered, their may be some issues you haven't considered.

[Jim Koepke]

So it's worth while filing the frog face,

Maybe if you are real good with a file. Otherwise lapping on a flat surface with abrasive papers is likely a better and easier way to go about cleaning the frog face.

jtk

[Warren Mickley]

So it's worth while filing the frog face, not to get a full contact rather so the machining mistakes (Stanley and their machining of green castings) don't interfere with the contact at the bottom.


It is a poor idea to file or abrade the frog without first identifying some performance problem with the plane that the operation is likely to solve. It would be like getting a hip replacement before learning to walk.

Machining mistakes? Just what are you talking about? I have used but one Bailey smoother for 35 years. It has done a beautiful job of planing everything set before it. I have never checked the machining on the frog. What is the point?

[Jim Koepke]

It is a poor idea to file or abrade the frog without first identifying some performance problem with the plane that the operation is likely to solve. It would be like getting a hip replacement before learning to walk.

Machining mistakes? Just what are you talking about? I have used but one Bailey smoother for 35 years. It has done a beautiful job of planing everything set before it. I have never checked the machining on the frog. What is the point?

In other words, if it ain't broke, don't try fixing it.

jtk

[Patrick Chase]

It is a poor idea to file or abrade the frog without first identifying some performance problem with the plane that the operation is likely to solve. It would be like getting a hip replacement before learning to walk.

Machining mistakes? Just what are you talking about? I have used but one Bailey smoother for 35 years. It has done a beautiful job of planing everything set before it. I have never checked the machining on the frog. What is the point?

I think he's talking about some of the post-WWII cr*p where they "value engineered" some of the post-machining steps in the manufacturing process.

Totally agree about not fixing stuff that isn't broke, I've been trying to say that for this entire thread.

[Ray Selinger]

Casting iron leaves stresses in the casting. As the casting ages the stress works itself out. Heating will also stress relieve a casting. If you machine a green casting , it will move after machining, like green wood. Almost as far! That's the reason you have to lap the sole of planes is green castings. I have a couple of Canadian made Stanleys from Roxton Pond , a blue #4 and maroon #5, they are both flat and square. Well made planes, so it is possible.

I'm retired ,now, but I worked as a millwright . I don't know how much time over the years I've spent fixing machine shop screw ups with a file.Yeah, I can use a file.

[Patrick Chase]

Casting iron leaves stresses in the casting. As the casting ages the stress works itself out. Heating will also stress relieve a casting. If you machine a green casting , it will move after machining, like green wood. Almost as far!

Hmm, all of the data I've seen say that cast iron doesn't creep much at room temperature even when internally pre-stressed nearly to yield, so I'm not convinced about the stress working itself out over time.

What you say about machining non-stress-relieved castings is very true, though. What happens there is that the stress distribution within the casting is non-uniform, so when you machine away part of the casting you change the stress distribution and that causes the remainder of it to warp. As a modern and extremely simple example, all of my Narex chisels tend to self-dub a tiny bit at the very tip when their bevels are reground. I'm almost certain that this happens because Narex's hardening process leaves the surface of the tool loaded in tension and the center in compression. When you grind the bevel you therefore change the force balance at and just behind the new edge, leading to dubbing. It only impacts the very tip because the remainder of the tool is so thick that the changed stress distribution doesn't cause detectable strain.

With that said, a frog is an extremely simple and "compact" geometry compared to a plane body or even a chisel. I doubt those warp very much during machining, both because the residual stress in such a simple casting shouldn't be all that high and because the geometry is inherently stiff and the amount of material removed is very small relative to the volume.

[Ray Selinger]

I've seen a couple of frog faces that were seriously concave across the width You see the machine marks on the face, and since it's not even, it's not a machine set-up error, you then have to assume it moved after machining. Most times though,it only takes a token stroke or two on the frog face.Jim is right, you have to be careful with the file. You see it most on the sole of some planes, the out line of the shrinkage. By the time I rescue a plane, they are well aged ! It's all understandable. From a business point of view, it doesn't make sense to have product in process for any amount of time. That's money sitting without earning interest. Bean counters freak.

Narex uses a single heat treating, that why they are inexpensive for what you get.

[Patrick Chase]

I've seen a couple of frog faces that were seriously concave across the width You see the machine marks on the face, and since it's not even, it's not a machine set-up error, you then have to assume it moved after machining. Most times though,it only takes a token stroke or two on the frog face.Jim is right, you have to be careful with the file. You see it most on the sole of some planes, the out line of the shrinkage. By the time I rescue a plane, they are well aged ! It's all understandable. From a business point of view, it doesn't make sense to have product in process for any amount of time. That's money sitting without earning interest. Bean counters freak.

Indeed. IMO one of the single-biggest plusses of the modern higher-end planes (LV, LN, etc) is that they stress-relieve their castings before machining. As you say a volume player like Stanley back in the day would have been hard-pressed to do that and still hit their cost targets.



Narex uses a single heat treating, that why they are inexpensive for what you get.

Yep. Narex integrates tempering with the main heat treatment (interrupted quenching). In theory that should lead to fairly low internal stresses, but only if they interrupt the quench for long enough to achieve uniform temperature. I bet their bean counters convinced them to take a teeny shortcut.

[Warren Mickley]

As I asked yesterday, what is the point? I still have not heard a single problem that refining the frog is supposed to address. If you don't have the skill to discern improvement, what kind of job are you going to do? It sounds to me like a big lack of connection between real world planing experience and corrections to the manufacture.

You can refine the frog to the 9th degree, but if you design a cap iron without first learning how to use one, you cannot expect a high level of performance. If you use a steel that was designed for can openers for a plane iron, what kind of results can you then expect? If the manufacturers barely know how to use a plane, how can they not spend resources on things that are unimportant while neglecting those things that are important?

[Stewie Simpson]

You can refine the frog to the 9th degree, but if you design a cap iron without first learning how to use one, you cannot expect a high level of performance. If you use a steel that was designed for can openers for a plane iron, what kind of results can you then expect? If the manufacturers barely know how to use a plane, how can they not spend resources on things that are unimportant while neglecting those things that are important?

Hi Warren; can you expand your thoughts further. The disconnect between knowledge by the manufacturer and proper use of the hand plane sounds intriguing.

Stewie;

[Patrick Chase]

As I asked yesterday, what is the point? I still have not heard a single problem that refining the frog is supposed to address. If you don't have the skill to discern improvement, what kind of job are you going to do? It sounds to me like a big lack of connection between real world planing experience and corrections to the manufacture.

You can refine the frog to the 9th degree, but if you design a cap iron without first learning how to use one, you cannot expect a high level of performance. If you use a steel that was designed for can openers for a plane iron, what kind of results can you then expect? If the manufacturers barely know how to use a plane, how can they not spend resources on things that are unimportant while neglecting those things that are important?

If you look up the thread you'll see that I've been agreeing with you all along (don't mess with it unless there's a clear performance problem) and Ray basically agreed several posts back. At this point we're just having a nice friendly back-and-forth about manufacturing processes.

Tying the two subthreads together, IMO Narex is a good example of a manufacturer who doesn't entirely understand the tools they make. These are after all the folks who shelled out $$$ for CNC stitching machines that presumably allow individual tooth placement, and promptly used them to make rasps with regular toothing.

[Ray Selinger]

Warren, as I first mentioned, my expertise is in machinery repair and set up. So when I see a woebegone plane ( chisels, braces,and handsaws as well) at the fleamarket for $5 or $10 , I can't help myself. It does have to have good bones,though.BTW, the post WW2 Stanleys I think when fixed, are better planes. I expect to fix things to be at the very least as good as new,or by either by proper fitting or modifying better than new. I have a saying "Sweat the details and the big picture takes care of itself." A frog's face and it's bed are two such details.

To be perfectly honest, it's a fool's errand. Buy a a Vertas and make shavings.

[Patrick Chase]

Warren, as I first mentioned, my expertise is in machinery repair and set up. So when I see a woebegone plane ( chisels, braces,and handsaws as well) at the fleamarket for $5 or $10 , I can't help myself. It does have to have good bones,though.BTW, the post WW2 Stanleys I think when fixed, are better planes. I expect to fix things to be at the very least as good as new,or by either by proper fitting or modifying better than new. I have a saying "Sweat the details and the big picture takes care of itself." A frog's face and it's bed are two such details.

To be perfectly honest, it's a fool's errand. Buy a a Vertas and make shavings.

I think you're misunderstanding Warren. He doesn't think that the *new* manufacturers know what they're doing. He's particularly enamored of LN and their choice to only offer A2 irons in their planes.