Plane Types & Choices | Using, Sharpening, And Tuning (Fettling) | Wooden Planes | Technical
Hand Plane Information Part 4 - Technical
(This part has the most technical stuff.)
Observing Frogs Bedding
In a recent post someone provided links to a discussion on another forum about tuning an antique infill smooth plane that didn't smooth decently. It was an interesting discussion of the things the author did to try to fix the problem, including wrong conclusions later revised, etc. The problem centered around bedding the iron in the plane well.
Someone in the threads observed that because of their construction, metal planes offer the opportunity to observe the bedding of the iron on the frog outside of the plane, where you could really see what's happening. They observed that in metal planes, if the iron starts out flat it bows toward the chipbreaker noticeably when the chipbreaker screw is tightened, and then when you lay the iron on the frog there is a big gap (well, only a couple thousandths, but clearly visible) in the center of the frog's length. Then when you clamp the lever cap on you can see the iron flattening out against the bed. It was surmised that all this was by design, as a way of ensuring that the iron is really tight against the front end of the frog.
Also, at about the same time Pablo wrote here about his experience making a compass plane. He mentioned having to hollow the bed in order to get the plane to perform well. That was the first time I had come across that idea.
That was all so interesting that I went out to the workbench and disassembled four planes: Stanley type 8 (#5-1/2) and 15 (#3), Keen Kutter (#6) (early round-sided Stanley Bed Rock), and a Record (#3) from the 1970s. I intended to look at a couple of LNs with Bed Rock frogs, too, but tired out before I got to them. Disassembling them gave a good look at the bedding of the iron to the frog. Not as good as a plane nicely sliced in half lengthwise, perhaps, but I didn't hear any of the planes complaining. I saw a few things that may or may not be able to be generalized, and thought some of you might be interested and might be able to add some insights. At any rate, it helped me understand some of the subtler factors that can keep a plane from performing as it should.
- The iron was in full contact with the Keen Kutter (Bed Rock) frog all the way to the bevel. Actually, the frog continued a little past the bevel. On the other hand the Stanley type 15 and the record frogs stopped a good 1/8" from the bevel. OK, so the rep the Bed Rock frog has of supporting the iron closer to the cutting edge is valid based on these three planes. Interestingly, though, the type 8's frog was also flat against the iron all the way to the bevel. So we also have the possible generalization that older Stanley Baileys also supported the iron closer to the cutting edge, which could partially account for many people's belief that the older Stanley Baileys cut better.
- The iron in the Record plane never did get pressed flat against the bed, but always had a gap throughout the middle third of the iron's length.
I tried one of the two-piece Clifton chipbreakers on The Record plane, and found that it did clamp the iron down flat to the frog along its whole length. In a review of smoothers in FWW just a few years ago, Garrett Hack said that the Clifton chipbreaker made the Anant smoother cut nearly as well as the LN, and said it made a bigger difference than replacing the iron with a thick aftermarket one.. They are identical to the old Record Stay-Set chipbreakers. I am not going to describe them here, Tools for Working Wood has a close up photo and a brief description of them at http://www.tools-for-woodworking.com/index.asp?PageAction=VIEWPROD&ProdID=601. (Incidentally, that photo also shows how a Bed Rock bed, of a Clifton plane in this case, I assume, supports the iron all the way to the bevel. The purported advantages are also fully described in the reprint of the 1935 book Planecraft, available from Woodcraft. It seems plausible that its ability to flatten the iron against the frog could reduce chatter enough to account for the improvement Hack noted.
- The mouth cutout in the body of the Record was considerably larger than that of any of the Stanleys. By drawing the frog back until the blade lay against the back of the mouth, the mouth could be opened up to a good 1/8 in. In past threads several people had mentioned possibly having to file open the mouths of Stanley planes to take a Hock or LN iron. That didn't make any sense to me, and I so stated, because most of my experience with metal planes and replacing irons was with my Record #3, #5, and #7 that have been with me for about thirty years. You would never have to file the mouths of those planes to take a thick iron, just shift the frog back. Now I understand that Stanley Bailey planes are different that way.
- Another thing that some people talk about that hadn't previously make any sense to me is setting the frog back far enough so that the frog surface is continuous with the back of the mouth. Many people say they set their planes up that way because it minimizes chatter. From what I saw on the Stanley type 15 and Record planes that makes sense because it supports the blade closer to the cutting edge. But I never understood why people would be willing to put up with such a large mouth to do that. I now understand that the large mouth that results on the Records I am used to is not so large at all on the Stanley Baileys.
Summarizing, in fewer words:
I didn't have time to try to draw any correlation of performance with bedding, but just take it as a plausible working assumption for now.
- Keen Kutter (early Stanley Bed Rock) and type 8 frogs bed the iron all the way to the bevel. The Stanley Bailer type 15 and Record ones stop 1/8" shy of the bevel.
- The Record iron was not clamped tightly against the frog in the middle of its length.
- The Clifton two-piece chipbreaker did clamp the Record iron flat against the frog.
- The mouth cutouts in my 1970s Record planes are significantly larger than those of the Keen Kutter or the two Stanley Baileys. The fact that the planes I had been using were Records accounts for why I couldn't understand why a plane's mouth would have to be filed just to accommodate a slightly thicker iron and why I thought moving the frog back until the iron would bed against the rear of the mouth as well as the frog would make the mouths too wide.
Working with only four samples, I don't know whether it is possible to generalize these observations in any way. Maybe some of you will be able to help with that. I am disappointed I couldn't get to the LN planes to see whether thicker irons would be bowed less by the chipbreakers. I would also like to know whether the new LN chipbreakers do a better job of that than the older Stanley look-alike ones.
I do think that these observations help explain why it is so important that the wedges in antique wooden planes be fitted carefully, because when they are done right, they press the iron firmly against the bed along the entire length, and the wedges are necessary for that because the chipbreakers do put a bow in the irons.
I'll come back to this sometime, but it will be a while because I am tired of playing this game for now.
Posted rfeeser 11/23/04
Importance Of Being Thin When Smoothing Hard Maple
In eliminating tearout when smoothing hard maple, the thinness of the shaving is more important than the sharpness, as long as the iron is reasonably sharp. That is in sharp contradiction to my previous belief that the iron needs to be just as sharp as possible for smoothing.
This also addresses the question recently raised about whether a Tormek alone makes a sharp enough edge, tending to support the answer, "yes."
I recently reground the bevel on the iron of a 75 year old Keen Kutter K5 (an early version of the Stanley Bed Rock #5 corrugated plane relabeled for Keen Kutter). I only reground it on a Tormek with the stone freshly reconditioned to its rough state, and did not follow up with anything finer nor add a micro-bevel. I did not do anything to the back of the iron, which was clean of rust but had moderate pitting throughout. I took the iron off of the Tormek and put it directly into the K5. The plane is exactly as I bought it, which is to say that the rust had been cleaned off but there were no signs at all of ever having been fettled.
Since I can never resist the temptation to take a few swipes at a piece of wood when I put an iron in a plane, I looked around for an appropriate piece of scrap. I saw a piece of hard maple, and picked that since vanguard had recently brought up the planing of hard maple in a recent thread. Most of my hand planing is with walnut and cherry, and it has been a long time since I have planed any hard maple, so here was an opportunity.
To set the plane up, I did some edge planing on the hard maple. The grain of this board changed directions three times in its 18 inch length, as is the wont of hard maple.
So, with this relatively coarsely ground iron in the plane I started taking air swipes along the edge, tweaking the iron down until it started cutting. Nice. Two or three strokes and the edge flattened out enough that the plane was taking nice, continuous shavings. The planing felt and sounded good, too. What's this? The iron isn't really sharp; in fact it isn't even close to really sharp. When I looked at the board's edge it was nice and shiny most places but had really bad tearout where the grain changed direction.
Hmmm. The shavings weren't as fine as I would have liked for smoothing, but rather medium thick (I later measured them; they were 0.002 in. thick), probably about as thin as I would be able to get easily with this old unfettled plane. So I started nudging the frog forward until the chips clogged the mouth, then backed it off about 1/8 turn of the frog adjustment screw. That's as tight as the mouth can afford to be for that thickness shaving. I took a few more full length passes on the edge of the board and examined the results. The amount of tearout was a little less, but not much; and the surface was still unsatisfactory. Closing the mouth as tight as possible was only a marginal help.
I then moved the chipbreaker down just as close to the cutting edge as I could safely set it (it had been about 3/64" back and was now just under 1/32" back). The amount of tearout did not change; moving the chipbreaker closer to the edge did not help. That didn't surprise me; I don't think the chipbreaker helps fight tearout until you start cutting thicker shavings than this.
So far, my understanding that the iron has to be really sharp to prevent tearout when smoothing difficult wood seemed to be born out.
Unfortunately for my preconceptions, I then decided to see how thin I could shave with this plane and its not very sharp iron. I was able to set the plane to take 0.001" shavings fairly easily. Surprise. When I examined the edge of the board I also found that at least half of the tearout was gone. That's all it took; reducing the shaving thickness from 0.002" to 0.001" with blade that is only coarsely ground. Happily, with just a little more fiddling I got the shaving thickness close to 0.0005". The cutting depth adjuster drove me crazy because it had well over two full turns of free play, but I did get the shavings that fine. After taking a dozen or so strokes along the edge to get it flat enough, the plane was taking nice, continuous shavings not much more than 0.0005" thick, something I didn't expect from an unfettled antique.
Not only that, but there was absolutely no tearout. Zero. None. I took the board outside into bright sunlight and went over it with a magnifying glass and found no tearout.
So, I went back into the shop, laid the board flat on the workbench against the stop and smoothed a face. I used another plane first, a #6 that was already set up for that use, to get the board nearly flat and then switched to the K5. It took a while, with such thin shavings, to cut down the high spots so the plane cut the entire surface, but once I got there I could plane in any direction without tearout. Any direction, meaning up the length of the face, down the length diagonally, or directly across the length.
My conclusion is that minimizing the shaving thickness has more to do with combating tearout than getting the iron extremely sharp. To be really exhaustive about this, I would have to go back and move the chipbreaker back to something near its original position and reopen the mouth, but I really don't see the necessity.
I still think that fighting tearout when smoothing requires a combination of at least four factors: a very thin shaving, a sharp iron, a flat sole, and a tight mouth. But I am now convinced that getting the thickness of the shavings down to 0.001" or less is the most important.
EDIT. Plus a very important fifth factor: the cutting angle. I didn't think to include that because my playing around did not include trying back bevels on the irons. However, the block plane with the iron with the unintended 35 degree bevel had a 55 degree cutting angle, and it cut that hard maple with no tearout without the help of a tight mouth. The cutting sure didn't feel good, though, because the high cutting angle requires a lot more force and variations in grain direction feel different. That's how I realized I had put a higher bevel on the iron than I had intended.
Posted rfeeser 12/16/04
The information I've posted here regarding hand planes was written and compiled by Robert Feeser, aka rfeeser
among the fine gentlemen who frequent the WoodNet Forums
. He has graciously allowed me to reprint his exceedingly helpful document here on my website where I hope to add to its value by formatting it for easy reading and re-reading, navigation and the addition of links to all referenced resources online.
Thanks, Bob. I suspect the effort you've put into writing and compiling this guide to hand planes will be a godsend to countless beginners like me. - T.J. Mahaffey [firstname.lastname@example.org