Mechanics of chipbreakers and high cutting angles in woodworking planes. Abstract.
Mechanics of chipbreakers and high cutting angles in woodworking planes.
Kees van der Heiden, The Netherlands, 2014.
Abstract.
When using handplanes, tearout is a typical problem. Two methods to prevent tearout are high cutting angles and chipbreakers set very close to the cutting edge. In previous work it was found that a cutting angle of 60° is equivalent to a chipbreaker setting of 0.1 mm behind the edge when the chipbreaker edge is beveled at 45°. Likewise an angle of 55° is equal to a 0.2 mm setting of the chipbreaker. To compare the two methods a planing machine is used with force transducers to measure the cutting force Fc and the force perpendicular to the wood surface, the normal force Fn. Fc proved to be 30% higher for the plane setups with a high cutting angle, compared to the equivalent chipbreaker settings. Fn is normally negative, pulling the edge into the wood in a standard 45° plane without the chipbreaker. When setting the chipbreaker close to the edge this negative force is slightly reduced, but in high angle planes this is reduced much more and tends towards 0 around a 60° cutting angle, under the circumstances of this experiment. A second experiment has been conducted to measure the forces after a planing distance of 100 meters. The rate of change of Fc is about equal for both methods. The rate of change of Fn is twice as fast for the high cutting angles. The conclusion is that the plane with a chipbreaker is technically more advanced then the plane with a high cutting angle. A hypothesis about how the two methods prevent tearout is proposed in this article too.
The complete article will be published on Steve Elliott's website http://planetuning.infillplane.com/, hopefully this weekend. As soon as I have a link I will post it here.
Time for me to spend time in the shop experimenting with BD double irons.
Quote:
The vertical axis displays the measured forces Fc and Fn. The unit is kgf/6mm. This is the force in kg measured on a wood sample width of 6 mm.
I was wondering what it meant when I first read it on the side of the graph.
kg/6 mm
?
So the sample planed was only 6mm wide ?
Or the sample planed was wider and the UNIT only is 1 6mm unit ?
Kind of leaves out the effect of the bending force of a significant / realistically wide cut with the blade.
Doesn’t it ?
I left the above thought in but now that I have seen the close up in the video and now I see the hewn stock was wider than 6 mm I see the 6mm is just one unit.
If a person took a cut on a plank the curl would be well over an inch wide perhaps even two inches wide. Oops, sorry I forget you use metric to.
well over 25 mm perhaps even 50 mm wide.
While taking a realistically wider cut like that, as compared to the narrow work being planed in the machine, the difference is bound to be significant especially when we include the issue of edge support at the throat or lack of it (see the illustration of the crossection of the plane's frog set forward to close up the throat) (wow I never reallized the support stared so far up the blade) and the difference between a 30° sharpening angle blade tilted up to SIMULATE a 60° BU and a true BU bedded at 12° supported much closer to the edge and sharpened to 48°
Again I would have liked to have seen a wider sample; wide enough to accommodate the full width that the blade could have taken normally in a normal planing operation on a face not an edge. That after all is what we are striving for, a chip out free face surface.
Face planing puts significantly more total force across the face of that blade per unit of time and so could, could mind you lead to the blade flex / oscillations I was talking about.
Quote:
The cutting speed doesn’t have much effect, certainly not at hand planing speed.
I think you will admit that planing at more than the rate shown, on the order of a dive down a plank by an adrenaline charged neander could have some effect on the data.
Cutting faster could increase the oscillations per second and amplitude of the oscillations. There is probably a surface feet per minute number where the friction/heat and the general resistance starts to multiply disproportionally. I don’t think it is at machine cutter speed but down in the hand planing speed.
Cutting is with the grain I believe in the charts. That kind of alternated in the text.
and yet we/you are talking about tear out, which happens against the grain . . . also when planing against the grain mightn't the Fn be different since the edge is being pulled down into the grain ?
OK I was with you up to that point preparing to submit to an over whelming onslaught over the walls of my fortress of peace and contemplative contentment.
I was starting to consider which TEAM of stones to use to do my final sharpening on my hari-kari knife . . . then . . . thennnnnnn
I saw it.
Following the link to David Weaver’s photo of the rowed grain mahogany before and after . . . I must say, I can see what appears to be chatter marks before and after in the tear out areas and they are still there in the tear out free photo.
so not AS good as a BU then ? Rather confirming my flexing blade observations in the past. I am just calling it as I am seeing it.
I CAN see where some one with a BD would then reach for a scraper or (whispering now as if introducing the topic of nipple piercing in a nunnery) sand paper.
I never, until now, really understood the attraction of scrapers. I have a lot of them (as a result of searching for some that are not ruined in the act of shearing or punching them out or what ever, and even found some that are good enough quality to be able to sharpen and use (just so I knew how) but never needed one really.
I noticed in the links the topic / goal of eliminated tear out and chatter was then modified with the words “Nearly” and “Reduce ”.
Kees I read your enlightening article and appreciate all your work. It is fantastic there are great articles still being published in the magazines, well in one magazine anyway.
In the next link to the next vid it looks like the lever on the lever cap was really closed with a lot of force. That could bend the blade further down and add clearance and so make up for some of the rounding from hand sharpening. That was a tip. I had shied away from setting the screw to put that much force/resistance on the lever. That has never felt right to me. Live and learn. I like the bench with the square dogs.
Once again a narrow strip of wood was used in the vid. Keeps the high forces off the less rigid blade configuration. Fairly soft wood. I would be more convinced by a wider face of more challenging wood/hardness and for a longer planing duration than a few strokes. Part of the proof is durability and performance over at least a few board feet of work face.
I know what the charts said. Lets see it on the wood.
It probably sounds like I am just being an idiot that will never allow himself to change but . . . at it’s worst 30% more effort and some reduction in durability (that means a lower percentage for many/ most some what less difficult applications) I might be willing to still go that rout for the trade off of the over all planing experience of the BU (I won’t hammer all that out again in text) .
Time for me to spend time in the shop experimenting with what I have learned and to see what I can do if I practice, practice, practice. I thought I had got past all that but . . .
Well it has been a freewheeling, fun filled, fantastic trip together guys.
I just have one question, I was a little unclear in the second link when you mentioned something called . . . a . . . sander ? ? ?
Kees what issssss that ?
TTFN
(ta ta for now)