Planing - exact relationship between depth and effort?

[bugbear]

It is a commonplace that thicker shavings are harder to cut with a plane; one of the commonest uses
of the depth adjuster is when the plane is too hard to push, and you back off the depth.

Now, (per other threads) it is apparent that planing is quite complex when you look into it, with interactions between edge shape, cap iron, timber grain, side conditions (the shaving's sides, that is) all playing a part.

But many of these factors can be simplified away. It's easy enough to remove the cap iron (use a single iron), simplify the edge shape (straight line), and get rid of the shavings edges by using a workpiece narrower than the blade.

Just to make sure I wasnt getting carried away with myself, I just tried planing the edge of a 3/4" workpiece with my Woden W78 rebate plane (1 1/2" blade). As predicted, increasing depth of cut (DOC) makes the plane harder to push. No surprise there.

But returning to my mathematical theme, what numeric effect does DOC have? Does doubling the DOC multiply the effort required by 1.4 (square root of two), 2, 4 (multiply by 2 twice) or even 8? 8 is not impossible - beam stiffness,for example, is known to vary with the cube of thickness.

Measuring this in a home workshop is very hard - planing force is not very constant during a stroke, so I suspect an answer to my question, if one exists, will come from a laboratory (like the UK Forest Products Research Lab or its Amrican counterpart), or a technical college.

So - does anyone know of the experiment being done, and what the result was?

BugBear

 

[Stuart]

I enjoy the forum and the threads but this is so OTT

 

[jimi43]

During the infill build, I did some research into cap irons and was reading THIS ARTICLE which contained a number of references to experiments carried out by Professor Yasunori Kawai and Honorary Professor Chutaro Kato, Faculty of Education, Art and Science, Yamagata University.

Although not on the same subject, I think that they might prove the starting place for this type of research....and if they haven't already done such experiments, I'm sure they would be up for it!

Jimi

 

[Graham Orm]

Try some candle wax.

 

[Sheffield Tony]

I haven't done (and won't be doing) an experiment, but thinking about mechanics for a moment, I'll punt for a square law for along the grain. The liftiing / curling away off the shaving is like bending a beam - as it gets thicker there are proportionately more fibres to bend, and the outer ones need to be stretched or compressed proportionality more.

 

[bugbear]

I haven't done (and won't be doing) an experiment, but thinking about mechanics for a moment, I'll punt for a square law for along the grain. The liftiing / curling away off the shaving is like bending a beam - as it gets thicker there are proportionately more fibres to bend, and the outer ones need to be stretched or compressed proportionality more.

Yes, my thoughts (guesses!) ran long those lines. I also thought that the power input requirments of a power planer might be handy measure, but (on further consideration) decided that the action of a power planer (removing successive scoops from rounded face) was so different to the hand planing action as to not be useful as a proxy.

BugBear

 

[bugbear]

I enjoy the forum and the threads but this is so OTT

Why, thank you kind sir!

BugBear

 

[Random Orbital Bob]

I bet Matthias Wandel would be up to having a punt. Might be worth pinging him because to be honest he's running out of ideas with his regular Friday project posts. Perhaps many wont know his style but he is a woodworking genius in many respects. He has often measured the empirical force of different glue holding strengths.

The test would just require your plane arm to be attached to a dial gauge somehow (or the plane itself).

Although I have to be honest, its a pretty dry theoretical for its own sake experiment. Not entirely sure there would be that much interest in the result. But you never know...

 

[xy mosian]

I wonder if a pane could be guided to move down an inclined plane under the influence of an adjustable weight? If the angle of inclination, slope, were kept the same then the effect of a deaper cut could be seen in the amount of extra weight required to achieve planing.
xy

 

[lanemaux]

I wonder if the Japanese group who did that chip breaker study might not have some relevant force data. They do seem to have taken their measurements of everything else quite seriously.
Regarding being over the top , BB is near 9000 posts , needs to stay fresh somehow. And congrats to BB on his approach to 9000 , way to go amigo!
P.S. Oops , I was inattentive , Jimi sited the reference first. Sorry Jimi , that will teach me to not just skim through eh?

 

[Mr_P]

Where is Maslow and his shovels when you need you him or was it Taylor.

Would have thunked we all had a different sweet spot and even an individuals spot would improve (get thicker) with practice but would also decrease with age / reduced activity.

 

[Bod]

I think a lay down in a darkened room, is in order.

Bod

 

[Jacob]

The place to attach the dial gauges etc would be around the operative's feet - a platform like a weighing scale but with measurements in 3 axes. Every action at the plane front would involve an equal and opposite reaction at the feet.

Hope that helps.

 

[bugbear]

The place to attach the dial gauges etc would be around the operative's feet - a platform like a weighing scale but with measurements in 3 axes. Every action at the plane front would involve an equal and opposite reaction at the feet.

Hope that helps.

That's an interesting thought - if you put the dials on the hands, the force would change rapidly and be hard to measure, but the mass of the intervening body if you measured at the feet would perform an excellent job of averaging.

Still a hell of a tricky experiment with everyday equipment though. I don't have a 3-axis strain gauge kicking about!

BugBear

 

[Corneel]

When you want to know something about plane cutting forces, have a look here:

http://www.amgron.clara.net/sciencereport16.html

For normal cutting angles there is a 1:1 relation between cutting depth and cutting force in the horizontal direction. The force you feel when pushing against the plane.

 

[bugbear]

When you want to know something about plane cutting forces, have a look here:

http://www.amgron.clara.net/sciencereport16.html

For normal cutting angles there is a 1:1 relation between cutting depth and cutting force in the horizontal direction. The force you feel when pushing against the plane.

Well, "oops".

I knew about Jeff's site, but had never taken (proper) notice of that page. Linear with depth - simples!

Thank you, that will be most helpful.

BugBear

 

[woodbrains]

Hello,

Who's going to say it, then? I can barely look! (hammer)

Mike.

 

[Dovetaildave]

The place to attach the dial gauges etc would be around the operative's feet - a platform like a weighing scale but with measurements in 3 axes. Every action at the plane front would involve an equal and opposite reaction at the feet.

Hope that helps.

Yebbut......... a cheaper and slightly less accurate version could be :lol:

Mebby, spread peanut butter on workshop floor, wear yer best smooth soled dancin shoes, measure the amount of slippage :lol:

 

[Trafalgar]

When you want to know something about plane cutting forces, have a look here:

http://www.amgron.clara.net/sciencereport16.html

For normal cutting angles there is a 1:1 relation between cutting depth and cutting force in the horizontal direction. The force you feel when pushing against the plane.

Well, "oops".

I knew about Jeff's site, but had never taken (proper) notice of that page. Linear with depth - simples!

Thank you, that will be most helpful.

BugBear

Jeff's site answers a lot of questions that come up on the forums, most recently the one about 'chatter and skitter.' He dispatched these issues with his usual aplomb and directness.

 

[woodbrains]

Hello,

So, no one is going to, then?

#-o

Mike.