All other things being equal in a finely tuned smoothing plane in hardwood, is it better to 1) have a fine mouth with slightly backed off chipbreaker (less choking) or, 2) a more open mouth with a very tightly set chipbreaker (even less choking)? How about some specific settings. Thanks.
Regards, John
Replies
I think both need to work together and it is not so much a give and take matter. If the mouth is two wide it will allow too thick of a shaving to be lifted. If the chip breaker is too far back you will probably clog the throat. Shoot for a tigfht mouth ( as tight as possible while keeping the blade supported to prevent chatter) and the chip breaker set just a hair back from the edge of the blade.
John
The problem with answering your question directly is that there are other variables to consider.
It depends on the wood and grain. With straight grain you can basically do anything you like.
If the grain gets gnarly, that is, starts to reverse on you, then a sharp edge (always taken for granted) and the cutting angle (especially the higher this becomes) is more important than either the size of the mouth or the position of the chip breaker. With Stanley-type bench planes (45 degree cutting angle) on gnarly wood, you will get more joy from a small backbevel than a tight mouth. Put the two together, however ...
The position of the cap iron is way overrated. Most cap irons are unnecessary - other than to stiffen up a thin blade as so reduce chatter. Back it out of the way. The only time it has been demonstrated to make a significant difference (on thin blades) is when positioned .5mm from the edge (I think it was the research of the Hitachi Corp.).
Regards from Perth
Derek
Thanks Derek,
What got me thinking about this was looking at the wide open mouth of my scraper plane and knowing that the scraper hook causes the shaving to immediately curl up, thus limiting tear out. So I thought that the tightness of the mouth might be over-rated, and maybe I should open up and just set the chip breaker as tight as possible to mimic the scraper blade. Said another way, does curling the wood fibers up when they are cut contribute more to minimizing tearout than does holding them down ahead of the cut with a tight throat? You seem to feel that blade angle overrides most factors. Thanks.
John
I think what Derek is referring to is that the steeper the pitch the less of a factor tightness of mouth becomes due to the fact that the steeper the iron is pitched the closer it comes to being a scraper. But like he mentioned earlier if you combine both, then you have something pretty amazing to work with. I have actually done direct testing of this with the planes I make in my shop. My small 50 degree small smoother with a .004 mouth produces a nice surface, however really gnarly areas that give it a small bit of trouble are easily handled by a 55 degree version of the same plane with the same tight mouth, the 5 degrees really does make a lot of difference. The 55 degree plane is however harder to push.Ron Bresehttp://www.breseplane.comIf you're too open minded your brains will fall out.
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