Measuring the mouth

Re: Measuring the mouth

Jim Crammond in Monroe, Mi.

>Kevin,

I'd say B. With the blade installed in the plane in the normal way, the largest size feeler gage that slips through the mouth opening is measurement.

At least that is my understanding.

Jim

Re: Measuring the mouth

Barry Va Beach

>Kevin, I think it can be measured a number of differrent ways and I am not sure there is any consensus. Fist - hold a feeler gauge perpendicular to the sole and try to pass it through the mouth. I think this is the method more commonly used when you hear about a few thousands. If you measure perpendicular to the sole, however, your reading is greatly affected by how far the iron is advanced. If you set it for a rank cut, the opening will be small, lighten the cut and the opening will read much larger. I think I saw that you read it when it is just cutting wispy shavings - though that is not quite a precise term. If you measure parallel to the iron, so long as the iron projects below the mouth, the opening should not vary much as you advance it. In theory, this reading tells you the thickest shaving that will pass through the mouth so a few thousands would probably not be useful as a plane because if the shaving grew to .003 the plane would choke. When I built infills ( St. James Bay Tool Co.) , I tried not to get too caught up in the measurement of the opening but instead shot for just getting the iron to slip through and then opening it a little more so that it would take an acceptable shaving without choking. Good luck. Barry

Combination screamed the crowd...

Doug Evans

>Hi Kevin:

There are good things to be gleaned from both of the responses. I use Jim's parallel to the iron method (it's a robust method) and I tend to agree with Barry to a point that it reduces to a matter of practical compromise.

We are heading back on the old saw (watch out for Panthers in the shed...) that no plane does all things. The gains as we approach specialization are countered by the losses in flexibility. I do not think it is a fluke that the vast majority of late 19th century infills are bedded at 45 degrees (could be that they worked on ancient Brazilian Rosewood all day long). What was good then may not be so now but methinks 45 is the best compromise today too. I also dont think that the boys at the seven crossed arrows in Sheffield decreed anything sacrosanct (not bad... WORD didnt kick that one out) either. Things just evolved the way they did. I digress...

Here's what you do... for starters... try to get the iron so it just barely DOESN'T pass through prior to the final rivetting... this stuff is just rivetting, isnt it?... Why? Because the rivetting process itself will cause slight distortion of sidewalls and sole.

Finish the rivetting. Flatten the sole. Then barely open the mouth. Pour in cold libation. The open the plane mouth...as little as you can. Run around the shop searching for scantlings of all the materials you like to use in the range of your work. What the heck... bust up that Snakewood skid you brought home from the local firewood dump last week... go on! Seriously, when the mouth is fine try out a range of your species, and open to taste (my guess at the range - 0.002" to 0.005").

Anyways, I think I'll head downstairs for a minute and open something to taste as well, although it does not have nearly as nice a bottle as that one Louis Bois has pictured over on sawmill.

Slummin it...

Doug

Re: Measuring the mouth

WoodburnBob

>Kevin, when I measure, I measure parallel to the iron. In the 2D plane of the sole, the measurement is independent of iron projection. Hence, it should be more reliable and valid.

That said, I have no faith it (mouth opening) has much correlation with performance (except at the extremes of so tight chips won't pass). I came to my bias from personal observation, as well as reading an analytical discussion of the underlying rationale for tight mouths that Clark & Williams had on their site. The Clark & Williams essay was an elegant rebuttal of the myth that small mouth size matters. I just looked and that essay isn't there anymore, sadly (http://www.planemaker.com/articles/).

Thanks for all the replies

Kevin F, New Zealand

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