A BU and BD observation and question. Blame it on the heat.

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Derek Cohen (Perth Oz)

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Blame this on the heat. It is 41.5 C (106.7 F) outside, and probably hotter than this in my double garage/workshop. It has been like this for some days and for much of the time (while I have been on leave from work) I have struggled to maintain enough enthusiasm and concentration for anything more than shortish projects - hence a spate of tool-building and resto work. I sharpenened and played with many of my planes. Which is what I am getting to. But it is early afternoon and I am waiting for the glue to dry on the form work (to laminate Jarrah strips) I have built for two matching half-round end tables. It has been a hot, dirty, dusty (bandsaw and planer-thicknesser) day and hot (did I mention that?) and dusty (in spite of a 2 hp cyclone) morning in a hot and steamy workshop.

A frequent question on the forum is in regard to cambers on smoothers. Now I am not debating whether they are important - I just accept that they are, and all my smoothers have a fine camber to avoid the dreaded tracks that otherwise occur when irons are left straight.

There is the question about honing camber on BU planes, and the answer that BU planes require greater camber to arrive at the same shape shaving as a BD plane.

As I noted, I have been sharpening up all my irons of my planes, and this was partly in preparation for my current project. With the exception of one, these are my planes and I do the best for each. They include: LV BU smoother (cutting angle of 62 degrees), Marcou S15 smoother (60 degrees), Stanley #3 infill (60 degrees), Spier smoother (47 degrees), HNT Gordon smoother (60 degrees), LN bronze#4 1/2 smoother (50 degrees), and LN iron #4 1/2 smoother (45 degrees). The last plane is a loaner. The first three planes are BU and the last four are BD.

Let us go back to that recommendation that camber on a BU iron is required to be greater than camber on a BD iron for the same amount of feathering at the edges of the shaving.

Why then do I consistently find that I require minimal camber necessary for BU planes compared to BD planes? We are talking fine shavings here, finishing shavings. With a straight edge on a BU iron I am able to obtain wafer thin, full width shavings - without tracks. Or, because the shavings are so fine, the tracks are essentially not evident to sight or feel.

With the same straight edge on a BD iron I get full width shavings with tracks. I can also feel that the outer edges of the iron are projecting further than the centre. This is with all the BD planes. I don't understand why - the irons are all honed on the same waterstones, all of which are prepared the same way (in fact I got so paranoid about flattening them with drywall mesh that I have now been using a diamond stone. Still scribbling on a pencil grid to check they are flattened evenly). All the BU irons are honed with the LV Honing Guide Mk II. The BD irons are usually honed freehand. I hollow grind the BD irons and micro grind the BU irons. When I began noticing this effect I swapped to using the LV guide for the DB irons as well. It made no difference. So I discounted the difference in honing strategy - actually, I find it easier to hone a camber on the BD irons when I work freehand.

I will add that all these planes function superbly. They are all capable of high quality smoothing. I am not drawing a distinction between BU and BD in terms of merit. NOT! It is just that they appear to need to be set up differently. Is this my imagination? Or is it the heat?

Regards from Perth

Derek
 
Maybe the heat Derek....could do with a bit over here, don't fancy exporting any do you? Could be a long and interesting, thread this one - Rob
 
Derek,

This is interesting to me.

Are your bevel down planes less flat in their width near the throat? This would explain more blade at edges than centre.

Alternatively is the bedding less than satisfactory across the width of frog, low down.

Or are your chipbreakers distorting blade edge.

Have you got a bomb proof method af examining blade camber? I use a square stick of dark industrial plastic like Tufnol.

David
 
Are your bevel down planes less flat in their width near the throat? This would explain more blade at edges than centre.

Alternatively is the bedding less than satisfactory across the width of frog, low down.

Or are your chipbreakers distorting blade edge.

Have you got a bomb proof method af examining blade camber? I use a square stick of dark industrial plastic like Tufnol.

David

I am battling to explain this. It is so frustrating as it should not be so. I keep blaming my honing technique, but this is too easy and still does not explain what I am doing.

I have examined the edges using a magnifying glass and a small square while holding the cutting edge against a light. The blades are flat, flat, flat.

As I noted before, when I doubted my freehand honing I used the LV Honing Guide (with the wide, flat roller) to check. There was no difference in the result. The waterstones are the same for both BU and BD irons. In case the BU blades were just less sensitive to an out-of-flat surface (which is an issue for discussion), I checked and double checked the stones for flatness, even changed the drywall mesh more frequently than needed, and even changed to flattening with a diamond stone. None of this made a difference.

The thing is, I would not have been aware of this issue had I not tested blades and planes (together and separately) and, to do so, used straight edges. If, as I have done for years, simply honed a camber on the edge as part of the usual preparation, I would be none the wiser.

As far as I can tell, the bedding is fine on all the planes. The effect of the chipbreaker? Well the HNT Gordon does not use one. But I did question this as well (on the Spier and the two LNs), so varied the pressure. Again no difference. I will check the LNs tomorrow (I cannot recall if I have already or not), but it would surprise me if there was an issue with one never mind both.

Let me repeat, all the BD planes perform superbly with a little camber. However, the BU planes perform as superbly without any camber.

Regards from Perth

Derek (needing another cold beer)
 
So Derek I take it that you don't have this obsession with the full width shavings that I now see everywhere. Never quite understood the obsession myself.
 
Hi Mignal

It dependson what you mean by "full width" shaving. It is no big deal to plane the width of a narrow board - that would be full width. However, I think you mean the full width of the cutting area of the iron, which excludes the cambered corners. I aim for that, but some woods make it easier/harder than others.

Here is the HNT Gordon on Jarrah - not easy keeping it together.

HNTGordonandJarrahshaving2.jpg


Regards from Perth

Derek
 
Blame this on the heat. It is 41.5 C (106.7 F) outside, and probably hotter than this in my double garage/workshop.

Derek

Hey Derek, move up over here! These days the minimum hits -25 or so with maximums in the -15 C range

That'll cool you down :lol:

DC

In balmy Ottawa

Interesting observations BTW, I have no answer however, I'll be following this thread with interest...
 
Derek,
This is really interesting. I have had my LN low-angle jack since last spring and have kept the edges straight on the irons (25* and 38*). I have also noticed that I can take whispy full-width (full-iron-width) shavings with it. I've considered putting a camber on the 38* blade.

I wonder whether the difference in downward pressure on a BU vs BD is part of what you are observing? I find it easier to find the right balance of pressure on the BU planes.

Sounds like some really hot weather. Today, next to Lake Champlain in Vermont, it's currently -14* C (7* F), which actually feels warm compared to some of the weather we've had over the last week. Yesterday, I blasted my heater just to get my shop up to 50* F (10* C). I counted on the aerobic exercise of hand tool use to account for the rest of the warmth I needed. (Chopping mortises).
-Andy
 
dchenard":3hk1s8kp said:
Hey Derek, move up over here! These days the minimum hits -25 or so with maximums in the -15 C range

I went downhill skiing last week in that minimum. You definitely don't want exposed skin. I discovered I need a more windproof toque as well. I have done relative heavy physical work in -25 to +40, and although the -25 is more comfortable (and less tiring), I still prefer +40. I also did some light hiking (no work) in a little over +50; that is totally brutal.

I have at least one BD plane (good quality) where an apparently straight blade (to my examination) definitely behaves as though the edges protrude beyond the middle. It is a smoother, so I just went on an put a camber in it anyway, but it always made me wonder. My other BD planes don't *seem* so sensitive, but they are also less used with a very light cut on flat surfaces.
 
I've noticed it myself. It seems more apparent with my Stanley planes than the LN though. I wonder if it has something to do with the chipbreaker. :-k
 
having been accused of asking this question "tongue in cheek" last week on another post, i wonder how we are going to get a definitive answer :twisted:

you seem to be saying derek that on fine shavings your bu's do not provide visible tracks, hence why camber??

i guess the other question should be, what happens when you go for thicker shavings :roll:

then we might well discover the truth.

paul :wink:
 
If all aspects are indeed the same.......straight edge.....dead flat backs.....etc..then, to me, it suggests the difference is in the general orientation of the blade to begin with.......ie......maybe the BD blade is being drawn down a touch in use due to the bevel overhang.

Whereas the BU being supported by the bed right to the edge along its back isn't allowed to flex down whatsoever.

I can't think of any other reason. Think its nice for some things to remain a mystery though. :wink:
 

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