Rabbet plane build (in progress)

Graywolf

Board of Directors, President
Richard
Staff member
Corporate Member
Thanks everyone. I put some watco danish oil on it last night and it is looking nice. I don't want to touch it right now to stage a photo but I will post one eventually.

I have heard that Larry Williams uses minwax antique oil, I wonder what the benefits of it are.

I haven't finished my other planes, and I feel like I have to either be careful about leaving dirty fingerprints on them or just give up on the cosmetics altogether. This is going to be a test to see how oil and wax holds up.
The antique oil is a good finish with a pretty fast drying time. Which is why I think a lot folks use it for that reason. That doesn’t mean I think you should rush out and get some. The Watco danish oil is just fine. I have used both and like them on an equal standing.
 

Scott H

Scott
User
The current thing I'm beating my head against is that the iron can be shifted laterally a little bit with firm finger pressure, if you press near the cutting end, even with the wedge as tight as it can be. I am not sure if it just needs tuning or what. I will have to think about it carefully. To get it as solid as it can be I have to really tap in the wedge hard and then you have to tap out the iron equally hard to get it to release, and even that is really not quite enough.

Rabbet planes are kind of at a real disadvantage because the wedge doesn't reach close to the cutting edge, and also the breast of the mortise is even farther away, so there is not a lot of force being transmitted from the body through the wedge to the blade near the cutting edge. Also, the tip of a wooden wedge is not particularly rigid, especially a more delicate wedge shape like mine, so the ability for it to transmit much force at the tip seems limited.

I wonder if there is some design detail I missed or if this is just going to be a case of chasing down high spots to move the strongest contact closer to the mouth. At least at one point, I had it so I couldn't get a 0.0015" feeler between the blade and the bed near the mouth, but I still had the same issue. I tried roughing up the mating surfaces on the iron and wedge with sandpaper since they were planed/polished but it did not seem to help much. Kind of feels like the problem is the most force is applied somewhere inside the wedge mortise so the iron can "pivot" with the pivot point inside the wedge mortise somewhere.

Haven't really read much about this problem in any literature, if anyone has any thoughts let me know.

I guess the other possibility is they're just all like this? Seems unlikely. It occurred to me you could avoid this problem by just making the iron tang the same size as the wedge mortise within a couple thou but then you have a separate problem -- which is if the plane body shrinks it's going to death grip the iron and probably crack around it.
 

bob vaughan

Bob Vaughan
Senior User
There's an old saying about one clamp is merely a pivot. It could be that there's a hump or high place somewhere.
A very slight hollowing out may be the solution as shown below in a very exaggerated red line

1    piv.jpg
 

Scott H

Scott
User
It stands to reason... The weird thing is there should already be a slight hollow in those places, but maybe I need to exaggerate them more, or perhaps the iron is not truly straight tapered and is thicker than it ought to be in the middle somewhere.

Thank you for the sanity check though, I know if I start tweaking things without really analyzing it is easy to run away with it and end up removing material I'd wished I hadn't...
 

Scott H

Scott
User
Took thickness measurements of the iron every 1/2" starting 1/2" from the bevel until it gets out of the mortise area. It looks like maybe there is a hump in the iron. This is using a $25 digital caliper that's 10+ years old so I don't know how much I trust it but it is in the right spot, but extremely tiny (0.001".)
 

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creasman

Board of Directors, Development Director
Jim
Staff member
Corporate Member
Check the bedding of the iron. In his video Larry Williams uses a black dry-erase marker to coat the bed side of the iron. Once it's installed and lightly wedged this way, drive it out. This will cause the black marker to be left on the high spots of the bed and remain on the iron at the low spots. You'll know where to float a bit more. It may take 2-3 iterations of this process before you get to the point where the black is being removed evenly.
 

bob vaughan

Bob Vaughan
Senior User
Took thickness measurements of the iron every 1/2" starting 1/2" from the bevel until it gets out of the mortise area. It looks like maybe there is a hump in the iron. This is using a $25 digital caliper that's 10+ years old so I don't know how much I trust it but it is in the right spot, but extremely tiny (0.001".)

I agree. .001" is virtually insignificant. I'm quite impressed with the accuracy of that taper. .010" might be a problem in the taper, but not .001".
The solution is likely to be elsewhere.

I've got two Stanley #92 rabbet planes (one for backup in case I drop one) and I'm still considering making one of those planes. This is a very inspiring thread. Capable and practiced craftsmen always make the work look easy.
 

Scott H

Scott
User
Check the bedding of the iron. In his video Larry Williams uses a black dry-erase marker to coat the bed side of the iron. Once it's installed and lightly wedged this way, drive it out. This will cause the black marker to be left on the high spots of the bed and remain on the iron at the low spots. You'll know where to float a bit more. It may take 2-3 iterations of this process before you get to the point where the black is being removed evenly.

I think part of what has me frustrated is I did probably 10 or 15 or more iterations of this a few days ago, and could never get it to totally fix this problem, so I ended up stopping because I knew I was chasing my own tail. I did think I had gotten it to where I had pretty good contact with the exposed part of the bed where the wider part of the iron was, especially near the mouth, but I guess not well enough. I think I need to give it some time and come back to it fresh.

I've got two Stanley #92 rabbet planes (one for backup in case I drop one) and I'm still considering making one of those planes.

I have a "newer" (bought new like 3 years ago instead of vintage) #92 and the blade is exactly the width of the body, so I think I got started on this thinking I could make one that I wouldn't have to keep switching which side the blade protrudes a hair on as I was fine tuning a rabbet. I am realizing that may be trickier than I originally thought but it is possible. I am also hoping the larger size and height will make it easier to keep it vertical.
 

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Scott H

Scott
User
Some encouraging progress. I have had no luck testing with shims, but today I tried far, far more shimming than I thought should be necessary near the mouth. This is 3 layers of blue tape on the mouth plus another half-strip to account for some possible twist. That should be in the ballpark of 0.011-0.015 of shimming. The improvement in iron grip is substantial and probably sufficient for use. It also works with thicker shimming. You still have to set the wedge pretty firmly but it holds better than anything else so far. Now I know for a fact that I don't have a hump this big anywhere on any of these mating surfaces, or a wedge angle off by that much, but it makes a huge difference.

I think maybe I have been thinking about all this wrong. I was thinking if I made perfect, clean surfaces that fit together very closely and had subtle high spots (a few thou) in favorable areas, it ought to work. I was rejecting the possibility that the high spots might need to be much larger than that.

That strategy had worked OK for the few bench-type planes I've made, but in this case we have a very small and delicate wedge and a thinner, less rigid blade (the tang is only ~0.200" x ~0.100" cross section and will be unhardened) and far less contact area overall, plus a significant distance from the wedge tip to cutting edge, and then wedge tip to abutment/breast. In addition to that you have significant lateral forces from the way the plane is used. I think this is a totally different ball game.

I think what you actually want here is to aim for elastic deformation of the wedge and/or blade in order to develop the spring force necessary to hold the iron in place laterally. I'm not a mechanical engineer, but I remember that for a simple spring the force of the spring is proportional to the displacement. And I know that the force of static friction is proportional to the normal force (which in this case is coming from the wedge action and the spring action.) More deformation (displacement), more static friction than you could get from the wedge alone. The tip of the wedge may be bendy and delicate, but once you preload it it can exert a lot more force!

I am staring at some pictures of metal rabbet planes and wondering how it took me this long to realize the high spot near the mouth might need to be exaggerated. If you look at this photo of a Stanley #39 (not mine) that has a fully-hardened machined steel blade and a cast iron body and a metal wedge, a much wider blade and a much wider wedge, you can see they put a land that appears to be at about 1/32" thick near the cutting edge. I measured my Millers Falls rabbet plane and it also has a land of about 1/32". Compare this to a metal bench plane whose frog is machined or lapped flat. You might argue that this helps them cut the cost of machining the entire bed or producing truly flat blades but I'm not totally convinced. Even the Veritas jack rabbet plane and skew rabbet planes have this feature, as do metal shoulder planes. Block planes have this feature too. I think it shows up on a lot of planes that don't have the luxury of a huge bed/blade contact area. The cap irons also have significant reliefs.

The other thing I am realizing is it is probably not a fair test to try to move the iron left, then right, then left, then right, etc. as that is not a pattern of force it would encounter in real use. Most likely the wedge will eventually loosen if you wiggle the blade laterally enough no matter how tight it is. (No matter how you adjust a plane you always have to tap the wedge, after all.) If you can't move it in one direction immediately after setting the wedge that should be sufficient.
 

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Scott H

Scott
User
I also have noticed the iron tang was slightly bent out of flat, in a way that would have caused more contact in the center of the bed, but bending it back to flat or counter-bending it in the opposite direction does not seem to improve it much beyond what this one well placed tape shim does. Some bending seems inevitable, especially the part of the tang that protrudes past the wedge mortise. I think that in practice much of the bend is being flattened by the wedge. Not sure that having a hardened steel tang would help much because IIRC the elastic modulus of steel does not change with hardening, only the yield strength, and the part that matters seems to be being elastically bent inside the mortise.

Still a little mystified as to why other wooden rabbet planes appear to work OK with a flat bed. I guess I have to get my hands on a well-functioning one to analyze and compare.
 

Scott H

Scott
User
Fiddled around with it today, roughed up the bed and wedge with some 220, which helped a little. I then found that if I just put a little slip of 2000 grit wet-or-dry sandpaper (abrasive facing the blade, nonabrasive side on the bed) near the mouth then the thing is solid as a rock.

It is really unobtrusive and mostly sticks to the bed anyway even when you take the blade out, so I'm going to just stop fiddling here. Working theory is the freshly polished blade may just be too slick to develop sufficient friction against the wood. Doesn't do that if you just use a paper shim.

I got a faint dark fingerprint mark on the plane today and reapplying wax rubbed it right off. Happy with the decision to wax the sides of the plane so far.
 

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