Sharpening Scrub Plane Iron w/ Scary Sharp?

[Doug Shepard]

Well my LV Veritas scrub plane was at the door when I got home today. I started thinking about sharpening the blade. I did a search on SMC past posts and found a few tips, but they all relate to conventional sharpening. I've been using the scary sharp method (plate glass & sandpaper) for quite a while and am pretty happy with it. I'd like to see if there's a way to do this with a scrub iron too. But I'm having a hard time picturing how to hone the scrub iron with the same method. The blade is normally perpendicular to your body as you work the edge back and forth over the glass/paper. One vague notion I've had is to make some sort of angled pivoting jig to hold the blade and swing it back and forth across the glass to retain the radius (3"), but I'm open to suggestions. The though of doing it freehand has me concerned about putting flat spots into the curve. Anybody else using the Scary method with scrub plane irons? If so, what tehnique are you using?

[Derek Cohen]

Hi Doug

I have two methods for you.

The first is based on the LV Honing Guide Mk II. You will need to go to http://www.woodcentral.com/cgi-bin/handtools.pl?noframes;read=72315 for a description and pictures of this method. Briefly, it involves using the Guide in an upside-down position. Don't laugh - it works!

Original article:
"The new LV Honing Guide Mk II excels at honing square bevels on blades. One of the areas in which a modification or accessory is being evaluated that of honing a camber on a blade. Below I am offering my strategy for honing the camber on scrub plane blades using this guide. I have no idea if LV will take this seriously – you are more likely to laugh when you first read my description – but it is a serious recommendation. I have used it successfully on a number of occasions, and will demonstrate this below.

I might add that there might be potential here for adding other forms of camber, such as to jack or smoother blades, but this is not its intended use at present since I am still evaluating it in that regard.

For scrub blade use, the only modification to the Honing Guide is the addition of a washer under the Blade Carrier Locking Knob (see Picture #1). This is to raise the height of the knob.

Set the Registration Jig for a 30 degree bevel angle (see Picture #2), lock it to the Guide, and then insert the blade upside down (i.e. as if you were going to hone the back of the blade – see Picture #3).

I hone on waterstones, and depicted here is my King 8000. The scrub blade has already been ground to 30 degrees (in this case on my belt sander jig, but alternately you could either use the existing factory grind if using the LV Scrub plane, or you could first hone a camber on a blade on lower grit waterstones).

Onto the waterstone I place a steel card scraper, and then onto this I place the Honing Guide upside-down so that it is riding on the Blade Carrier Locking Knob. This scraper blade raises the angle enough to hone a 1 degree micro bevel (see Picture #5).

I pull the blade towards myself since pushing it is likely to cause it to dig in. It requires only a few strokes to create a full micro-bevelled edge (see Picture #6 – you can see the glint of the micro-bevel).

Stroke off the wire edge (or use David Charlesworth’s Ruler Trick to do so), and you are ready to go."



The second method is to make a jig for yourself. Below is a picture of this. Basically just a bolt with a round head. You could simplify it by just fixing the blade in place by suspending it with extra nuts.

In both methods, whether you are going SS or waterstones, run the guides on an old scraper blade to protect both the round bolt head and the sharpening media. The added advantage of the scraper blade is that it enables one to hone a microbevel, so set the jig for 30 degrees, then place it on the scraper blade (lifting it up about .5 - 1mm).

Regards from Perth

Derek

[Rob Lee]

(insert mandatory joke about Australia, and using things upside down here )


An excellent example of latera^h^h^h^h^h^h inverted thinking... :)

[Mike Wenzloff]

Well my LV Veritas scrub plane was at the door when I got home today.
Well, congrats.

I started thinking about sharpening the blade.
Sooner or later one does need to!

The though of doing it freehand has me concerned about putting flat spots into the curve. Anybody else using the Scary method with scrub plane irons? If so, what tehnique are you using?
Doug, first just let me say that small flats or irregular shaped scrub irons are absolutely unimportant. Unless you are going to use the texture as a design feature, and even then probably not by its very nature.

As I mostly sharpen even scrubs on a series of stones it applies to the SS system. And you even have more room to do it than I do on a stones surface. For a stone, envision the stone placed at about a 45 degree angle versus running straight away from where one stands.

With the blade held at the far end of the stone, at the angle I am sharpening, and the blade tilted up on the near corner, I simply rotate my wrists as I pull the blade towards me.

I use a 320 grit diamond for shaping an already shaped scrub (to get rid of any flats that are building). I then use a 1000 grit stone, followed with a 2000 grit. During use I hone on the 2000 grit.

I use this same technique for my pattern makers planes and the rounds from my H&Rs and they need to conform the their respective curved soles. The motion is easy to get use to. After that it is all muscle memory.

Mike

[Doug Shepard]

Thanks guys for the feedback. I've got an idea for a jig that I'm hoping to get made this weekend. It all depends on whether my neighbor takes me up on my offer to help him with a little WW project. Looking over your suggestions, unless I'm missing something I still think they're based on moving the blade over stones or glass/paper with the wide side of the blade facing you. While I like the Scary method, I've never had good results using it with guides, or the blade in that orientation due to the paper bunching up or the blade digging into the paper. What I've been doing with regular plane blades and chisels is just freehanding - keeping the bevel flat on the glass and moving the blade back & forth with the edge of it facing you. I was looking for a way to use the same orientation on the glass. I've got most of the jig designed in my head and hopefully I can get it made the weekend and post pics. The only issue I'm still mulling over is how much (if any) adjustability I want built into it for different curve radii. No adjustability is the simplest but might not be the best long-term solution.

[Derek Cohen]

Doug

This may promote a few ideas. It is a linkk to a jig I made to grind different cambers on blades, in this case focussing on scrub blades. It uses a belt sander and is extrenely accurate and fast.

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=17400

Regards from Perth

Derek

[Doug Shepard]

Thanks Derek
It's pretty cool when you can trade ideas back and forth with someone on the other side of the planet. Your jig link was something more like what I was picturing. I took the time to scribble up a pic in Sketchup of what I've been thinking about. My idea is to set this whole thing on the plate glass and pivot the top piece back and forth to move the bevel edge across the glass. What I'm still toying with is whether to cut a couple of different sized slots up the middle of the base piece to allow the pivot pin to be slid up/down the base and tightened down with a nut to allow different radius adjustments. The top piece would be dado'ed out in the middle to the blade thickness. What do you think? Would this work?

[Mike Wenzloff]

I wish you luck with this. I'm not sure it will work. The pivot point would have to be the center of the radius in order to enable contact on the blade's edge all 'round.

This means at minimum you will need to make a movable pivot as once the blade wears down, it will need to move closer to the glass. Probably a holder using rare earth mags that in turn is afixed to the pivot would be neccessary to get that close. I didn't measure though, so I'm probably wrong.

I don't know which method you afix the sandpaper to the glass, but I just went out to the shop and tried both spray adhesive and the tension of applying water to a granite surface plate. Both held the paper more than sufficient to hand sharpen and hone the scrub blade.

You aren't needing to create the "perfect" bevel as one would do on a smoother. Your hand can allow a bit of "wobble" as you hone.

[Derek Cohen]

Hi Doug

Interesting jig, and I think you have been very creative. However, I think that you are missing an important point (or perhaps I am being dense and don't understand). There are two stages of preparing a scrub blade. The first is to grind the radius (the primary bevel). This is an huge task, one I would only ever do on a power grinder, such as a bench grinder or a belt sander. If you are planing to grind on your jig, then I think you are going to be disappointed. The second stage is to hone a sharpening bevel. The latter is done as a microbevel. Once the primary bevel is created, a jig is not really necessary for a microbevel. And if you plan to use a jig, the simpler the better - KIS.

I designed my jigs for others. I actually freehand my microbevel on my scrubs. The version based on the bolt is for those who do not have the LV Honing Guide. The upside-down Honing Guide works very well indeed. I really developed the idea as a challenge to use the LV Honing Guide for this task (since others had said it could not be done).

You said early on, "The thought of doing it freehand has me concerned about putting flat spots into the curve". You really do not need to be concerned about that. Firstly, a scrub plane ploughs a rough course through the timber surface and a few flat spots, if present, are not going to be evident. Secondly, a "wiping" motion during honing will minimize any flat spots on the bevel.

If a scrub plane were to use a bevel up blade, I would say that a honing guide would be essential. But for a bevel down blade the accuracy of the microbevel is unimportant. Anything close to 1-5 degrees is going to be fine.

Let us assume that you used my jig based on a round-head bolt (the upside-down LV Guide is much easier, if you have it). With the blade clamped in a platform at the top (ala the LV guide), what you will discover is that the blade will pivot on the round head and roll on the cambered bevel. The amount of honing required to create a microbevel is really minimal at this point. Really - about 8-10 strokes. Pull back a few time, then wipe. Remove the wire edge. The only advantage of this jig over freehand is that you maintain a consistence microbevel angle.

Regards from Perth

Derek