Seeking practical advice for scratch stocks

[Scott H]

I'm trying to get better at using scratch stocks so I thought I would ask for some advice. The two major uses I am interested in are making small molding pieces and defining/repairing the soles of molding planes.* I built a stock that looks basically like these woodsmith plans and I have made a few cutters out of cut up card scrapers. The cutters I am basically sharpening like you would a standard card scraper, with a square edge and burrs on both sides.

The first problem I tend to have is the profile ends up nearly full depth in the center of the workpiece, along the long axis, but it's shallow on the near and far end, so you sort of get a dished look. I suspect this is mostly a technique thing, about where you start strokes and in what direction and where do you stop etc. -- if anyone wants to share the technique they use that would be very helpful.

The second problem is that the cutter doesn't establish a full depth profile because it stops cutting at some point, usually like at 90% of depth. I don't think it's just from the cutter getting dull; I think this is a cutting geometry thing but I am not sure what the 'right' way to fix it is. I believe the core issue I'm seeing is that, since it's prepared like a card scraper, if the cutter is not pitched at an angle so that the burr engages, it won't cut any deeper. But you have no choice to reach full depth than to have the cutter at 90 degrees to the work at the end, since I'm (currently) making them as exact negatives of the molding profile. It seems to hang up particularly on the "horizontal" parts of circular profiles (like the top of the circle part of a bead.) You could maybe fix this by adjusting the shape of the cutter to an angled projection of the desired profile, like molding irons are, and using it always at a pitch, but there's no way to precisely control the pitch angle on a scratch stock to begin with, so you could end up cutting deeper than intended. I feel like I am missing something fundamental here. Should I be using a different sort of bevel or burr?

If anyone has any thoughts I would appreciate it. I am sure I could spend more time experimenting but I don't have as much time to dedicate to that at the moment as I'd like.

* I am aware that there is a scratch stock jig Bill Anderson recommends for molding plane soles, and I believe @creasman may have built one? I have the plan somewhere, and I'm aware Bill recommends thicker, high hardness cutters, but I feel like step one is getting good looking moldings, before I move on to something more advanced.

 

[jlimey]

In my experience you do not need a burr on a scratch stock cutter. Try just stoning the faces flat and see how many of your problems are solved.

 

[jlimey]

In my experience you do not need a burr on a scratch stock cutter. Try just stoning the faces flat and see how many of your problems are solved.

 

[creasman]

I'm familiar with the one Bill Anderson uses in his classes. The ones I made are slightly different and are from ShopNotes.

These work well, but I plan to make one like Bill's at some point. For plane soles I believe his might be more ergonomic to use.

You'll notice the bar of the ShopNotes ones is rounded. This allows you to pivot the stock while using to get the best cutting angle. That feature is nice if you're cutting a design. However, for plane soles I don't find this to be helpful. I've taken to filing the cutters straight across without adding a burr. This means they cut well in one direction (i.e., towards the burr left by the file) and not so much the other direction.

To ensure an even sole work all the way across. You can tilt the stock slightly on the first passes, but I try to end with the cutter as vertical as possible as the material is removed. The key is a consistent angle so you don't hollow it out in the middle as you describe. I check with a straight edge and work the cut more on the ends if that is happening. It helps to have a plane vise like the one I have in the resources section. This allows you to raise the plane body as you continue to cut rather than adjust the cutter tilt.

I make most of my cutters from sections of an old hand saw blade. I have a few that were made from a grill spatula. Your use of card scrapers should work just as well. At one of the plane making classes I took, the instructor used sections of a wide bandsaw blade.

 

[Scott H]

I finally got back to messing with this again this weekend. I think am getting better results.

The main things I changed were:

• No burr - just 90 degree edges, all stoned.
• Cleaned up the scratch stock's reference surfaces. @pop-pop showed me a picture of his scratch stock, and I sent a picture of my stock, and in the process I realized that mine had a bit of a flat on the horizontal beam part that would probably have made it "rock" a lot just as the profile was bottoming out and the cutter was becoming vertical. @pop-pop also very kindly offered to let me borrow his scratch stock to compare further which I have not taken him up on yet.
• Technique - Really focus on getting the ends of the profile worked down to a lower depth than the middle part first, trying to keep it so I was always going downhill off the ends.

It is still tricky for me to get the very ends down to depth because, at least with this stock, you start running out of reference surfaces to bear against your workpiece as you go off the ends. I still definitely got some chatter and chowdered up the rabbets near the ends due to the cutter accidentally rubbing against them. There's also not a lot of vertical bearing surface on this profile the way I did it.

The profile I tried this time is a replacement window grid part for my mom's house that went missing during painting & cleaning. I did this one with hand tools. I will admit that I originally thought I was being obstinate because I could probably find a router bit to do this profile, but once I started measuring it, the round part is actually not a quarter circle. (You would think it would be a 1/4" radius quarter circle in a 1/4"x1/4" area, but it's actually a 5/16" radius in a 1/4"x1/4" area.) So it's probably actually more accurate in the end since that seems like it'd be a weird bit to find.

Holding the profile was the hard part. Probably would have been easier if I just did the profiles along the edge of a larger board and then ripped off the molding, but without a table saw I wasn't confident I could actually plane it flat after hand ripping, with the shape of the profile being what it is.

I also used fences on the work for guiding the rabbets to remove most of the waste. I have not gotten the hang of dropping a rabbet plane into a marking gauge line like Matt Bickford recommends, at least not four times in one profile, especially with how narrow & deep two of them were.

 

[Scott H]

@creasman I also finally looked at the plans for the plane vise -- I didn't realize it had depth adjustment screws, and also looks like it lets you essentially use a bench vise for the compression so you don't have to fiddle with clamps as you raise and lower it? Interesting idea. I think that solves all of the issues I was worried about with scraping a plane sole.

Do you have a ballpark estimate of how much you raise the plane between passes of the scraper?

 

[creasman]

I also finally looked at the plans for the plane vise -- I didn't realize it had depth adjustment screws, and also looks like it lets you essentially use a bench vise for the compression so you don't have to fiddle with clamps as you raise and lower it? Interesting idea. I think that solves all of the issues I was worried about with scraping a plane sole.

Do you have a ballpark estimate of how much you raise the plane between passes of the scraper?

You're correct about the design. It has adjustment screws and I made it so it fits into a standard face vise -- for the reasons you state. I don't recall the thread size I used on the adjustment screws. They are probably 18 - 28 TPI, depending on the size of stove bolt I used. I typically turn each screw about 1/4 turn, scrape until it mostly stops cutting and then raise it another quarter of turn. I have a mark on each screw head so I know where it's currently set and keep the two in sync. The design has worked surprisingly well.

 

[Scott H]

That makes sense. If I'm doing the math right that gives a cut depth of 0.009-0.014" which is a manageable number of passes on typical hollows/rounds. Even on a 1" wide hollow/round that only requires worst case ~15 passes starting from a blank, flat bottom.

 

[creasman]

Typically for a plane sole I first rough out the shape with other planes. It's a lot faster that way, rather than doing the full profile with a scraper.

 

[mpeele]

I have been using Garrett Hacks technique for years. He uses spring steel but I use worn out ban saw mill blade stock. I've made maybe a dozen or more over the years.

Make Your Own Scratch Stocks - FineWoodworking

In this article Garrett Hack demonstrates how to make your own scratch stocks. The two he uses most are for beading an edge and excavating for string inlay.

www.finewoodworking.com

 

[Ricksmi]

I been using the Garrett Hacks technique for years as well and old band saw blade stock, one band saw blade will make enough scratch stock cutters for years to come.