Advice for lapping the back of new chisels
Hi all,
I have a new set of Narex Richter chisels which I am going to sharpen for the first time using a scary sharp system (float glass and lapping film).
I’ve never sharpened a chisel before and want to make sure I’m doing it correctly.
I’ve gathered advice from reading and watching YouTube videos, but am wondering if anyone has any further advice to what I have found.
I think there are three main points.
1) How do you know when the back of the chisel is perfectly flat?
From watching videos by Rob Cosman, Matt Estlea and others, it seems that after each lapping stage the back of the chisel should have a uniform appearance, with the scratches reaching the very tip.
Anything else to look for to help ascertain flatness?
I’m assuming as you move to finer grits you would simply be looking for an even shine as the scratches would not be visible?
2) What grit range to use?
Advice in Collins Complete Woodworking and Rob Cosman’s chisel preparation video suggests starting with 1000 grit. Rob then goes to 6,000, and then 16,000 grit.
I’ve seen other videos starting at a lower grit. Would this make the process quicker?
I’ve also seen other videos end at a lower grit (8,000 often). Is 16,000 necessary?
Would a greater range of grits between the starting and finishing one make for less time at each grit? I can probably only use 4 grits on my float glass plate given the lapping technique involves being side-on to the stone (1 sheet of lapping film at each side on the front and back).
3) lapping technique
The most common technique I’ve seen is positioning the chisel at a 45 degree angle to the stone (to prevent it rolling over) and then moving back and fourth.
In Rob Cosman’s video, as he’s moving the chisel back and fourth he also moves it inwards and then back outwards again (to prevent a ridge forming in the chisel from staying in one place).
Anything else to note for flattening technique generally, or when flattening any spots on the chisel back that are not level with the rest?
Thanks for any advice. Want to be well prepared in my understanding before starting this.
Replies
Those are very nice chisels, I doubt you will ever regret buying them. I have a set and they are comfortable to use and keep a very good edge. I did need to put some work into getting the backs flat, but they came fairly flat. One easy way to check for flatness is to either draw a grid on the back of the chisel (or using a fattie magic marker just pain the whole thing) and start with a fairly high grit. You will abrade the high spots first. If they are very out of flat, you may have to step down to a coarser grit. The courser the grit, the faster the cut, but then you have deeper scratches to get out by using successively higher grits, so you need to find the right compromise between spending a lot of time flattening and spending a lot of time trying to get the scratches out. You will know you are done when the back of the chisel is polished. You can experiment with technique, there is no one perfect way to do it, but the examples you gave above are a good starting point. Just be patient and get it right the first time. You only have to flatten the back once, and it's time well spent. The longer I have done woodworking, the more I have learned to enjoy the process, rather than being in a rush to get it finished. Of course, as an amateur, I have that luxury!
Thanks very much. The idea of drawing a grid or using a magic marker on over the whole of the back seems like a clever way of checking for flatness.
Thanks as well for the information on the high spots being abraded first - that makes very obvious sense nice to know beforehand.
It's also helpful to know that I have to find a compromise between time spent flatting and time spent getting scratches out when it comes to choosing starting grits.
Yes, I'm going to spend an evening or two on the set I think. Just take my time and do it properly!
Cheers!
It would be rare to get a chisel or a plane blade that was perfectly flat. The higher cost planes and chisels, like from Lee Valley or Nielsen's would likely be flat. I don't know about Narex. The Narex I bought weren't.
Whatever grit you sharpen to, you then need to go to that grit each time to remove the burr in the end. Therefore, I have only bought stones to sharpen to 8,000 (Shapton Glass Stones which might not be exactly the same as other 8,000 stone.). I think 8,000 is sufficient anyway.
If you use more grits in between, I would guess that your time on each grit would be less, but likely not significantly.
The most important issue in flattening and sharpening is that your sharpening stones or glass to which you attach your sandpaper is completely flat. Otherwise no amount of flattening will do the job.
The only way I've ever determined flatness of the back is by sight. The scratch pattern needs to look uniform. As you go up in grits, it will become a little easier because it is more polished and it's easier to see the scratches if any exist.
Yeah, I'll be applying the film very carefully to the glass to ensure its as flat as I can get it. Float glass is supposed to be a very flat surface and good for sharpening.
Thanks, will be checking carefully for a uniform scratch pattern before moving on from each grit.
Cosman teaches a 25 degree primary bevel. Once you have the primary bevel then you do a secondary bevel. You just lift it a few degrees more than you did for primary bevel. The key is to check that the secondary bevel goes to each end and is the same width across.
The reason for the secondary bevel is you don’t have to sharpen the primary bevel each time you sharpen. You just feel for the primary, lift a few degrees more and sharpen the secondary for 32 seconds.
Stumpy Nubs (James Hamilton) advocates using 3M Cubitron II sanding disks plus other 3M disks . His YouTube video looks pretty impressive. Their claim to fame is they cut very fast and last a long time.
I got mine from:
https://taytools.com/products/3m-775l-cubitron-ii-stickit-5-psa-sanding-discs?variant=32066568781911
I got the 6" continuous grit
This page also have 600 and 1000 aluminum oxide disks.
You can verify the flatness by examining the reflection of the back once you are done with 1000 grit. Look for any waviness in the reflection, especially at the edges of the back
First advice is don't over think this. You will melt many brain cells watching too many YouTube videos and will get many "experts" claiming their method is the best.
Think about what you are try to accomplish, get a flat surface on the back of a piece of metal. To accomplish this you simply need to keep the back of the chisel flat to an abrasive surface that is flat. What most new woodworker don't understand is the the entire back of the chisel doesn't need to be perfectly flat. Focus on the first ½" nearest the cutting edge and the edges. If you have achieved uniform scratch marks in theses areas low spots in the center of the blade don't matter. That does bring up the type of issues that you can encounter. Hopefully if your chisels are not flat they are low in the center not the edges. If the edges are flat and the tip is flat that is all you need, but if the edges are low and you are only getting scratch marks in the center you have your work cut out for you. High spots in the center of the blade can keep your chisel from properly registering in a jig, rocking slightly side to side, making it all but impossible to get a good edge. You do mention "flattening any spots on the chisel back that are not level with the rest" this is not the proper way to think of the process. You can't focus on particular spots you must evenly grind the back down until there are no spots. If you start trying to apply pressure to particular spots you will create problems.
As for technique, I believe in keeping all my scratches perpendicular to the cutting edge having read a detailed and scientific article on what makes a great cutting edge many years ago. Scratches parallel to the cutting edge tend to be weaker and more prone to premature wear so avoid them never use a motion that moves parallel to the edge. I will hold a finger parallel to the edge underneath the chisel about 3" back from the edge to act as a stop. I then push the chisel in and out while sliding along the entire long edge of my stone/plate. I move laterally simply to insure even wear of my abrasive. This motion does tend to leave angular scratches but that doesn't matter early in the process but once I am satisfied that the back is flat and I'm ready to move to a finer grit I will take a half dozen or so strokes without moving laterally to insure all my scratches are perpendicular to the cutting edge. Never change grits until you are totally satisfied with the surface. If you are frustrated with removing an imperfection it will only be more difficult at a finer grit, if anything go back to a coarser grit until you have the results you want.
I your case with the Richters I would start with the equivalent of a 1000 grit to get a feel for how flat the back is, the Richters I bought my son were pretty impressive and needed very little work, if the the backs are flat a few strokes on the 1000 grit then move onto 4000 and optionally 8000. If they are uneven step back to your coarsest grit until the backs are acceptable then go back to the 1000 and so on.
I have attached 2 pics, the first shows a chisel with high spots in the center and is unacceptable the second shows a chisel back that is perfectly fine and even though it is low in the center the cutting edge and side edges are all flat.
Hey,
Your advice not to over think this is good. Looking forward to spending time on it tonight.
Thanks for the guidance on the important parts of the chisel to flatten and the attached photograph illustrating this - that's really helpful information.
Thanks also for the correction on the idea I had of trying to focus lapping on 'problem spots', and how doing so would actually create problems.
The description of your technique is really clear, as is the rationale behind it. I'll go with that to start off.
Thanks for the grit suggestions for the new Richters. I have micron grades that are close, so will position them on the four side edges of my float glass.
Ready to start tonight now.
Could I ask how you clean your lapping film after each use?
Just a water rinse is all I do. My current shop doesn't have running water, the reason I switched to the films in the first place, I just spray them my spray bottle a time or two and wipe with a paper towel. Unlike waterstones the 3M films don't create a slurry so they are much less messy.
Perfect - thanks very much.
Yes, photo #2 is essentially the same as most Japanese chisels, slightly hollow ground on the back to make honing easier. You are only removing material around the front and edges. Of course, over time as you shorten the chisel with many sharpening (and grinding if you use a grinder), your edge will reach the hollow and you will need to re-address the back. I completely agree with your technique of starting with about 1000 grit for a good chisel and assess how flat it is. If you have a lot of work to do, then move down a few grits. Otherwise, you can quickly move up in grit until you are polishing the back. I also agree with the comment above about not watching too many videos. Once you have the basics down, just start doing it. Practice makes perfect (well, maybe not perfect, but good enough!) Good luck, and have fun.
Go look up WoodByWright YouTube videos. He's probably done a review on these. If I had to guess, you could probably use them as is for quite some time as you build up skill.
I would just add to my previous . . . I use diamond stones for the coarser grits. Since they are given in microns/mesh I don't know the exact grits, but something like 220, 400, 800, 1200. For the final finer honing I have Shapton Glass Stones of 2000, 3000, 4000, 8000 (although I may skip one of those). The 8000 does a great job and I really don't fell I need to go above that.
The other suggestion I have is to be sure to use a honing guide, especially during your learning process. I found that a good honing guide takes the guesswork out of sharpening and avoids any rounding over or uneven sharpening. I'm sure some will say to just do it without the guide, but my results are much more consistent with a honing guide.
Started lapping two of my chisels for the first time and wondering if I could get judgement on what work there is to be done. Would bring confidence to continue if my (brand new to this) judgements were on the right lines.
You can only see a portion of the chisel well because of the lighting.
Scratches have touched all of this part (similar picture futher up), so no big dips anyway.
The first inch after the cutting edge. This is quite flat, although perhaps a little dip on the top right of the chisel where it appears somewhat darker?
The centre of the chisel. This has a bit of a dip, though this would not be an issue if it didn't extend as far to the sides, and a little more of edge sides were uniform with the tip?
I think I should go to a low grit and grind till at least the first half inch after the cutting edge is uniform, and the dip in the centre doesn't extend as far to the edge.
Without knowing how much effort it took to get to this point it's hard to say for sure but trust your instincts if you feel the result you want requires stepping down a grit do it, you won't do any harm and when you come back to this grit it will be only to remove the coarse scratches and will be relatively easy and quick. That goes for both chisels you have shown.
Thank you - I only spent a couple of minutes on the chisel pictured in this post. After seeing the scratch pattern with apparant dips I stopped to consider whether it needed more serious grinding.
Ill give it a shot.
Hmmmmm.
If you want the back of the chisel to be dead flat up to the cutting edge (for serious paring purposes where the flat back jigs the edge to exactly the same height at what the chisel is resting on) you need to flatten the *whole* of the back, as the whole of the back is likely to get used to so-jig the edge. If you only flatten the half of the back that you seem to be working on, you're unlikely to end up with a wholly-flat chisel back suitable for ultra-precise paring.
True paring chisels are very long for a reason. With them, you would flatten the back from the edge only as far down the chisel length as you would use for resting on something to jig that sharp edge to the same plane as the "something". Bench chisels are not ideal paring chisels because they're relatively short.
Of course, the work surfaces you're going to jig them on might all be short too - but that's unlikely, the more work pieces you make.
This is the reason why some of us use the ruler trick on bench chisels. You only need flatten (but not polish) a short section of the back next to the edge because you'll be using that chisel largely un-jigged: to chop, dig, slice and even pare small or short pieces; or pieces where the paring can be relatively imprecise.
If you sharpen your bench chisels (or some of them) for this less-precise-than-paring work you needn't make all the back dead flat up to the edge. You can flatten and polish the back next the edge for about 2cm, only more roughly flattening any serious distortions further along the back. You then put an absolutely minimal ruler-trick micro-bevel on the back side of the edge.
This is far, far less work than having to make the whole chisel back dead flat and polished.
But you still have to do that full flattening and polishing (to a degree) of the whole back for any chisel that's going to be used for "proper"paring with precision. I'd advise getting some true paring chisels for that (200 - 250mm long with a 20 degree primary bevel, only ever used with low force by hand).
https://workshopheaven.com/narex-8132-paring-chisel-natural/
PS, As the Workshop Heaven blurb mentions, manufacturers usually apply a lot more attention to making the backs of paring chisels dead flat out of the box than they do with bench chisels.
I think this one has more work to do as there appears to be quite a large dip behind the first inch or so from the cutting edge, which extends down the chisel before scratches I made resume.
This needs ground down till at least the first half inch from the cutting edge and the edges of the chisel arounds the dip all have uniform scratches?
Thanks guys. If I know I am judging reasonably well with these two, it would give me confidence to continue to go through the process.
Hi all,
I have spent over an hour on my 1 inch chisel. This has included about 20 minutes on 100 micron film (about 170 grit equivalent.
I'm wondering if I could get thoughts on whether I need to go back to the 100 micron to flatten the chisel. The scratch pattern appeared uniform after 20 minutes at 100 micron, however, after moving to finer grits, there is a cloudier patch in the middle of the chisel, and at tip there is a patch of the same colour (obscured by light in the photo).
Although it may be hard for you guys to see, I'm assuming such a marking pattern might suggest that the tip and this patch further down are slightly lower than the shinier portion of the chisel?
If this were the case case, should I go back to the course 100 micron grit? Everything did look uniform at this level before. Alternatively I could go to something quite course like 40 microns and see if I can get a uniform pattern at this level? (I wonder if the deeper scratches somehow obscured a slight dip).
P.s for some reason the photo made the tip look really squint - its not actually like that.
So many things can go wrong. When attempting to get a perfectly flat back, the object you are lapping it on needs to be perfectly flat. If it's off, the chisel will be off. But on that grit, it looks right.
Then you go on another grit, and that may be off in a different way. Now the lapping marks have a conflicting pattern. Go to another grit -- anyway, it can be like chasing your tail. Add in differences in technique, and it's a huge pain in the butt.
I apologize for not giving a helpful shortcut to getting your backs flat. But this process can be a ton more work than it seems it should. I've put a lot of hours into doing it. But I never will bother again. It's just not worth the time and trouble. I'd much prefer buying a premium chisel and avoiding the hassle.
Also, remember -- not much in life needs to be perfect.
I'm sorry for not being more helpful.
I am going to dive in with a very controversial statement - the back of the chisel does not have to be perfectly flat.
I know. About half of you died and the other half are reaching for your keyboards but hold with me for a second.
Yes, you need to be more or less flat. Flat enough to be a reference surface, but we are not talking machinist perfect here.
It does not even need to be shiny (shock, horror...)
What does matter is that the bit at the edge is perfect. That's the only bit that matters.
You can actually use the ruler trick on chisels and they work perfectly. I have tried it and you do in fact get a shaving sharp edge, and you'd be unable to tell the difference. The tiny uplift is sufficiently small as not to affect the performance of the tool, but it does allow a perfect mating edge that is dead easy to polish.
Since I have previously been through the flatten the whole thing pain, most of mine are in fact mirrors, but it's not actually essential so if you have a stubborn corner and are losing the will to live, don't be afraid to use a very thin ruler to lift the chisel and put a tiny tiny back bevel on.
You will of course spend all of eternity in purgatory, and none of your woodworking friends will talk to you, but you will have a sharp tool and be back to work faster than you can say sacrilege.
I use the ruler trick on my everyday chisels. It adds a bevel that is a couple of thousandths wide. It doesn't affect the function, not even a tiny bit. Well, I should say it doesn't negatively affect the function. It does positively affect it by quickly and easily give you a super sharp chisel.
It's worth having a look at vids from two of the interweberator's online WW titans, Stumpy Nubs and Rob Cosman, regarding the prep of chisel backs.
Mr Nubs advocates use of the ruler trick back bevel whilst Mr Cosman insists that a fully flattened and polished (to 16,000 grit!) chisel back is necessary.
Both make cogent arguments for their beliefs; and they make demos of chisels cutting various things to underpin their theories.
First link is to the Stumpy Nubs vid and the next to the Cosman vid.
https://www.youtube.com/watch?v=30cB6L_6OiY
https://www.youtube.com/watch?v=uB_sveNY08A
Personally I find the Nubsy arguments & demo more convincing, not least because I sharpen many of my chisels with a teeny back bevel and find that they do indeed make them highly usable but without the immense effort of flattening & polishing a large area of steel - especially to 16,000 grit.
If one considers the geometry of using a chisel back to jig on a workpiece surface so as to trim that surface by a chisel-shaving you realise that, in practice, you must lift even a fully-flat-backed chisel ever so slightly to get it to bite. Cosman states this need as one requiring the chiseller to "put pressure on the front of the chisel".
If the chisel back is being jigged on an already flat workpiece so as to cut down a raised part in front of the chisel blade, the one or two thou height of a back-bevelled chisel edge above the reference surface is not going to prevent the chisel biting; and may still bring down the protrusion to a condition where you can't even feel the one or two thou bit still sticking up.
Nevertheless, I still like to have wholly flat back paring chisels for that co-planar chiselling down of protrusions. For example, taking a dowel end down to be co-planar with the flat surface it was sticking up from seems best done with a truly flat-back paring chisel. Even a couple of thou of dowel-end raised above a very smooth surface can be felt with the finger tips. On the other hand, so what? :-)
I have not been able to measure the size of the back-bevel. It would not be as thick as paper, so under I guess 0.003". I lack instrumentation sufficiently sensitive!
I consider Christopher Schwarz and expert on a lot of hand woodworking subjects, but one he excels at is sharpening. He does have a very inexpensive book out entitled "Sharpen This" published by Lost Art Press. You might check this out. It's inexpensive. If you go to the Lost Art Press website, there is a synopsis of the book with Table of Contents. It covers the basics which is a good way to work through your own method of sharpening which you can perfect.
Also, I would suggest seriously thinking whether using the ruler trick, as some have suggested, is for you or not. Once you do use it on a chisel, going back to flattening the entire back is a laborious process. Plus, it only works on chisels. You cannot do this with a plane blade. I used the ruler trick on a chisel as a test a long time ago. I wasn't satisfied with the results. From that point forward, I just bit the bullet and flattened at least an inch of the whole back; sometimes much more, depending on my energy level at the time and how flat the chisel back is to begin with.
While I too am no fan of backbevels, especially on chisels, for several reasons, I will point out that if you try one you do not need to reflatten the back to remove it. A back bevel can be removed either by simply honing the secondary bevel until it is removed or worst case regrinding the primary bevel followed by a new secondary bevel.
Yes. Grinding a tiny bit off the bevel will remove the teensy back bevel. I can get rid of it with 4 or 5 strokes on the primary bevel on a 4,000 grit stone.
It's a really really tiny back bevel.
When I first got interested in woodworking I found Cosman and then McLaughlin. I just stick with them and no one else. I thought I might be pushing it trying to follow 2 people but McLaughlin builds period furniture which is my art. Learn the basics from one and follow your art with another. I learn faster that way.
The many first class craftsman who produce how-tos of all sorts for us are certainly a good - perhaps the best - source of WW information. But I wouldn't dream of confining myself to just two of them; or to following whatever they say unquestioning of the content.
Eventually you learn mostly (and continuously) from your own experience. The various experts (those genuinely expert, not the many often dangerous loons) in the mass media can provide a very, very good start and accelerate one's learning process. But no one is infallible.
There's also, I'm sorry to say, the factor of commercial interests involved. For example, Mr Cosman has relationships with all sorts of manufacturers, which he always makes explicit when doing tool tests or techniques, even for the historical-but-ceased relationships. Nevertheless, as he himself is at pains to point out, this can influence his preferences or even prejudices (his word).
There is no single right way to do all sorts of woodworking things. There are alternatives with various differences but the same objective. Woodworking isn't a religion with a bible and some dogma; or if it is a religion for some of us, it does best as a very broad church. :-)
Well, I’d think the hobbyist would have enough sense that once the basics are learned, one could seek alternative methods that suit the experience that one had acquired over that time. I mean if for no other reason out of boredom. But while one is learning I don’t want to have to muddle through endless content or alternatives. Do apprentices work with multiple masters? I don’t know, maybe they do!
Every single forum I visit says the same thing about Cosman. He’s no different from anyone else. I can learn everything I need about the basics without spending a single dollar on him. That’s what shopping’s for. But I will out of appreciation.
Anyway I'm close to retirement so I don’t have much time. I want to learn as efficiently as possible.
I can't imagine changing from what I'm doing to sharpen right now; improving some of the tools I use to sharpen maybe but not the concept/process. Once you are comfortable with a method and get great results, staying with it and getting even better would be the goal. As you use the method more you get faster and who doesn't want to get done with sharpening faster to get back to work? I personally feel that I'm confident in my method and have the sharpest tools I have ever had. No point in messing with a successful thing.
Learn the basics from one of the experts. It really doesn't matter who as long as it's a woodworker who has a reputation for knowing about sharpening. Then develop your own version of that and perfect it. Then stick with it.
Gr,
Yes. If there were like buttons I’d give you one.
Not a fan of overdoing it on chisels. I use an oilstone with cutting oil to do the back. I grind the fronts on the wheel, which gives a nice hollow ground. Then I put a secondary bevel on the front on the oilstone. This can be done with little effort and renewed for a very long time.
Unless your chisels are way out of flat on the back, all you really want is a surface flat within a thousandth or so to register against the wood for paring or chopping to the line. Wood is no flatter than that, in most cases, so why does your chisel need to be? You can get that easily on an oilstone. I happen to use a figure 8 motion (and I do it every time I sharpen the front), for maybe a half a dozen laps. I do use a leather strop to quickly hone both sides. That's enough to remove the burr without dulling.
Never bothered with the ruler trick, either. I get decent results and have tried this with a variety of chisels, from Narex to Stanley to Two Cherries and Lie Nielsen and Blue Spruce.
Sorry to hear that it is taking so long to get the back as flat as you would like. One of the things I have done is to take 80 grit sandpaper and attach it to the back of a board that has been planed flat. It is on the order of 4ish feet long. It does a quick job of flattening things because of the coarse grit and the long length that you can make each stroke. I've done this on vintage chisels. I've also got a piece of some sort of stone or tile that goes where the doorway meets the floor that was really flat and have used that to flatten vintage chisels. The "stone" like synthetic was like $20 or less.
Like a few others have said, unless needing dead flat for paring, you are likely fine with the work you have done.