Lapping options

[John Crawford]

Hi Folks:

I know lapping has been covered in many threads (and I have read them!). I'm getting information overload.... I'm looking to move away from sandpaper, and was hoping to be able to lap (1) plane blades and chisels (old ones, not A2), and (2) occasionally lap my oilstones.

So, my questions are:

Is there something I could use for both of these tasks?

And could you recommend your preferred option? I'm leaning simply toward the glass / silicone carbide, but wonder if you would steer me in another direction.

Thanks for your help!

[bridger berdel]

loose grit sc works really well, and is cheap. glass is good if it's thick enough, or if it's on another nice flat surface. scraps of granite countertop or granite tiles are also good options. whatever you use, pick something you can get for cheap because it gets worn out of flat pretty quickly. biggest downside is it's messy. i usually do it outdoors and just hose the mess off into a plant watering basin.

diamond grit is marginally faster cutting, but the higher cost makes me use it slower and be unuasy about just hosing it away. sc works just fine, better than a diamond wetstone for lapping, better than sandpaper. best option, imho.

[John Crawford]

Thanks Bridger! For my purposes it sounds like this is probably the way to go. Good advice about the quick wear on the plate, and doing it outside.

Is there a grit you have found works better for tools like chisels?

[Jim Matthews]

If the substrate is harder than the compound, how much dishing really takes place?
Our local monument maker can regrind to flat for a six-pack.

I see reasonably priced steel plates available from LV - would those work as dedicated surfaces for finer grinds?


If you're concerned about the expense of replacing a raw substrate - would a large ceramic tile be sufficiently flat?

[bridger berdel]

i have 3 grits of SC. i think 90, 320 and 600. silicon carbide is harder than granite by quite a bit- it bites right into it. having your lap surface harder than your abrasive is suboptimal, and in the case of SC pretty much means a solid diamond lapping plate, which I can't find in any of my tool catalogs. start at the grit appropriate to the flatness of your thing and work up. if you know a guy with a monument lap great. i don't, so I use cheap disposable surfaces. I have never found a ceramic tile flat enough, but granite 12 x 12 often are. if in doubt bring along a straight edge and check it.

[Jim Matthews]

So you get a fresh piece of granite 12 x 12 when you feel it has a dish?

Is that an expensive proposition?
Can the same be done with MDF, or is that just too much yield in the material?

[Georg Zudoff]

Hi Jonh,
I use for this purpose (lapping olg blades) a binding cover used for paper spring binding over a glass sheet (10 mm) and SC of different grits. You can use this method for oil stones flattening too. For waterstones with fine grit (over 1000) I use Shapton plate (thank you to Jim Matthews) but for coarser ones - 200 and 400 grits - binding covers with SC are matcheless.
Main reason - you can use one glass plate or granite plate and different covers for different SC grits. And you can throw away worn cover - they are much cheaper than even glass plates.

Regards from Ukraine,
Georg.

Some additional info - here in Ukraine the cheapest granite plate can be obtained from companies who make tombstones.
But "flat" for tombstone is not 'flat' for woodworkers. Here you need check all these polished granite pieces with line gauge of high accuracy and one from the 20-30 is 'enough' flat.

[bridger berdel]

mostly i use the sc to flatten whetstones, then use those to flatten my chisels. if the chisels need more work than i want to try to do with the stones alone i rough them in with an approximately 2" diameter pneumatic angle grinder. not very neander, but it works for me