Shop made lapping plates

[EclecticNeophyte]

Some time back, I was inspired to make a set of (3) lapping blocks, using 6" diameter cast iron rounds purchased from McMaster-Carr. I first faced them off on the lathe, then cut grooves using my sliding miter saw and a diamond blade. Following that came hours and hours of lapping each of the three blocks (labeled A, B and C) against each other. I didn't reach total optical flatness, but the results were good enough to use for general purposes. I now have three lapping plates that I can re-cut and re-surface whenever needed, just by rubbing them together in the proper sequence.









It wasn't difficult, just a bit tedious with a lot of repetition during the lapping process.

-EN

[DIYer]

Thanks EclecticNeophyte! We've added your Lapping Plates to our Sharpening category,
as well as to your builder page: EclecticNeophyte's Homemade Tools. Your receipt:

Lapping Plates by EclecticNeophyte

tags: sharpening, plate

[tlnixon]

I have a antique small square lapping plate that was made to sharpen hair clipper blades.

[N4NV]

I made mine out of the same McMasterCarr drops as well:

Vince

[EclecticNeophyte]

Starting in the mid 1970's, my first real 'career' was as a factory trained diesel fuel injection repair tech. The shop owner had a square one about the same surface area as the 6" dia plates. We used it to lap internal sections as well as the nozzle tip, when rebuilding unit injectors for Detroit Diesel engines (which were two stroke in those days). Anything that required a metal to metal seal would be hand lapped on that little cast iron block. Muscle memory still allows me to do the figure eight pattern, without hesitation...I sometimes wondered if I did it in my sleep!

-EN

[satx]

Some time back, I was inspired to make a set of (3) lapping blocks, using 6" diameter cast iron rounds purchased from McMaster-Carr. I first faced them off on the lathe, then cut grooves using my sliding miter saw and a diamond blade. Following that came hours and hours of lapping each of the three blocks (labeled A, B and C) against each other. I didn't reach total optical flatness, but the results were good enough to use for general purposes. I now have three lapping plates that I can re-cut and re-surface whenever needed, just by rubbing them together in the proper sequence.


It wasn't difficult, just a bit tedious with a lot of repetition during the lapping process.

-EN

I saw youtube where the person lapped an iron flat against surface stone, using diamond grit powder

did you use any grit?

[EclecticNeophyte]

I saw youtube where the person lapped an iron flat against surface stone, using diamond grit powder

did you use any grit?

Sounds to me like the method used to flatten a granite surface plate, but yes I did (more than one actually). You can use common valve grinding compound to start, and then move to finer grits once the plates show good flatness. I think I started with Timesaver #111 (green can), then moved to finer grits from there. Tom Lipton has a good set of videos on YouTube. He's also the one who encouraged me to make a set. The idea of using a sliding miter saw to cut the grooves was my small contribution to the effort...

Hope this helps.

-EN

[Moldyjim]

I have a antique small square lapping plate that was made to sharpen hair clipper blades.

I have one too! It was a flea market find.
The seller had a bunch of new/old stock kits.
Mine is about 6" and round.
Came with a bottle of liquid lapping compound.
Works well for flattening small perts.

[Moldyjim]

Small PARTS!

[the harmonious blacksmith]

Generating a flat surface cast iron surface plate, actually three, is done in the same manner, marking one with another then hand scraping the high spots repeatedly until the high spots are all the same height as the lowest. Then parallels, angle plates and other shapes are hand scraped to the surface plate, generating shapes to use as marking standards to hand scrape machine tool ways for accuracy. Prussian blue is used on the marking tools or surface plates then rubbed against the part being scraped. Tolerances scraping the masters can be held to .0001 inches using this method. At some point even the extremely thin layer of the prussian blue is too thick and alcohol is wiped on and dried to a haze, the marking tool leaving tiny shiny spots to scrape. Hand scraping is quite an art, taking a long time to master but that is how all machine tools were made to such accuracy, even to creating the grinding machines used to grind the precision modern ground ways on machines made today.

I've done some of this over the decades but don't consider myself any sort of an expert at it. For one thing I don't have the patience.

Most all of my ancient lathes, mills, even a surface grinder, being 100 years old or more were hand scraped new and in rebuilds in later years. I took much of my early machinist training was in line shaft driven shops, even one small lathe I first learned on was originally powered with "velocipede pedals". I have no CNC experience and very little NC in earlier punched tape equipment.