The Benefits of Using square cast iron lapping plates

Kemet Lapping Plates are crafted using a uniform combination of synthetic resins, metal particles, and key bonding/hardening agents. These plates are specifically designed to complement Kemet's advanced lapping technology and are perfectly compatible with Kemet Liquid Diamond.

Link to Hengfeng

Utilizing Kemet Lapping Plates offers a range of advantages. Firstly, these plates securely hold diamond particles, ensuring efficient removal of material and consistently achieving a desired surface finish for components. Their ductile properties act as a cushion for the diamond particles, safeguarding the workpiece against any potential damage. Moreover, Kemet Lapping Plates are available in various hardness values, catering to even the most delicate materials. This versatility allows for safe and effective lapping with diamond particles without the risk of impregnation. Additionally, these plates offer easy control, facilitating optimal flatness during the lapping process.

Whether you use lapping or polishing techniques, Kemet provides plates that can accommodate lapping machines of all brands, with plate diameters reaching up to mm. The lapping plates are designed to dissipate heat and prevent the occurrence of laminar flow on the lapped surfaces, ensuring efficient cooling and consistent results. To maximize stability, Kemet Lapping Plates come supplied with a cast iron backing plate. This robust support enhances the overall performance and reliability of the lapping process. When precision flatness and superior surface finish are of utmost importance, Kemet Lapping Plates are highly recommended. Their exceptional quality and compatibility with Kemet Liquid Diamond make them an ideal choice for achieving outstanding results in applications requiring the highest level of accuracy and refinement.

If you are looking for more details, kindly visit square cast iron lapping plates.

Featured content:
Ground Anchor Innovations for 2025: What to Expect

Which Lapping Plate to use?

Iron Lapping Plates

Widely utilized for general-purpose stock removal and lapping operations.

Copper Lapping Plates

Employed for lapping softer materials, emphasizing fine lapping and polishing as the primary objectives.

Copper SP2 Lapping Plates

Suitable for lapping or polishing hard and medium hardness materials.

PR3 Lapping Plates

Utilized to achieve a highly reflective surface finish, ideal for pre-pad polishing to minimize roll-off.

XL Lapping Plates

Serve as a replacement for Lead/Tin plates, specifically used for mirror polishing purposes.

XP Lapping Plates

Enhance the production of flat and polished surfaces on various materials.

Tin Lapping Plates

Among the softest Kemet Plates, ideal for mirror polishing with fine grades of Kemet Liquid Diamond.

Ceramic Lapping Plates

One of the hardest Kemet Lapping Plates, commonly used for special applications that require a cleaner lapping process.

FP Plates

Serve as a substitute for the Kemet Lead/Tin Plate, offering efficient stock removal, high-quality surface finish, and flatness when used with Kemet Diamond Slurry.

Cast Iron Hand Lapping Plates

Hand Lapping Plates made of durable cast iron are ideal for laboratories, toolrooms, and maintenance workshops. They excel in achieving remarkable flatness for small quantities of parts. Crafted from premium, low porosity gray cast iron (Grade 300 to BS), these plates typically feature a square cross-hatched pattern for enhanced grip. Additionally, solid (unserrated) hand lapping plates are offered for delicate workpieces. When paired with abrasive grit, which is applied as a paste, these plates provide a consistently smooth matte finish on a diverse range of metallic and non-metallic materials. While three standard plate sizes are available, custom sizes can be requested.

Hand Lap Plate Disc Diameter 2” 3” 4” 6” 8” 10” 12” 15" 18” 20" 24” c/hatch Grooves  - - - Solid -

We offer a variety of sizes from 3” to 24” diameter (Other sizes available upon request).

Soft Metal Alloy Hand Polishing Plates

Hand polishing plates made of a malleable metal alloy are designed to be used alongside diamond abrasives, in either paste or spray form, to create polished finishes on various components. The plate consists of a white metal composition conforming to BS/F, primarily composed of lead, tin, and antimony, with small amounts of other metals. This specific alloy serves as an excellent matrix for diamond particles due to its softness. To facilitate the process of preparing the lap plate for polishing, a compact charging block is included to apply the diamond abrasive onto the soft metal surface. Two plate sizes are currently offered for selection.

Contact us to discuss your requirements of Cast Iron Straight Ruler. Our experienced sales team can help you identify the options that best suit your needs.

Diameter Finish Code 6” (150mm) Solid 12” (300mm) Solid

I'm trying to see how flat can I get a gauge block sized hardened steel part (o1 - hrc ~56) while maintaining flatness with hand lapping. I'm after some advice on this.

I have a number of mild steel serrated (and smooth) lapping plates that are flat to 0.5 micron across their size (100mm/4in).

My first try wasn't that encouraging. I used wet lapping with Sic and semi-dry with diamond. I'm after some technique tips as well as when to use wet(free abrasive) vs dry(fixed abrasive, but with liquid lubricant). There is plenty of materials that explain the difference between both processes, but I haven't found any info when to prefer which? Also, when to use serrated and when smooth laps? Likewise with the abrasive choice. Sic or diamond? (we're only talking about hardened steel workpiece and mild steel laps - no cast iron is available to me in sane prices).

The blocks were not ground to a great finish to start with so I used 50 micron silicon carbide (240 grit) first to take out grinding marks. This was in a form of a very small amount of paste. Some light oil was added on the lap to lubricate.

Once done I then used 14~9 micron (500~800 grit) SiC paste in kerosene which resulted in a really nice matt grey finish.

Then I used 3 micron diamond. I pressed it into the lap with a hardened steel block before use,but I haven't cleaned the lap after so there may have been some free diamonds rolling around. (I'll try to embeds it properly with a steel roller next time)

I finished with 1 micron diamond. The finish was nice, but not quite mirror finish. Still it was reflective enough to use an optical flat to check the surface.

Unfortunately my block wasn't flat, but was convex with 2 micron difference between the peak and sides.... So I lapped it at least twice worse than it started with... I already have some ideas where I might have screwed up (too much abrasive, too much pressure when lapping, not cleaning free diamonds ). Also I removed a total of 7 micron (about 3 tenths)? Is this too much to expect it to remain flat within half a micron? The next try will be with much better grind so I can start with 3 micron diamond, but I thought to ask for any tips and advice on the above (when to use dry/wet, which lap, which abrasive, how much material is reasonable to remove and remain flat etc).

I've done a lot of searching on the subject, I read what the machinery handbook has to say as well as the Whitworth book. But some questions still remain.

You've got to get the amount of grit or paste right or you will have flatness issues. Too much will basically float the part. Better too little than too much.

I'll try a lot less.

I like grooved plates because they help to mitigate that problem, giving the excess somewhere to go. Also, watch your speed. Moving too fast will start to float the part too. I like to run drier, with less grit (if lapping with loose grit) and with slower movement when I'm really shooting for best flatness.

I felt this floating/hydroplaning when trying the figure of 8 movement . I don't normally do figure of 8 movement. I'm doing the movement shown in one of Tom Lipton's videos on lapping. This is a series of small circles while trying to cover entire surface of the lap and rotating the part /switching hands every short while.

You've also got to watch the geometry of the part at the very beginning. If you have a convex surface to begin with, it can b very difficult to get it to flatten out. I like to start with a flat to slightly concave surface. If I don't have that, I create it by selectively lapping a small hollow in the middle of the part to get a stable contact with the lap.

The second time I reground the blocks much more carefully. I've switched off the mag chuck for the last pass hoping it would "unspring" the parts, but I didn't dare clear residual magnetism (my mag chuck has a switch that gives it some AC which demagnetises it almost completely). I was afraid coolant pressure will lift the parts off the chuck and they'll crash into the wheel... So it is entirely possible the parts are very slightly convex when leaving the grinder. I'm not sure if residual magnetism is enough to spring a 9mm thick, about an inch long and 3/4ths wide block of hardened o1 by a micron or two. I know I can't pull the parts off the chuck with no power unless I press the clear button.

So I'll have to measure the parts better before lapping. It is not easy to measure fractions of a micron using contact methods and at that time the parts are not reflective enough for optical flat method.

This time I tried the hardened steel roller and pressing the diamonds in as well as stripping them from the lap afterwards (with a single edge razor-like blade, and a flat stone) just to see the difference.

However, the second attempt ended very similar to the first(slightly better):

I've yet to implement your advice.

How I achieved Ra 0. microns (0.02 microinch)

Hi there! I've made a video about how I achieved a surface roughness of 0. microns - in my attempt to win the Zeiss #measuringhero award for the smoothest surface. Here's the link to the video: https://youtu.be/6YsMfFBQmJM

This is really impressive :-)

Speaking solely for myself, when hand lapping I generally do straight lines or small circles while moving in a straight line. Dependent on how much lapping is needed. Pressure always as close to the center of the part as possible. Sometimes I stick a small piece of double sided tape on the part to keep my finger in the right spot and give a little more grip. Occasionally I will attach a weight to the part to help keep the pressure even.

Thank you, this is very helpful. I did see an improvement when I started putting my finger on the center of the part. I can't decide yet if figure 8, straight lines or small circles are better for me, I'm trying all of them at different times. However, I'd prefer not to wear my laps in the middle so figure 8s are probably the least favorable.

About cast iron (multiple posts mention it, so I haven't quoted a specific one). Can anyone say what are actual advantages on using cast iron in manual lapping plates for hardened steel? I have read the same old text ls where they say: "steel works fine, cast iron is best", but they don't actually say why... With my limited experience I can only think (other than more even/predictable bahavior during changing temperatures) about cast iron being better because it's harder to "ding" it. Having a number of them I've already dinged my mild steel laps a few times. Every time I had to stone the dings with the precision ground flat stone, then lap it a little to ensure it doesn't protrude even a little bit. It can really annoy you, having to do that when you're trying to get a part done.

Anyway, I've found a supplier locally that will sell me grey cast iron disks at a price of about 7eur per kilo(that's tool steel prices around here BTW). I might order a few 4in ones in future just to see for myself the difference.

We lap precision parts on a 6" disk of Durabar about an inch thick. Diamond paste is rolled in with a dowel pin and aluminum bar. Way better than diamond lapping film in terms of flatness- we also use a lot of that.

I like that method (rolling in the abrasive into the lap with a roller). I use a cheap ball bearing (roughly 1.5'' OD, half inch wide) with a piece of stainless tube for a handle. It is important to clean all the loose abrasive afterwards to only leave stuff embedded in the lap. This works not just with diamond, but with silicon carbide paste (probably alox too). It can be used dry for a bit too.

I like this method, because it makes the plate wear a lot less and the type of finish is different. (as mentioned before free abrasive vs embedded). Free abrasive results most often in matt finish, embedded is shiny, mirror like.

You know cast iron lapping plates (for lapping machines) are hardened? Mehanite is it called if I remember correctly. It is significantly harder than untreated cast iron.

I didn't know. It is interesting. I might make my own little bench top lapping machine similar to what Stahli makes.

I was reading this thread... and was amazed to see my own video about Ra 0. micron roughness here. I feel flattered!

Lapping is easy... when you know what to do. It's like learning to play a musical instrument. There just aren't many corners to cut. It takes ages.

The picture of your last attempt is impressive: half a lightband! That is 150 nanometers for the non-lapping-humans.

Thank you :-) I've since managed to get it a tiny bit better. It is still near a quarter light band, but rather than a dome-like shape it is flatter in the middle which mattered to me.

Lapping machines have conditioning rings to keep the lapping plate flat during lapping. With handlapping you don't have that. When you're lapping, you remove material from the part AND the plate. Removal of the plate goes faster when it doesn't have the mehanite hardness. So you might get unflat areas in your plate if you lap in one place.

That's on my mind all the time when lapping :-) but with the abrasive embedded in the lap this is less of a problem.

For lapping I use diamond emulsion - no suspension or paste. That usually is on epoxy lapping plates. For the mehanite plates I use lapping oil with ceramic powder. The oil is rather thin.

I would be very interested in seeing some sort of a chart (if it exists) what oil viscosity with which abrasive grain size. However this information is very hard to come by. Most lapping oil manufacturers don't even publicise their viscosity numbers (maybe they tell their customers, but not the public). One that does listed one if their oils as iso 4. This is very thin indeed.

The best flatness is achieved by proper lapping. I'd skip the abrisive film. :-)

Definitely :-)

But there is one thing that helped me tremendously. In one of unrelated Robin Renzetti's videos(about sandpaper "lapping" on an old surface plate) he mentioned "you can't get flat parts on concave lapping plate, but you can on convex plate so it's better to wear your plates convex". Two of my laps were very slightly concave. When I changed them to slightly convex (about half a micron) I got much better results. It is also possible I've had more practice by then which contributed, but anyone making their own laps I'd definitely say to have your plates slightly convex rather than concave.