[ardenum2]

Hi all - The three blocks are curing, I float a little water on them every day and so far its been absorbed quite easily. But that's slowing down now. We wait for at least two weeks I think, then release them and start lapping. I've prepped the test coupons moulds and may be able to cast them in the next couple of days... Next few days are really busy with other stuff. Peter

really looking forward to the three plate method results, have you got a granite plate to confirm the final results?

[peteeng]

Hi Ard - No reference plate, been looking for a scanner or a flatness checker for some time. Whitworth and others started with nothing, so I suppose I tread the same path... The water surface image prior I expect to be optically flat. So I want to use a PMMA resin to seal the surface. It should look like that when I finish. One of sikas videos describe the self levelling surface as mirror flat. I don't think so! So far anyway. I'm looking for some valve lapping grit that's not suspended in oil at the moment... Just want the grit...I may have to wash it....Peter

[joeavaerage]

Hi peteeng,

been looking for a scanner or a flatness checker for some time.

What you want is an Autocollimator. I have wanted one for a while. Credible second hand collimators range from $1000USD to $5000USD.
Despite being in different countries we could make a deal to share one....after all you're only going to use it every once in a while. If we found another two, three, four Kiwi/Aussie
enthusiasts we could get a highly versatile and usable instrument.

https://www.ebay.com/itm/20438923779...3ABFBMsMj-wbJi

https://www.ebay.com/itm/31468007669...Bk9SR7DI_sGyYg

https://www.ebay.com/itm/25569843093...3ABFBMssj-wbJi

Craig

[ardenum2]

Hi peteeng,



What you want is an Autocollimator. I have wanted one for a while. Credible second hand collimators range from $1000USD to $5000USD.
Despite being in different countries we could make a deal to share one....after all you're only going to use it every once in a while. If we found another two, three, four Kiwi/Aussie
enthusiasts we could get a highly versatile and usable instrument.

https://www.ebay.com/itm/20438923779...3ABFBMsMj-wbJi

https://www.ebay.com/itm/31468007669...Bk9SR7DI_sGyYg

https://www.ebay.com/itm/25569843093...3ABFBMssj-wbJi

Craig

fox lives somewhere in nz

https://www.youtube.com/@PiotrFoxWysocki/videos

christian in brisbane

https://www.youtube.com/@machsuper/videos

[joeavaerage]

Hi,
they are so remarkably simple and yet so accurate. Like any analog optical equipment it takes some skill to use and interpret but thereafter you can measure 'a pimple
on an ants dick at a mile' no trouble. You'll wonder why given it simplicity you didn't think of it yourself!

There use to be one at the University in the Mechanical Eng Lab, we used to go a grease up to the tech whom looked after it, and once we convinced him we weren't going break it
and promises of beer he'd let us use it. Old style oak box with all dovetails, polished to the max, brass hinges...brass clasps....you'd swear it was bomb aiming equipment from
a Lancaster bomber from WWII !!!. It was Hilger-Watts, identical to one that I linked to, but it had all the accessories.

The Nikon one sure looks the part, and the Japanese sure do make nice optics.

Craig

[peteeng]

Hi - Evening all - I released the laps today (or as the Yanks say demolded ) and although I don't have grit yet I started lapping with the self generated grist. Stonemasons and Egyptians have been doing this for centuries. I removed the meniscus with grit paper and also dressed the arrises. I use a HB pencil line for contrast and only rub in one direction., The aim is to get a consistent scratch across the two lapping surfaces then move onto the cross direction or another plate. I'll try to get some grit this week. Seems the middle is lower than the sides but they do float when a smear of water is used, so I think its close.

[peteeng]

Hi all - Been lapping a bit every day. AtoB. When they match its AtoC then CtoB then back to AtoB etc until nirvana is reached. Ommm.. Will be slow but progress will accelerate as the surfaces improve. B is better then A. Been looking for the original Whitworths paper he presented to the English academy. But the result shows it will make a flat surface good enough for my gantry laminations.... Peter

[peteeng]

Hi All - The lapping is going well. My pencil lines are disappearing and the edges of the valley contours are changing every 10mins so I know progress is happening. I also wash the B plate and use it as "blue" contrast to show what's happening on the A plate. The B plate cast is the one that's different. I did not mix B as long and when I poured the cast I found lots of stuff stuck in the bottom of the "square" container. Seems to be a bit gritter at the surface then the others. But its working. I'm tossing up what to seal these with when the time comes. I keep coming back to my favorite epoxy. Some years ago I was involved in a special shaft for a device that used a sprayed TIO2 coating. It was sealed with secret loctite type material so it was not porous. The company would not tell use what it was so we had to do many tests to figure that out. The best stuff was about $400AUD per 500ml !! but we finally found that loctite 290 was fine. We had to find this out because the company stopped doing the TiO2 coating that they had been doing for 15 years. We had tries with other coats but they were no good. The TiO2 provided indefinite shaft life. We found with the other coatings the lip seal was cutting off the shaft at 2000hrs not pretty... Our life target for the shaft was 10,000hrs. The shaft was 4140 heat treated to max hardness as well. Onwards. Peter

[peteeng]

Hi All - I was in town so bought some P120 wet and dry to see how that goes. My original idea was to w&d the laps until flat then finish with grit. That's why the laps are this size, they match the std w&d size. I didn't have any w&d when the laps were ready so started self grinding... and since it made progress I didn't bother. But the 120 grit removed material so much faster so now I'll get a graded batch of paper and go back to my original plan... wet cutting is good but then its hard to change the paper from one piece to another using contact spray.... Certainly is getting flatter and smoother... getting a bit of suction when pulling them apart dry. If wet they are stuck and have to be slid apart. If wet they do float for quite a while when brought together. Cross hatching gets removed easily so good progress. A couple of valleys in the middle to deal with then its onto cross cutting. My intent with these laps is to use them to create a "flat" laminating table to make gantries and other parts on.... Peter

[Mr-MaW]

Share a piece of my work, have you ever done horizontal machining centers? A base made of mineral castings.

[Mr-MaW]

Share a piece of my work, have you ever done horizontal machining centers? A base made of mineral castings.
CNC

[peteeng]

Hi - seems the images didn't attach - Peter

[peteeng]

cnczones gone bonkers again!!

[peteeng]

Hi All - I have been looking for SiC grit and have found that lapidary supplies have them in various grades. Common ones are 90-180-280-400-600 so I'll mail order some of those... Peter

[ardenum2]

Hi All - I have been looking for SiC grit and have found that lapidary supplies have them in various grades. Common ones are 90-180-280-400-600 so I'll mail order some of those... Peter

are you using lapping powder on those plates too or just pouring some water every now and then?

[peteeng]

Hi Ard- Initially I just did them dry with no grit. Concrete makes its own grit. Occasionally use some water to clean the surfaces and to establish flatness like using blue. The other day I used some P120 sheet and it moved the process along much quicker. But using sheet means they will not match perfectly so at some point I'll have to use grit. Not sure what grit plates are finished to. I think I'll go to P400... Maybe P280. P120 is very smooth to the touch. I'm also looking at surface checkers.. Peter

I'm still working on A-B plates. There's a couple of valleys/hollows to get to the bottom of before I consider A-B a match... then I can change to A-C...

[joeavaerage]

Hi peteeng,
there were some very good videos posted on Ytube by Stanford Granite where they did a blow by blow account of certifying granite surface plates including lapping.
For lapping or resurfacing granite they used cast iron laps, and they had three which were kept in a state of flatness according to the method of Whitworth.
Also showed the use of a Hilger-Watts Autocollimator and a Rhan......something or rather meter.

Craig

[peteeng]

Hi Craig - Typically a lap is made from something softer than what you are lapping, The grit is then charged to the lap. Being softer the grit is imbedded in the lap. The lap also can have grooves to hold the slurry. But in the case of two plates like granite I don't want grooves. So its a case of slowly slowly working the surfaces until flat. SiC grit breaks down as its used to smaller and smaller grit until it nearly disappears. Diamond grit does not break down. But you have to get the lap "flat" so you have to start somewhere. Maybe I program my router to push pull the lap!! The ??? meter is a repeatometer... basically its a dial gauge with mechanical amplification... I don't think the method is complex just keep at it until its flat... It must become flat at some point. Its an averaging technique. The surfaces will get flatter and flatter as you rotate the plates. Measuring the flatness is another story... If I get the plates to float I'll be happy... Peter

whitworths original notes

https://en.wikisource.org/wiki/Misce...or_True_Planes

The process can be summaries as 1) identify high spots and bring these down 2) if a metal plate the highs can be scarpped 3) if granite or stone or concrte use a coarse grit/paper until thge surface average is consistent 4) keep at ot until it floats

When I was fairing boats we did it both ways.1) we identified hollows and filled them with epoxy filler 2) then we scrapped that until the highs and lows averaged 3) then we contrasted the surface and did the whole thing again until the surface was a mirror...

[joeavaerage]

Hi,
this is not the one I was thinking about but.......

https://www.youtube.com/watch?v=VrodNx759oo

Maybe this one:

https://www.youtube.com/watch?v=EWqThb9Z1jk

Craig

[joeavaerage]

Hi,
the explanation given for the use of cast iron laps is that the grinding crystals tend to embed in cast iron and work better, but the cast iron itself is somewhat more resistant to wear,
ie would hold the flatness for longer before having to repeat the Whitworth process.

Craig