The 20 " grind has begun

[Rustysplit]

Looking fantastic Rick. Have you made up your pitch lap yet?

[JRM]

Thanks Alan,

no pitch lap yet but will probably pour it this week some time, I took a couple more pics of the surface after the 5 micron grind though.

and this one

 I did another 3 wets today, 6 trips around the barrel, not that it needed it, dont ask why I would take the chance of scratching the

surface but I did them just to make myself feel like I did more then enough wets with final grit size.

you can almost read the paper through the glass after 5 micron, looking real good..

The itch to polish has begun..till then.

Rick M

[JRM]

Just wanted to update...

   I made a total mess when pouring my 16 base for the pitch lap, mixed enough hydrostone to

make a 2 1/2" thick 16" base but everything went wrong and I lost more then half the pour onto

the floor, with no more hydro stone to attempt a pour again it appears im done with grind and will

not be polishing tell later this year when things warm up, will give me time to fix me up a pitch lap
tool, so until May my trips around the barrel are at a stand still... but I will be around for any question

anyone may have about the grind and such... thanks

Rick M

[Rustysplit]

Sorry to hear that Rick. How frustrating for you. On the plus side, I think the polishing will go better with a higher ambient temperature anyhow. The pitch should remain more responsive without having to do hot water baths all the time. Does this give you some time to work on the actual scope it is going in? Or is this all sorted?

[teleskopjo]

do you have a chip there on the edge? ouch! (

[JRM]

Thanks Alan,

 no plans for the scope as of yet, but yes the warmer weather should make for better

polishing and pressing.

teleskopjo, there is an area about the size of half a Canadian dime that I ground down

and smoothed somewhat but this chip barely makes it inside the bevel of the glass,

I debated wether or not to flip the whole thing over and grind the mirror from other side,

then decided not too as it is only a cosmetic issue, if I were looking for perfection I would

save lots of money and buy a ZOC mirror, believe me as much as I would love to own

one I could never afford such a treasure.but one can dream for sure, Thanks

Rick M

[JRM]

Hi All,

 Time to get back in the saddle as they say, over the last couple day I have redone the top of my work station with a 1/2 inch layer of

plywood cut to 36" round, and far from being a perfect circle to boot.

its all painted, made new blocks for securing the glass to the table and have new clothes under the glass.

Today I cleaned the tile tool and secured 25 polishing pads to its surface then placed it back ontop the glass to help

secure them even more.

I am currently being the mad scientist and instead of buying it, I am destilling the water for my polishing mix, its a slow process.

Hope to polish for a couple hours tomorrow, if everything goes okay the pads should put a real good dent in the polish time, if

not, no problem, I will be pouring a pitch lap next week either way.

Will let you know how it goes tomorrow.

Rick M

[mapstar]

Nice work there Rick.

I have today moved onto the 400 grit  (17 micron)  for my blank which is looking good. Had a few problems and also have a cosmetic chip in the side too. I'm taking my grind to be given the once over by John Nichol today who has given advice and encouragement throughout the process. Now first light is getting closer it all seems worth it. 80 hours work up to now and probably another 40 hours to complete? 

Keep up the good work and thanks for the read

Damian

[JRM]

Thanks Damian, you are well on your way as well, please keep me posted on your progress.

Today I polished for 50 minutes with the pads,easy enough to work up a sweet doing this, more labour intensive then I expected, and to think this is only pads, pitch

lap should be a real treat.

Even after only 50 minutes it is easy to see the difference on the surface, if it keeps going this way it should only take a couple more hours to polish out,as it stands the

surface is polished more in the center and you can still see the haze in the outer 4 inches or so as is to be expected, will make stokes longer during next session.

and yes the pads are on the fullsize tool.

Here are three pics to show the changes from when I began to end of 5 micron and to now after 50 minutes on the pads.

This is at 220...

this one is 5 mic

and this is after 50 minutes with polishing pads

Quite the difference and you can notice the light reflection is hazy.

thats it for now, have a good day all.

Rick M

[JRM]

Just to update,

Tuesday evening I polished again with pads for 1 hour and 10 minutes polishing time, bringing total polsh time to

2 hours with the pads and things are looking great. This time I did a W stroke instead of just C.O.C. to work the outer area more.

There is still some haze in the outer 2 inches but hope to have that gone this evening. I am going to try to get 2 hours of polishing

in this evening and then will clean and check the polish to see if more is required, but if I am correct I do believe it will be finished

(poilshed out) by then.. It is a sweat inducing process even with the pads and my work area stands at 64 degrees F .

so far I have used 2 of the 6 ounces mixes, each containing 3 rounded teaspoons of ceo mixed with water to the 6 ounce mark. 

thicker then I would use it for pitch but it is working good, I also have a spray bottle with distilled water incase it gets dry but mostly

just add more mix and continue, its pretty much non stop polishing.

I took a pic of the tool with the pads on it and will post that this evening for those who want to see.

all for now, take care...

Rick M

[crashtestdummy]

Nice skills,looks good.I'm going to be starting off again with 400g next week after I move my mirror to the new house.maybe another hour to get all the 220 pits out th n waiting for some 600, pitch and cerium oxide then the polishing begins.

[JRM]

Thanks Crash, I have been keeping up on your blog, your doing great, keep er coming.

Here is a pic of the tile tool with pads on it...

I did a total of 2 more hours polishing over last two days, 1 hour 20 min, Wed and 40 min thur.

It gets hard on the arms after an hour non stop polishing,can not wait to push the pitch lap....

I underestimated how log it will take to polish out to the edge of the glass, one has to remember

the further you get out from center the more surface area you are trying to polish, but it looks

real good after 4 hours, not much more to finish polishing out, more is better then less when it 

comes to being polished out, I will not stop till I am absolutely positive it is polish out completely.

another round tonight.cheers...

Rick M

[mapstar]

Thanks Crash, I have been keeping up on your blog, your doing great, keep er coming.

Here is a pic of the tile tool with pads on it...

Mirror 029.jpg

I did a total of 2 more hours polishing over last two days, 1 hour 20 min, Wed and 40 min thur.

It gets hard on the arms after an hour non stop polishing,can not wait to push the pitch lap....

I underestimated how log it will take to polish out to the edge of the glass, one has to remember

the further you get out from center the more surface area you are trying to polish, but it looks

real good after 4 hours, not much more to finish polishing out, more is better then less when it

comes to being polished out, I will not stop till I am absolutely positive it is polish out completely.

another round tonight.cheers...

Rick M

Hi Rick

I have today done another hour with the 400grit and (as I have been doing) used an inverted eye piece to check for pits.

Happy to say its nearly time for the 600grit which myself and crash (Rich) will be acquiring next week along with some pitch and cerium oxide for the polishing and figuring.

How are you going to be testing whilst doing the figuring Rick?

[Rustysplit]

Coming along nicely now Rick, really nice job. What are the polishing pads you are using? I have read about using them to polish out, but never really known what they are. Where do you get them from?

[JRM]

Hi Damian,

  sounds good, you and Rich  are hard at it, keep up the hard work, its worth it. I plan to test with a foucault tester and ronchi, but my most important test

will be the star test, once I get a secondary I can make a rig to test, might even try the artifical star test but need to read up on it more.

I am not after perfection just higher quality i guess.

Alan,

   The pads are used by the eye glass company I think, to polish surfaces that do not need a perfect figure and can therefor be polished fast,I purchased them

from gotgrit in the U.S.A, they are not expensive, a roll of 50 for $16.50 U.S. but the shipping can be a killer, you should be able to get some over your way,should

not be to hard to find, they are about 2.5 inches in size. I put 25 on the tile tool. trust me, they will not give you a nice finish, you may have hills and even zones

if you dont change stoke up when using them, but they sure polish fast and it should not take long to get surface smooth and to a sphere once you do make and

start using a pitch lap.

I did two polishing sessions today, the first was 30 minutes and the second was 50 minutes for a total of 6 hours thus far. I see no hase at all now and will have to get

a laser light to check surface better, I will be taking a leave from working on the mirror for the next two weeks or so, will be tears of joy this week and tears of sorrow the

next,somewhere in between all this I will build a better test platform for the work ahead.  I plan to pour the pitch lap in early July but I will check in here when I get the chance.

till then, take care...

[crashtestdummy]

Well after nearly a month off I'm back into the grind.Did a quick half hour with 400g today after cleaning everything from the trip down to avoid any contamination.600g soon then that pitch lap is getting close!!

[JRM]

Welcome back to the grind Rich, you are coming along just fine.

I went down and did a laser test today and as I thought the outer 5" at the least shows thelaser on the surface, so remember that old saying, when you think its polished out it likely in not, polish more and then polish some more. I will make a pitch lap when I get back at it, pads have done well but I do not want to use them when they have been left to dry out for so long.

Rich and Damian, get a laser pointer if you do not already have one, it will help to avoid the haze,till then...

Rick M

[crashtestdummy]

Im going to be using my hotech laser collimator

[mapstar]

A couple of hours with 600grit today and unfortunately a scratch.

Have more pits to remove so will persevere tomorrow with more grinding and at least when the scratch is ground out I know the pits will be.

[JRM]

Okay, I am back, after a leave of absence and a few days without power due to a storm named Arthur.

I sure hope that scratch came out without issue Damian,

during my timeout I did peel the pads from the lap and wash it down to get all the ceo off the surface and ou of the grooves between the tiles,and

yes I will be using the tile tool to make a fullsize pitch laptp polish with,should be a real workout but will give it a try, hopefully the pour goes down tomorrow

but wednesday at the latest,tell then...

Rick M

[JRM]

Hi All,

   This afternoon I prepared my tile tool for the pitch,placing two strips of heavy duty ali foil ower the surface and used duct tape to make the dam, I melted the pitch

in a pot on top the kitchen stove well my daughter complained of the smell. I droped two ounces or so of beeswax in and turned the burner to its lowest setting, 2kg

of pitch plus the beeswax was stirred every now and then but more and more often as the pitch melted to help keep the heating even, it took one hour and forty

minutes to completly melt all the pitch and after mixing for a minute or so to insure the wax was well blended I poured the pitch onto the aluminum foil covered

mirror to be waited just a minute before placing the tile tool on top,after about maybe 20 minutes I slowly pulled the duct tape dam away, insuring the pitch was stiff

enough before hauling it all off,then I removed the lap from the top of the mirror, a couple hours later I pulled the aluminum foil off the pitch and made a guide for

channeling with 1-1/2 inch wide painters tape,will start channeling tomorrow, see how it goes, for sure it will be messy but hopefully everything will go okay and I will be

polishing with a fullsize 20 inch pitch lap tomorrow, only time will tell, will take some pics tomorrow as well. till then..

Rick M

[crashtestdummy]

Hope you have better luck first time than I did fella.learned a lot of valuable lessons though so hopefully the next try will be much better.

[mapstar]

Following with interest Rick

I've finally ground out with 600alu oxide today after what has been quite a troublesome affair!

So I'm ready for the pitch lap and cerium oxide which I hope goes easier.

Good luck and looking forward to the photo's

Damian

[JRM]

every lap we make is an experience Rich, we hope to get better and really over time we do, but my goodness it is a tedious time consuming, messy as heck type of work channeling a 20 inch pitch lap, did I say it was messy believe me it is. back aching too, I got an hour and a bit into  the channeling today and only have six done so far, put on old clothe and latex gloves or the likes, even old shoes because pitch sticks to everything, how did I ever forget how messy this stuff really is,if ever I have to make a lap this big or any size for that matter I am going to make a new base and do the cut squares and attach, might be a better idea but it would still have some issues.

Damian, glad to hear you finished grinding out, its all a learning experience and sometimes a struggle but it help us with future mirrors if we can remember, best to keep a journal or such and by the way... making a large pitch lap is a test of your patience, determination and nerves and it can drive you right batty at times,I made a few 10 inch pitch laps before but this large lap is a monster in comparison, not liking it at all..

A photo to show you the meesy work..

once all these channels are cleared out I will run tape in other direction to finish making the squares, can not wait to get through the channeling process and put that all behind me, tomorrow I hope, till then...

Rick M

[JRM]

Channel cutting is done, I never want to do it that way ever again, some 6 hours of slow tedious work over 4 days, its not pretty but it's done, a couple photos...

and

it is rough looking but it will press out just fine,hopeful to start pressing tomorrow,with luck.

Rick