crashtestdummy

I am going to go back to my original 2" overhang stroke instead of the 1/3 through centre as I didn't get scratches doing the initial stroke and still had good contact and even polish

Yeah I did the cold press for 15 mins with a cerium wash.when I do my second mirror I will make no mistakes :)

Have polished for 4 1/2 hours now and a few more fine scratches are evident now probably just because it's easier to see them now.I can't get them to show up in photos so obviously they are pretty fine.spoke to John Nichol who saidits hard to get it perfect so going to keep polishing for now then have him look when we test it at the mirror making seminar in two weeks.if they are too big I will go back to 600.I have loads of time so its no buggy I just want to make sure it will coat ok

Did a 15min wet press today which went much better so will do that in future if needed :)

The scratch is shallow enough that my finger nail won't pick it up but after doing an hour today I'm not 100% sure it's lessened or not but will have a look in the light tomorrow.

The scratches won't effect performance or the coatings but I will know they are there!!

Tbh the contact on my lap is good enough that I don't need to press.I'm using a sub diameter lap and all the squares aredull so won't bother pressing anymore.

Daniel no I didn't think of that tbh :(

Had a look today and have two scratches.will polish tomorrow and check to see if the scratches are lessening and then decide if I need to go back to 600.or not.

You live you learn :)

Yeah I didn't fancy pushing a 10kg+ plaster tool.

I think the scratch was from not cleaning the lap off properly.bit of a rookie mistake really :(

Have some more grit so will do an hour with 400 this arvo :)

The scratch was just a little too much to polishing out so used some of my old 600 which put a bigger scratch hence the back to 400.lessons learned :)

From what I be been told,machine polishing is slower than hand polishing but I've got plenty of time so if it takes longer then it's no big deal.I have 2kg of gugolz pitch winging it's way to me :)

yeah I definitely think those W strokes have probably been causing the scratches as ive only had that one sleek in 4hours of 600.We keep forgetting that we are still grinding novices and we are still learning all the time.Im glad im making my mistakes on this small mirror so when I do a big one it will be right :D :D :D

The plan is to take it to john for final checking before it goes to be coated plus im in email contact with john if I get to a point im not sure about.I wouldnt have got anywhere near where I am now without John and also damian who is doing the other 22" grind.its been great to swap ideas and techniques.the figuring is the bit im not confidnt about. Tbh anyone with patience could get to where I am now.

Yeah would have been nice to see the tour winding through the dales :)

Yeah its really hard to avoid little bits of tool coming off, not a problem when you are doing 60, 80 or 220 grit but disaserous on the finer grits.maybe its those new tiles as mine dont flake as much now they are thinner.im really really carefull putting the tool on now and I only lift it off every half hour, I just keep topping thw grit up every few minutes

Im considering resin coating the back of my tile tool to stop the risk of bits of cement falling off it qnd for better grip when lowering the tool on to the blank.

Another update monday hopefully

Rented accomodation so unfortunately modificatiom is unpermitted.if I could I would concrete the grinding table into the floor for stability.

You will love the feathertouch and SIPS system,it oozes quality!!can't wait to see pictures of the nexus system.it's probably something I would never go for but I like the way the encoders work :)

Thanks for your comment.part of the reason I decided to do the grinding blog was due to the mass of sites giving conflicting information on how to grind and what to use at each stage so hopefully this will be a little less confusing as I run through it stage by stage.obviously it's still my views and how I've been shown :)

My mirror has pretty much settled at F3.5 from my initial 3.6 aim.I did 10 minutes tonight with 400grit and the pencil test shows great contact so I think it's getting there well now.It's amazing how smooth the grinding strokes get with finer grits and how much much more the tile tool sticks.the pitch lap is you goibg ti take some pushing around!!

Not a clue,I can only estimate.I've done nearly 73 hours so far but I could knock 10-15 off that if I did another.I have 400 and 600 to go with a couple of hours of each,then say 2 hours to make a pitch lap and then maybe 10 hours of polishing so that's another 16-20 hours before testing then the hard bit, figuring.this could take 40 or 50 hours,you just don't know.I would hope I'm over half way by now but if I'm not then it will just take a bit longer :)

I may be out of grit by the time you get back fella as I've used way more getting down to 10mm than I thought.I'm going to order some 600 grit so if you Wed any more grit I will tag it onto my order if you want to split the postage :)

thinking about it I think I will end up redoing my bevel to 3-4mm then spending further time with a 2" overlap to see if the pencil test improves.i can afford to lose a bit of edge thickness to about F3.8 if necessary to have a better shape for figuring as time spent getting it right now will be much more time saved at the figuring stage.should get some wisdom in the next day or two and will update the progress

The sharpie test only test for good contact between tile tool and blank but I've had to make my sagitta shallower so it changes the way you grind so contact is different.

I will know how close it is to a sphere tomorrow when I have it checked and then just 1mm to grind to get back to sagitta then it's polishing and figuring.

See Damian I told you to stop being a drama queen!!;) really glad it's salvaged good and you ha e your mojo back.will be starting to look for some pitch next week

A lot of wasted grit but it is my first grind.I think by the time I'm back to sagitta I may be beyond a sphere so still plenty of work to do but yeah,I'm getting there :)

Nah it's not too hard at the moment I just want to make it sound harder than it is ;)

Yeah I've been told the polishing stage could be a two man job but I'm sure I will man up to it :)

Yeah you still use grit.I'm continuing using the 60 I have left but ideally 80 would probably be better as its a bit less harsh.when I get the tool ground in well and the pencil test is well done I will switch to 220 grit until all the 60 pits are gone then 400 and polishing before testing it with the ronchii :) then paraboidalising/figuring.still lots of work left!!

yeah the diamond tool was a god send!!!!!yeah as discussed in my text,seems as though I did the same,too much overhang to start with but will rectify it when I do my next hour.

The curve on the cement tool is cast on the mirror itself thats why it's the same.I spent some time smoothing the first coat of resin on the tool so it was free of imperfections and then the same with the tiles.