#1  
Old 10-04-2020, 11:06 AM
mura_gadi's Avatar
mura_gadi (Steve)
SpeakingB4Thinking

mura_gadi is offline
 
Join Date: Apr 2019
Location: Canberra
Posts: 829
Grits for the Grind

Hello,

I have been looking at grits and have either a lapidary store (cheap starter packs) or a more commercial supplier in Sydney (a lot more variety of grits on offer).

What grades of grits do I need to step through the mirror making processes. I would prefer to spend longer at each level of polishing, over buying a lot of various grits.

For the final polish I was going the cerium oxide, is it worth the extra money over tin or the aluminium oxides?

Any suggestions for good suppliers to work with, or the brands that supply well graded grit compounds etc would be welcome.

Thanks
Steve
Ps. I'm working at F6 FL's, so I am hoping this will make my 1st project a lot easier.
Reply With Quote
  #2  
Old 11-04-2020, 08:17 AM
Rod
Registered User

Rod is offline
 
Join Date: Sep 2006
Location: Mount Martha
Posts: 369
Hi Steve

If you want to use the minimum number of grit stages then make sure you read Mel Bartel's guide to mirror making. That's the way he works:

https://www.bbastrodesigns.com/JoyOf...ing/Intro.html

I would also suggest you read through the stellafane site. Here is a link to their section on grit:

https://stellafane.org/tm/atm/mirror-refs/grit.html

I purchased my grit from gotgrit.com

You use silicone carbide for the first 2 to 3 grades of grinding then switch to aluminium oxide if you can. It's smoother and quieter to work with.

Cerium oxide is used throughout the polishing and figuring process. Some people use rouge for the final stages but that's not essential.

You will also need some pitch or aculap to make a polishing lap.

Hope that helps,

Rod.
Reply With Quote
  #3  
Old 12-04-2020, 03:24 AM
mura_gadi's Avatar
mura_gadi (Steve)
SpeakingB4Thinking

mura_gadi is offline
 
Join Date: Apr 2019
Location: Canberra
Posts: 829
Thanks for the reply, I have been reading the "The joy of.." and watching the John Dob videos. I am trying to read/watch all I can to find one guide I think I can follow from beginning to end.

The Stellafane suggestion that the coarseness starting levels depends on the size of mirror was a great tip I hadn't seen or read before though.

Waiting on smaller thin blanks to start practicing each of the stages with, I'm sure it will all make more sense when I'm covered in sparkle dust...
Reply With Quote
  #4  
Old 12-04-2020, 10:57 AM
sopticals's Avatar
sopticals (Stephen)
Registered User

sopticals is offline
 
Join Date: Jun 2010
Location: Oamaru, New Zealand.
Posts: 226
Grit progressions

Hi, I've just finished grinding a 33"f3.55 mirror (all without the use of any machinery). Grit progression I used: (All Sic) #36,(hogging),#60,#120,#220,#400,#8 00 (22"glass tile tool).Now ready to polish using Cerium Oxide.

For small mirrors (up to 8-10") I have used #80,#220,#400#800 grits only.
For Medium size (12-16") #60,#120,#220,#400,#800 is OK.

No need to obsess overly on how close/wide the grades are.

Stephen.
Reply With Quote
  #5  
Old 13-04-2020, 12:12 PM
dave brock's Avatar
dave brock
Registered User

dave brock is offline
 
Join Date: Dec 2011
Location: hamilton nz
Posts: 82
Quote:
Originally Posted by mura_gadi View Post
Hello,

I would prefer to spend longer at each level of polishing, over buying a lot of various grits.
If you don't get the grind fine enough you might change your mind on that after hours of polishing.

Dave
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 06:54 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement