Mirror Making: DIY Spherometer Part 1, The Build
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- Опубліковано 28 сер 2024
- In Part 1, Gordon Waite shows how to build an inexpensive DIY spherometer. This instrument can be used by amateur mirror makers to accurately measure the radius of curvature and focal length when grinding a telescope mirror.
Saw your entire series. Many things made clear. Thanks.
Nice! Just what I was looking for! ❤
Grazie Gordon :) ...guardo sempre i tuoi video :)
Thanks! Glad you are enjoying the videos.
Very informative and very well explained I always wondered if this could be done. Love all your videos
Thanks! Hope you get the chance to try grinding your own.
This is great. I just built one of these using a 10" pulley off Amazon that looked ideal. Only problem was the opening was 3/4", McMaster no longer seems to have a suitable pulley with spokes. So I had to buy two spacers off McMaster, and one was 3-thousands too large. So I bought an ID lapping tool and lapped it to the right size and now everything fits! Thanks for the concept!
Glad to hear you are enjoying your project! You can get good pulleys from McMaster. Search for: pulleys zinc, spoked body. With a 1/2" hole, they run around $20 to $25 in the 6" to 7" range.
Brilliant!
What cap nuts work instead of ball bearing balls? The cap nuts just screw on.
What was the largest mirror that you ever had the pleasure of grinding?
The largest that gave me pleasure was a 25". All of them bigger than that weren't any fun at all. ;)
Yeah, I guess when a mirror requires a crane to carry it around it takes the fun out of it.
I really appreciate your videos. Did you build your grinding machine yourself? I have been looking for a plan to build one myself. Do you know of any plans available? I'm ordering the materials for the spherometer now. where do you buy you blanks? Thanks for any info.
Thanks! I did build all of our grinding machines, but we don't have plans available. Fixed-post machines are so simple, you can pretty much knock them together out of spare parts. You can buy glass blanks from glass fabricators like Swift Glass.
Hi i have dial gauge of 0.0001"-0.050" and i dont know how to take reading of it. I have done all the things what you haved show but i dont know how to take reading for spherometer. My dial gauge hase length of 1cm. Means in 1cm it take 5 round of scale on dial gauge. Plz tell me how to measure the dial guage
Can you give me a link to your gauge?
simple, *fantastic* ....
Sir what size of spherometer is required for a 12 inch mirror?
Smallest, maybe 4", 5" is better, 7" or 8" if you can swing it.
inspiring video.... but in the UK there are no such pulleys that I can find. An alternative is to use a 'diamond cutting disc' - very flat and stiff (used at 6000rpm, etc). Get one with the cutting teeth in multiples of 3, e.g. 12 teeth. Use bolts and BBs as usual in the circular holes. Fill the 7/8in center with a 'flanged bearing' to reduce to 3/8" =9.53mm. Now use a dial indicator with this thickness stem (ADG standard) or use a 10mm/8mm split bearing to get to 8mm inner diameter. Voila!
does a 5 in sphereomter works on a 12 in mirror?
+John Batchler Sure! In general, the bigger the better, but a good 5-inch is useful on a wide range of mirrors. I even use a 5-inch when I am grinding on a 25" mirror.
i tried makin mirrors but they broke
@rocketeer090
I've got the same problem as rocketeer090, any way you could supply us with the product number for that pulley?
you do not need specific pulley, you need 3 point contact - a metallic plate with holes in it may do as well
Inches? In this day & age? Baffling.
notthenutter Amazingly, the inch is just as accurate today as 100 years ago....
GordonWaite And just as much of a pain in the arse!
Inches are much easier for those whom spell ass correctly. And we still know how to convert. In fact, resolution of instruments has increased the definition of 'accuracy' of inches as well as mm's.
inches is fine, the precision does not depend on being inch or mm,you can measure things down to a millionth of an inch! (all my instruments are in inches, my brain works well in inches, it's those 1/32 1/64 1/128 ,that add to the confusion);
still,once in a while, there blows (literally!) another project (even at NASA!) , because inch and mm got mixed up ,or used to,before ;
mms are more logical,more intuitive,easier to use,really worth converting to.