Page 1 of 3 - Alternates To Dental Stone as Binding Agent For Grinding Tools ? - posted in ATM, Optics and DIY Forum: Im just gathering up materials for grinding my first mirror. Of course being a skin flint, I love to save money. Being lazy also predisposes me to convenience. I notice the gang uses dental stone, seemingly …
Difficulty getting good contact (rough grind) - posted in ATM, Optics and DIY Forum: Hi all,Im currently finishing rough grinding of my 6 f11.5 mirror. Im using 80 grit.The pencil test seems to consistently show poor contact towards the outside edge of the mirror-- lines gone at the center, gradually getting darker towards the edge.Ive tried …
steel grinding tools ? - posted in ATM, Optics and DIY Forum: Hi All,Im thinking about making my own 8 mirror, and Ive been told professional optics is often made with cast-iron grinding tools.For another hobby Ive built a cnc-mill which could be used to cut the required convex shape + grooves into a steel tool. The cutting tolerance is around …
Rough Grinding to Fine Grinding... When? - posted in ATM, Optics and DIY Forum: At what point do people typically stop hogging out the mirror with the larger grit and move on to finer? Im using 80 grit on my 6 mirror and am at approx fl = 41in(f6.8), and Im aiming for fl = 36in(f6). Ive read that some people choose to overshoot during the rough …
Mirror-o-Matic and fixed position tool grinding - posted in ATM, Optics and DIY Forum: I plan on using a Mirror-o-Matic type grinding machine soon. The fixed position technique Mark Cowan uses is one I’m very interested in. Mark has spoken about this to me and on this forum, as recently as today in the thread “Grinding my 18 f/6†. To …
You can do what many people do (myself as well) just extend each grind beyond what is required simply to plane down to the previous grit size. Subsurface damage is a widely unrecognized source of micro-roughness, and there's always a hydration layer that penetrates down any microfractures left over from each grit.
Could this be fixed by grinding? - posted in ATM, Optics and DIY Forum: Hello: Ive long wanted to grind my own mirror. Seen the 10 f/7 mirror from this add with the fracture on the back. Wondering if this could be removed by flat grinding? Is it worth the effort? Is there someone with grinding machine that would be willing to fix this problem …
Rough grinding procedure - posted in ATM, Optics and DIY Forum: Hi everyone! I started working on a 7.3 Pyrex glass with an identical glass tool and in the …
Help ! rough grinding 16" mirror - posted in ATM, Optics and DIY Forum: Hello, Grinding a 16 blank, plate glass....I am currently 5/8 - 3/4 from the outside edge using a ring tool (7.5 lb. barbell plate, by hand) around a 55 gallon drum. I would like to get 1/4, or 1/8 from the edge, if possible. ...
Page 2 of 3 - Types of grinding/polishing machines - posted in ATM, Optics and DIY Forum: Here is a pic of my spindle grinder on which I am currently rough gring a 90mm objective lens, the spindle …
Hello all, I'm fascinated by those who can grind and figure their own mirrors for reflecting telpes. With the availability of kits to finish beautiful ATM dobs from …
Page 1 of 2 - rough grinding trouble - posted in ATM, Optics and DIY Forum: Im working on a 10" blank. Its dark tinted glass but is well annealed, plate glass, 1" thick. You can refer to my hogging thread for additional pics and info if you like. Im using a method I found online which that person was successful. I hogged the mirror out by hand …
Rough Grinding Edges - posted in ATM, Optics and DIY Forum: I am trying to correct a deep sagitta on a 6 blank, and have hit a snag. At first, things were going in the right direction, and I was able to bring it from 0.076 down to where it is now at 0.057. After ten wets with #80 grit this morning, my sagitta is still at 0.057 with no change.
ATM Forum Message. Forums: ... Is there any rough rule of thumb aboout how grinding time changes with mirror size (assuming all other variables are kept fixed)? Follow Ups: Grinding time - bobmay - November 15, 2002 - 06:17 UTC. Thanks Bob - a follow up question - billw123 - November 22, 2002 - 01:38 UTC.
ATM Journal: Rough Grinding By Gordon Tulloch, RASC Winnipeg Now that we have a grinding tool, we can proceed to rough grind, the first step of which is commonly …
Rough grinding. This step is about making one side of the glass concave. It will give your mirror its overall focal ratio. If you make the centre deep, you will end up with a fast telpe (e.g. F/D = 4) well suited for deep …
Rough Grinding. Unless the mirror comes pre-generated, the initial curve will have to be ground into the mirror. A ring tool of half the diameter of the mirror used on top of the mirror's flat face with the coarsest grit will …
can tile tool work for fine grinding?? - posted in ATM, Optics and DIY Forum: Hi, I know plaster and tile tool work well for rough grinding and hogging, can we use the tool until last fine grinding like 320# SiC? because tile was made by sands, but 320# will be very tiny powder, it seems that sands from tile will scratch the mirror. Could you mirror …
But for a smaller mirror there is no need to use these. OP, grinding is a function of pressure and dwell time. The more the tool passes over a given area on the mirror, and/or the more pressure applied to the tool over that area the faster the removal rate there. So to deepen the center ensure the tool is passing over there more than other …
For a 6" F8 for example you would only be removing .047" of material at the deepest point. I dont think the average CNC router will maintain much accuracy (<.01") in the Z axis. There is usually quite a bit of slop in the rails, etc. You would need to do some rough grinding to get back to a sphere.
Rough grinding a 6" f/6 could be done with this device going at 40 rpm (or slower for larger optics) in an hour and a half! Then I discovered that grinding was so fast that I could work with 20 minutes per stage, skipping every other abrasive. Even with pyrex. And so my sequence became: 80, 220, 500, 12, 3.
What grinding tool - posted in ATM, Optics and DIY Forum: I plan on ordering supplies to make my first mirror. Thinking an 8 f/6 From doing a bit of reading and watching the Dobson video, it seems that the tool used for rough grinding is *another* glass blank (the tool goes convex while grinding the mirror concave). So am I looking at …
Stellafane ATM Main Page. Amateur Telpe Making Main Page. Russell PorterGrinding a Mirror. "For it is true that astronomy, from a popular standpoint, is handicapped by the inability of the average workman to own an expensive astronomical telpe. It is also true that if an amateur starts out to build a telpe just for fun he …
This page describes the rough grinding process. Before You Start. Use this checklist to make sure you are ready to start rough grinding: You have selected a mirror diameter and focal ratio, and have use these to calculate a target sagitta.; You have a way to measure sagitta.; You have an appropriate size mirror blank, you have selected a surface to …
Rough grinding operations are most effective when the coarse grit rolls between the tool and the glass causing a fracturing of the surface. My grinding wheel method kept the grit from easily rolling …
Rough grinding is often called "Hogging Out", as your goal is to remove the majority of the glass needed to form the curve of your mirror. It is not particularly elegant work, being the noisiest and messiest part of the whole mirror making process.
CNC Grinding mirror - posted in ATM, Optics and DIY Forum: Hi, has anyone tried to work the optical roughing phase or even to make on holes with a CNC ? I mean home-made CNCThanksA. ... If you use a tile tool or similar working tool, then it is only necessary to put a rough curve on one piece of glass as the tool can be made …
rough grinding with ring tool - strokes? - posted in ATM, Optics and DIY Forum: When carving out the initial curve with a ring tool, for an f/5 mirror, what are the best recommended strokes?One recommendation Ive seen is center-over-center with only a little overhang at the ends - would that work okay?Another recommendation Ive seen is stop …
Grinding back of 6" molded blank? - posted in ATM, Optics and DIY Forum: Ive started rough grinding a 6 full thickness Supremax blank. The back, however, isnt completely flat... it seems slightly …
Grit Material & Sizes. Grit Size Table. Polishing Compounds. How to Mix Cerium Oxide. Pitch. How Much Grit, Pitch & Polishing Compound will be needed? Safe Handling & …
10 fine grinding question - posted in ATM, Optics and DIY Forum: This is my first mirror, my first telpe.I finished rough grinding with 60 grit a few weeks back. Hit my target of 1/8" or f5. I then moved on to fine grinding with 80 grit. Spent about 5 hours on this grit, and regardless of MOT or TOT I gained an extra 0.007" in depth which I can …
Technique. Hold the mirror blank flat with one hand, and rub the stone at a 45 degree angle along the edge. Use the coarse side of the stone if you have a choice. Rotate the mirror as you work, keeping the work area and stone wet. You want approximately a 1/8-inch (3 mm) bevel at 45 al around the mirror. Some people might call this a chamfer.
Took 38 minutes for rough grinding with concentric circles, spaced by 4 mm and took 39 minutes for fine grinding using downward spiral with 0.5mm radius decrement. Here is the finished product. Attached Thumbnails. PrestonE, Tom Stock, skround and …
John Dobson did a 24 inch with a 1 inch thick mirror. Italian amateur Fabio Marioni made a 40 inch telpe with a 1 inch thick plate glass mirror shaped in a meniscus.. German amateur Time Klose finished a 28 inch dob weighing only about 80 pounds recently, made with a 1 inch thick mirror.. A few months ago Mel Bartels …