Sanding Glass Tube

[srdevil]

I've been searching for this on the site but coulnd't find something that was similar.

Lately I did cut a Optima Fortuna Glass Syringe for my combustion engine. However it wasn't a very nice cut so I needed to sand the tube to get a nice edge. I've been sanding this tube for at least 2-2.5 hours but I do keep getting the same problem. Please look at the images posted below.

The edges of my glass seems to keep 'breaking' off while sanding. The grits I've been using is as following: Grit 60, 120, 180, 400 (wet). Its taking ages to get of 0.1 mm but the edges doesn't seems to get smoother, sometimes it even looks worse.

Are there any tips on getting this edge nice? The combustion plan I'm making:http://heetgasmodelbouw.ridders.nu/Webpaginas/pagina_1-cilinder_glas_4takt/1cil_glas_frameset.htm

Is it actually necessary to get a better edge? Of course the glass will get hot but its not like hot -> cold -> hot -> cold. So if i keep it like this breaking might not be a problem?

 

[solarenergyadventures]

Hi Srdevil,
I like to use a diamond whetstone like the type used for sharpining wood working chisles. The diamond
cuts the glass much better than sand paper, so you can use lighter pressure. Plus the whetstone being
flat and ridgid makes it much easier to get a flat end. If you go this route, find one that the back plate is metal and the entire surface is diamond grit. If you are in the US, Woodworkers Supply has them. I'm sure other places have them too, but thats is where I got mine. The cheaper ones with a plastic back plate and lots of little divits in the diamond don't work nearly as well. Hope this helps!
Cheers,
Chris

 

[canadianhorsepower]

The edges of my glass seems to keep 'breaking' off while sanding. The grits I've been using is as following: Grit 60, 120, 180, 400 (wet). Its taking ages to get of 0.1 mm but the edges doesn't seems to get smoother, sometimes it even looks worse.

get rid of that paper under 180 use 330 and 400 grit whet and ALWAYS IN A CIRCULAR motion
oh yea, some elbow greasse also

 

[TorontoBuilder]

I know that in University we always cut our glass by scoring first with a diamond file, snapped the cut and put the end we handled in the bunson burner to round off sharp edges... that and pulled molten glass apart for pippettes.

Not sure what your cylinder ends call for or if your plans would allow but after lapping the end on a diamond file as suggested I'd consider a quick flame heat of the end to round off the edge if there is a chance the edge would be exposed.

FYI, for anyone buying syringes... Optima Fortuna syringes are made of Durobax tubing... so if you have a local lab supplier you can get clear plain tubes with a lot more material at a low price point rather than buy syringes.

 

[rsendys]

Hi,

Try using turpentine to wet sandpaper.

Robert

 

[ConductorX]

I wish I could contribute a suggestion. I do wish to point out that you have an awesome camera!

"G"

 

[srdevil]

A littlebit late response by myself, but I've been sanding like a maniac with 400grit sandpaper and the edges are smooth now.

The way i've done it:
Sanding the tubes shown in the picture a littlebit more with the 400 sandpaper till i thought it was looking ok. After that I've been sanding down the outside edges of the tube only till all uneven glass was removed. At last I took al small piece of paper and I've been sanding the edge of the inside tube. This was a bit more difficult because it was inside and only a small paper could be used. At the beginning the paper was wearing quite fast because of the bad edges, but it went looking better and better after time. It looks perfect now.

Short summary: I've been making a chamfers on the syringe so on the edge the size isn't fully correct anymore but this should not be a problem because the cylinder will only be running in the middle (and its 14mm long) so that the edge doesn't meet the tolerance anymore is no problem.



@conductorX: The camera is a panasonic lumix dmc-tz20, but I was a little bit disappointed in the picture quality. My old Canon Powershot A80 looks way better, but it has been dropping on the ground to often..