How can I smooth the trackball plexiglass hole? (ouch! it's sharp)

[sofakng]

Last night I found my trackball mounting screws and attached the trackball.  I'm a little bummed and the trackball is below the plexiglass (it's flush to the top of the mdf though).  The problem is that the hole in the plexiglass is sharp.  It's not able to cut anybody but when you roll the trackball forward (or backward, whatever) you can feel the plexiglass hole and it kind of hurts.

Now I already have EVERYTHING mounted (buttons, joysticks, etc) so I'm not sure what I'll be able to do, but I was wondering if I should file the edges of the plexiglass hole with a metal file to make it smoother.... or perhaps use sandpaper (that causes TONS of scratches on the plexiglass surface though).

Any help would be GREATLY appriciated.

My cabinet will be almost complete after this!

[CthulhuLuke]

I believe careful sanding w/ sandpaper should leave you without any visible scratches.  As long as you're careful to only have the sandpaper scrap against the inside of the hole, it should smooth out the edges.

[Sylentwulf]

Someone in the past week had a GREAT shot of what to do with the plexi around the trackball. It involved routers and such, but the last part involved attaching something to a dremel to buff the plastic smooth...

[ras2a]

or you could use a router and a 'bullnose' laminate cutting bit!..this will probably give you the best finish.  I haven't actually tried this myself yet but am going to do once I get my plexi/acrylic sheet

[patrickl]

Someone in the past week had a GREAT shot of what to do with the plexi around the trackball. It involved routers and such, but the last part involved attaching something to a dremel to buff the plastic smooth...

Yeah, that was in one of the previous threads you (sofakng) started about trackball mounting. You should go back to that previous question and read the suggestions there.

[sofakng]

Yup, I remember that thread.

The problem is that I already have my plexiglass attached to the control panel.  All of my buttons are in place, etc.  If I was going to re-route the plexiglass (with that chafner/bullnose bit) I would need to remove ALL of my buttons, right?

If I don't need to remove all my buttons to re-route the plexiglass hole please let me know but I'm thinking with all the buttons on the control panel the router wouldn't have a flat surface to ride on.

So... I'm looking for something simple I can do just to smooth to edge a little bit.  Is regular, 400 grit sandpaper my best bet? ...or would a file work better?

Would a dremel work better than sandpaper? (I don't have one, but perhaps I could get one)

Maybe I should use one of those drill-sanding bits?  (those round bits for a drill with sandpaper attached to it)

[Witchboard]

I would do it by hand.  Just drop your trackball and get some fine grit sandpaper and run it across the sharp edge a couple of times to smooth it down.  If you use a drill or dremel, it's possible you'll dip it.  Those things may not be very powerful, but plexi isn't all that tough and it will sand faster than you expect.

[patrickl]

If you sand or file it then you'll still have a frosted look. You can then polish that. I think that's what the dremel was used for, but I don't remember the whole thread. It might be pretty hard to sand/file it and have a consistent bevel.

Using a router would be difficult with the controls attached yes. You could have routed the hole before you attached the controls though Or take the controls off again. You don't seem to learn that you need to double check things before you do it    On the other hand, I'm still quadruple checking myself and I'm not getting anything built  

[sofakng]

You live and learn I guess...

If I did it over I'm not sure I would have changed anything though... I've spent sooo much money on this project that even another $20 (for a chafner/bullnose bit) seems too much.

Two questions about sanding:

1) What grit sandpaper should I use?

2) Should I only sand the flat (inside) part of the trackball hole, or should I sand the edges of the hole as well?  

I'm just a bit worried about having the sandpaper scratch the rest of the plexi.

[FractalWalk]

I would not use a power tool for this.


The easiest way is to remove the plexi. But is you want to leave it intact,  then with the trackball removed (leaving just the hole) use a sheet of sandpaper (I'd use 200 grit) by hand and go along the flat inside rim of the hole.  This may be hard to do , depending upon how you cut out the panel.

It should only take a minute or so to get it smooth. Then carefully sand the egde applying the paper at around a 45 degree angle.  Be very careful with this part as you can easily scratch the surface around the hole.

As was stated before, when you are done, you will have a frosted look, which I think looks OK. Or if you don't like it you can buff it out, but again, this may be difficult without removing it first.

[sofakng]

Ok, what grit sandpaper should I buy?

Any other tips for sanding the edge of the hole?  Maybe I should cut a strip of sandpaper so that I only have a little bit of sandpaper exposed to the plexiglass?

Oh... and does Home Depot sell any polishing stuff I could buy for after I've sanded the hole?

[Witchboard]

Any other tips for sanding the edge of the hole?

LOL.... Sorry, I'm in a mood.  I would cut the paper down to a reasonable size.  This will keep you from scuffing areas you don't want to hit.  Here is the polishing compound that was mentioned in this earlier thread you started.  Not sure if it would be available at Home Depot.

[ras2a]

mask off the area sorrounding the lip with masking tape etc so that you don't scuff the area sorrounding the hole..just leave a tiny gap around the diameter of the hole for sanding back

[sofakng]

Excellent tips, thank you!

What grit sand paper should I use?

...and what type of tape should I use?  I don't want to use something that will stick to the plexiglass and won't come off cleanly...

Thanks again everybody!

[FractalWalk]

As I stated, I would use 200 grit. Masking off the area is an excellent suggestion. Regular masking tape will work and it shouldn't leave any residue. But if it does, it can easily be cleaned.

You can cut the paper to size or just fold it in a manner to leave a small are exposed. I prefer folding it as it gives you a bit more bulk to hold onto.

[sofakng]

Sorry, you did say 200 grit above... I missed it.  Masking tape sounds good, I'll pick some up tonight.

Thanks for the help!


Thanks everybody!  I can't wait to show my finished cabinet

[ras2a]

We can't wait to see it!  These boards really do offer an unrivalled 'community' spirit quite unlike any other I've experienced in my time online - Everyone is supremely helpful

[fredster]

Drimmel tool with a sanding disc does wonders.

[ThePaul]

sofa do you have a photo of the problem? How did this happen? I didn't run into this problem.. I think my TB has a "lip" on it though.. maybe that's why I didn't have the problem.. the lexan and "lip" are flush with each other, there is no gap .. so even if the lexan is sharp .. a hand never touches it. I'd like to see a photo of your prob.

[Witchboard]

You probably have a "high-lip" trackball where his is a standard trackball.

[sofakng]

Ummm...  I think I have a high lip trackball... It's the one that was recently on sale on Happ's... The "Golden Tee 3 inch Trackball".

(edit) This is my trackball, I double checked:
http://www.happcontrols.com/trackballs/56010011.htm

Am I not supposed to use the spacer they included with the trackball?

The trackball didn't come with any instructions... I just assumed I was supposed to use it...

* Walking away hanging my head in shame... *

[Witchboard]

If you don't use the spacer, you shouldn't need to do anything with your plexi if I understand correctly.  Just cut your hole and the lip slides into it and is flush on the top.

Here's the spacer explination from Happ.

[sofakng]

Ok, I'm using the standard 3" trackball mounting kit (which I recessed into the top of my control panel making it flush).  I didn't buy the 3" High-Lip trackball mounting kit.

Does that matter?

Here's the part I ordered:   (55-1101-00)
http://www.happcontrols.com/trackballs/55110100.htm

[Witchboard]

I honestly couldn't tell you, but if they make a specific mounting kit for the high-lip, then that's probably where you strayed.  At this point it really doesn't matter unless you're wanting to cut a new peice of plexi and buy another mounting plate.  I would just go the route you've already taken.  If you didn't know the difference before, then neither will anybody else.  It's just one of those things to look out for on your next cabinet.    You may want to post a pic now, so we can see exactly what you're talking about.

Edit:  I don't see a specific mounting kit for high-lip trackballs.  You may be able to just remove the spacer and it will bring up the lip.  Not sure how it would feel now that you've bevelled your plexi though.

[sofakng]

I'm posting from work... I can't post any pictures but I haven't beveled anything yet.

When I cut the hole in my plexiglass I cut it exactly 3".  So, if everything works OK then when I remove the spacer the trackball will be raised and fit through my plexiglass hole.

I will be THRILLED if this works....

[ThePaul]

Sofa,

My TB mounting kit came with a spacer. I did not use it.

The lip and the Lexan were exactly the same height/thickness. So once I cut the hole in Lexan (using TB hole - 3" as a guide) the lip itself fit up into the Lexan.

See

There is no gap at all between Lexan and trackball lip, well maybe a microscopic one, but nothing that you can feel.

Also it seems that if you don't use the spacer your TB will be sitting higher.. which IMO is nice.

[foomench]

As for grit, I think the original thread said to start with something rougher (not rough, however, by sandpaper standards), maybe 200, and finish with really fine, like 400.

For polishing, I found my Home Depot had a Dremel kit for about $12 that included the polishing compound, numerous cloth attachments, and some other cleaning attachments. I bought this, but haven't used it yet.

-foomench

[Witchboard]

I'm posting from work... I can't post any pictures but I haven't beveled anything yet.

When I cut the hole in my plexiglass I cut it exactly 3".  So, if everything works OK then when I remove the spacer the trackball will be raised and fit through my plexiglass hole.

I will be THRILLED if this works....

Oh.. I thought you had already bevelled your edge.  Plan to be thrilled then.  

[sofakng]

It worked PERFECTLY!!!

Ok, maybe not perfectly, but pretty darn close.  The trackball lip fit perfect into my plexiglass hole making it *nearly* flush.  It's still a tiny (very tiny) bit below the plexiglass but it's 10x better than the way it was.

I also sanded the plexiglass trackball hole.  I only did the flat part, not the edges.  I know I probably didn't need to do this but I figured what the heck.

I'm very very happy with the way it worked out.

Thanks for all the help!

[KrawDaddy]

BTW you should always finish your lexan with 2000 grit wet sanding!  Try it

[Mameotron]

Sorry, looks like I saw your post too late.  Oh, well, here is what I did...

Use a deburring tool on the sharp edge.  Start with just a light pressure, it will take the sharp edge right off.  Press harder and you can chamfer the edge.
They sell for about $3.

http://www.grizzly.com/products/item.cfm?itemnumber=G5618