Round over radius?

[Phil_S]

Man....do I feel silly asking this after looking at Decko's maple cab. Isn't that something!

I've got an ordinary pine head case glued together (dovetail joints). I intend to cover it in black and I want to use corner covers. So, I have some questions.

What is the proper round over radius for the metal corners and what kind should I get.

Here is a random choice for some visuals: http://www.parts-express.com/brand/penn ... 2_647-2040

Should I use metal 2 leg or 3 leg type? Or should I just get the plastic kind like this: http://www.parts-express.com/pe/showdet ... er=260-708

Am I correct in thinking I need to run the round over bit over the dovetails and all around the outside of the front and back?

Beyond the corner hardware, should I round over the inside edge, maybe 1/4" radius. Will that make wrapping the tolex easier or more difficult?

Many thanks for your patience!

Phil

[Structo]

Place holder for Taylor.

[martin manning]

1/2" radius is standard for the metal corners found on Fender amps. Typically all outside edges are rounded, and the 2-screw "lipped" corners are used. They are finished in either chrome or nickel. Marshall Nylon corners are made to fit a 3/4" radius, but the back edges are not rounded. I think you'll want to break the corner on edges that are not rounded over, maybe chamfer ~1/16".

[Blackburn]

Man....do I feel silly asking this after looking at Decko's maple cab. Isn't that something!

I've got an ordinary pine head case glued together (dovetail joints). I intend to cover it in black and I want to use corner covers. So, I have some questions.

What is the proper round over radius for the metal corners and what kind should I get.

Here is a random choice for some visuals: http://www.parts-express.com/brand/penn ... 2_647-2040

Should I use metal 2 leg or 3 leg type? Or should I just get the plastic kind like this: http://www.parts-express.com/pe/showdet ... er=260-708

Am I correct in thinking I need to run the round over bit over the dovetails and all around the outside of the front and back?

Beyond the corner hardware, should I round over the inside edge, maybe 1/4" radius. Will that make wrapping the tolex easier or more difficult?

Many thanks for your patience!

Phil

Yeah Martin's got it. 1/2" is what I ended up with after trying 1/4". If you're not so picky about the inside edges, I'd just go over it lighly with some not so rough sand paper just to get rid of the harsh 90* angle. Maybe 220 grit? I'm not too informed on those as I just use what's lying around.

[Phil_S]

Martin,
Thanks very much. You seem to have an endless supply of knowledge on amp topics. Impressive.
Phil

[martin manning]

I picked up a few things working with Taylor on a couple of cabs ;^). BTW, you'll want to drill and countersink the holes before you put the covering on.

[xk49w]

For the 1/2" radius corners, which all Penn-Elcom seem to be, a 3/8 can work once the covering has been laid on which seems to increase the radius a bit.

I have found a couple of corner types which may fit a 1/4" roundover. The small plastic interlocking type seems to be made for a smaller radius. In metal, the early Ampeg corners in both 2 and 3 prong have a smaller radius. They are at Fliptops and also at Vibroworld (apparently closed at the moment?) which states the radius at 5/16".

I have only tried the plastic corner with the 1/4" roundover.

[Phil_S]

I picked up a few things working with Taylor on a couple of cabs ;^). BTW, you'll want to drill and countersink the holes before you put the covering on.

Thanks....obvious is not always. I actually wondered about the wisdom of pre-drilling and was about to ask.

I've also got to work through the chassis mounting method. This is a lips on the side turned in chassis. I was actually thinking about taking some of the 3/4" L aluminum stock I bought to make transformer brackets and mounting it to the outside of the chassis so I wouldn't have to deal with lips turned in. I have speed clips to use for lips turned in (or out). What would you do knowing that I've got limited tools? I'm not fond of speed clips.

I fully realize that I've got to drill the box before I drill the chassis so that I can place the punch mark on the chassis in exactly the right place.

If I have front and back panels also covered, I imagine they need to be fitted to allow for the double layer of covering at the edge. That seems like a difficult call.

For those panels, is it worth the bother to put hardware inside the holes and use machine screws or not bother and just use wood screws? What would you do?

Thinking aloud, without a drill press to assure the holes are all straight and plumb, anything but wood screws is probably a silly idea. Hand drilled holes mean the panels will only work in the orientation in which they are originally drilled. Rotating them assures the screws won't fit for both angle and placement, no matter how carefully I measure.

[martin manning]

I picked up a few things working with Taylor on a couple of cabs ;^). BTW, you'll want to drill and countersink the holes before you put the covering on.

Thanks....obvious is not always. I actually wondered about the wisdom of pre-drilling and was about to ask.

I've also got to work through the chassis mounting method. This is a lips on the side turned in chassis. I was actually thinking about taking some of the 3/4" L aluminum stock I bought to make transformer brackets and mounting it to the outside of the chassis so I wouldn't have to deal with lips turned in. I have speed clips to use for lips turned in (or out). What would you do knowing that I've got limited tools? I'm not fond of speed clips.

Speed clips (Tinnerman nuts) are ok, but the ones I've seen don't work if the chassis material is thick aluminum. If you have room in the cab on the sides for the aluminum angle I think I'd do that, then you can use screws and elestic stop nuts. The other way to avoid the blind nut problem is to use long bolts that extend through the chassis and put the nuts on the top.

I fully realize that I've got to drill the box before I drill the chassis so that I can place the punch mark on the chassis in exactly the right place.

I've done it the other way, but it isn't easy. Making a paper template from the chassis seems to be the best bet in that case, and the holes should be a bit oversized too.

If I have front and back panels also covered, I imagine they need to be fitted to allow for the double layer of covering at the edge. That seems like a difficult call.

Measure the covering thickness to get an idea of how much clearance you need to add. You need to make this allowance around the perimeter and in the set-back of the blocks to which the panels are screwed.

For those panels, is it worth the bother to put hardware inside the holes and use machine screws or not bother and just use wood screws? What would you do?

Not wood screws per-se, but screws with a full-length, non-tapered thread are fine, just drill a pilot hole through both parts at once for the minor diameter, and then open up the hole in the panel for the major diameter. Oval head screws with finishing washers are the ticket. A good hardware store will have them and I like stainless steel for these. If they lose their grip at some point (not likely) you can always install a T-nut on the inside.

Thinking aloud, without a drill press to assure the holes are all straight and plumb, anything but wood screws is probably a silly idea. Hand drilled holes mean the panels will only work in the orientation in which they are originally drilled. Rotating them assures the screws won't fit for both angle and placement, no matter how carefully I measure.

If you need help drilling holes perpendicular to the surface with a hand drill, make yourself a wooden angle from 3/4" thick stock, about 1-1/2" wide on the outside dimension and ~1-1/2" long (I'm assuming that you can make a square cut on the ends somehow). You can stand this thing on the surface you are drilling into and use the inside corner or one of the outside corners as a reference.

[amplifiednation]

Sounds like you guys have this figured out

I form most corners to the cab with a white rubber mallet if they don't sit flush. Some of them don't need it.

[Phil_S]

Gosh, you think a black rubber mallet will be OK to use?

Bad news on a good idea. The aluminum L stock I've got is .75", the box is 17 5/8" inside, and the chassis is 17". <shrug> I did not think of long bolts all the way through the chassis. IOW, you mean I need 3" bolts; 2" for the chassis, less than .75" countersunk in the wood, and something to stick out the other end for the bolt. Capital idea! I'm still not convinced I can get the holes to align, but I've got time to contemplate this. I've used the paper template in the past....maybe I'll use thin cardboard this time.

Setback blocks for the front/back panels! Hmmm...I'm obviously a novice. I was going to just run screws through the side. Gibson did that in the 60's. They used black elephant hide with finishing washers and screws colored to match.

The drill guide is a great idea. I think I can make one.

Thanks.

[rp]

I form most corners to the cab with a white rubber mallet if they don't sit flush. Some of them don't need it.

Me too, sometimes you really got to let them have it too!

Tips from me: if ordering the cheap generic fender chrome corners (Mojo) you should inspect them on arrival as I've had many that weren't even chromed or chromed so poorly they might as well not been. I only found out months later when I put them on and then only noticed more months latter when I saw them in good light. This happened on more than one order. Had to replace them all as it made me ill looking at them. This guy has been higher quality: http://www.speakerbuildersupply.com/servlet/StoreFront

And BTW with Mojo check your Tolex and your grillcloth too on arrival and in good light, as I have two cabs with shit flawed cloth - light dark bands, mojo credited me but I'm not going to suffer to redo them now and sorta sucks.

I've been using 3/8 round over as that is what someone told me before there was an internet, and yes it works ok. It's hard to use a 1/2 round-over w/ a hand router, a milk crate, spring clamps, on 3/4 pine - not much for the bit to ride on. If setting up get a counter-sinking bit for the corners made for oval head screws and countersink before you do the tolex. Mark the corners inside where they go as they are poorly made and after hammering they become kinda custom.

[martin manning]

I am giving Mojo a thumbs down. I have had quality issues with their parts and documentation, and their web site does not provide basic specs for the electronic parts or hardware they sell. I'm hearing the same from others too, so they are at the bottom of my supplier list.

[Blackburn]

+1 on Mojo's not so great rep... Or should it be -1?

I was talking with a cab dealer a while back asking him if he bought their stuff and he said that the back covers on Mojo cabs didn't fit each other when he tried to switch them. These were identical cabs. I'd assume they've gotten better about this kind of thing as I've ordered two 5E3 cabs from them last year. Not bad, but I'm really not crazy about the fact that their cabs are noisy. Rattles and resonating wood and what not. When I made myself my 1x12, I glued the shit out of it as well as the baffle and it's a zero noise box. Really like that cab in wine red.

[rp]

he said that the back covers on Mojo cabs didn't fit each other when he tried to switch them.

Sounds like they build just like me. Wonder if they build in their kitchen on milk crates too?