12" Cab Diary Continued

[tauzero]

Note to self: don't leave Tuffcab sitting in the pot for three years waiting to b applied. Still mostly liquid but some bits have turned semi-hard.

 

Basically, I got as far as assembling the cab but didn't get round to rounding off the edges, then other things got in the way, and then Covid and no gigs, and then I got a really lightweight combo...

 

So I finally decided that I should get it done, and now it's sitting outside with its bottom Tuffcabbed and the first coat on for the rest of it. And I'll soon be able to get rid of the cardboard box with the woofer in and the other cardboard box with all the other bits in which are sitting on the coffee table, so I can find something else to put on the coffee table and annoy Mrs Zero.

[tauzero]

The old adage "measure twice, cut once" can be extended to cover orientating twice and drilling once. Eagerly pressing on as I was after Tuffcabbing the whole cab, I put the corner protectors on the back corners, drilled screw holes for all four, and then realised that I'd put them the wrong way round and the drill holes should have been on the sides and bottoms, not the back. Holes drilled in the proper places and corner protectors fitted, and a little wood filler to fill the holes, which will be given a dab of Tuffcab.

 

Doing a test fitting of the grille, I found it was very slightly oversized - a mm or two. I have assorted implements of destruction to rectify the situation - I think an angle grinder or bench grinder would be a bit extreme, a power file or belt sander seems more appropriate. Does the BC massive have an opinion? Just holding it on edge is going to be a bit tricky. I'm inclined to the power file (more suited to one handed operation).

[Downunderwonder]

You need a way of securing the grill while you grind. Either that or use the bench grinder.

 

Either way you also need a place to rest on so nothing is completely "freehand".

[Chienmortbb]

On 09/10/2023 at 13:14, tauzero said:

Note to self: don't leave Tuffcab sitting in the pot for three years waiting to b applied. Still mostly liquid but some bits have turned semi-hard.

Been there, done that and I share your frustration.

[Downunderwonder]

2nd thoughts

Might be easier to take half mm's off the inside edges of the surrounding cabinet with a sanding block until the grill fits.

[sandy_r]

11 hours ago, tauzero said:

The old adage "measure twice, cut once" can be extended to cover orientating twice and drilling once. Eagerly pressing on as I was after Tuffcabbing the whole cab, I put the corner protectors on the back corners, drilled screw holes for all four, and then realised that I'd put them the wrong way round and the drill holes should have been on the sides and bottoms, not the back. Holes drilled in the proper places and corner protectors fitted, and a little wood filler to fill the holes, which will be given a dab of Tuffcab.

 

Doing a test fitting of the grille, I found it was very slightly oversized - a mm or two. I have assorted implements of destruction to rectify the situation - I think an angle grinder or bench grinder would be a bit extreme, a power file or belt sander seems more appropriate. Does the BC massive have an opinion? Just holding it on edge is going to be a bit tricky. I'm inclined to the power file (more suited to one handed operation).

 

...no (Black&Decker type) workmate available, owned or loaned?  A suitable block of wood against the middle area of each face of the grill should hold secure for 1 or 2-handed destruction activities 😉

 

Edited October 12, 2023 by sandy_r

[tauzero]

30 minutes ago, sandy_r said:

 

...no (Black&Decker type) workmate available, owned or loaned?  A suitable block of wood against the middle area of each face of the grill should hold secure for 1 or 2-handed destruction activities 😉

 

 

Yes, I think I see a way doing that.

[tauzero]

2 hours ago, Downunderwonder said:

2nd thoughts

Might be easier to take half mm's off the inside edges of the surrounding cabinet with a sanding block until the grill fits.

 

If it wasn't painted up and with adhesive foam strip in place, that would have been the better approach.

[stevie]

I'd use an angle grinder to do this, but I think it depends on what kind you have. The small, battery-powered ones with three-inch discs are quite controllable, and thin discs are available specifically for cutting (rather than grinding). The bigger grinders might be more unwieldy.

The main thing is to wear eye protection. That's really important.

[LukeFRC]

13 hours ago, tauzero said:

The old adage "measure twice, cut once" can be extended to cover orientating twice and drilling once. Eagerly pressing on as I was after Tuffcabbing the whole cab, I put the corner protectors on the back corners, drilled screw holes for all four, and then realised that I'd put them the wrong way round and the drill holes should have been on the sides and bottoms, not the back. Holes drilled in the proper places and corner protectors fitted, and a little wood filler to fill the holes, which will be given a dab of Tuffcab.

 

Doing a test fitting of the grille, I found it was very slightly oversized - a mm or two. I have assorted implements of destruction to rectify the situation - I think an angle grinder or bench grinder would be a bit extreme, a power file or belt sander seems more appropriate. Does the BC massive have an opinion? Just holding it on edge is going to be a bit tricky. I'm inclined to the power file (more suited to one handed operation).

Can you rout the wood on the edge out so it fits? Wood is easier to bodge than metal 

[nekomatic]

18 hours ago, tauzero said:

Doing a test fitting of the grille, I found it was very slightly oversized - a mm or two. I have assorted implements of destruction to rectify the situation - I think an angle grinder or bench grinder would be a bit extreme, a power file or belt sander seems more appropriate. Does the BC massive have an opinion? 

I also feel your pain (in my case the proverb being measure twice, order once, cut not at all). I used the metal cutting disc on the Dremel, which was easier than I expected. And don’t ignore Stevie about the eye protection. 

[Downunderwonder]

8 minutes ago, nekomatic said:

And don’t ignore Stevie about the eye protection. 

Aye. Despite eye protection I got a spark in my eye at work. That was some nasty pain. They packed me off to the doc who found a rust stained divot in my eyeball. Not recommended one little bit.

[tauzero]

I used a straight edge and found a couple of places where the edge was slightly proud (rather like a fret rocker), then used a couple of long pieces of wood with the grille sandwiched between them as suggested by @sandy_r to hold it in the workmate with the wonky edge uppermost (as it was landscape rather than portrait it didn't fit between the threads of the workmate). I'd used masking tape to put along the edge so I could see the sticky-out bits, and attacking them with a power file sorted that out. Once I'd worked out the approach, this was the best solution as it was the grille that was misshapen, not the cab.

 

So then I came to putting the LF driver in, and one allen bolt crossthreaded and jammed firmly and I managed to push the T-nut out of the baffle trying to extract it. I can see enough of the shaft to Dremel it off when I regain my morale. I've cut a groove in the baffle where the T-nut prongs go though so I'll need to make that good - araldite? I'm going to put a board over the driver while I perform the operation to try and avoid putting my hand or a power tool through it. It's just one thing after another, with the finishing post in sight.

Edited October 12, 2023 by tauzero
Credit where credit's due

[Phil Starr]

T nuts are a pain. I always use fingers to put the bolts in and get them finger tight before using any tools. They are usually cheap and nasty so this discovers the rough threads before you get stuck. You have my sympathy there. I never hammer them in any more, apart from being too close to a cut edge you rarely get a tight fit for all of them. Without the speaker present I pull the prongs in with a bolt and a penny washer.

 

you only need to stop the t nut turning until it is finger tight, you might get away with it just using a bit of gaffer tape to hold it. Don’t tighten any of the bolts up until they are all finger tight as it stops you having any sideways forces on each bolt. it’s easier if you have a slight bit of movement available to line up all the holes and bolts.

[3below]

2 hours ago, Phil Starr said:

T nuts are a pain. I always use fingers to put the bolts in and get them finger tight before using any tools. They are usually cheap and nasty so this discovers the rough threads before you get stuck. You have my sympathy there. I never hammer them in any more, apart from being too close to a cut edge you rarely get a tight fit for all of them. Without the speaker present I pull the prongs in with a bolt and a penny washer.

 

you only need to stop the t nut turning until it is finger tight, you might get away with it just using a bit of gaffer tape to hold it. Don’t tighten any of the bolts up until they are all finger tight as it stops you having any sideways forces on each bolt. it’s easier if you have a slight bit of movement available to line up all the holes and bolts.

My tactic on these is G clamp them into the hole, making the hole as tight as possible.  If you could start again, speaker chassis would have better clamping arrangement(s)....

[stevie]

When they work, T-nuts are definitely a superior fixing, but they do demand a certain amount of Fingerspitzengefühl, as @Phil Starr has mentioned. I've fitted hundreds if not thousands of the things, and I still make the first couple of turns by hand - just to make sure. And I watch out for any unwanted resistance when I'm screwing them in.

 

Because woodscrews are a lot more forgiving, I think i would probably recommend woodscrews with lock washers nowadays for self-builds. They can (and will) work loose, however, if you don't use lock washers.

 

On my LFSys cabs, I use socket head machine screws and T-nuts. Although not absolutely necessary, I fit lock washers and also secure the T-nuts with staples from behind for extra security.

Edited October 13, 2023 by stevie

[Squitti]

Are the flatpacks still available and, if so, how may I go about obtaining one?

[Aidan63]

I don't think so, but contact Stevie direct, he builds cabs

[stevie]

The flatpacks were a limited run, @Squitti. Since then, the cost of CNC woodwork has almost doubled. So they'd be quite pricey now.

 

I am still supplying the occasional crossover on a nice fibreglass PCB. That seems to be the area that most builders struggle with.

[LukeFRC]

19 hours ago, Squitti said:

Are the flatpacks still available and, if so, how may I go about obtaining one?

Buy a whole cab from Stevie pre made and all the design and DIY niggles taken care of!  

[Pea Turgh]

If I were still gigging loads (or at all it seems), I’d be getting on the LFSYS train.

[tauzero]

On 13/10/2023 at 10:30, Phil Starr said:

T nuts are a pain. I always use fingers to put the bolts in and get them finger tight before using any tools. They are usually cheap and nasty so this discovers the rough threads before you get stuck. You have my sympathy there. I never hammer them in any more, apart from being too close to a cut edge you rarely get a tight fit for all of them. Without the speaker present I pull the prongs in with a bolt and a penny washer.

 

you only need to stop the t nut turning until it is finger tight, you might get away with it just using a bit of gaffer tape to hold it. Don’t tighten any of the bolts up until they are all finger tight as it stops you having any sideways forces on each bolt. it’s easier if you have a slight bit of movement available to line up all the holes and bolts.

 

Having finally restored my morale sufficiently to attack the bolt with a Dremel (it succumbed quickly enough once I decided to not be a wuss and whack the thing up to full speed), and refinished the back where I put the corner protector screw holes in the wrong place, I now have the task of putting the speaker in again. I think one other T-nut didn't want to thread up properly so I shall check them all. This does leave me with the problem of the knackered one, as my endeavours to extract the bolt have basically cut a moat around the hole so I'm not sure that there's anything for a replacement T-nut to bite on at the moment. Would Araldite, the goddess of mending things, work? And if so, smear it over and into the moat and let it cure before putting the T-nut in, or fix the T-nut in place using it?

[stevie]

The problem with filling the hole first is that you need a filler that will grip and hold the t-nut when you reinstall it. I'd be worried that the Araldite would crack under pressure, although I'm not speaking from practical experience here. My choice would be to use Araldite to glue the t-nut in place. Just be very careful not to allow any glue onto the threads of the t-nut and make sure it's accurately aligned.

 

If it fails, you could always fill the hole with fibreglass filler or bodyfiller or even Araldite and use a wood screw (predrill first).

[3below]

3 hours ago, stevie said:

The problem with filling the hole first is that you need a filler that will grip and hold the t-nut when you reinstall it. I'd be worried that the Araldite would crack under pressure, although I'm not speaking from practical experience here. My choice would be to use Araldite to glue the t-nut in place. Just be very careful not to allow any glue onto the threads of the t-nut and make sure it's accurately aligned.

 

If it fails, you could always fill the hole with fibreglass filler or bodyfiller or even Araldite and use a wood screw (predrill first).

If you were unlucky enough to get Araldite into the t-nut thread you may be able to clear it (carefully) using the correct size thread tap. 

[SamIAm]

Could you fill the existing hole/gap with something like this

and then drill a new right sized hole?

S’manth x