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I'm sure this is a really stupid question, but how do i go about drilling the chassis mounting holes in a trainwreck type head cabinet? i mean the holes for the 4 bolts that hold the chassis in the cabinet. Im sure there's a really simple solution, but i just cant seem to come up with anything.
Thanks!

After rerrading what i wrote, i realized i didnt really explain my question. Im not sure how to mark the wood for where the holes should be drilled. Is there some sort of tmplate i can use/make?

Put bolts in the chassis FROM THE INSIDE OUT, so that the tips of the bolts just barely protrude from the chassis. Set the chassis gently into your head shell. When it's positioned perfectly, press down firmly on the chassis, thus marking the wood with the bolt tips.

I knew it would be something ridiculously simple like that! Thanks, much appreciated!

Or you can do it the old fashion way and grab a ruler and start measuring.

I figured i was going to have to do some measuring, but if the past is any indication, i would have found some way to screw it up!

The potential problem with what xitan suggests is one of orientation. If your chassis holes are all precisely in the same relative position, you'll be fine. If not, or you aren't sure, what i would do is this.

Get a roll of heavy paper so you can rip off one sheet that is sized for the whole chassis. (Brown paper they give away at the garden section at Home Depot, cut a paper grocery bag, or use wrapping paper.) Then stick the bolts in with the points coming from the inside. Use that to mark the paper. Mark the inside vs. outside, and front vs. back, so you don't get confused. Now, with the bottom of the cab facing up, flip the paper over (inside against the cab) and use that to mark the cab for drilling. I've done this many times. It's easy to do.

One thing I've learned from experience is that I don't know how to use a ruler for this.

Phil_S wrote:The potential problem with what xitan suggests is one of orientation. If your chassis holes are all precisely in the same relative position, you'll be fine.

Ooh, I failed to mention that I put the chassis in exactly the right place, not on the reverse of where it will be. The trick to drilling holes from the inside of the cabinet is that I have a right-angle drill. Gotcha!

I like your idea...but how would you know where to position the holes to align the chassis perfectly with the valence?

As I (think I) put in the build guide, use a plexiglass template with holes to mark your screw positions with a spring punch.

xtian wrote:I like your idea...but how would you know where to position the holes to align the chassis perfectly with the valence?

Valence? I don't need no stinking valence!

Sheepishly...I admit to using a ruler and figure it will be close enough. It requires a lot of measuring. Carpenter's rule, measure twice cut once. I measure many times. It is good the holes go in the bottom. They can be plugged and re-drilled without too much shame.

Who owns a right angle drill?

edit: So, after sleeping on this I can't live with the deception. I don't really use a ruler very much because it does not promote precision. When I build a head shell, I stop at the point after I have the 4 sides together and that is the stage when I drill the bottom for the feet and for the holes to hold the chassis. This holds whether it's getting tolex or wood finish. The front and back panels are made and test fitted with the chassis in place. My cabinet making skills are not that good and I don't have a real shop with table saw, drill press, and other table-type equipment because my house lacks a dirty room where it is OK to make copious amounts of sawdust. I have to do all of this outside. I made a sturdy workbench a couple of years ago and have learned to do what is necessary with a circular saw, router (hand held with improvised fences), and hand tools. There are times when I can't get the precision that I'd want, but I have learned to work around it and deal with "almost" on a regular basis. The purchase of a new and much better router a couple of years ago was a great improvement. One day I'll get the plunge base for it, but that costs almost as much as another router! Maybe I should haunt to pawn shops.

I have been thinking about cutting a relief in the outside work table to insert a plate to hold the router upside down, and some dados in the edges for a fence system. On the latter, I haven't yet figured out how to make the improvised fence perfectly square, and if that is lacking, what's the point?

Sorry to the OP for the hijack. Maybe you'll get a useful takeaway from this ramble.

I keep a bottom plate around pretty much standard hole drilling among various chassis I've used.

Throw in a spare face plate up next to the valence then the bottom plate mark holes on to painters tape stuck to the cab floor and right angle drill.

Or a clear plexi as Ron stated that works very well.

I think it's the right hand drill that's the issue, I didn't have one.... still don't so you have to make a template and measure very accurately on the bottom side....... then hope for the best....... if you make you holes slightly larger then there's some wiggle room.



MC

norburybrook wrote:I think it's the right hand drill that's the issue, I didn't have one.... still don't so you have to make a template and measure very accurately on the bottom side....... then hope for the best....... if you make you holes slightly larger then there's some wiggle room.



MC

Drill it from the bottom, no right angle drill required!

I speak as a 'Ready, Fire, Aim' guy. This is why it is called the ART of cabinet making. You get to ARTFULLY fix the FUBARs. I used to freak out about the holes. Miss aligned holes can be plugged and redrilled. Save the panic for the visible parts of the build. I don'r even waste good wood on the bottom - I use plywood it seems to lower the pain threshold significantly.

One of the most useful tools I have is the combo square. I figure out what the offset from the front edge of the case to the back of the front plate, then lock that into the combo square. I then flip the cab on it's top, set the chassis on it and use the square to 'push' the chassis to the correct offset by sliding the square along the front edge.

Then measure the sides and get the chassis centered and check the front alignment with the square again. Take two clamps and the lock the chassis so it won't shift. Check it again with the [you guessed it] square. Mark and drill the holes. If you mount the front plate - do it after you drill and install the chassis - it will always be snug that way.

I use a drill guide - nothing more than a hardwood block drilled on a drill press - to align the drill. You can get hardened steel drill guides on line.

my house lacks a dirty room where it is OK to make copious amounts of sawdust.

Phil, My first house sounds like yours - I ran a 3HP cast iron saw in a room with carpeting to built a doll house for my wife at the time. Shop vac sucked up a lot of saw dust!

Russ

Funny you should mention the combination square. I've misused a small roofing square for years to help me run my circular saw for cross cuts. I recently acquired an antique combination square when my mother-in-law moved and we cleaned out the basement. It had some rust to clean off, but it seems to be in good shape. I haven't had a chance to use it yet. I've walked by the Swanson speed square in the hardware store a bunch of times and restrained myself. I recently bought a blem machinist square on eBait for cheap to check the blade alignment on my circular saw. The square "family" of tools is really versatile. You can't have too many of them.