Rear cavity templates?

[Mike Kolb]

Currently in the process of building a small bass body out of walnut. I'm looking-around for anyone that may sell a compact rear-cavity routing set.  

StewMac sells a set but it's a taste on the large side for what I need... http://www.stewmac.com/Luthier_Tools/Types_of_Tools/Routing_Templat...   (it's almost 8" x 3.5" or so).

Last week a Samick guitar was in for some work and the control cavity cover was a nice size, being only 6" x 3.5" so I traced it just to have a reference.

Anyone got an idea of where to source a set similar to this? 

[Andrew]

Theyre not too difficult to make from the material of your choice, just drill pilot holes and rough cut it out with a fine tooth coping saw blade, and refine with small files/scrapers and whatever. But I get the feeling this is something you already know...

[Mike Kolb]

Hi Andrew.  Oh yes, I know the theory.... it's my execution that always seems lacking :)  

Making a one-off isn't too bad, but trying to custom-make a cavity cover plate that nicely matches the custom-made cavity is where it all usually falls apart for me. 

Maybe I'll give 'er a go. If it goes south, there's always the StewMac version but, dammit, they get plenty of my money already! 

[Andrew]

Yeah making the cover is still tricky for me too. I always end up making them by hand taking a little at a time until I get a nice enough fit. Theres gotta be a way to making a matching cover template without going all CNC techy. Ive never really thought about it much because it seems I usually do odd shaped cavities as one offs and it seems just as easy to shape the cover by hand as it does to make a template, which would also be shaped by hand... 6 of one half dozen of the other kinda thing.

Maybe someone will chime in and educate us lol.

[Randall Curtis Bowman]

Use this method all the time. Works quite well; just rout the cavity to your liking, making a rabbet to screw the plate into, and tape down your paper over it for the pattern. Rub the pencil over the edge of the opening. It will make a darker line where the edge is.Tape the paper to the plate, or rubber cement it, and cut out. I make them just a fraction oversize and trim with a sanding plate a bit at a time.  

http://www.wikihow.com/Make-a-Gravestone-Rubbing

[Andrew]

Yeah thats essentially what I do. It works fairly well, but the rubbing method can create a bit of distortion to size/shape, so its not super precise.

[Mario Cardenas]

you can check at www.

bestbassgear.com (or something like that). They carry a lot of templates. 

[Mike Kolb]

Thanks, Mario.... I checked with them and (while they do carry many templates) they offer nothing for rear cavities, but I appreciate the thought :)

Gonna' bite the bullet here and do a "from scratch" one-off. It'll require making 3 items: (1). a template for the interior cavity. (b). a slightly larger template for the recessed flush cover and, finally (c). the cover itself. 

The search, however, tells me there could be a market for this sort of thing.  CNC'ers, take note!

[Andrew]

I think your plan is the best bet for a one off. Shouldnt be too hard to make a matching cover template by scribing the recess template carefully and working the cover template just past your scribe mark.

When I make covers/recesses I like to make them easy to get off one of two ways: I either make a little thumbnail catch in the cover (some might consider it unsightly though - I dont), or I make a little divot inset from the inner edge of the recess with a knife or chisel so when you push down on that area the cover pops up. The latter is my favourite, but it only works if you have enough ledge to make a divot thats large enough, and of course it only works if the person trying to get in knows its there. Oh, and the divot thing has to be located in a small enough radius to work well.

Just a small thing Ithought Id share.

[Richard Bales]

I start by making a template that's 1/4" bigger all around than the cover I want.  Then using a 1/4" bit and a 1/4" template guide, I lay the template on the material and cut out the cover.  Then I lay the template on the surface the cover is to fit on and using a 1/2" template guide route the "lip" of the cover recess to a depth equal to the thickness of the cover.  Then without moving the template, I switch to a 3/4" template guide and route the cavity to the desired depth.  One template works for all cutting.  And the router cutter remains the same.  Just the template guide changes.  The template guide is just a collar that fits into a router base - they are available in a number of sizes.

[Mike Kolb]

Thanks, Richard.   See, here's what an idiot I am:  I had no clue that "template guides" existed.... are those the brass collars that come in sets?  Pardon me while I slink out of the room. 

Yikes, it may be time to return to remedial "Routing 101".  

[Andrew]

Thats them lol. I have a set that Ive never used. Never got the hang of accounting for the difference between the guides and the bit so Ive stuck with bearings. Maybe I need to try them again! (Probably wont though hehe)

[Mike Kolb]

What usually works best for me is sleeping on a problem.  So, after mulling-over all the good advice from the troops, the "light bulb went on" regarding Richard's use of template guides and only needing a single template to rout the cover, the recess and the cavity with just one template...  it's brilliant.

Made my template this morning (with hole saws, rasps, small sanding drum, the kitchen sink, etc.) and now I'm waiting for Amazon to deliver my set of brass template guides... $23 total.

Thanks to all, particularly Andrew for the do-it-yourself encouragement and Richard for the means to actually see how it can be done with but a single template...  As always, indebted to everyone.