[spike7638]

I'm trying to fabricate something from fiberglass for a boat project, and one step of the process requires that I make a hole with a particular shape.

The "foot" of a marine toilet that I'm working with has an "H"-shape ... actually, if you imagine a wide letter H made of wax that then melted, so that all the corners get rounded -- that's the shape.

I can mount a piece of masonite to the toilet base and chase around it with a flush trim bit to get an H-shaped piece of masonite, which I'll call an "inside template".

What I need is an "outside template" -- something that, when traced with a flush-trim bit, will produce a hole into which the inside template will fit perfectly.

I'm pretty sure that this can be done with something like an oversize bearing, or ... who knows? But I don't actually know much about routers, or what bits/tools/whatever might be available -- in all my years of messing with boat stuff, they haven't come up much. So in explaining how to do this, please don't be afraid to talk down to me, and to explain the tiniest and stupidest detail -- I promise not to take offense.


Can someone point me to a quick tutorial, or just say "That's easy! You simply do X, then Y, then Z and you're done"? Thanks in advance.

 

[Quillman]

A graphic representation.

 

[spike7638]

That link shows a picture of three templates, and offers me a chance to pay $10 to see how they were made. That seems more like a repetition of my question than an answer, but perhaps I'm missing something. Maybe this was a subtle hint that I should stop by the local library to borrow a book about routers rather than wasting the time of the experts here asking basic questions ... and I guess I can do that.

 

[kp91]

Basically you are looking for an inlay bushing kit.

http://www.newwoodworker.com/rotrinlays

https://t.harborfreight.com/solid-b...552.html?utm_referrer=https://www.google.com/

They are pretty easy and cheap.

If you have a set of router guide bushings you can figure the math yourself, or just pay $10 for the kit. Lots of YouTube videos show these in action.

If you want another way, cut your master, trace it on a template blank using a washer to offset it the diameter of your guide and cut it out with a Scrollsaw, coping saw, or freehand it with your router.

 

[JOAT]

I do things somewhat similar to what Pat is describing. But, if it comes down to explaining how to do it, and do it right, especially considering your lack of experience, between me and Pat, go with Pat, money well spent.

 

[spike7638]

Solved

Thanks, folks. That Harbor Freight thing is just what I need -- I guess as much as anything I needed the right name for the thing I was looking for. If anyone ever has a boat-building question, perhaps I can return the favor.

 

[kp91]

Glad to lend a hand

 

[old55]

Welcome to the forum John.