# Perfect Fit Every Time



## Tbagg (Mar 15, 2008)

We've all cut mounting holes for one reason or another, and unless you have the perfect sized hole saw or nail it with the circle jig/router, there always seems to be some trimming and/or sanding that is required. And of course that hardly ever results in a perfect fit. Below I show how I go about achieving a great fit when the item I am mounting does does not have a mounting flange, ie your hole must be spot on if you care about fit and finish.

Below is a battery switch I recetly installed in my boat. The switch is a Blue Sea 9001E. 










The hole saw I used to create the mounting was about 1/16 too small. I used my oscelating spindel sander to enlarge the hole, but of course when I was done, the hole was no longer perfectly round nor did I acheive the fit and finish I am accustomed too. 



















I routed a typical rabbit around the hole. This will provide more surface area for the body filler to adhere to.










I taped the switch to protect it then inserted the switch in the hole temp. holding it in place with clamps.










Useing body filler, I filled in the rabbit and gaps between the wood and the switch. I was in a hurry and did a pretty messy job, but you get the picture. 










After the filler cured, I sanded it flush to the wood and the switch. 



















Next I worked the switch free from the body filler by gently twisting it free. 










After removing the tape from the switch I reinserted the switch to check for fit. A bit more sanding just to knock of the edge and I'm left with a much better fit than what I started with.


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## GLN305 (Nov 2, 2007)

It's not too often that I learna good fabrication trick online, but this is one to add to my list. I normally would use bodyfiller to make the item fit, but rabbeting around the hole is a perfect idea.


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## Tbagg (Mar 15, 2008)

Thanks, I think that the rabbit is the real tip here. My original hole was only off by a few 32nds of an inch. Forcing body filler into a small gap like that and expect it to stay is probably unreasonable.


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## ItalynStylion (May 3, 2008)

Tbagg said:


> Thanks, I think that the rabbit is the real tip here. My original hole was only off by a few 32nds of an inch. Forcing body filler into a small gap like that and expect it to stay is probably unreasonable.


Indeed. Great idea. I need to get one of those bits.


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## B_Rich (Mar 29, 2009)

I may be a little last responding here, but that is very nicely done.

I'll have to keep this in mind for the future.


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## psud3ity (Mar 10, 2009)

I really cannot believe I never thought of that before.

Thanks for the idea!


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## 12vTools (Jan 15, 2009)

ItalynStylion said:


> Indeed. Great idea. I need to get one of those bits.


I can help you with that =)


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## omadawn (May 12, 2009)

great tip!


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## Viperoni (Oct 14, 2006)

Awesome tip, thanks!


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## Tbagg (Mar 15, 2008)

Thanks for the kind words. I'm glad I can give something back to this board.


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## Second Skin Rep Jon (Oct 5, 2007)

Dang! it's not too often I read one of these and go "Wow, why the hell didn't I think of that...". Nice job!


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## eriley (Apr 12, 2009)

I think the Coors Light helps too 

This is an excellent idea though, I'll be sure to remember it.


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## AdamTaylor (Sep 7, 2008)

very nice


now i just need a router


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## chad (Jun 30, 2005)

Badass! I used the same idea with plastic epoxy, Vaseline, and blue tape for my dash trim. Never thought of using that for body filler though, did you have to use a mold release agent?


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## TheDavel (Sep 8, 2006)

noobs- lol


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## chad (Jun 30, 2005)

NotTheDavel said:


> noobs- lol


ever seen blue tape stick to body filler?


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## TheDavel (Sep 8, 2006)

define stick- never had an issue- sticks when tape is applied to filler- does not stick when filler is applied to tape-


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## chad (Jun 30, 2005)

I've had filler stick to tape WAY more than once.. I use a mold release... likely home-brew ghetto


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## Tbagg (Mar 15, 2008)

I did use just a little polishing compound, but not sure it did much to help release the bond between the tape and body filler. In this situation, there wasn't too much surface area of contact between the tape and the body filler. Maybe 3/8" wide all the way around. So there wasn't much resistance when I had to seperate the two.


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## dannyboi (Jun 11, 2009)

good job, i'm sure this will come in handy soon


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## rkb993 (Apr 10, 2009)

Nice tip. This should be useful.


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