by geolemon » Tue Feb 28, 2006 8:46 pm
OK, the technique is pretty simple, I'll leave most of it for you to ponder... but the concept is simple:
You can "trace" any pattern (or actual unit to be installed
) with a flush trim bit - bearing rides the pattern, cutter cuts out an exact duplicate... but the duplicate shape is a positive, and you need a negative.
But what else did you cut out?
...an oversized negative, didn't you?
Flush trim bits come in different diameters - but all of them standard... like 1/2", 1/4", etc.
Your oversized cutout is exactly 1/2" oversized, if you used a 1/4" bit.
Look at that master bearing kit... you can remove the stock bearing on a flush trim bit, and replace it with an oversized one - and create another negative that is shrunk down - with a 1/4" oversized bearing, you'll recreate your exact size hole, a negative of your positive original pattern.
And, if you use one of these kits with a rabbet bit instead (or work off a positive, the inverse of this trick), you can do enlargments rather than reductions.
Anyway - it's so accurate, that if you are going to upholster using vinyl - I suggest (in fact, require!) that you wrap your original positive pattern with the vinyl you are going to use - just wrap a stripe of it around, so the bearing rides it on it's original pass.
Now, when you reduce it, it'll be the size you need, minus your vinyl - and when you add the vinyl, you'll end up with such a tight pressure fit, you could mount it in your roof and not have it drop out.
OK, the technique is pretty simple, I'll leave most of it for you to ponder... but the concept is simple:
You can "trace" any pattern (or actual unit to be installed ;) ) with a flush trim bit - bearing rides the pattern, cutter cuts out an exact duplicate... but the duplicate shape is a positive, and you need a negative.
But what else did you cut out?
...an oversized negative, didn't you?
Flush trim bits come in different diameters - but all of them standard... like 1/2", 1/4", etc.
Your oversized cutout is exactly 1/2" oversized, if you used a 1/4" bit.
Look at that master bearing kit... you can remove the stock bearing on a flush trim bit, and replace it with an oversized one - and create another negative that is shrunk down - with a 1/4" oversized bearing, you'll recreate your exact size hole, a negative of your positive original pattern. :cool:
And, if you use one of these kits with a rabbet bit instead (or work off a positive, the inverse of this trick), you can do enlargments rather than reductions. ;)
Anyway - it's so accurate, that if you are going to upholster using vinyl - I suggest (in fact, require!) that you wrap your original positive pattern with the vinyl you are going to use - just wrap a stripe of it around, so the bearing rides it on it's original pass.
Now, when you reduce it, it'll be the size you need, minus your vinyl - and when you add the vinyl, you'll end up with such a tight pressure fit, you could mount it in your roof and not have it drop out. :cool: