few thou ofset router bit

[Alan m]

hi there
i have a bit of a situation where i need to make a jig very acuratly  so that other parts will fit in snuggly. i need various slots and holes in jigs to suit guide bushs  exactly (not too tight not too loose)

i am finding it very hard to get the slots and curves and holes the right size accuratly without wandering a bit. i have sanded and scraped etc bit it just isnt acurate enough.

i know i could get them cnced but that costs money that isnt in the budget.

i was thinking of a flust triming bit in the router bit with an ofset of a few thou.
does anyone know of a bit like this. i dont mind buying a bit as i will always have it .

i envisage taking off a few thou with the ofset bit  then fliping and using a flush bit to even it up and sneek up on the fit.
i think i need a really high end bit or a really low end one.

anyone know of such a bit or another way to accuratly do a job like this

 

[mouppe]

I have a rebate router bit set from Freud. I think the largest bearing leaves a 1/8" rebate. You could wrap some blue tape around the bearing until you get the offset you need. Then replace it with the flush trim bearing.

[2cents]

Alternatively you could use a hand plane or spokeshave- nothing more precise than that!

 

[RONWEN]

As usual Richard is right on.  [wink] 
I love CNC machines but I don't always have access to them to "play" especially for woodworking.  The blue tape around bearings works well.  On the router table & table saw I often use shims (playing cards=.0117", copier paper=.0037", etc.).  I also use adjustable parallels and/or planer gauges precisely set to specific dimensions to reference work pieces.  Whatever it takes...  [tongue]

 

[MarkF]

Whiteside makes a .490" bearing for flush trim bits reduced from sharpening.  You could try one on a new 1/2 flush trim bit and get a consistent .010" cut.
They also have square bearings made of Teflon.  You could file off a few thous from each side creating a smaller bearing than the bit.
http://www.whitesiderouterbits.com/wm_catalog_2007.pdf

 

[morts10n]

Have a look at Her-Saf router bits. I recently bought a bit that was .015" over 3/8" . I think they have many straight bits that are .015" under and over.