decimal indexed router bits?

[Stan Calow]

Does anyone make straight router bits in decimal inch increments, like indexed drill bit sets? I need to cut some slots for keys in boxes* that are .090 and .100 inches. I can get close with a 5/32" bit (.0938) but would like to be more precise. Any workarounds?

* Cutting slot for keys (aka splines) in small box corners for reinforcement. Keys are metal so sizing is critical.

[Joe Jensen]

I haven't seen any. Would a jig that lets you make two passes work for this project?

[Stan Calow]

Thanks Joe. I dont have much confidence at that fine a level of detail to use a smaller bit in multiple passes. .090 is pretty thin.

[ChrisA Edwards]

You can get CNC router bits, 1/8" collet size, that go from 0.5mm to about 3mm.

0.09"-0.10" is 2.28mm to 2.54mm.

If mounted in a router table with a fence, you could use these.

They can be found on Amazon and are reasonably cheap.

When cutting, you need to set the depth about 50% of the diameter of the bit, although 2mm, you could probably get away with a 2mm depth of cut as long as you feed slowly.

[Richard Coers]

You can get router bits ground to any diameter you want.

[Wes Grass]

You can get carbide endmills in decimal sizes. At that size, I think the spiral flute would be an advantage. It certainly wouldn't be an issue with wanting to pull in.

You'll likely need a 1/8" collet though. Depending on your router you might find those at Precisebits.

[Bruce Wrenn]

Could you stack some Diablo 7 1/4"blades on the table saw to get desired thickness. Use a file to flatten the bottom of the cuts.

[Steven Cooper2]

Harvey tool has a huge selection of tiny end mills. They probably have something in stock that would work.

[Stan Calow]

Thanks everyone. I did some googling for end mills. I may go for the metric set on Amazon. I only found one .0900 CNC end mill on Amazon but it was $125+ . I may decide to go with a 5/32 bit which I already have, (.0938)and shim. Its a small project and I dont want to invest too much in it.

[Wes Grass]

I only found one .0900 CNC end mill on Amazon but it was $125+.

Yikes!

No idea what inventory they actually have, but the prices are slightly better:

https://www.the-carbide-end-mill-store.com

[Mark Woodmark]

Thanks everyone. I did some googling for end mills. I may go for the metric set on Amazon. I only found one .0900 CNC end mill on Amazon but it was $125+ . I may decide to go with a 5/32 bit which I already have, (.0938)and shim. Its a small project and I dont want to invest too much in it.

I have used end mills in my routers. From my understanding the flutes are a slightly different shape. They work, but you need to go slower and take multiple passes. They don't seem to clear the chips as well and have a tendency to chatter. You will probably need to buy a collet adapter also as the shank is usually the same diameter as the bit

[Mark Woodmark]

I have used end mills in my routers. From my understanding the flutes are a slightly different shape. They work, but you need to go slower and take multiple passes. They don't seem to clear the chips as well and have a tendency to chatter. You will probably need to buy a collet adapter also as the shank is usually the same diameter as the bit

There are cheaper places to buy end mills online. I purchased 1/2 inch diameter ones 8 inches long for mich less than Amazon. Monster tools comes to mind

[Stan Calow]

Thanks for the other options to look at. I just assumed there would be a bigger demand for decimal sized bits.

(couldn't edit previous post - 3/32 bit comes close - .09375)

[Jim Becker]

A lot of the precision work has moved to CNC and you don't need or necessarily want tooling that's the exact size of a recess you are cutting in the material...two passes with a smaller tool to get an exact width is a very common way to do things that have to be an exact, specific width. The same technique can be used with a router table or router, too, although it requires moving the guiding resource to generate the final width.

[Stan Calow]

Jim I understand. If I had CNC-precision-like routing skill, I'd be more confident to try multiple passes. With each of my planned boxes needing 12-16 splines, only 1/2" deep, and 1/2" long, I was looking for a one-pass solution. Marching on. The one thing to be careful of is collet requirements for these small spirals.