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

(https://www.the-carbide-end-mill-store.com/End-Mill-Filter-Search.html?m5:search2)

[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.

[Jim Becker]

I guess the best solution is to choose tooling that's as close to what you desire proportionally and match your splines to the recess you can cut. It's actually easier to size the spline material to match the groove than it is to size the groove to the spline. :)

BTW, my mention of CNC was only as an example because a lot of this kind of tooling is aimed at that market these days.