3.2mm radius roundover bit with 9.5mm bearing?

[Franco]

I'm having trouble finding a 3.2mm radius router bit with a 9.5mm bearing. I have found many with a 12.7mm bearing and have also found some with a 9.5mm bearing but these ones have a shoulder and are more of an ovolo cutter.

My problem is I'm following a profile that has a few 5mm internal radii's and so the bearing diameter can be no larger than 10mm. Cutting the profile with a 1/4" flush trim bit is no problem, I just need a small roundover bit to bevel the edge. I'm cutting 3mm acrylic and the 3.2mm radius bit will give an almost complete bevel.

Has anyone seen a ~3.2mm unstepped radius bit with a <10mm bearing?

 

[Calpol]

Why not just change the bearing? Just an allen key will do it...

 

[jasonB]

Whats the bearing running against?

You can get a 3.2mm Radius cutter that uses a 9mm pin as the guide, Trend pro range ref 7E/01

Why not just change the bearing? Just an allen key will do it...

That won't work in this case as the cutter needs to have the teeth flush with the 9.5 bearing, if you change the bearing to get rid of the quirk the dia will be too big.

Jason

 

[Franco]

Thanks for the help.

Yeah that bit looks like it will do it, its a bit pricey at £31 though but hey...

The bearing/pin is running against a brass template I made to make some button bezels to surround some pushbuttons for custom Xbox 360 controllers. This is the routing/drilling template:

I use the template to drill the hole posistions and then I stick it to 3mm acrylic to route the holes and profile. The end result looks something like this:

Ignore the pink, the actual bezel for this carbon fibre arcade stick will be mirrored acrylic, I just practiced on some scrap 3mm pink I had lying about. I used a 3.2mm radius cutter with a 1/2" bearing for that one. It gave a full radius apart from where the 5mm radii's are. It leaves a bevel but obviously not a full radius as the bearing is too large for the corner. Its not a big deal, I'm just being a bit anal.

I may give that cutter a go. Do you think it would run against the brass template ok?

 

[jasonB]

It should be fine against the brass, you only tend to get a broblem with some woods or plastic as the pin can scorch/melt due to it having more friction than a ballrace.

Nice work on the jig BTW

Jason