Bearing guided router cutters - accuracy

[Knaus]

Hello,

New user here, first post

Seeking advive from those more experienced, on buying bearing guided router cutters

I am speciafically trying to find out which brands are acknowledged to have a high accuracy between the diameter of the bearing and the diameter of the cutter

The reason for my equiry is that I will be routing puzzle joints, from template, in plywood up to 3/4" (19mm) thickness

Any recommendations gratefully received - thank you in advance

 

[custard]

That's a good question, I'll be interested what others have to say.

Most of my bearing copy bits come from Wealdons or Whiteside. I tend to use Wealdons disposable blade cutters for most furniture work as that way you're sure of a sharp cutting edge, plywood will murder your bits so that's worth considering.

https://routercutter.co.uk

http://www.wealdentool.com/acatalog/EasiTip_50.html

But there are cases where I use different copy bits, for veneered work I prefer a spiral cutter copy bit. Whiteside make some beautiful bearing copy bits with reverse spirals top and bottom for double sided veneer work. They're not cheap but they leave a superb finish that's ready to receive lipping with a flawless, virtually invisible glue line. Whiteside also have copy bits with double bearings, which may bring a little more precision. For critical work I often wrap a turn of masking tape around the bearing for the first cut and then remove it for a final pass, that may be relevant for you as you can get "micro spelching" in ply, i.e. not enough to be immediately visible but you then see it in a jointed edge or when finish is applied.

Really cheap copy bits are just money down the toilet, if the supplier doesn't offer replacement bearings from stock then that's a clue not to buy.

Good luck!

 

[Beau]

Had a quick measure of my CMT one and the bearing measures 0.2mm larger than the cutter.

 

[custard]

I've never put the callipers on the bearing/bit, but I'll often put a square on the copy template while the machined workpiece is still attached to check for copy accuracy.

 

[Knaus]

Had a quick measure of my CMT one and the bearing measures 0.2mm larger than the cutter.

Thanks Beau - as I'm cutting long interlocking puzzle fingers then over two adjoining pieces that a compound 'variation' of 0.8mm

It will be interesting to see what other router bits/bearings measure and what their discrepancy is

Thank you for your post

 

[giantbeat]

i use a lot of bearing cutters ,nothing that requires your accuracy & tolerance but one thing to remember is the cutter will only be as accurate as it can be when new, as you sharpen the bit, the dia changes by small amounts.

 

[Stanleymonkey]

Read the post because I has a cheapo router bearing fly off yesterday and I carved a chunk out of my project as a result. :-x

Fascinated by what you are doing though. Do you have any pictures? Sounds like fun (but I guess it's a headache for you)

Good luck - hope it all goes well

 

[Wizard9999]

Whiteside make some beautiful bearing copy bits with reverse spirals top and bottom for double sided veneer work. They're not cheap....

Blimey, just looked at their flush trim bit and nearly fell off my chair :shock:

But maybe that is just the price of precision. Interesting thread as I can say with certainty that the bearing and cutter are definitely not the same size on the flush trim bit that came with the cheap starter set from Trend I bought (cutter a little bigger than the bearing).

Terry.

 

[Knaus]

Thank you for all your replies - it is really appreciated.

I'm back from holidays earlier than expected so will start contacting manufacturers and find out what their accuracy is. My preference, if I cannot find absolute parity on diameters is for a cutter bigger than the roller - this is easier to compensate for.

My use is to cut accurate fingers for butt jointing thin (4, 5 , 6mm) marine plywood for boat building. My template is currently being manufactured from 5mm aluminium, working from my own CAD files

Thanks again for your courtesy