Thread: Please excuse my ignorance but am I using round nose router bits right?

CMT, Freud or Trend (in that order) are the best brands you can get and will truly out perform anything else.

The problem may be that as you are trying to plunge the very center of the bit isn't doing any cutting due to its geometry.

The word "diamond" threw me; a quick EBay search threw up grinding bits for granite! I assume that this is the brand name, and if so it may be a generic Chinese POS. If I'm right throw it away and replace it with a quality bit. If you're on a tight budget the Axminster own brand stuff is acceptable but still many orders of magnitude below what CMT quality.

If you're really stuck for funds then do what you did before and route a groove first then use the ball end to finish off. Plunging in at an angle (known as "ramping") might work also but you are using small pieces of timber here and I wouldn't feel comfortable doing that on a table mounted router. I'd build a jig to hold the workpiece and use a hand held plunge instead.

+ 1 here - plunging large round cutters does have its hazards. Certainly keep fingers away, once a cutter grabs the timber goes lightening fast from the router bit. It will be interesting to see what tips come from this thread.

Very many thanks for your help. Looks like ai need to buy a different and better bit.

regards

Paul

Hi Paul,
Any chance you could post a pic of the cutter? I think it might be a 'bull nose' bit (= "ball" in Chinglish?) in which case it should still plunge in to the required depth?
i'm guessing you are routing grooves about 1mm deep and 12 wide for pens to lay in?
fletty

http://www.ebay.com/itm/Core-Box-Rou...-/371205623580
This one? Should be able to plunge with that.

I've a couple of Yonico bits. They've held up well.

If its the one that NCArcher has found, I can see why it doesn't plunge well. The top of the cutters won't overlap at the very centre.

On straight bits they do, which is why they plunge, as it's effectively over-routing the very centre with a slight overlap.

In order to make a smooth circular bottom this bit stops at the centre. As you push down, it's creating a swirly-nipple that is being ground down, not cut. I'd suggest drilling a small pilot hole to start.

With small stuff, as people say above, I use my wooden clamps to hold the piece.

These are the set that I bought. There are no maker's names on so I assume they are Chinese

radius cutters.jpg

Many thanks

Paul

Originally Posted by fletty

Hi Paul,
Any chance you could post a pic of the cutter? I think it might be a 'bull nose' bit (= "ball" in Chinglish?) in which case it should still plunge in to the required depth?
i'm guessing you are routing grooves about 1mm deep and 12 wide for pens to lay in?
fletty

<script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/a97b8e31/background/helpers/prefilterHelper.js"></script>

Hi Fletti - I forgot to say, the intended coves will be about 7mm deep and 15mm across so that a fountain pen can lay in it

Regards
Paul<script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/a97b8e31/background/helpers/prefilterHelper.js"></script>

I have never had any trouble with the cheaper bits, I admit they don't hold there edge as long as the bigger name brands but you weigh up how often you are going to use them as against the cost of the big name brands. If you have a wood router cove bit you shouldn't have any problem plunging them as the blades protrude above the body of the bit,at seven mm deep i would do it in two passes. I would also recommend that you make a small parts sled for safety, something along the lines of this one.


small-parts-sled.pdfsmall-parts-sled.pdf.

Regards
Harold

As Chief Tiff says, some ball nose cutters will not plunge cut because they leave a small section between the 2 carbide inserts where they don't cut. To get over this you need to move the workpiece along slightly over the cutter as you plunge. That way the little spigot that is not cut away will be removed as you move along. You don't have to move very far as you plunge, just far enough for the cutters to remove that centre piece which could be only a few millimeters.

Those core box cutters should plunge. Mine do (Carb-i-tool).

As previously suggested, try using a fence and a plunging/sliding cut to a preset depth.

You can safely cut "both ways" when fully plunged as the cutter's pressure should be equal on both sides of the groove.

Many thanks for the link to the sleds Harry. I have made one previously but these look better and will be next on my list to do. And thank you everyone else for all of the help and advice
Regards
Paul<script type="text/javascript" src="safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/d1624f71/background/helpers/prefilterHelper.js"></script>