How do YOU decide when the routing bit is worn out?

[j ferguson]

I've started using an AMANA 1/16 carbide downcutting spiral bit in my 6040 cnc router. It cost $26 compared to the 6 for $10 bits I had been using. I cut 1/16 and 1/32 baltic 3-ply with it. At 25000 rpm and 6 ipm, it makes very nice cuts, very little dressing to finish parts. I know I can push it faster, but I'm still getting used to how much my DIM (Done It Myself) vacuum table sucks

Is there any other way to determine its sharpness than waiting for the cuts to become lousy? Somehow looking at it with a microscope doesn't sound right. ??

 

[ewkearns]

Nothing wrong with visual inspection! Spindle current draw? Drive motor current draw? Sound? Shape of chips? Vibration? Time in cut? IMHO spindle HP may be the best, yet totally impractical, due to small cutter diameter....

So, yeah, I vote for visual assessment to develop a "time in cut limit".....

Making a vacuum table is a major PITA, I helped develop a system to mill thin Micarta™ counter plates for the converting industry. Given the parameters, it was not fun.

 

[j ferguson]

But this thing is 1/16 inch in diameter.

 

[ewkearns]

As you suggested, magnification......

 

[coherent]

it should be pretty easy to see when the cut quality starts to fade a bit. Just check regularly. The cut quality is the best indicator.

 

[tq60]

Contact the manufacturer of the bit and ask them.

It is very safe to assume they have extensive QC that is used on finish produce and as part of that determined how to test for wear consistently and cheaply as part of the development of said tool.

It may be a simple visual with a microscope or a dragging of something along the edge to see if it still cuts or an amp meter measuring current.

If spindle is running less than 15 amps on 120 vac a simple off the shelf item is called "kill a watt" or something to that effect and hf has them.

They plug into power then device plugs into it and it reports instant and total amps or watts along with being voltmeter.

It could be used to collect total power for a count of operations when new then repeated measurements compared but operations need to be same as the length of cut would need to be same to mean anything.

If same operation started taking a few more watts each then 10 would be more obvious.



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[JimDawson]

I just use the cut quality method. When the cut is no longer acceptable, I change bits. Also you can hear and feel the machine, with some experience, you just ''know'' when it's time to change bits.

 

[4GSR]

On a 1/16" dia. bit, you're more than likely to break it off before realizing it is dull.

 

[ewkearns]

That is very true and echoes my experiences...... in fact, we went to a single flute carbide end mill to give enough strength to the tool to last any meaningful length of time. I had to make those, but it appears that they are, now, commercially available....

http://www.harveytool.com/prod/End-Mills-for-Plastics/Material-Specific-End-Mills/Browse-Our-Products_253/End-Mills-for-Plastics---Square-Downcut---Single-Flute_114.aspx

 

[j ferguson]

I guess I can conclude that running it until I don't like the cut is the way to go. I suppose I should have said that I was cutting 1/16 and 1/32 3ply baltic plywood at 6 inches/minute.