How long should a bit last?

I am wondering how often bits go dull. Now I know it depends on a million things, but I bought 2 - 1/4" bits when i first got the xcarve, both 2 flute upcut, one steel and the other carbide. I did quite a few cuts with the steel one, a lot of deep big pockets, which wasn’t the most efficient (should have gotten a 3/4" cutter). All of the cuts were in wood, but when i did MDF, I think I ran the bit hot as when it was done i could see the end of the bit was discolored. Ever since then the bit leaves frayed hair like pieces on the edge of the cuts, which I’m guessing is a good indication the bit is dull.

I then tried out my carbide bit for the first time and what a difference, super clean, super quiet while cutting. But now after less than 8 hours of cutting its starting to have a screeching sound every so often ( like the steel one had) and I feel the bit is dulling already.

Anyway that’s the backstory, so here’s what i do to try and save the bit. I try to keep the proper chip load to avoid overheating, My feed rate is about 65ipm into pine lumber and the Dewalt set to 1, and using the chip load formula this is still super slow. The chips look like adequate size, not powder. So I feel like I’m doing a better job taking care of the bit.

What signs are there that a bit is dull? What is the best way to take care of bits to make them last the longest? Is carbide worth getting over steel? Do they last longer?



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I have had a much better cutting experience with carbide over high speed steel and they tend to last longer in wood and MDF.

On the bits, once they run hot and get discolored, they are pretty much spent. I’ve done it to a few as well and just tossed them out…at this point they are probably very dull.

I run them until the cut starts to get a bit rougher and not as clean. I tend to buy the cheap chinese carbide bits off of ebay as I can buy 10 for the price of 1 very good bit and I get great life out them as long as I cut at correct feeds and speeds.

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I am looking for some inexpensive .125 upcut spiral end mills with a flute length between .75 and 1 inch. The shank size can be .125 or .25.

Have you come across any? All I am finding have flute lengths under .75 inch.

Someone selling packs of 10 would be even better.

I ordered more of these last week…22mm cutting length (0.86")…

Not spiral, but I have had good luck with these. Mostly I use them for cutting out pieces from 3/4" stock.

I also picked up these ballnose ones with a 22mm cutting length.

Exactly what I needed, just ordered a set! Thanks

Those bits are hardly over a dollar a piece! Do they really work well enough to use? Any troubles at all?

I noticed a lot of bits are 22mm vs. 1/4" shank. I’ve heard 22mm bits are much cheaper than the 1/4", have you found that to be true? Did you get an adapter collet?

Is there any way to sharpen these bits yourself?

The 22mm is the cutting length, these are 1/8" bits.

I have collets for my dewalt for 1/8", 1/4", 4mm and 6mm so I can use most any bits.

I have had good success with these bits, I cut almost entirely wood with a little MDF on occasion. These bits work great on pine, cherry, maple and walnut (probably more, but that is what I cut most of the time). The nice thing is, if they only last a couple of months, no big deal as they are cheap.

A lot of times the 4mm and 6mm bits are much cheaper then 1/8" and 1/4" bits. I purchased collets from I have never been a fan of the adapters, I prefer a collet sized to the bit.

I don’t know what I was thinking, I meant the metric version of the 1/4" lol. Why don’t you like the adapters?

I have found them to be unreliable. I have had bits slip and on the ones I have used, I can see the bit tip wobble (runout) while it is running. With a properly sized collet there is no visible runout and the bit stays where it is supposed to.

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Gotcha, that makes sense.

So as far a speed and feeds, going too slow (feed rate) it will overheat the bit and will dull the bit, what will happen if I go too fast? Break the bit I suppose? Do you calculate chip load?

There are calculators that let you calculate chipload…I go with what I have used in the past. I prefer to test a lot of feedrates with bits in the materials I use the most. I go with what produces the best finish and chip size.

So yes…too slow you get overheating and burnt bits and wood. Too fast and you can break bits or even stall the machine. Too deep a cut and you get broken bits and burning and stalled machines…lol

It is a balancing act of feedrate, depth of cut and router speed setting.

I prefer to keep my router at speed 1 or 2 and adjust feerate and depth of cut to get the best performance at that speed.

Okay, that’s what I figured was you need to balance. My thought is I know running at 40ipm is too slow, I’m running at 65ipm now which is not stalling the machine or breaking bits, thus I should be taking better care of my bits. Basically, as far a dulling the bit, the faster the better for keeping the bit sharp?

It all depends on the material, but normally yes. Heat is your worst enemy for dulling bits.

Perfect, that’s what I kinda thought. I have pushed the machine to where it stalled, so i know when fast is too fast.

So in general how long do your bits last? You said months, is that carving once a week? day?

I usually cut things a few times a week with the same bits…depends on the bits and how I am using them…I have tapered ballnose bits that have lasted months and are still good. I usually get a few months out of the straigt flute endmills I posted above.

Also keep in mind that some materials are more abrasive to the bits than others. The glue in mdf and to a lesser extent plywood is particularly damaging, and some tropical hardwoods contain abrasive compounds. I’m new to the cnc scene but know from many years a woodworking shop that a little bit of use in abrasive material can really knock the edge off your tooling. Some manufacturers make bits specifically for these types of materials, but the prices start to get high pretty quickly.

Is pine wood, such a a 1x12 lumber is considered easy/soft material to mill?

Pine is a soft wood.