Lokheed

So, I'll admit it right off, I am fairly new to woodworking in general and using a router in particular. I am sure that I am making a boneheaded mistake.

I am currently working on a project to create built-in bookshelves for my home office. It's pretty standard construction - a base unit, and then a series of boxes that are roughly two feet wide and seven feet tall. In order to install the shelf standards, each long side of the case on the inside has two grooves routed 3/4" wide and 1/4" deep. The material is plain old MDF. The router is a Craftsman 11 amp 2 HP fixed base router installed into a normal router table, and the bit is a Bosch 3/4" x 5/8" double flute carbide tip straight bit with a 1/4" shaft.

Starting with a brand new bit right out of the package, I was able to route the two grooves on the first board without a problem. By the first pass on the second board, however, the router started to overheat and was leaving a ragged edge on the cut. I don't think I am feeding the board through too quickly, but I reached the point where I would have to feed maybe half the board through before the bit seems to jam or the router overheats. I would have to let the router cool for several minutes, then finish the cut, and then sand the edges to smooth it out.

Obviously I am doing something disastrously wrong. A brand new bit shouldn't get dull after only two passes through wood should it? It doesn't seem like 1/4" is too deep to do in one pass, either. What am I missing?

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AxlMyk

MDF can dull a bit quickly because it isn't all wood. 1/4" shouldn't be too much to take off. The router WILL get very warm, and hot at the collet.

A tip: If you have the bench space, place the shelf sides together and make one rout to get a groove in both pieces at once. Makes it easier to get them lined up.

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Lokheed

So, if I'm working on a project like this where I need to ultimately make twenty separate passes of over seven feet each (five cases, four tracks per case) in MDF, what can I do to preserve the bit? I can't imagine it is reasonable to plan on buying ten router bits to go through... is MDF just a really bad material to be using a router on?

AxlMyk

Try making the first pass just deep enough to break the surface, 1/16th or so, then cut the deeper pass..

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bobj3

Hi Lokheed]

What you maybe missing is a good router bit,,, they are not all the same, that said MDF can play hell with router bits...once the bit gets hot that's it,, it's done and will load up the router and stop cutting...

You didn't say what brand of bit you are using... the router bit has a VERY small edge that does the cutting and heat can make it into a boot anchor in one pass..
Not all MDF is the same, the clean white is best the light brown is hell on bits...


You can try this ,make a 1/8" deep pass to get that sharp edge and then drop in down to 1/4" and make one more pass....but listen to the router it will tell you what you are doing or need to do,,,,a nice hummmmm is best ,it's like welding, the egg sound cooking on a hot plate is best just like a router has a voice so to speak..

Bj

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Lokheed

It's a Bosch bit, and the MDF is the light brown stuff. Looking at the bit, I can see where it is discolored in the top 1/4" where it was doing the cutting. So it sounds like I toasted the bit, that makes sense. I don't mind going out and buying a new one, as long as I have a better idea of what to do to make the next one last longer. Sounds like what I need to do is make two passes instead of one, and probably not run the full seven feet in one go. Beyond that, is there a better brand or type of bit to look for, one that will hold up better? I don't mind paying for quality at all, particularly it's something like paying twice as much for a bit that lasts three times longer...

Thanks for the advice, it's a real help.

bobj3

You'er Welcome Lokheed

I don't know who makes the Bosch bits, But when I have a hard job to do I like to use the CMT brand...they are a bit higher in price but they do last a bit longer than the norm....when using MDF stock for a project...

Here's a small tip that some with say your nuts but it works, I take a rag and get it wet then wipe the MDF down with the wet rag... I know it sounds nuts, but it helps keep the bit cooler

Bj

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Mike

Bosch makes some of the finest tools you can buy but their router bits are not among them. Where you live will determine which bit is the best price in your area. Whiteside (made in the USA) has always come out on top of any bit testing as the highest quality. CMT (made in Italy) is also at the top along with Amana (made in Israel) If ever there was a good time to buy a higher quality bit this is it. Rockler is clearing out their stock of Amana bits at 50% off till August 31st. At least this is the case of my local Rockler store, just got the email. Freud (made in Italy) has some new bits with both up and down cutting edges that are supposed to make super clean cuts. I havent tried one yet but I am very pleased with their saw blades; super performance for a very reasonable price.
I would give the bit time to cool down between cuts, even on the top quality bits. Anything you can do to reduce the heat build up is just more life for the bit.

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Broken Arrow

I'm a new woodworker myself, and this thread is a little confusing to me.
I've used carbide cutting tools in Die Planing for 30yrs, and never saw where heat actually hurt the carbide, and I've plowed through 1/4" deep cuts 7/8" wide in Brake Die Steel for hours and the carbide held up fine.
I know there are different types of carbides out there(and the company i work for uses the cheapest stuff available), are woodworking carbide-tipped tools able to keep their edge? even with heat?
Or is it because the carbide is glued(welded) to a hi-speed cutter and the glue fails?

bobj3

Hi Broken Arrow

When used carbide cutting tools did you run cooling fluid over the bit and the part to take the heat away ? ,so the bit would not turn blue and I'm sure you know once it turns blue the HT is gone... and it can't hold the edge.




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