carbide spiral upcut bits don't plunge?

[LCHIEN]

I tried one of mine (from Holbren, I think) and it wouldn't plunge cut to start a spotted dado for nothing. Just burned the wood and burnished it.

I was using a table mounted router, a guide fence and I dropped the wood onto it with a jointer style push block pretty hard. No cutting except a bit at the edges, Big hump in the middle wouldn't cut.

I guess the run of the mill carbide spiral bits won't plunge, eh?

For some reason i thought they would.

Started the hole with a brad point drill bit and then tried to cut a 1/2" wide, 1/4" deep stopped dado, very slow cutting and burned to heck. I know better about that too but i was being lazy.

[Kristofor]

I haven't tried what you did on a table. But I have one that I've used handheld for 96 (I think..) mortices on a set of tables with an edge guide. It wasn't a great plunger but it wasn't too tough, and would do the job if there was slight lateral motion while plunging...

[Uncle Cracker]

You may have a bit that is left-hand spiral... They come that way, but I'm not sure for specifically what purpose. Perhaps somebody else here will know.

[cabinetman]

You may have a bit that is left-hand spiral... They come that way, but I'm not sure for specifically what purpose. Perhaps somebody else here will know.

Maybe a down cut spiral.
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[charliex]

I had a 1/2" MLCS UCS bit that did not cut. I had ordered a set so I tried the 3/8" and 1/4" and they worked fine. MLCS replaced the defective one.

[Uncle Cracker]

Maybe a down cut spiral.

Here's what I was looking at... from Brian Holbren's site...

[SARGE..g-47]

I had an upcut spiral in my tool bag and admit I have never used one before. I did use it two days ago. I got as far as 3/8" on a plunge cut before the smoke set off my smoke alarm. The cut was just like my wife likes her steak... charred. I took it off.. let it cool then threw the bit in the trash as it was dis-tempered. Go figure as I don't have time to research why that happend so hopefully you guys will come to a conclussion here and I can read about it.

BTW.. a standard 1/4" straight bit finished the cut with ease. I don't have an up-cut spiral bit anymore. That's life I suppose! haha..

[gsmittle]

Here's what I was looking at... from Brian Holbren's site...

Isn't left-handed the opposite of a router's usual rotation? If so, you were trying to cut with the back of the edge. (Keep in mind I usually have no clue what I'm talking about.)

I wonder if these are some sort of industrial line-boring kind of bit… Or meant for export to Australia.

Since I'm left-handed, maybe I should buy a bunch of these…

g.

[cabinetman]

I also don't use the spiral type bits. Straight faced bits work just fine. They worked before spiral bits, and work for tip in's as was done before plunge routers, and will work for those that don't have a plunge router.
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[Uncle Cracker]

Isn't left-handed the opposite of a router's usual rotation? If so, you were trying to cut with the back of the edge.

Yes, they are, and that is why I can't think of what they're for. Anybody know? This would certainly explain why Loring's won't cut...

[RayintheUK]

Does this help?



Ray

[Stytooner]

This is a little different, but I have to be careful when I order my end mills. They must be what is known as "Center Cutting." NCC or Non center cutting will not work for what I do.

I don't recall seeing that spec on router bits though. I did run into basically the same as you with burning when I made some chess boards. Stopped dado's were hard to start. All I did was drill a hole in the start point and had no trouble after that. The hole can actually be smaller than the router bit as well. The flutes will shear off the edges leaving a clean dado. It is only the center portion of the bit that really holds it off the work. Take that out and it plunges right in.

[LCHIEN]

Looks like I'm going to have to do more research.
Here's an article on Spiral vs straight bits, by well regarded router expert pat Warner.

http://www.woodcraft.com/Articles/Ar...?articleid=445


I don't know if the part about plunging (he says Spiral is better than straight) is true, I think it depends on the end design of the cutters. On a plunge cutting bit (either spiral or straight) the cutters have to wrap around the bottom and overlap - if they don't it leaves an uncut area in the center and you'll just burnish it as I did and it won't go down.

Regardiong left handed bits - I just can't see any reason for one to exist. Now there are upcut and downcut spirals and at first look they look right and left handed:






However, on close inspection its seen the cutting edge is in the clockwise direction (with the bit pointing down of course, all referenced router directions are usually for handheld orientation rather than table-mounted)
and the spiral direction is up or down rather than right or left.

I wonder if someone thought a upcut bit was a left-handed router bit?

Finally, in reference to Sarge's use, an overheated common HSS bit when made of steel is distemepered, e.g. looses it's heat treating that gives it hardness when its overheated and turns color and it rapidly dulls after that. However, Tungsten carbide bits are not HSS - they are not heat treated so do they get "distempered" from heat like HSS? I don't think so. An article I just read says "Hot Hardness - With temperature increase to 1400°F, tungsten carbide retains much of its room temperature hardness. At 1400°F, some grades equal the hardness of steels at room temperature." indicates to me it should be OK after overheating in wood.

[LCHIEN]

when i have a bit of time i'll examine the cutting tip of my router bits and see which of them will theoretically plunge.

[garymuto]

Could it be that left handed bits are used in machines that have ganged bits? Similar to Line boring?