router bit trouble

Bits were 1" cutting length, only using the top 3/16". Both bits were new so I assume they were sharp. When using the spiral cutter I would expect I should be ble to use a feed rate of 3-7 in/sec as thats what the bits do in a CNC machine

Dull bits? Long bits? Your feed rate is definitely too fast for your setup, find the weak link and you can increase the feed rate..

I then switched to a a second 1/4" bit, this time a two flute carbide tipped straight cutter -- broke it as well after about 4 linear feet of milling.

Both bits snapped right at the collet so the whole bit broke, rather than just the tip.

now admittedly the second bit was not top of the line (it was from rockler) but to have two bits break doing the same operation in such short amount of time seems a bit weird. Both bits were 1/4" shank. I have been unable to locate a 1/2" shank witha 1/4" straight cut -- 3/8" seem to be as narrow as

I was doing this in a router table with a PC7518 router mounted in a PRL. My feed rate was reasonable, _maybe_ 1"/sec

Anybody else had this problem -- I'd like to do some thinking before I head back to the shop and snap another bit !

Cheers Eric

ago I asked about "climbing" bits as my onsrud spiral cutter was coming out of the router. Followed the advice ftom several folks on the wreck and all went well....... exect that I broke the router bit.

straight cutter -- broke it as well after about 4 linear feet of milling.

have two bits break doing the same operation in such short amount of time seems a bit weird. Both bits were 1/4" shank. I have been unable to locate a 1/2" shank witha

rate was reasonable, _maybe_ 1"/sec

the shop and snap another bit !

Are you trying to cut the full 3/16" in one pass?

seem to be as narrow as 1/2" shank bit go.

couple of days ago I asked about "climbing" bits as my onsrud spiral cutter was coming out of the router. Followed the advice ftom several folks on the wreck and all went well....... exect that I broke the router bit.

tipped straight cutter -- broke it as well after about 4 linear feet of milling.

than just the tip.

rockler) but to have two bits break doing the same operation in such short amount of time seems a bit weird. Both bits were 1/4" shank. I have been unable to locate a 1/2" shank witha 1/4" straight cut -- 3/8" seem to be as narrow as 1/2" shank bit go.

PRL. My feed rate was reasonable, _maybe_ 1"/sec

head back to the shop and snap another bit !

yes -- I was under the impression that if the depth of the pass is less than the width of the cut then only one pass was / is necessary -- perhaps I am a bit to aggressive ?

A 1/4" bit should be able to handle this. IMO Rockler bits are crap. I routed a couple hundred feet (1/4" deep cut) of thermofused melamine and dulled the heck out of one -Freud two flute bit but it never broke even at the rate I was pushing it. I also bought an Oldham HD special to do some more grooving and it held up well though the 1/4" groove was slightly more than 1/4". The Freud had a much tighter tolerance in the finished cut.

Get a good bit. CMT, Amana, Freud, Whiteside.

Gary

Yes thats the general rule of thumb, and a good -quality- bit should handle it. The way I see it is there are 4 options:

1. The bits are total pieces of s*it and are defective.
2. The cut depth is too deep for YOUR feed rate.
3. Router speed is too slow for the depth of cut at YOUR feed rate.
4. Your hard maple has a rockwell hardness of 60 Take a guess where I would start at?

To the OP: and be sure to avoid Woodline bits. they are unmitigated crap! I like my Amana, Bosch, Freud and CMT bits. Haven't tried Whitesides yet.

dave

GeeDubb wrote:

I think 3-7 inches a second QUITE fast. Too fast!.

You could try to do it in two passes. Also if the router is variable speed... speed it up.

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Update:

Got an Viper bit from the borg, 1/4" shank, 1/4" cutter

Freud makes a 1/4" cutter with 1/2" shank 11-136...

A 7518 is a high torque router that will NOT stall. You need a very slow feed rate with a 1/4" cut that deep.

The router is more than capable, the bit is NOT.

SamTheCat wrote:

ago I asked about "climbing" bits as my onsrud spiral cutter was coming out of the router. Followed the advice ftom several folks on the wreck and all went well....... exect that I broke the router bit.

straight cutter -- broke it as well after about 4 linear feet of milling.

have two bits break doing the same operation in such short amount of time seems a bit weird. Both bits were 1/4" shank. I have been unable to locate a 1/2" shank witha

rate was reasonable, _maybe_ 1"/sec

the shop and snap another bit !