Bent cutter need help

[Len-Tikular]

I'm not seeing any issue with your .crv file. The toolpath that VCP is generating is stepping your v-bit down in 0.2" passes as shown in the two pictures.

The first picture is a side view of the toolpath and the blue lines represent the tip of the v-bit as it makes the passes. You can see how multiple passes are being made in the deeper areas.

The second picture shows the toolpath preview approximately 1/3 of the way through. I used the replay commands, specifically the "run to retract" button which is circled in red, and this shows how the first pass of the deeper cut areas is being cut in passes.

As others have said, the v-bit will progressively cut deeper based on the pass depth you have set. So assuming your machine can handle a 0.2" pass in oak at 100 ipm then you need to look at issues created beyond the software and some good suggestions have been presented.

Tim

Thanks Tim, I have attached a picture of the cutter and the job part done to the point where I stopped the machine.
is near to the 6 oclock position on the picure of the wood. I still cant understand how the cutter is descending at 0.2" per pass. It almost seems like the gantry moves to a new position then plunges directly to the maximum depth of that point then progessess to make the cut. Maybe I'm not explaining myself very well.

I have now done a test cut by drawing a circle 100mm diameter then offset it out by 5mm. Usin a new 60 degree v cutter the cut was made in one pass at 4.33mm deep another pass was made in the opposite direction at the same depth.(I expect this was a clean up pass) The pass depth was still set at 0.2"

I repeated the job but this time set the pass depth at 0.1", first cut went to 2.54mm, going anticlock starting at 9 oclock second cut went to 2.54mm going clockwise starting at 9 oclock. Third pass went to 4.33mm going clockwise from 12 oclock and the final pass at 4.3mm going anti clock starting at the 9 oclock position again. All was fine with a clean cut in some birch ply.

So thats 4 passes in all, i'm assuming this is correct.

I think the net result is I may not have tightened up the collet sufficiently and may have been trying to eat too much wood in one go (5.08mm). Happily my machine survived, there is no run out on the collet so no dmage.

[tmerrill]

So it sounds like you have this behind you. The picture in your last post did show very poor cut quality that could be a result of dull bit, too large a pass depth, moving too fast or a combination of them.

One precaution with bits like a v-bit, where the diameter increases as you move up from the tip, is the material removed in each pass will increase significantly. If you set the pass depth to a large value, the first pass may be fine but subsequent passes maybe too aggressive. To protect against this, I normally set the pass depth to a small amount suitable for the final pass. Hopefully that makes sense.

All that said, I am very impressed with the bend you put in that shank!!!

Tim

[Len-Tikular]

So it sounds like you have this behind you. The picture in your last post did show very poor cut quality that could be a result of dull bit, too large a pass depth, moving too fast or a combination of them.

One precaution with bits like a v-bit, where the diameter increases as you move up from the tip, is the material removed in each pass will increase significantly. If you set the pass depth to a large value, the first pass may be fine but subsequent passes maybe too aggressive. To protect against this, I normally set the pass depth to a small amount suitable for the final pass. Hopefully that makes sense.

All that said, I am very impressed with the bend you put in that shank!!!

Tim

Looked good din't it Tim

[RoutnAbout]

WOW, I had never seen a bent shank like that. Usually after a few revolutions they'll snap off and end up like a missile.
What brand if I may. I haven't seen that large of a V-bit with a 1/4" shank
I have a Whiteside 90°V x 1-1/2" with a 1/2" shank and works really good.

Am glad to see you've figured it out.

[Len-Tikular]

WOW, I had never seen a bent shank like that. Usually after a few revolutions they'll snap off and end up like a missile.
What brand if I may. I haven't seen that large of a V-bit with a 1/4" shank
I have a Whiteside 90°V x 1-1/2" with a 1/2" shank and works really good.

Am glad to see you've figured it out.

Dont know the brand Don, I'll try and find out.
I have ordered two more. Tell me, if you were to do the job would you have taken a different approach ?

[Gerry Perrault]

HI
something like that happen to me 2weeks ago,the problem was my collet holder there was a crack on the collet
and my bit slided 1/4'' down enough to spoil my job on HDU.since then i chek my collet every time.
Probably this was your problem, my bit did not bent because i was on hdu, it would have done probably the same as you.Chek your collets.Gerry

[ssflyer]

Just out of curiousity, were you watching the bit when it did this? Almost looks to me like a collet loose enough for the bit to spin - basically stop spinning. I've never seen one like this, either!

[Gerry Perrault]

Nope i was in my office,the sound rushed me to my cnc,what is a pain in the h....
was ihad done a job previous to that and this was repeat and scraped everything.1.5 hr and 4 sqare feet of hdu 1.5.Gerry

[Woodbutcher-59]

WOW, I had never seen a bent shank like that. Usually after a few revolutions they'll snap off and end up like a missile.
What brand if I may. I haven't seen that large of a V-bit with a 1/4" shank
I have a Whiteside 90°V x 1-1/2" with a 1/2" shank and works really good.

Am glad to see you've figured it out.

Dont know the brand Don, I'll try and find out.
I have ordered two more. Tell me, if you were to do the job would you have taken a different approach ?

Len,

Don touched upon this....that IS a pretty big bit for 1/4" shank. Personally, anything bigger than about 3/4" d in a 1/4" shank
is a little scary and cuts should be on the conservative side.

If you have 1/2" shank capability that would be the way to go.

Just my .02 cents worth, can"t afford much more .....

Jeff

[tmerrill]

I think the cause is contained somewhere in this thread but we will probably never know exactly what it was.

But one thought in this case is the ability of the small shank to absorb the lateral forces by bending may have saved the machine from more significant damage. If the shank hadn't absorbed it the next weakest component would have had to.

I think this is an excellent thread supporting the need of proper speeds and pass depths, collet condition, maintenance and tightness at all times.

Tim

[gravirozo]

it is really interesting how big should be a head on a routerbit...

in this case 1/4 to 1 1/4 (5x larger)

on th ephoto, the bit has 1/2 inch shank and approx 2 1/2 dia head (same, 5x larger)
made by amana tool... and i wondering if amana thinking on it could bend by a force...
and acting like a missile....

since the two bit is same scaled.....


collets, i using er collet... i had no experiment with slipping bit.. true, i always drop some oil on the collet, and in the nut... so they sure tigth... so taking care each time changing bit, a good practice..

[Len-Tikular]

I think the cause is contained somewhere in this thread but we will probably never know exactly what it was.

But one thought in this case is the ability of the small shank to absorb the lateral forces by bending may have saved the machine from more significant damage. If the shank hadn't absorbed it the next weakest component would have had to.

I think this is an excellent thread supporting the need of proper speeds and pass depths, collet condition, maintenance and tightness at all times.

Tim

Thanks to everyone for responding to my original post. I was fearsome that somebody might have given me a good rolicking for bending a cutter, instead, there have been many bits of good advice (scuse the pun). Tim, your spot on, had the shaft not bent then the damage to the machine could have been greater. I recut the job last night using a 60 degree cutter with a step depth of 2mm and a flat depth of 6mm. I also slowed the machine down from the 100 inches per min to around 40. Things ran quieter and smoother. The cut was good although it did take a little longer. Once again, many thanks everyone.

To summarise,
Cheap cutter, head to big for its body, feed speed to high,too much material in one pass.
All of these are good lessons.