Insert knifes breaking

[Chuck Keysor]

Hello Botters. I have been breaking the insert blades on my Amana "In-Groove CNC Insert Engraving System". This is really driving me crazy!

Background: I purchased this set a bit over a year ago. At that time, I had the tip break off a 60 degree bit with a .005" flat on the end, and on a 30 degree bit with a .005" flat on the end. Each of these bits broke when I was doing test lettering carving in MDF. I only got perhaps 10 minutes of carving in on each of these tips before they broke. Before they broke, they provided exceptionally clean letters! I was cutting at 10,000rpm for sure, and either at 1.5 or 2 inches per second.

Well, tonight, I thought that with a year of V-carving under my belt, I would try the Amana Engraving bits again. This time I used a 30 degree bit with a .010" flat on the end. I was cutting at 1.5IPS @ 10,000rpm. This time I was cutting vinyl floor tile. I have cut this same design probably 30 times before without any problems using my CMT Laser bit. Each tile takes about three hours to cut. Tonight, after LESS than one minute, I was suddenly not cutting. I turned off the Bot, and found the tip was broken off. That is shown in the picture with the blade mounted in the holder.

What could I be doing wrong? Certainly the Amana bits are capable of cutting MDF and soft vinyl. The Amana bit holding system seems idiot proof, and the fact that the lettering I was cutting last year looked wonderful, until the bits broke, would in deed suggest I had them mounted correctly.

The only wild guess I can come up with, would be that the Amana engraving bits are damaged by the Z zero routine on the Bot (using the plate). This is a wild guess. But since I have no clue what forces are excerted in that operation, maybe there would be something to this.

Any suggestions, before I bust the remaining 4 bits in the set? (Though I don't really see much use for what I have left..... :() Thanks, Chuck

PS: I have nothing against Amana. I bought their big spoilboard flattening tool many of you recommended, and that works great!

[Brady Watson]

Harvey Tool (http://www.harveytool.com/cat/Browse-Specialty-Carbide-Cutting-Tools---End-Mills/Other-Specialty-Profiles/Engraving-Cutters_168.aspx) has what you need. Tip on or tip off. Order both.

I doubt the Zzero routine is breaking the tip unless you have poor grounding.

-B

[knight_toolworks]

I wonder if it is a chip loading problem?

[gene]

call a amana tech person and see what they say is wromg.:confused:

[feinddj]

I second the grounding check, having lots of problems with the zzero routine, turned out to be an intermittent short in the ground plate wire. fixed it, no more problems.

D

[Mayo]

Here's another line of thought...
Maybe there's something about the insert bit or the holder that makes it have less conductivity than other bits? Is there a film of anti rust coating of some sort? If the grounding plate is becoming pock marked by the tip of the blades, that would indicate the blade is traveling farther than it needs to. This would happen if electrical contact is not being made until greater pressure is exerted, and maybe the greater pressure is what allows electrical contact to happen through the slight coating on the holder or the blade.

A way to check if there's good contact being made (without damaging a bit) is to just lightly touch the flat of the grounding plate against the tip of the blade you plan to use, and look at the Shopbot Position display on your monitor and see if the input button lights up red.

If there is a coating on the blades or holder, you could try using Denatured alcohol or acetone to remove it.

[gerryv]

IF not a ZZero issue:Bringing the cutter down to where it will only lightly etch a polished piece of material and then turning the (unpowered) spindle by hand should show if the tip is turning on its axis as it should or cutting a tiny circle. If the latter, it could either be a case of an improperly ground cutter or a spindle bearings problem. At least this might help rule out a spindle issue. As to it not happening with the other tooling, cutter brittleness could be a factor that makes the Onsruds more susceptible to eccentricity. Just a thought.

[dlcw]

I've been using the Amana insert v-bits for a couple of years now. I've not had a problem with tips breaking off but the bits staying sharp for very long is another matter.

I can cut one sign and the v-bit insert is dull. The cutting results in soft woods is also horrible. They have also proved useless on panels with laminate (Formica, Wilsonart, etc) applied. I get a nice notch in the insert where it is cutting the laminate. The substrate (MDF) is cut just fine. I think they are using some pretty soft carbide for these bits. I have been thinking about switching to something else.

I'm going to look at the Harvey Tools bits that Brady suggested/

[Brady Watson]

I forgot to add that I have heard of others complaining about how delicate these inserts are. The larger v-insert tooling is a LOT beefier than the InGroove ones - and I have had fantastic results with them - but I have never used them to engrave. I either use a Harvey or Micro100 engraving bit whenever doing engraving work on dense materials or metals. The shape of the cutter and the fact that it is solid carbide works really well. Just don't expect to v-carve with these things...they are for engraving only.

-B

[knight_toolworks]

I've been using the Amana insert v-bits for a couple of years now. I've not had a problem with tips breaking off but the bits staying sharp for very long is another matter.


I'm going to look at the Harvey Tools bits that Brady suggested/
I think this comes back to chipload. on these bits I bet the chipload is a much lower number then regular v bits. I bet feed rates need to be pretty low to get the right chipload.
one of the woodworking stores I do work for tried to talk me into buying the set. glad I did not. but my competitor who had been doing cnc work for 4 months did (G)

[dlcw]

Steve,

I normally run at 12K rpm and 1.5ips with these bits. In hardwood they work great and leave a wonderful finish. In softwood, the results are not good.

[Bob Eustace]

Chuck we have about the same experience as you and coming from the metal industry always tend to be very conservative on speeds and feeds. We bought the Amana set just for doing perspex trophies. Same problem as yours - tips simply break for no reason. Have even tried Z down to ridiculously low levels. In Australia we easily get our money back for gear that doesn't perform as advertised. Do you guys have anything similar, as these cutters aren't cheap? You might all laugh but we use Rockler vee bits exclusively and have zero problems. We use new ones on perspex then when they lose their edge, relegate them to hardwoods for a week's moore cutting. We buy then only when on special at around $12. Great on PCB's tooooooooo!

[jim_vv]

Greetings, Chuck

I purchased the 30V and 60V In-Groove System sets a couple of years ago. I too had tips breaking off in MDF! I confirmed speeds and feeds with Amana's tech support. I sent them all back to the dealer I bought them from and received a refund. I currently use the Onsrud carbide tipped V bits for big text/V-carving and the Onsrud solid carbide 30V and 60V .005" tip engravers for small text/V-carving. I have had great success with Onsrud, but when I wear them out I may try some other brands to see if I can get even better results.

Kind regards,

JIM

[Chuck Keysor]

Hello everybody! Thanks for all of the helpful replies. Usually my first response is that I am doing something wrong, but finding that others have had the same problem is actually very important for me to investigate this.

I took as the top recommendation, the idea to contact the supplier (Tools Today). I briefly described the problem I am having, and then included a link to this thread so they could see the pictures, etc. I asked them to let me know what options I have. I am assuming the options will be connecting me with Amana, getting a refund/credit, or a sorry you are out of luck because my invoice is dated 9/5/11, which is over a year ago.

Also the Tools Today website touts these bits for V-carving, and that use is demonstrated in the following video. http://www.toolstoday.com/p-6009-in-groove-cnc-insert-engraving-tool-body-replacement-knives.aspx

Again, I have read through everyone's replies, and appreciate your input. I will investigate the diagnostic options, in part based upon what I hear back from Tools Today. And I will let you know what they tell me.

Thanks again, Chuck

[knight_toolworks]

looking at that video the cutting speed may be about .5 ips. I jsut wonder if any decent cutting speed is just too fast?