Broke a cutter, not sure why (G code in here)

This forum is dedicated to those Hobbyists Interested in CNC machining in their home shops. (Digital Read Outs are also topical, as is CAD/CAM as it relates to CNC)

Moderator: Harold_V

User avatar
GlennW
Posts: 6359
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Broke a cutter, not sure why (G code in here)

Postby GlennW » Sun Feb 05, 2017 3:42 pm

Success!!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

User avatar
ctwo
Posts: 2452
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Broke a cutter, not sure why (G code in here)

Postby ctwo » Mon Feb 06, 2017 11:45 am

It was painfully slow. The video is 20x normal speed. Each full pass takes 9 minutes. Two things I changed is the starting path does not cut so deep or wide. I started the first pass at 0.100" DoC, second pass was 0.100" DoC, and finish was 0.050". Width was down to 0.012" starting pass and then 0.020" all others. I used a mister for the second part.

I used a Kenametal 5" DA200 collet extension this time. I do not know how those are normally used. I mounted it in a fixed 3/4" tool holder and discovered more stick-out that I was expecting. Run out was over 4 thou, but I was able to get that out by clocking it just right. OK, down to 4 tenths at the end mill tip...

I made both halves as shown, then parted on the lathe and glued the two halves together with super glue, then filed the seam smooth. Next year it needs to be made as one piece. Maybe I will make one a bit larger and then two more a bit smaller... I like the rough cut and how it catches the light, for now...
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

RET
Posts: 656
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Broke a cutter, not sure why (G code in here)

Postby RET » Tue Feb 07, 2017 9:59 pm

Hi ctwo,

Congratulations! It works. To me 0.100" is still too great a depth of cut for that diameter end mill, but you made it work. I would have used 50 thousandths instead to be on the safe side.

I also think that Glenn is right; your spindle speed needs to be a lot higher. If it were, you should be able to use 3 to 4 times the present feed rate. If you have a Bridgeport or its equivalent, I would try an auxiliary high speed spindle that mounts in the original spindle collet. As Glenn says, you need Dremel speeds (15 to 25 thousand rpm.) for that cutter even although it will work with less but at a slower feed rate. Yes, I don't have that capability either, but I'm willing to live within my present limitations. Maybe in the future, I'll build something better (faster & stiffer), but for now I'm happy to use what I've got.

Your video is quite impressive, as is your finished product. I use Varsol for tapping aluminum & it works well, but I haven't tried it as a milling lubricant. I would think it should work, but I can't say it would be any better than what you are using.

If I were trying to do that part, I would likely draw the part in Synergy first (a 3D CAD program) then also use Synergy to create the G code. I could tell the software I wanted climb milling and it would write the code to give me that.

Anyway, congratulations.

Richard Trounce.

User avatar
ctwo
Posts: 2452
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Broke a cutter, not sure why (G code in here)

Postby ctwo » Wed Feb 08, 2017 2:53 pm

I have been thinking about this and some of the comments. I have always been able to make my part, and maybe it takes more than one try, but it gets done. This last one I did similar a year ago, with about the same parameters, no cutters were harmed then. (viewtopic.php?f=9&t=102883)

There needs to be progress and improvement. That can no longer be measured in terms of parts, but in refinements... Success this time will be recognized later if something was learned. Ok, I am off to work in DoC and WoC into my spreadsheet.

But a question, since I foresee a division problem. I have 3/16 end mills that have 2 inch long flutes. It is so long I cannot see touching the end of it to anything and expecting it to cut reasonably, and certainly not the entire length if taking just a light finish pass, so what use are they?
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

RET
Posts: 656
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Broke a cutter, not sure why (G code in here)

Postby RET » Thu Feb 09, 2017 9:00 am

Hi ctwo,

3/16" x 2" length of cut sounds like a special. I have used 1/4" x 1 3/4" length of cut (both ball end and regular end) because I needed to get down inside the part I was making and that was the longest commercial length I could get.

Because of the length, I had to take a light depth of cut and a slow feed, but it did work. Actually, the CNC helped because of the steadier feed over doing it by hand, to say nothing of the ability to do curves and diagonals.

Keep them around, you never know if someday you will need one. They must be sharp and climb milling is much better. If you try to sink with one, you have to go down very slowly while travelling horizontally and it still doesn't like it. The ball end would be much better for sinking because it can act like a drill.

I have been manual machining as a hobby for quite a number of years (about 30) before I started in on CNC and that has helped a lot to know what speeds, tool bit shapes and feeds to use, but as I've said before, CNC opens up a whole new world of possibilities and capabilities that simply didn't exist before. Its great.

Hope this helps a bit.

Richard Trounce.


Return to “Home Shop CNC”

Who is online

Users browsing this forum: No registered users and 1 guest