Ok, Rookie Here-- What Am I Doing Wrong?

[randyc]

Sorry buddy but your maths don't add up here. By my calculations 90 surface feet per minute is 687 rpm for a 1/2" diameter end mill, I'm not sure where you get 180 rpm from...

Rob, you didn't read the following posts where Tom corrected his figure, see #22. No offense - I'm not directing this specifically at you - but it seems a common practice for people to respond to a perceived error without reading the posts that follow

 

[JimDawson]

I figured out the key/slot situation, and I think I have that under control. I'm still working on excessive runout caused by rough internal collets, and internal tool holders- need a way to clean this up.

A small hone?
.
.

 

[markknx]

Bob,
I have nowhere near the experience these guys do, but I have read and been told 1st. these charts are to get you close, 2nd they are for production work, were labor to tool costs come into play, 3rd all condition need to be right, speed, feed, sharp tool, known materials.... I think 180 seems slow for a 1/2 end mill, but hey you can try.

Now where I can help you a little bit more is I started like you no training and these guys to help me, and a manual machine. I would bang my head over speed and feed charts, ask questions and get all sorts of answers. as far as feed goes unless someone can see you milling it is hard to say to fast or slow. hard for me to come to grips there. But once I got a little feel and understanding it got better quick.

If you get the RPMs right or a little slow (I have seen nothing to tell me lower RPMs are all that bad) higher RPMs will dull bits fast so better a little slow you can always go faster if things are going well. The feed will be easier to feel the cutter will make chips with little effort on the hand wheel. if the chips are stringy (I mean thin slivers) crank a little faster. if they are coming off blue slow down a little. a nice straw color is good. Watch some you tube videos of mills cutting and pay attention to the chips.

+1 on all of what Jim and Randy have told you. the guys are pros so try what they said. and good luck.

Hey glad you like it here at HM Oh my bet is the end mill is toast, but don't pitch it. and get used to killing them as you learn. I would buy cheaper ones till you get a handle on speed and feed.
Mark

 

[Bob V]

Thanks, Mark,
I already know a bit more than I did -- just from this one thread!
Best regards,
Bob

 

[Pops]

I started machining when I was 16. Had several classes in high school on machining and also some college training. During college I got a part time job in a machine shop. I had a wonderful tool maker boss. He saw I was very interested to learn and really took me under his wing and taught me a lot. One of the things he impressed is that while most of the charts out there on speeds and feeds are just basic and will get you "close" to what the feeds and speeds actually should be. There are so many variables, material, condition of cutter, etc. that it would take many long charts to solve every problem. He said it is mainly time and experience that will do the job. I have been doing machine work for over 50 years and very seldom use a chart. It comes down to feel, sound and experience to get machining right. If you get everything "right" your tooling will last you a long time.
I use a good grade of cutting oil very sparingly applied with an acid brush. They are sold in a package of about 20, I believe, from harbor freight. While applying oil you can also brush off the chips. I never use air; makes to much of a mess!

Happy machining,
Barry


Sent from my iPad using Tapatalk

 

[brino]

I bought some fine emery cloth and cleaned up one toolholder with a M2 taper so I could attach my Jacobs chuck-- and the emery cloth reduced runout of the chuck from 35 thou to 2 thou-- but obviously no mirror finish!

Thanks for publishing those numbers Bob.
Wow, that's quite a change. I never thought the before and after could be so different from a mild clean-up with emery.
I may have to check a few of my own.......
-brino

 

[Bob V]

I started machining when I was 16. Had several classes in high school on machining and also some college training. During college I got a part time job in a machine shop. I had a wonderful tool maker boss. He saw I was very interested to learn and really took me under his wing and taught me a lot. One of the things he impressed is that while most of the charts out there on speeds and feeds are just basic and will get you "close" to what the feeds and speeds actually should be. There are so many variables, material, condition of cutter, etc. that it would take many long charts to solve every problem. He said it is mainly time and experience that will do the job. I have been doing machine work for over 50 years and very seldom use a chart. It comes down to feel, sound and experience to get machining right. If you get everything "right" your tooling will last you a long time.
I use a good grade of cutting oil very sparingly applied with an acid brush. They are sold in a package of about 20, I believe, from harbor freight. While applying oil you can also brush off the chips. I never use air; makes to much of a mess!

Happy machining,
Barry


Sent from my iPad using Tapatalk

Thanks, Barry, nothing quite like 50 years of experience.
Bob

 

[Bob V]

Thanks for publishing those numbers Bob.
Wow, that's quite a change. I never thought the before and after could be so different from a mild clean-up with emery.
I may have to check a few of my own.......
-brino

Hi brino,
Yes, the change from 35 thou (I could see the chuck wobble) to two thou surprised me too. I used "fine" emery paper-- but I don't know what grit it was-- certainly didn't leave a shiny finish.