[Swami]

Im using a 3/8 2-Flute Carbide Endmill. Plunging with full cutter width at 80mm/min, then feeding at 350mm/min down the X axis.

The plunge works great, no chatter. Most of the run down X is find too. Its the transition from the plunge to the X-feed. It hums BAD right at that moment. All the chips on the workbench hop. Im afraid that will damage my mill. Comments?

How could I avoid all the chatter I am getting between the plunge and x-feed?

Thanks,
Swami

[HuFlungDung]

How deep are you going in one pass?

You might try retracting from the hole just to make sure the cutter has cleared its flutes properly. Then, move a few thousandths in the X direction and plunge again, then feed. Us professionals would likely use some kind of a zigzag or helical entry to make the plunge opening larger than the cutter to start with.

You might also ramp down for the full length of the cut, then come back at full depth, fixed depth.

[Swami]

Thanks so much! That was educational. I have absolutely no one I can learn from "in person" A lot of this is being learned through the "stumbling fool" method!!

Thanks,
Swami

[Ken_Shea]

A lot of this is being learned through the "stumbling fool" method!!

Hey Man, are you making fun of my education, experience and pain are the best teachers

[Swami]

LOL

I forgot to respond that its doing cuts of 1.5mm in a pass with seemingly no difficulty. I actually have no idea how far I can push it. RPM is limited to 2400 (Sherline 5400)

[Ken_Shea]

I would not think that .0004 would offer any problems up-to your max of 2400rpm. If it is cutting 1.5mm (.059) for us Imperial fans effortlessly then that is a great opportunity to increase the feed by 10% and try that.

[nervis1]

quote:

A lot of this is being learned through the "stumbling fool" method!!

Hey Man, are you making fun of my education, experience and pain are the best teachers


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LOL, took the words right out of my mouth!

There are probably a more than a few of us stumbling fools here.

[HuFlungDung]

To be an expert, you have to make all the mistakes yourself, first.

[Swami]

I would not think that .0004 would offer any problems up-to your max of 2400rpm. If it is cutting 1.5mm (.059) for us Imperial fans effortlessly then that is a great opportunity to increase the feed by 10% and try that.

I forgot to say that I am already at my maximum feedrate (13 IPM).
I would love to go faster, but it would obviously be a hassle. I could probably rewire my unipolar steppers to work with a new controller...

Since I am at my max feedrate, can you also effectively increase feed by taking deeper cuts? Is it literally the same thing (asking the cutter to do more)?

Swami

[Ken_Shea]

Swami,
I checked some of the feed rates and with what you mention you are (according to this ) going to fast, this can also cause some of the transition roughness you mention. This experimentation is necessary for you to understand the limits (and they all have them) of your machine.

If you do not have ME Consultant 2.0 I would highly recommend it, it is not a answer all absolute but it is a great help for those of us that are new to this type of need.
just do a google search for it.

[Swami]

Thanks thats a great tool.

So is it the RPM that is holding me back from using higher feeds?

Swami

[Ken_Shea]

Available RPM is one of the factors to be sure, in your case if you had 4000 RPM available feed would jump from 9.7 to 16.2 and if 6000 RPM then 24.2 so you can see the difference. You can play around with what ifs on ME 2.0 so give it a go and it will also help you learn to use it to your best advantage.

Aside from RPM there are many other limiting factors, rigidity of the fixturing, manner of fixturing, weight of the machine, horse power, machine condition, quality cutters vs cheap cutters, controller settings, length of tools and the list goes on.

If you have long cutters leave no more then necessary sticking out, but be careful that you have your tool length and/or top of material settings correct.

I am not particularly familiar with the Sherline 5400 but I believe it to be of good quality but a light hobby machine so you might try backing off the .059 DOC to say .030 and give that a try.

[Swami]

Thanks Ken,

I have to say I am pretty happy with the results even "overfeeding" like I am doing. If the only consequence is a poor finish, I can live with that.

If the overfeeding can somehow damage the machine, then I would want to turn it down.

The sherline has these plastic-like (maybe teflon?) gibs. I am guessing they would get beat up but the rest of the machine would survive. Any opinion on that?

Thanks again,
Swami

[Ken_Shea]

Swami the final judgment must come from you but if my machining was at times so rough that "All the chips on the workbench hop" that would not be acceptable to me at any time and I would do what was necessary to alleviate that. If it takes an extra hour or whatever to machine because you slow it down or reduce the DOC, does that really matter in the end. If you are making thousands of these then that is an issue but not for just a few. If you are going to make thousands of these then you have purchased the wrong mill anyway

You might want to check that the gibbs are tight, could be there is play (would not take much) and that will cause the problem you mention as well.

[HuFlungDung]

"All the chips on the workbench hop"

Or you could perhaps solve the problem by getting a heavier benchtop Really, sometimes a sympathetic harmonic can occur that makes things seem worse. I have the same problem with my Bewo cold cut saw. Its built on a crap factory sheetmetal base, and vibrates like a bas..... like a son of a gun under certain sawing conditions. I've a mind to pour the thing full of concrete next summer.

[bookwurm99]

"I've a mind to pour the thing full of concrete next summer."

Why not fill it full up with lead?