Newbie looking for some help with CCMT21.5

[Harold_V]

@Harold,

Can you please give a little more info on the mistake of using inserts vs. grinding my own tools. Yes, my thinking was use inserts to save the learning curve of grinding my own. My thoughts were just stick the insert in and go, looks like I might have been mistaken.

My position on that subject is much the same as learning to play a musical instrument. There's no shortcuts---you must learn the scales, and practice. The point being that unless you understand cutter geometry, you can't evaluate problems when they arise, as they have in your case. By grinding HSS tools, you gain the required understanding---which then allows you to solve problems without being at the mercy of suppliers of carbide tooling. If you expect to perform at a specific level, you must jump through the hoops required.

Few with small machines benefit from insert tooling. It's costly, and often can't be used to the advantages offered by carbide, due to lack of rigidity and power at the spindle. The only real benefit is using carbide for hard or abrasive materials, where HSS may not offer the necessary wear resistance. I'm not trying to judge your machine in this instance, but it's something you should do in order to ascertain that you are truly benefitting by the use of carbide. If you have a fractional horsepower motor on the spindle, it's highly unlikely you are benefitting at all----made obvious by the fact that you're not achieving your goal--that of machining.

In your first post you made a comment that is troubling. There was some mention of the tool being parallel to the face. That's never acceptable. When machining, the contact of the tool should be limited---for the greater the amount in contact, the greater the chance of chatter. That's the reason form tools perform poorly on small machines. So then, if the tool contacts the entire face of the part as you feed in, you should expect trouble. A few degrees of clearance is always a good idea. Relocate the tool so only the tip makes contact, then give the setup another try.

I took note of the comments to Pix---that the chuck is new. Most likely it's not sprung. You may simply be asking too much from a small machine. Such machines are not generally up to the task of running carbide to its ability.

Harold

[jpad]

There's no shortcuts

You'd think I knew this by now.

It's the toolholder that is parallel to the face. The design of the toolholder provides a 95 degree approach.

Let's say I was to look into hss, does one typically secure the tool in the toolholder location of my turret style toolholder or do you use the rocker type holder?

Thanks again.

[Harold_V]

It's the toolholder that is parallel to the face. The design of the toolholder provides a 95 degree approach.

Good that it does, but bad in that that isn't the reason for your problem.

Let's say I was to look into hss, does one typically secure the tool in the toolholder location of my turret style toolholder or do you use the rocker type holder?

Let me begin by saying that I worked in machine shops for all of my 26 years in the trade. I routinely used a mixture of HSS, brazed carbide and insert carbide tooling, whether using a quick change, or a square block (my preference for small work). The geometry of the cutting tool remains the same so long as you don't use a rocker (lantern type) tool post. The only real difference in geometry between HSS tools and carbide is generally the relief angles. Carbide, lacking tensile strength, tends to be ground or formed with minimal relief angles, to bolster strength. The only real difference beyond that is the chip breaker, and the ability to create them. That spells the difference between a person that is truly a machinist and the guy that thinks he is. Chip breakers are key to success and safety.

There's a lot to be gained by learning to grind tools. You'll come to understand the relationship between rake and relief, and how they interact to fine tune a cut. It's unlikely you'd gain the same understanding from running carbide---you select an insert and that's what you use. If it performs, you use it. If it doesn't, you select another. You may not even understand why it does what it does, or what it takes to make a useful change. In a nutshell, you are short changing yourself. Cheating at solitaire, if you will.

Don't misunderstand. I'm not against the use of carbide---I simply don't think it's the answer to everyone's problems, and it isn't. Part of the false promotion of carbide use is at the hands of CNC operators, many of whom have no clue about grinding tools, nor could they benefit by having the required skill and talent. CNC's demand the ability to replace cutting edges without having to re-program. That's not a necessity for manual machines.

If you'd like to pursue grinding HSS, there's quite a lot of useful information posted in the Resource Library. Take a look if you're interested. http://www.chaski.org/homemachinist/viewforum.php?f=44

Harold

[qualitymachinetools]

Try to look up the speeds and feeds for the insert that you are using. Do you know what brand it is? As richard said though, you probably have to really crank up the speed, and the feed too. There are inserts that I use, that if you are going at a slow feed rate or too slow RPM the same thing will happen, but if you crank the speed up, you get a beautiful mirror finish and they last a long time.

It could also just be the insert. There are a lot of cheap ones out there, and I've used them with results like you have.
Send me your name and address (address for post office) and I will mail you a TMX Insert, see if you have better luck with that to eliminate the insert as a problem. Email it to matt@machinetoolonline.com

Most plain cold rolled is 1018, which as already said, isn't the best for machining compared to the leaded steels, but, you should be able to get a good finish on it.

But I also agree a lot with Harold, it is always good to learn to grind your own tools. That was the first thing I ever learned in machine shop school, before actually using a lathe. But now, the only time I grind tools is if I absolutely have to, and that isn't very often.

[Richard_W]

Try to look up the speeds and feeds for the insert that you are using. Do you know what brand it is? As richard said though, you probably have to really crank up the speed, and the feed too.

The rule for carbide is if the carbide is braking speed it up. If the carbide is burning up slow it down.

I am thinking that for as light of a cut he is taking he should be running around 700 SFM. Most likely his lathe won't go that fast. About 2600 RPM.

Richard W.

[jpad]

Thanks all,

I've only had a few minutes to tinker but some quick tests have shown the following. I tried taking a deeper cut but i must have some looseness, or the machine is simply not rigid enough to handle the load because the chatter is terrible. But, I cranked the speed to 2100RPM with no more than .002" cut depth while turning and the finish was very acceptable to me. If I take any deeper cut it chatters again. While turning I had about 8" extended and 4" in the chuck. If the machine was rigid, I should be able to take a deeper turning cut right, or would I have to turn between centers to help support the outboard end.

[Harold_V]

You just defined your problem. Rule of thumb dictates that you should turn objects extended from the chuck no more than three times the diameter of the material (without support by the tailstock or a steady). It is totally unreasonable to expect to face a piece of stock that is extended 8" unless it was at least 2½" diameter.

A real test will be to chuck the material extending only a half inch or so. Take a serious (facing) cut, running at the highest speed at your disposal (assuming it's not greater than 2500, and the material is 1" diameter or less). If you get no chatter, problem solved.

Harold

[jpad]

Yes, I'm looking forward to the next test, can't imagine why the higher speed wont fix that problem too.

[MasterMaker]

It could very well be a question of rigidity rather than the cutting tool/feed/speed.

I removed the compound on my lathe and replaced with a solid block of steel of the same height as the aforementioned compound.

All of a sudden I got great finish on steel's that previously refused to give me anything close to what I would define as finish.



Fixed it!

[PixMan]

I don't know where you are hosting that photo from but I suggest you delete it immediately and find Photobucket or some other reliable and safe host. Clicking on that photo resulted in all kinds of spam diversions.

[MasterMaker]

I get no spam(popups) when I click it only a windmill add(green energy) as an cover ad the first time I click on an imagevenue link(if I log of and log on again it repeats) I use it because it is consistently the most reliable image host I have found(I don't think I have ever seen a missing image(unless removed by the uploader)from them).

Granted I do use firefox with the "no popups" and "AdBlock plus" addon but.....

[Fullautomike]

I got the windmill pop-up and an adult site, pop-up