Fastest way to remove 1/2" of AL from a round

[marka]

Howdy,

I'm making some wheel spacers. They're similar to this:


Except the hub really sticks out 1/2", not 1/4" like the drawing shows.

I turned the first one on a small Southbend 9C lathe, and will eventually drill the holes on a mill w/rotary table. However, my question is really related to what the best way to remove the 1/2" of material from ~6" down to the hub flange @ ~3" is. Doing this on the lathe took quite a while, as the lathe didn't want to make a facing cut of more than about .050" without struggling. Also, I'd have to stop mid cut to clear stringers away or they'd get jammed up between the cutter (I was using triangular carbide inserts) and the workpiece.

I'm curious if I'd be better off for faster material removal to rough the part in on a rotary table with a roughing cutter in a mill (RF-45 clone).

Any advice? Material is 6061 AL.

Thanks!

Mark

[Harold_V]

Also, I'd have to stop mid cut to clear stringers away or they'd get jammed up between the cutter (I was using triangular carbide inserts) and the workpiece.

I am likely well known for speaking out against the use of insert tooling on small, light duty machines. They serve no purpose unless you are machining materials that present difficulties, and even then you may not benefit in the way one should.

I'm curious if I'd be better off for faster material removal to rough the part in on a rotary table with a roughing cutter in a mill (RF-45 clone).

Roughing end mills have relief ground in keeping with the needs of machining harder materials. That's not to say they won't cut aluminum, but you can achieve better performance with end mills ground specifically for aluminum. They tend to have greater relief angles along with polished flutes, so chip welding problems are reduced.

Any advice? Material is 6061 AL.

Yep.

Learn to grind proper tools in HSS. By applying a facing tool with a ground chip breaker, you would eliminate the string problem, and you may find that you can take a cut of better proportions. You would be limited by the power of your machine, obviously, so the benefits of the right tool may not be fully realized.

Given enough power and rigidity, removing the ½" you spoke of could be accomplished in about a minute, yielding either tight coils, or even C's or 9's for chips.

Harold

[marka]

Howdy,

Thanks for the reply!

The use of this:

I am likely well known for speaking out against the use of insert tooling on small, light duty machines. They serve no purpose unless you are machining materials that present difficulties, and even then you may not benefit in the way one should.

Is due to a lack of this:

Learn to grind proper tools in HSS. By applying a facing tool with a ground chip breaker, you would eliminate the string problem, and you may find that you can take a cut of better proportions. You would be limited by the power of your machine, obviously, so the benefits of the right tool may not be fully realized.

Is there a web reference or something that'll show me how to grind a good HSS facing tool? I'm not opposed to doing it, but you rightly assume that I don't know how to.

Being able to remove 1/2" off the face from 6" to 3" in a minute... Is that realistic with a smaller lathe like a 9" workshop? I wouldn't have been asking the question if I could have done it even in 10 minutes, but as is probably clear I'm not much more than a hack with this stuff. I mostly know how to keep my hands out of the machine and that's about where my real knowledge ends.

Appreciate the response!

Mark

(also, anyone know why I have to keep logging into this forum? I'm using Chrome and am setting the "keep me logged in" checkbox...)

[BadDog]

Long feed will pretty much always allow heavier cuts than cross just due to the geometry. And unlike facing, you keep the same speed in the cut (albeit short). So I would expect the best solution is to make a rapid series of cuts at max removal rate to about 0.450 leaving 0.050 or a 1 or 2 pass facing cut (depending - more if needed for tolerance). While speed is for all practical purposes almost unlimited when using carbide for aluminum (somewhat less so for HSS) on typical HSM machines, you'll likely need to drop speed to get torque multiplication at that diameter on that lathe. As you get closer to center, increase the rpm to keep speed up. Not sure where the sweet spot would be, but I would hate to try to cut aluminum with carbide at speeds that SB can sustain.

As someone who once was where you are (but using a Griz 9x20), and having no idea what to do with HSS, I would suggest taking (making) the time to read the various FAQ threads covering that subject here. It was reading and pondering those posts that finally made things start to "click" for me, and though I do still use both brazed and inserted carbide, I'm very comfortable with HSS and use it frequently.

And I would certainly do it on the lathe.

[John Evans]

Mark: Go to the sticky at the top of this forum "The Resource Library" , there you will find a LOT of info on grinding HS tooling.

[GlennW]

Welcome to the group Mark!

Actually, this is the link to "The Resourcr Library".

http://www.chaski.org/homemachinist/viewforum.php?f=44

[jim rozen]

Russ's suggestion is a good one, I think that sort of stock removal is often called "step facing"
because when you are done, the material is faced off, but it's done in a series of longitudinal
cuts. Often I leave five or ten thou of material left to allow a final facing cut.

For aluminum the machine should be run at its maximum speed, consistent with enough
torque available at the larger diameters as has been mentioned.

WD-40 makes a convenient, good cutting fluid for aluminum.

Jim

[Harold_V]

Howdy,

Thanks for the reply!

Welcome!

Being able to remove 1/2" off the face from 6" to 3" in a minute... Is that realistic with a smaller lathe like a 9" workshop?

No, which is why I alluded to the idea that you likely would be limited by the power of your machine. Rigidity also plays a huge role, both of which are most likely lacking on a 9" machine of almost any description. However, the concept of using slower surface speeds with greater depths of cut and faster feeds is very important if you'd like to avoid the strings you spoke of. I used the minute example to illustrate that it's possible, but it's not going to happen with your machine.

I see that you have been directed to information on grinding HSS turning tools. Do yourself a favor and pay strict attention to the process. Once you understand how to grind tools and chip breakers, you can handle tasks of this nature quite easily. Because you can tailor the cutting tool to the job, you often can remove far more metal than you could using carbide. That isn't necessarily the case for the guy with plenty of horsepower and rigidity, where the benefits of carbide can be used to advantage, but your case is very unlike that.

I speak out against the use of insert tooling as a substitute for going through the learning curve of grinding HSS. It is likely the biggest mistake a newbie can make. Mastering the art of grinding tools provides more than just the tool---you gain a functional understanding of tool geometry---which will serve you from that day forward. When you look at a tool, you can analyze why it performs as it does, and can make corrections to turn a poor performing tool into one that performs well. That isn't likely if you don't understand the geometry.

I wouldn't have been asking the question if I could have done it even in 10 minutes, but as is probably clear I'm not much more than a hack with this stuff. I mostly know how to keep my hands out of the machine and that's about where my real knowledge ends.

Not a problem. None of us are born with this kind of knowledge----it is often hard to come by if you don't have someone to set examples. I was fortunate to have had a myriad of journeymen to help me learn the machining trade.

(also, anyone know why I have to keep logging into this forum? I'm using Chrome and am setting the "keep me logged in" checkbox...)

In order for the board to remember you, you must allow cookies. That may or may not be the reason you aren't enjoying success. If you allow them and are still not remembered, perhaps others with greater computer skills can make a suggestion.

Harold

[lakeside53]

Why bother with a rotary table for the holes? Calculate your hole placement with one of the many free bolt-circle calculators available on the web, and use your dials or DRO for XY positioning. I never break out my rotary table for that type of work.

Not withstanding all the good advice you're getting about the use and grinding of HSS, there are some very good carbide inserts made expressly for aluminum - highly polished, razor sharp with a very positive rake, and they do not need big lathes for them to cut very well. I've used them on a 10 inch lathe and the results were excellent.

[marka]

Howdy,

Thanks for the help folks. Can't believe I missed the FAQ stuff on grinding HSS tools, I'll go check that out. Sorry about that.

For the next ones I'll go with the step facing approach and try my hand with some HSS tools. I'm travelling right now and the SB9C was my dad's lathe. When we're back home and I have time to hit this again I'll have access to an SB 16 or a heavy 10, so I might get a little improvement just from that.

As for why the rotary table for bolt circles, it just seems easier. I've got to indicate in a starting location either way and once I've done that and offset the table for the bolt circle diameter, the rotary table lets me just crank one dial in one direction until I'm done.

But its certainly food for thought, particularly if I don't have a rotary table available.

Appreciate the newbie advice!

Mark

[marka]

Howdy,

Also, its a pretty minor point but I was using the wrong terminology in my first post with regards to "stringers" it seems like...

In my case the inserts were trying to produce spirals with the chip breaker that was there. I believe the inserts were TCMM inserts (I'm guessing, based on the picture at littlemachineshop.com looking like the inserts and holders I was using). They looked like these ones: http://www.littlemachineshop.com/produc ... &category=

The issue came that the spiral would often be a little too big or perhaps start too quickly, such that the end would wrap over and get caught between the piece and the toolholder, gumming up the works. Once that happened, it would produce stringers, shooting the long chip out whichever way it could fit until I'd stop, clear it all, and keep going.

I eventually cheated and probably horrified OSHA inspectors everywhere and used the end of a large flat screw driver held back just a bit from the cutting surface to guide the spiral away for a bit. That would produce a nice 1/2" diameter or so spiral that went off out of the way. Or at least out of the way until it got really long and eventually hit something and got caught up in the works. To stop _that_, I'd interrupt the cut to break the chip.

I just figured I'd post some more examples of how much I don't know...

Mark

[marka]

Howdy,

(also, anyone know why I have to keep logging into this forum? I'm using Chrome and am setting the "keep me logged in" checkbox...)

In order for the board to remember you, you must allow cookies. That may or may not be the reason you aren't enjoying success. If you allow them and are still not remembered, perhaps others with greater computer skills can make a suggestion.

This prompted me to go look at the cookies that were being set (yes, they're allowed). Turns out the cookie that was being set was owned by "chaski.org" and I was using the "chaski.com" url to get here. I imagine that's why the cookie wasn't being found.

I switched my bookmark to use .org to match the cookie, so I imagine it will work now.

Thanks for the prod in the right direction!

Mark