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calixt0
03-04-2015, 05:09 PM
Hello all,

So I ground my first tool.. a simple tool for turning right to left. I can take pics if wanted. well I'm turning some 6061 al, and it appears likes its tearing chunks out of it instead of a smooth nice looking cut (again can take pics if needed). I've tried turning at around 300 rpm up to 1100 rpm on my little 7x14 lathe. I used the autofeed as well as turning by hand to slow it down. Depth of cut was between .005 and .001".

Any advice would be appreciated.

Shaun

Mike Burdick
03-04-2015, 05:16 PM
Is the tool bit on the centerline?

Let's see the photos...

calixt0
03-04-2015, 05:16 PM
To the best of my ability yes. Mike.

ahidley
03-04-2015, 05:16 PM
Make sure the cutting edge, that you ground, is at dead center or a few thousandths below. Center being the axis of rotation of the aluminum stock that you are turning down

ahidley
03-04-2015, 05:19 PM
If it's above it will chatter. If at or below it won't

dp
03-04-2015, 05:21 PM
Pictures would be a definite plus.

calixt0
03-04-2015, 05:25 PM
will get some pics. and will also try lowering it in the qcth. thanks for the help guys. it may be chatter but it doesn't look like any chatter i've ever seen before.. but i'm new to this stuff.. so????

Forestgnome
03-04-2015, 05:37 PM
A good way to check tool height is to pinch a 6" steel rule between the tool tip and the work. Adjust height until the rule is vertical.

Paul Alciatore
03-04-2015, 05:40 PM
Slow it down? Your RPM figures are worthless without a diameter so that SFM can be calculated. Heck, you may need to speed it up.

Aluminum can be gummy and that can cause what you describe. It builds up on the cutting edge, effectively dulling it. The next two ideas are to fight this.

Use some cutting fluid. WD-40 works great for aluminum.

Is your tool dead sharp? If you just formed it on the bench grinder, try finishing it with a fine oil stone. For cutting aluminum, I like the tools to have a mirror finish. This can also be accomplished on a belt sander with a fine belt (perhaps even a worn one) and a bit of cutting oil added.

Do you have a proper clearance angle on your tool? If not, then you are plowing instead of cutting.

PStechPaul
03-04-2015, 06:06 PM
You should be getting mostly continuous curly swarf that resembles a "slinky (http://en.wikipedia.org/wiki/Slinky)". I thought it was actually "invented" by a machinist when he saw how the swarf from lathe turnings acted. It looks like this:

http://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/2006-02-04_Metal_spiral.jpg/350px-2006-02-04_Metal_spiral.jpg

Here is some swarf, but mostly from drilling, so it has a conical shape matching the cutting angle of the drill bit:

http://enginuitysystems.com/pix/tools/Swarf_1271.jpg

For turning, the cutting action is mostly on the left side of a right-hand lathe bit, and it should be perpendicular to the axis of the spindle, or slightly angled so the outer diameter is cut more than the inner diameter. I have found that a tool shapened to about 90 degrees and positioned so that the tip has a few degrees of relief behind the cutting edge makes a pretty good finish. It's also important to have a slight radius on the cutting point, and the cutting edges should be honed with a fine diamond file or stone until it is smooth.

Here is a video clip showing me turning an aluminum disc:
http://enginuitysystems.com/pix/engines/DSCN0855.AVI

mattthemuppet
03-04-2015, 06:12 PM
ditto what everyone else said. In addition, at those depths of cut any flex or movement in your compound, cross slide, toolpost etc will push the work away and then you'll get it springing back for a deeper cut, then push away. Try a 0.01 or 0.02 cut at least and see how it cuts. If you're not getting a good cut, something else is going on.

calixt0
03-04-2015, 06:16 PM
will try the level with a steel rule trick. Paul, sorry i did use the oatley cutting oil. will try wd40 as well. stock was originally .750 diameter and last cut was measured with a mic at .690. I do believe i have proper clearance angle and even tried playing with the angle tool approaches material to several different tries.. pics to follow

tool http://i1134.photobucket.com/albums/m614/calixt0/GEDC0018_zpsmskafck3.jpg

material http://i1134.photobucket.com/albums/m614/calixt0/GEDC0017_zpstco0fy0a.jpg

angle of approach.. tried this to a straight 90° http://i1134.photobucket.com/albums/m614/calixt0/GEDC0019_zpspb237c4b.jpg

i will do some more but i did do some honeing with my lansky fine and ultra fine stones.. again thanks for all the advice keep helping a newby guys

goose
03-04-2015, 06:32 PM
You might be getting vibration in the stock. Depending on how far it sticks out the chuck, and also how far it sticks out on the left hand side of the headstock. Shorter stock is less prone to vibration, which can lead to chatter or a grainy, irregular surface.

Have you tried turning between centers ?

calixt0
03-04-2015, 06:45 PM
Gary will put a center and see if it helps

brian Rupnow
03-04-2015, 06:51 PM
Your cutting tool shouldn't have a sharp tip like a dagger. It should have a very small radius, about .030" on the tip. This radius is best achieved by "wiping" the tip along an oilstone. The right hand side of the tool just adjacent to the tip should be just a small bit off parallel from the side of the workpiece. It is too aggressive the way you have it set up.---Brian

polepenhollow
03-04-2015, 06:59 PM
Cutting tool on center. !!! Put scale between tool tip and work. If it is vertical, tool is on CL.

Face off piece and notice center tip on the work after face off. If there is a Dia there, you are below CL, or watch, you may be above center.

calixt0
03-04-2015, 07:02 PM
Brian, my first go round i did swipe and radius the point. after not getting good results i tried the sharp and thought i'd try again.. will swipe again as well as all the other advice 1 thing at a time

brian Rupnow
03-04-2015, 07:07 PM
A couple of things--First, you don't really need any top rake on the tool for aluminum. In fact, I don't even put any top rake on for turning steel. With an AXA style toolpost, this is a big plus because you don't have to keep fiddling with the height of the tool as it is ground away when sharpened. I just turned this piece of 3/4" aluminum at 1000 RPM with no coolant nor lubricant. It is smooth as a babys bum!!! The tool does have the small radius turned at the tip, and you can see in the picture how the surface immediately to the right of the tip is almost parallel to the side of the workpiece.---And yes, it is on center. Your maximum depth of cut shouldn't be more than 0.005" (that amounts to .010" on the diameter) for rough cuts, and should be reduced to .002" depth of cut for your finishing pass.
http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow024/CUTTING%20TOOL%20001_zpsbe6qbpcn.jpg (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow024/CUTTING%20TOOL%20001_zpsbe6qbpcn.jpg.html)

calixt0
03-04-2015, 07:25 PM
ok.. rounded the corner, and supported the end with a live center and ran another test.... much better thanks for helping a newby like myself

Mike Burdick
03-04-2015, 07:27 PM
From your photos, it looks like the bit is rubbing. Try making a deeper cut - like 0.050" and see what happens.

From your photos it appears that the tool bit doesn't have any back rake. On low horsepower machines that makes a big difference. Got any photos showing the side view of the tool?

vpt
03-04-2015, 07:39 PM
angle of approach.. tried this to a straight 90° http://i1134.photobucket.com/albums/m614/calixt0/GEDC0019_zpspb237c4b.jpg



You said you are running this tool from left to right? Try running it the other way and see what it does.

calixt0
03-04-2015, 08:00 PM
yes there is a back rake and yes i tried cutting left to right.. didn't do any better

Paul Alciatore
03-04-2015, 08:26 PM
According to my calculation, your speed should be up to 3000 RPM. I generally find that faster speeds produce a better surface finish.

Does that tool have a negative rake angle? I have never tried that when cutting aluminum with HSS. All my experience is with positive rake tools. It seems to me that a negative rake tool would be pushing the chip back into the work. That seems like a bad idea with a soft metal like aluminum.

https://images.search.yahoo.com/yhs/search;_ylt=A0LEVjuTsPdUprQAbMklnIlQ;_ylu=X3oDMTB0 N25ndmVnBHNlYwNzYwRjb2xvA2JmMQR2dGlkA1lIUzAwNF8x?_ adv_prop=image&fr=yhs-mozilla-002&va=lathe+tool+rake+angle&hspart=mozilla&hsimp=yhs-002




will try the level with a steel rule trick. Paul, sorry i did use the oatley cutting oil. will try wd40 as well. stock was originally .750 diameter and last cut was measured with a mic at .690. I do believe i have proper clearance angle and even tried playing with the angle tool approaches material to several different tries.. pics to follow

tool http://i1134.photobucket.com/albums/m614/calixt0/GEDC0018_zpsmskafck3.jpg

material http://i1134.photobucket.com/albums/m614/calixt0/GEDC0017_zpstco0fy0a.jpg

angle of approach.. tried this to a straight 90° http://i1134.photobucket.com/albums/m614/calixt0/GEDC0019_zpspb237c4b.jpg

i will do some more but i did do some honeing with my lansky fine and ultra fine stones.. again thanks for all the advice keep helping a newby guys

Rosco-P
03-04-2015, 09:01 PM
ditto what everyone else said. In addition, at those depths of cut any flex or movement in your compound, cross slide, toolpost etc will push the work away and then you'll get it springing back for a deeper cut, then push away. Try a 0.01 or 0.02 cut at least and see how it cuts. If you're not getting a good cut, something else is going on.

Ditto the above, you are rubbing with that light (.001-.005") doc, not cutting. Also as Paul A. stated, your rpm is too low. Try 2000rpm, doc .01, use WD-40 or Kero and see if the finish doesn't improve. Then repeat it at 2200 or 2500rpm and see if the finish is even better, then 3000rpm and see if you don't get a mirror finish. It's speeds and feeds, got to master them.

calixt0
03-04-2015, 10:29 PM
will up the speeds. as far as the cutter geometry i have 8-10°of side, end, relief and about the same of side rake with little to no back rake. again finally got it to but decent and will up the speeds and see if it helps.

thanks guys Shaun

calixt0
03-04-2015, 10:45 PM
I tried mimicking this video for the tool grind. https://www.youtube.com/watch?v=qCpIxq0kHzo

Mike Burdick
03-04-2015, 11:41 PM
... with little to no back rake. ...

Back rake should be anywhere from 5 to 20 degrees for aluminum. Here's a link that shows up to 35 degrees.... Basically, your bit is just removing the aluminum by scraping!

http://littlemachineshop.com/instructions/GrindingToolBits.pdf


Oh, one other item... dress the grinding wheel often to expose new abrasive elements - it'll make grinding the tool bits much easier, faster, and cooler!

Here's a typical wheel dresser; they cost less than $10.00.

http://d2pbmlo3fglvvr.cloudfront.net/product/full/2X951_AS01.JPG



.

PStechPaul
03-05-2015, 12:52 AM
There are other good videos on tool bit grinding. This one is pretty good:


https://www.youtube.com/watch?v=bvJhRtRR7rk

Also Mr. Pete (TubalCain):
https://www.youtube.com/watch?v=hrDr4rYLiAk

And this has a lot of detail. He shows a toolbit with an angle a little sharper than 90 degrees which can be used to turn to a square shoulder as well as for facing:
https://www.youtube.com/watch?v=i6-58tjALc0

As for wheel dressing, the type shown above is useful to deglaze a wheel, but to true it up you should use a single point diamond tool. I just bought a 1 caret tool 1/2" diameter and 6" long for less than $20 including shipping.
http://www.ebay.com/itm/371269190834 (http://www.ebay.com/itm/371269190834?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)

https://www.youtube.com/watch?v=ob97o7IyNNc

It worked quite well on my small K-mart grinder.

http://enginuitysystems.com/pix/tools/Grinder_Kmart_1155_800p.jpg
(That's before I used the diamand wheel dressing tool)

darryl
03-05-2015, 01:53 AM
I usually grind my cutters to a sharp point, making sure I've removed any 'rounding over' from cutting, then put the radius on with a diamond stick. One light drag of the stick across the top to remove any burrs, and it's ready to cut.

There are differences in the quality of HSS blanks, even when they look the same, etc. Some just seem to dull more quickly, while others seem to take quite a beating before needing a resharpen. Something to be aware of-

You should probably be looking carefully at the various plays on the carriage, and whether the tool post is free of rocking, etc. The crisper you can make all this work without binding, the better is the potential for getting good results. Also you might do some tests to see whether you have some play in the spindle. I've read that some of the 7x12 and 7x14 lathes don't have particularly tight spindle bearings. You should also check to see whether the carriage is contacting the rear way, or whether it's sort of floating just above it. There is a tendency for the front way to be taking most of the weight of the carriage and related assemblies, so a dubious contact to the rear way is entirely possible. Every area I addressed with my own lathe made an improvement in how nice of a cut I could get.

There must be a forum for those lathes- I'd be looking into that and reading all I could.

Forestgnome
03-05-2015, 08:55 AM
A couple of things--First, you don't really need any top rake on the tool for aluminum. In fact, I don't even put any top rake on for turning steel. With an AXA style toolpost, this is a big plus because you don't have to keep fiddling with the height of the tool as it is ground away when sharpened. I just turned this piece of 3/4" aluminum at 1000 RPM with no coolant nor lubricant. It is smooth as a babys bum!!! The tool does have the small radius turned at the tip, and you can see in the picture how the surface immediately to the right of the tip is almost parallel to the side of the workpiece.---And yes, it is on center. Your maximum depth of cut shouldn't be more than 0.005" (that amounts to .010" on the diameter) for rough cuts, and should be reduced to .002" depth of cut for your finishing pass.


Wow! It must take you a long time to make things. I usually rough cut at .075 DOC or so, and finish at .010 DOC on aluminum.

brian Rupnow
03-05-2015, 10:14 AM
ForestGnome--The man is using a mini-lathe, as explained in his first post. My lathe is a 10 x 18" unit, and although I can take a .010 depth of cut in aluminum it really makes it grunt. A .075" depth of cut would either fry the motor or blow out all the gears on a lathe as small as the o.p. is using.

Fasttrack
03-05-2015, 10:16 AM
Wow! It must take you a long time to make things. I usually rough cut at .075 DOC or so, and finish at .010 DOC on aluminum.

Ditto - I don't think any money earning shop in the world would limit themselves to DOCs less than 0.005"! Surely Brian Rupnow's statement is specific to the OPs 7" by 14" lathe. Although, even on my little Smithy piece-o-junk, I took 0.05" DOC in aluminum with no issues whatsoever.


Edit: Oops - I see Brian beat me to it!

Forestgnome
03-05-2015, 06:23 PM
ForestGnome--The man is using a mini-lathe, as explained in his first post. My lathe is a 10 x 18" unit, and although I can take a .010 depth of cut in aluminum it really makes it grunt. A .075" depth of cut would either fry the motor or blow out all the gears on a lathe as small as the o.p. is using.

Okay. I'll share my method. Increase DOC until you hear things slow down, back out a bit.

PStechPaul
03-05-2015, 06:31 PM
The power required to make a cut depends on the amount of material being removed (DOC * feed) as well as the speed (SFM). It also depends on the sharpness of the cutting tool and its geometry as well. When I was just starting out, and even now, I have usually run my 9x20 lathe at the lowest 120 RPM. When I was turning a large diameter, such as the 6" chuck adapter, or turning the 5" aluminum discs to 3-1/2", the lathe would stall if I tried to take more than .005 to .010 DOC (on radius, so twice that on diameter). But on work smaller than 1" diameter I've been able to take 0.030 cuts. I have usually used manual feed, but more recently I've been comfortable using power feed at about 0.005 to 0.008 per revolution. My lathe also has a torque-limiting clutch on the low speed, which just makes an awful noise when overloaded, and I'm usually ready with my hand on the switch when doing anything "dicey".

I don't have experience with the 7x10 to 7x14 mini-lathes, but I think they use a variable speed control and maybe only a single high/low gear change for spindle speed, so you may not get any more torque from lower speed. I think the motor is fuse-protected and I have heard of blown fuses on some of them. It's a good idea to get a few spares before you need them, as they may not be readily available from local stores.

Mike279
03-06-2015, 04:38 PM
I picked up a Mini Lathe before Christmas and have just gotten around to firing it up. It has the 500 watt motor belt drive. Just chucked a piece of aluminum tubing about .875 and .150 wall. Using the HF carbide cutter with a speed of 600 RPM I made a few passes with different DOC. I did not check the power feed rate but it is the out of the box gearing for that. Since the chuck is so small, the scrap is sticking out farther than I like. Anyways got up to .100 DOC before deciding I was not making the little lathe even grunt. Then a pass at 1000 RPM with a DOC of .005 and a pretty nice finish shows up. Now I know I did not grind this bit but I wanted a reference for the comments about this guys Lathe. I have to say this little lathe will not replace a good Lathe but it will make chips. Mikehttp://i158.photobucket.com/albums/t87/tashjian319/IMG_0519_zps9lldvfc8.jpg (http://s158.photobucket.com/user/tashjian319/media/IMG_0519_zps9lldvfc8.jpg.html)http://i158.photobucket.com/albums/t87/tashjian319/IMG_0520_zpscfj1boxc.jpg (http://s158.photobucket.com/user/tashjian319/media/IMG_0520_zpscfj1boxc.jpg.html)