Atlas 12/36 Question

[the gentleman]

Steve, Taper was probably the wrong word.. I should have said inconsistant diameters.

I imagine that tightening the carriage, by pulling it down, would stop potential chatter, but wouldn't help with uneven cuts being that the carriage still drops into the low area of the ways. Thanks for your and everyone elses input. Chuck

MAKE SURE YOU ALWAYS MAKE A CUT TOWARD THE HEADSTOCK AND NOT THE OTHER WAY :nono:

 

[tripletap3]

Just to throw my 2cents worth in Chuck. I know I preach this all the time to Atlas owners. CAN THE CARBIDE! Get HSS. Arthur Warner Co sells indexable HSS bits and holders that will perform a zillion percent better than carbide inserts do on the Atlas lathes. I personally hate those triangle insert lathe tools but If you don’t want to spend the initial investment on a new tool You might be able to buy just the HSS the inserts for your current ones. http://littlemachineshop.com/info/inserts.php. You will be amazed at the difference. To explain this the fastest way I can. Some people think that carbide is just better than HSS because it is stronger and stays sharper, but the two actually work completely different to remove metal. HSS cuts away the metal as carbide microscopically chips it away. This is why carbide requires much faster speeds AND more rigidity on the work piece and tooling to make a smooth cut. A exaggerated example would be if you were to lay a bock of wood on your work bench and slice a chunk off with a knife while holding it, this would be like HSS. Carbide would be like taking the same block and take a wood chisel and hammer and chip at. You would remove much more wood faster but you would get a inconstant finish and it would be more difficult to hold the block steady making the finish worse. Clear as mud yet? Loose machine tolerances are not as noticeable when using sharp HSS. My new lathe is much more ridged and powerful that my old Atlas but I still use HSS on 90% of everything. They are easy to resharpen and you don't have to figure out angles or have special grinding wheels just a flat stone and a drop of oil. http://www.youtube.com/watch?feature=player_embedded&v=LKGkkGFsF50

 

[ChuckB]

MAKE SURE YOU ALWAYS MAKE A CUT TOWARD THE HEADSTOCK AND NOT THE OTHER WAY :nono:

Yes.. it did sound like I was going away from the headstock.. I have been cutting from right to left.

You can buy a lot of HSS for the price of carbide. Yes it gives a better finish.

In the work shop, we do not care about spring as we will turn to an oversized diameter and then walk it over to the cylindical grinder and finish to size. Now most all home users do not have that type of equipment so going to finish size with a bit of polishing at the end is what one has to do.
Pierre

PS The Landis 12X24 cylindrical grinder that was listed in the posting about equipment for sale sold for the extremely high price of $330! The owner did drop the ball and did not get in on it. We still need an other one!

Increasing the spindle speed will help that.
Check the tip of the bit to make sure it isn't chipped.
I have several of those bits and they readily chips if you run them past the center when facing.
HSS bits will help, too. Do you have any you could try?

If you aren't addicted to this stuff yet, you aren't doing something right.

I have a lot of HSS.. I just haven't mastered the art of sharpening.. but the again, I haven't tried too hard.. had saw some great videos on youtube.. one by tubelicane comes to mind. I will give it another try.. only reason I used the carbide, because I had them and they were ready to go.

Just to throw my 2cents worth in Chuck. I know I preach this all the time to Atlas owners. CAN THE CARBIDE! Get HSS. Arthur Warner Co sells indexable HSS bits and holders that will perform a zillion percent better than carbide inserts do on the Atlas lathes. I personally hate those triangle insert lathe tools but If you don’t want to spend the initial investment on a new tool You might be able to buy just the HSS the inserts for your current ones. http://littlemachineshop.com/info/inserts.php. You will be amazed at the difference. To explain this the fastest way I can. Some people think that carbide is just better than HSS because it is stronger and stays sharper, but the two actually work completely different to remove metal. HSS cuts away the metal as carbide microscopically chips it away. This is why carbide requires much faster speeds AND more rigidity on the work piece and tooling to make a smooth cut. A exaggerated example would be if you were to lay a bock of wood on your work bench and slice a chunk off with a knife while holding it, this would be like HSS. Carbide would be like taking the same block and take a wood chisel and hammer and chip at. You would remove much more wood faster but you would get a inconstant finish and it would be more difficult to hold the block steady making the finish worse. Clear as mud yet? Loose machine tolerances are not as noticeable when using sharp HSS. My new lathe is much more ridged and powerful that my old Atlas but I still use HSS on 90% of everything. They are easy to resharpen and you don't have to figure out angles or have special grinding wheels just a flat stone and a drop of oil. http://www.youtube.com/watch?feature=player_embedded&v=LKGkkGFsF50

Thanks for the info.. Everyone has told me to same... ditch the carbide and try HSS!! I will give it a try.

Those HSS inserts are amazing!! I want some!

 

[ChuckB]

I thought everything was fine after I turned the large diameter piece.. Tried some smaller pieces <1" .. horrible finish.. inconsistant diameters..( maybe that could be a clue??)

I sharpened some HSS and I thought the bit looked pretty good, but same results. Took the motor drive apart and shimmed to remove any play that i could find and it did lessen the vibration, but same results.. This is why I lost intrest when I first bought this a couple years ago.. it's all coming back. I have spent at least 40 hours within the last week trying to get this to work for me. I am so fustrated..

 

[pdentrem]

I think you are seeing the difference between turning a large stiff piece vs a thinner flexi piece. The finish will not be the same if the cutting forces are not matched. What I mean is that the stiffer the work the deeper the cut in theory and vice versus with a lighter or longer part that requires a smaller cut and feed rate. Also is not supported enough. Using a tailstock to support the other end can have a very large effect of the final finish.
For example I regularly turn 4" long rods that are .420" +0/-.005". I have the rod supported with a center via the TS other wise you can visually see the part deflect away from the tool. Also if I take a heavy cut the center of the rod will be different than the two ends.
Tool sharpness, feed rates, tool height all have a bearing on the finish product.
Pierre

 

[ChuckB]

Where are you in Florida?

Did you get the problem with the front of the carriage fixed?

What shape did you grind the bit?

I am in Loxahatchee. I don't see any way of resolving the carriage play at the front, the ways on that side are worn. I ground a right hand bit, probably not perfect, but even when I used a carbide bit, I got the same results.. Maybe I should make a youtube video to show you..:thinking:

funny I was even thinking of putting an ad on CL looking for a retired machinist that could come by and show me whats wrong..

 

[ChuckB]

I think you are seeing the difference between turning a large stiff piece vs a thinner flexi piece. The finish will not be the same if the cutting forces are not matched. What I mean is that the stiffer the work the deeper the cut in theory and vice versus with a lighter or longer part that requires a smaller cut and feed rate. Also is not supported enough. Using a tailstock to support the other end can have a very large effect of the final finish.
For example I regularly turn 4" long rods that are .420" +0/-.005". I have the rod supported with a center via the TS other wise you can visually see the part deflect away from the tool. Also if I take a heavy cut the center of the rod will be different than the two ends.
Tool sharpness, feed rates, tool height all have a bearing on the finish product.
Pierre

I am staying close to the headstock and things are still lously.. Maybe I should try a long piece and use the live center.. I don't have a steady rest.

I checked the alignment of my tailstock using the center to center method.. found the tailstock to be too low when it dropped into the worn ways.. I shimmed the front of it to get it higher don't know if it right or not..

 

[pdentrem]

How are the spindle bearings? Can you move the spindle back and forth?
Did you tighten the gib on the back side of the carriage? Not the one on the underside, the one pushing against the side of the ways. This one is critical for a good finish.
How about the cross slide gibs? Top swivel bolts and top slide gibs.
Is the tool on center?
What does the leadscrew look like? How worn is it in the first 6" vs the last 6"?
Just some ideas. I had an Atlas as well for 20 yrs before upgrading. I had to fight some of this stuff all the time.
Pierre

 

[ChuckB]

How are the spindle bearings? Can you move the spindle back and forth?
Did you tighten the gib on the back side of the carriage? Not the one on the underside, the one pushing against the side of the ways. This one is critical for a good finish.
How about the cross slide gibs? Top swivel bolts and top slide gibs.
Is the tool on center?
What does the leadscrew look like? How worn is it in the first 6" vs the last 6"?
Just some ideas. I had an Atlas as well for 20 yrs before upgrading. I had to fight some of this stuff all the time.
Pierre

I checked the spindle for runout looks good. I put a long bar in the chuck and pulled it up and down and sideways with an indicator.. it changed and never went back to zero!!.. ahh haa!! turned out the 3 jaw chuck wasnt holding the bar in although tightened very tight.. I then switched to another chuck. Same test shows the spindle bearings are tight. Tried turning with the different chuck.. same results.. Tightened all gibs to the point of being too tight.. I only see the ones that are pushing against the ways in the back. I didn't see any on the underside.. Just plates and shims. Same goes for the cross slide and top slide gibs (compound). Swivel bolts are good and when disassembled had the two little angled rods. To center the tool, I use a fishtail up against the piece and make sure it's 90 degrees or a little low if any thing. The lead screw and nut are probably in very bad condition.. I turn the wheel to take up the play though..

 

[ChuckB]

Chuck,

You are correct, there are no gibs on the bottom, but you still have to adjust the spacing by using the shims. It should be .001 to .002. If your ways are worn, then the spacing should be set at the thickest area.

I had a problem with my spindle and long story short, the drive belt can mask slop in the bearings. To be sure, slacken the drive belt and repeat your test. With mine, originally, it was .002 with the belt tight and .016 with it slack. That might not be part of it, but you need to know for sure.

You know what ?.. maybe I had the belt tight when I did the test.. I will try it again... but I was really pull on that bar hard.

The shims increase play. I removed the shim in the front to try to tighten it up. Even with it removed I have .007 in the worn zone next to the headstock (eariler .005 post was in error). All the way to the right is tight.. around .001 or so I tried removing the shim in the back and it was too tight. I had to put it back.

I think the worn ways would account for the measurements of the piece changing from end to end.. but shouldn't I be able to get a good finish?? User error??