Poor Surface Finish

[Tom S.]

I'm new to using bulletin boards so if I am not following the rules correctly let me know and I'll adjust.

I recently bought a used Enco 12 x 36 lathe model number 110-2072 built in 1989. This is a Taiwanese machine, not mainland China. Before making the puchase I ran it in several speeds with the longitudinal and cross feeds engaged. It ran quiet and smooth. I was not able to make a trial cut because the tool post was missing. The lathe is in good physical condition as there is no noticeable wear on the ways or cross slide gibs. And the paint is in relatively good condition for its age. For info the lathe was mounted on a wood bench and has the original 1-1/2 HP Chinese motor wired for 110V and mounted it on a Harbor Freight metal lathe stand with vibration isolator type pads.

The problem I have is the gear noise is now much louder and the surface finish is poor. I attribute the increased gear noise to the metal stand. The tool bit curls a nice chip but the surface has a spiral pattern. I've checked the spindle bearings with an indicator while prying lightly radially and axially on the chuck. There is virtually no detectable movement. I visually inspected the headstock and change gears and they look to be in good condition and changed the idler change gear bearings because they were a little rough. The head stock oil was drained and refilled with Mobil DTE Medium/Heavy spindle oil.

Before spending a lot of money replacing the headstock bearings I'd like to get feedback on what is causing the poor surface finish. Could the problem be in the apron gear train? How about the change gear mechanism?

Thanks in advance for helping solve my problem.

Tom S.

[Boostinjdm]

I've been running into the same problem off and on with my recently purchased lathe. Check for slop first in your carriage, cross slide, and compound. Then look at your cutter geometry. I found my insert tooling (negative rake) works best with very heavy cuts and my brazed carbide (zero to positive rake) for lighter. From what I have read around here, HSS is a good choice too.

[AiR_GuNNeR]

I had a similar problem a while back. For me it started quite suddenly. No matter what I did, I ended up with chatter, and a pattern on the cut. It wasn't until I tried cutting some pretty darn hard steel, that I noticed with the increased cutting force, when I entered the cut, I could see the cutter deflecting downward. It turned out to be a chip underneath my QCTP was allowing it to rock. Like Tom S said, check for slop and looseness from the carriage on up to the tool holder.

[squirrel]

I'm new to using bulletin boards so if I am not following the rules correctly let me know and I'll adjust.

I recently bought a used Enco 12 x 36 lathe model number 110-2072 built in 1989. This is a Taiwanese machine, not mainland China. Before making the puchase I ran it in several speeds with the longitudinal and cross feeds engaged. It ran quiet and smooth. I was not able to make a trial cut because the tool post was missing. The lathe is in good physical condition as there is no noticeable wear on the ways or cross slide gibs. And the paint is in relatively good condition for its age. For info the lathe was mounted on a wood bench and has the original 1-1/2 HP Chinese motor wired for 110V and mounted it on a Harbor Freight metal lathe stand with vibration isolator type pads.

The problem I have is the gear noise is now much louder and the surface finish is poor. I attribute the increased gear noise to the metal stand. The tool bit curls a nice chip but the surface has a spiral pattern. I've checked the spindle bearings with an indicator while prying lightly radially and axially on the chuck. There is virtually no detectable movement. I visually inspected the headstock and change gears and they look to be in good condition and changed the idler change gear bearings because they were a little rough. The head stock oil was drained and refilled with Mobil DTE Medium/Heavy spindle oil.

Before spending a lot of money replacing the headstock bearings I'd like to get feedback on what is causing the poor surface finish. Could the problem be in the apron gear train? How about the change gear mechanism?

Thanks in advance for helping solve my problem.

Tom S.

Post a pic of your set up and a close up of the surface finish. Most of the time its issues with the material and tooling. If your trying to run something like 1018 it will look crappy. Get a piece of 12L14 and it should be smooth and shiny. That is a quick test to eliminate mechanical issues.

[Tom S.]

I've been running into the same problem off and on with my recently purchased lathe. Check for slop first in your carriage, cross slide, and compound. Then look at your cutter geometry. I found my insert tooling (negative rake) works best with very heavy cuts and my brazed carbide (zero to positive rake) for lighter. From what I have read around here, HSS is a good choice too.

Thanks for your feedback. I'll inspect the carriage, cross slide and compound and see if any of these are contributing. I'm using HSS with positive rake for the trial cuts in aluminum. Haven't tried carbide yet.

[Tom S.]

Post a pic of your set up and a close up of the surface finish. Most of the time its issues with the material and tooling. If your trying to run something like 1018 it will look crappy. Get a piece of 12L14 and it should be smooth and shiny. That is a quick test to eliminate mechanical issues.

I'll take some pictures and forward them. Using HSS on aluminum the finish is shiny just not smooth.

[SGW]

Yes, what kind of material are you cutting? If you can get a piece of 1144, try that.

Here's a suggestion: look for something amiss with the gear train, a bad shaft bearing or even a chip wedged in the gear teeth. The spiral pattern to me suggests something periodic, not spindle bearings.

[PixMan]

Where are you located? These problems are often easily diagnosed by having a second set of eyes look at things. If you were within an hour or two drive of me, I'd be happy to help.

That's the thing about the internet; it can be helpful, but nowhere near as good as two guys getting together and talking things over as you look at the problem.

[PeteM]

If you're getting a "spiral pattern" chances are the feed rate is too high. Try a sharp cutter but with significant nose radius, the proper speed, and a slow feed.

The other issues, plus belt and motor vibration, are other possible issues. Depending on the material you may also need to have at least a modest depth of cut and a high positive rake to avoid tearing.

[Tom S.]

Post a pic of your set up and a close up of the surface finish. Most of the time its issues with the material and tooling. If your trying to run something like 1018 it will look crappy. Get a piece of 12L14 and it should be smooth and shiny. That is a quick test to eliminate mechanical issues.

OK I'm stumped. How do I attach files to a response?

[Tom S.]

Yes, what kind of material are you cutting? If you can get a piece of 1144, try that.

Here's a suggestion: look for something amiss with the gear train, a bad shaft bearing or even a chip wedged in the gear teeth. The spiral pattern to me suggests something periodic, not spindle bearings.

We're on the same page. I suspect the problem is in the gear train as well.

[Tom S.]

Where are you located? These problems are often easily diagnosed by having a second set of eyes look at things. If you were within an hour or two drive of me, I'd be happy to help.

That's the thing about the internet; it can be helpful, but nowhere near as good as two guys getting together and talking things over as you look at the problem.

Thanks for your offer. I see you are in Massachusetts. Unfortunately I'm in California.

[Tom S.]

If you're getting a "spiral pattern" chances are the feed rate is too high. Try a sharp cutter but with significant nose radius, the proper speed, and a slow feed.

The other issues, plus belt and motor vibration, are other possible issues. Depending on the material you may also need to have at least a modest depth of cut and a high positive rake to avoid tearing.

I'm taking cuts at the finest feed rate on the chart, about .005 per revolution. The drive belt has been changed from a standard "V" to a Fenner Powertwist. The belt seemed to help but hasn't cured the problem entirely. Next step is to run the motor without the belt and see how smooth the motor is.

[Carld]

To attach photo's to a post you have to use PhotoBucket or a similar site. You upload the photo to PhotoBucket and then click on the img line in the drop down under the photo and it saves it. Then you open the reply window and hold down ctrl key while you hit the V key and a series of numbers and letters will appear in the reply window. when you hit Submit Reply the photo will be in the post along with any text you type into the reply window.

The very top thread in the General page tells how to use PhotoBucket.

[PixMan]

Thanks for your offer. I see you are in Massachusetts. Unfortunately I'm in California.

It's not just that I'm offering to help, but just planting the seed of thought so that you might ask someone near you to visit and offer help.

Others near you might offer without prompting if you'd add your location to your profile. I know I'll help anyone near me who wants it without obligation, reciprocation or compensation, and do so with a "your shop or mine" offer. The only caveat being you have to put up with an hour or more of ME and my unending diatribe.