Atlas 3995 Chattering

[gedkins]

Here is a bit more input. I took a bar of 6061 and chucked up close to chuck. Faced off end and drilled and countersunk the end. Put in a dead center, lubricated the center. Pulled the bar out with tail stock at far end of bed and made a cut as near the tail stock as could get. I believe this is telling me my headstock bearings are done.

 

[4WHLDRFTN]

The bearings are not bad.. Just loose.
Use a pointed bit and drop it down from center a few and cut away.

 

[gedkins]

All,

I have tossed in the towel on this one. Putting it up for sale. Thanks for all the input.

 

[Charles scozzari]

All,

I have tossed in the towel on this one. Putting it up for sale. Thanks for all the input.

Ahh don't do that. Cover it up and go back to it in a while.

 

[Backyardmachineshop]

Tighten the bearings slightly more than atlas tells you to and try it again. Im Betting you can tighten that out. My 3396 that I converted to a bench top was an absolute basket case when I bought it and it makes a fine finish, but I slightly overtightened the bearings and I run it very wet

 

[Backyardmachineshop]

As basket case vs how it cuts now

 

[matthewsx]

Well, you made it pretty now you need to make it work.

I was extremely frustrated trying to get a good finish on my Seneca Falls Star lathe but eventually got it done. Key was grinding the bit properly, I don't know if you can buy ones pre-ground that are worthy but what finally worked for me was one ground standard RH with a generous radius.

Massive thread here but if you haven't started grinding your own bits you really need to break out the grinder and start.

Thread 'Models for grinding HSS Lathe Tools'

Sep 9, 2017

In a recent thread by @Darkbluesky, http://www.hobby-machinist.com/thre...tools-ideas-of-what-to-buy.62043/#post-511618, @ttabbal joked about sending me blanks to be ground into lathe tools ... he was joking! But it got me to thinking ... yeah, I know it's not a good thing when Mikey gets to thinking ... but it got me thinking that reading about how a tool is ground and having a decent tool in your hands that you can see and touch are two different things.

So, what if I ground a set of tools from 3/8" mild steel keystock (just to discourage some bozo...

• mikey
• Replies: 1,878
• Forum: A BEGINNER'S FORUM (Learn How To Machine Here!)

• 

Maybe someone who lives near you can come by, or send you a couple of bits that should work with your machine.

@gedkins TLDR: If you read nothing else read this post from the thread.

Post in thread 'Models for grinding HSS Lathe Tools'

Sep 12, 2017

HUMBLE PIE

I looked all over my shop and couldn't find my early lathe tools. I wanted to show them to you guys so you know that we all start at the same place and that there is a good chance that I hold the title for THE worst lathe tools ever ground. Anyway, I finally remembered (Oh yeah? Wait until you pass 65 years of age) that I might have given them to a friend who was going to grind over them and use them on his little Sherline lathe. This must have been over 20 years ago. It was a long shot but I called and asked if he still had any of them and he said he did. I arranged to...

• mikey

• 

John

 

[gedkins]

All, It is 2:30 AM and I am 99% sure I have figured the problem out and the clues were there all along, even before I started rebuilding it. I will know within 24 hours, Here is my hypothesis. When I took the lathe apart I noticed, but quickly dismissed that the two spindle v-belts were in tough shape, but in a way I had not seen before. They had shards of rubber sort of peeling off from the sides and at the top of the belt. Who am I to say why, I figured they were REALLY old. Fast forward. I installed Power Twist belts from Fenner to replace them. I know this will cause many to say "see, those things are terrible", but hear me out, they may be terrible and I will soon know. I noticed about a week ago that the belts were rubbing up against the base of the headstock as they exit to the lower cabinet countershaft. The light goes on! Add up what I have witnessed (some of which I did not bring up here prior as I saw them as not connected).

1. Old belts oddly worn.
2. Bad surface finish on workpiece.
3. Under higher speed settings motor gets quite hot.
4. At highest speed setting, chuck takes a LONG time to get up to speed
5. Spindle speed slows and many times does not recover if cut is heavier.
6. Surface finish is generally slightly better at higher speeds, but still really poor.

Here is my thinking on this. At higher speeds the centrifugal force is higher on the belts. They press harder on the casting. Which impedes its ability to spin back up. At higher speed the Twist belt links are passing the casting at a higher frequency and thus the slightly better surface finish. More power is needed to turn the restricted belts, thus the motor works harder and gets hotter. The old rubber v belts wore themselves out and eventually were barely rubbing. Since they were smooth backed, unlike the Power Twist, they did not impart a beat frequency like the Power Twist does into the headstock.

As I sit here and type this I certain this is the issue. I am hoping someone here can tell me the A number for the belts I need. The first thing I am going to do is yank the head stock and grind a relief for the belts in that casting. Reassemble and try the Power Twist for clearance, but since they sit high in the pulleys I may have to abandon them. Anyone have a belt number for these beyond 1/2 inch by 44 (I think that's what the manual lists)?

Pretty sure I found the problem, does anyone concur?

 

[matthewsx]

That could do it.

First rule of troubleshooting for me is there may be more than one cause for any problem.

I’d replace those belts with standard power transmission ones from Gates. If they are the right length now just take one to your local NAPA auto parts store and they’ll hook you up.

Wouldn’t modify the headstock, it was right when they sold the machine new.

Also, fire up the grinder and put a little more radius on whatever tool you’re using.

John

 

[Charles scozzari]

All, It is 2:30 AM and I am 99% sure I have figured the problem out and the clues were there all along, even before I started rebuilding it. I will know within 24 hours, Here is my hypothesis. When I took the lathe apart I noticed, but quickly dismissed that the two spindle v-belts were in tough shape, but in a way I had not seen before. They had shards of rubber sort of peeling off from the sides and at the top of the belt. Who am I to say why, I figured they were REALLY old. Fast forward. I installed Power Twist belts from Fenner to replace them. I know this will cause many to say "see, those things are terrible", but hear me out, they may be terrible and I will soon know. I noticed about a week ago that the belts were rubbing up against the base of the headstock as they exit to the lower cabinet countershaft. The light goes on! Add up what I have witnessed (some of which I did not bring up here prior as I saw them as not connected).

1. Old belts oddly worn.
2. Bad surface finish on workpiece.
3. Under higher speed settings motor gets quite hot.
4. At highest speed setting, chuck takes a LONG time to get up to speed
5. Spindle speed slows and many times does not recover if cut is heavier.
6. Surface finish is generally slightly better at higher speeds, but still really poor.

Here is my thinking on this. At higher speeds the centrifugal force is higher on the belts. They press harder on the casting. Which impedes its ability to spin back up. At higher speed the Twist belt links are passing the casting at a higher frequency and thus the slightly better surface finish. More power is needed to turn the restricted belts, thus the motor works harder and gets hotter. The old rubber v belts wore themselves out and eventually were barely rubbing. Since they were smooth backed, unlike the Power Twist, they did not impart a beat frequency like the Power Twist does into the headstock.

As I sit here and type this I certain this is the issue. I am hoping someone here can tell me the A number for the belts I need. The first thing I am going to do is yank the head stock and grind a relief for the belts in that casting. Reassemble and try the Power Twist for clearance, but since they sit high in the pulleys I may have to abandon them. Anyone have a belt number for these beyond 1/2 inch by 44 (I think that's what the manual lists)?

Pretty sure I found the problem, does anyone concur?View attachment 516373

The only thing that bothers me is it doesn't seem to show that on the cut. Are the belts running in the right direction. The belts may not stretched to the same equal lengths.