Turing a 4.5" dia. on Logan Lathe

[dnp101677]

I have a Logan 10" x 31" lathe. I am trying to turn a flywheel out of a solid piece of 4 3/4" aluminum rnd (the print is attached). I have not had my lathe for very long so I haven't gotten to know it real well yet and I have some questions/doubts. When I am face cutting down the piece to make the .750" hub sticking out of the face, I can only take about a .010" DOC and even that sounds like the spindle in going to snub out at any second. The closer I get to the middle the easier the spindle turns. I understand that I will lose power the further out I get, but to this extent? I realize this might be hard for someone to answer without know all about my lathe. I just thought maybe someone could tell me whether or not they have this problem with a similar size lathe. I do have a back gear that I can engage, but I thought that was only for really hard materials, etc.

Any thoughts are appreciated. BTW, ,my motor is 3/4 HP and the lathe has a flat belt/ cone pulley drive system.

Thanks,
Dan

 

[Deanofid]

Hi Dan;

Not sure what you mean by this;

sounds like the spindle in going to snub out at any second.

This lathe should have no trouble turning that piece of aluminum into chips.

You don't mention how fast you're turning it, how far the piece is sticking out of the chuck, or what type tool you're using.

The back gear is for slowing down the lathe, whatever you're cutting. If you need it to go slower, use it.
Here's a short list of things that may be causing your trouble:
RPM too high.
Tool not sharp.
Gibs not properly adjusted.
Too much sticking out of the chuck.

Give us some particulars and someone will be able to tell you what needs to be done.

Dean

 

[steamer]

Nice list Dean...I agree,

Two others I might add,

Is the tool is hanging out of its holder out too far?

And a modification of Deans dull tool question:

Is the tool ground to the correct geometry for the material.

However, with aluminum, and simple facing, geometry is not so sensitive as perhaps some other materials:

As Dean pointed out, it's tough to diagnoss, but 1 photo would help dramatically.

Dave

 

[Stan]

If I understand your problem, the most likely thing on a Logan is a slipping belt or not enough HP. On a 800 series it is likely the countershaft to spindle belt and on the 1800 series, the motor to countershaft belt slipping.

 

[dnp101677]

I'm turning at 1700 RPM. The piece is sticking out about 1.250". I'm using a carbide indexable tool. Gibs are tight.
I guess I could try a sharp HSS tool bit. I think the problem may be the belt slipping as Stan stated. I have had some trouble with the belt slipping off when I first turn it on. What can I do about that. I have tried all the adjustments mentioned in the manual, but it still slips off sometimes.

Here are some pictures of my set-up.

Also Deanofid, by "Snubbing the spindle out", I mean losing power to the point of stopping the spindle.

 

[steamer]

A HSS tool with the proper top rake will require less power than the carbide tool. Carbide has little rake, and takes power to drive through. Something most of us don't have a lot to spare. I would try HSS and see how you make out

As I recall, Aluminum requires quite a bit of top rake.

Stone the edge. A polished tool cuts a polished surface.

If the rest of the lathe is in good order, you should see a big difference.

Pay attention with aluminum. It can pull the tool in and cut undersize on you.

And a little kerosene does wonders as a cutting fluid. In place of that, a shot of WD-40 I find very helpful as a cutting fluid....albiet an expensive one.

Check back when you done and tell us how you made out.....

By the way, nothing screams at me about your set up. Seems reasonable.

You'll notice your chips. From here, they seem like you plowing through the material instead of cutting through it.....To me that re-enforces my previous statements......but time will tell.

Tell us how you make out, we can all learn something!


Dave

 

[Stan]

In general, I find carbide a poor choice for aluminum on a Logan or similar sized South Bend. Good advice from steamer on HSS tools.

On the flat belt drive issue, make sure that the countershaft bearings are adjusted properly to make the belt track on the center of the pulley. From the picture, I can't tell what kind of belt you have. If it is leather make sure you have the smooth side on the pulley. If it is synthetic or leather and adjusting the tension until the cover just lifts doesn't stop it from slipping, then use belt dressing.

Feed rate is the other criteria in HP needed. Use the power crossfeed and start with a low feed rate and increase it until your belt slips or you run out of HP.

As a side note to one of your comments. Many years ago I was called to hook up the electronics on a used engine flywheel lathe. This lathe had automatic speed control that increased the speed as the tool moved toward the center to maintain optimum material removal with the HP available.

 

[kvom]

I have a carbide insert tool made for turning aluminum and it works great. Your insert in the photo looks angled vs. the side of the part. WD40 also helps.

Make sure the tool height is correct.

 

[PaulG]

Looks like the Bull Gear Pin is pulled out to me.

Paul

 

[tel]

I'm turning at 1700 RPM. The piece is sticking out about 1.250". I'm using a carbide indexable tool. Gibs are tight.
I guess I could try a sharp HSS tool bit. I think the problem may be the belt slipping as Stan stated. I have had some trouble with the belt slipping off when I first turn it on. What can I do about that. I have tried all the adjustments mentioned in the manual, but it still slips off sometimes.

Here are some pictures of my set-up.

Also Deanofid, by "Snubbing the spindle out", I mean losing power to the point of stopping the spindle.

1700 sounds awful fast to me as well - for that sort of diameter I am usually down to 300 or less on the Myford.

Wire that carbide tool to an anvil, go down to the crick and chuck the lot in the deepest hole you can find. HSS for a job like that.

Belt slipping (within reason) is a good thing IMHO - better a setup that slips than one that hanfs on til the destructon of something else..

The larger piece in this pic (bronze) was taken down from over 5" to 4 1/2" with a HHS tool that was rather in need of a sharpen

 

[Maryak]

dnp101677,

Try at least half the speed and check your feed rate around say 0.002"-0.006" per revolution. Your chips have a long heavy spiral which is either as Steamer says or a too high feed rate.

HSS is better that carbide for this job.

Hope this helps and Good Luck.

Best Regards
Bob

 

[steamer]

Yup,

You could definitly turn the speed down as well as the feed.

Gererally, you cut aluminum as fast as you can, but we're in problem solving mode at the moment, so slowing down is not a bad thing.

When you get closer to center, your speed drops because the radius is smaller. If its chattering at the larger radius only, then speed is not helping the situation.

A sharp tool is still very important though.
Let us know!

Dave

 

[Huntinguy]

RPM does sound high... a usable formula is (CS x 4)/Dia=RPM
I prefer a tool with more shear for aluminum, tmp style.
I have seldom had luck plowing with the tool tip. I prefer to have the tool tip run a little behind unless I am going to a shoulder.

But that is just me.

 

[dnp101677]

Wow! Thank you all so much for the great feedback. I used a little bit from almost every post. HSS really worked better for this application. Slower speed, some belt dressing and a little patients really went a long way too. I am now halfway done the flywheel; it's turned around and indicated in both directions in the 4-jaw. All the really crucial features are finished. Now it's just matching the other side to look as good as the first. I meant to take some pictures, but forgot. I will however be posting some pictures of the finished engine.

Thanks again for the feedback. I was really impressed with all the knowledge and eagerness to help! I hope I can return the favor sometime soon.
Dan

 

[steamer]

Great to hear! And you learned something about your lathe and your set up.

I am glad it worked out for you and I am eager to see your engine!

We were all taught by someone........

Dave