Problems with face cutting on lathe, wavy pattern

[OldRon]

I have an Enco lathe that is giving me a weird wavy pattern when I face a piece of bronze bushing stock.
I have tried different spindle speeds, feed speeds and cutters.
It almost seems like the pattern follows the turning of the cross screw, even though I have snugged up the gibbs tight and locked down the compound slide.
I just installed the new tool post, but it seems quite rigid.
Any suggestions as to what is causing this and how to fix it?
Does it have to do anything to do with the bronze material?
Thanks,
Bryan

View attachment 108810 View attachment 108809

Question: Does that condition exist with a substantial depth of cut or only on light finish cuts?

Put a known to be straight edge such as the ruler out of a combination square in the chuck and tighten the chuck just enough to maintain the ruler. Level the ruler and then dial indicate the ruler edge using the cross slide. Chances are you will have discovered your problem before you have the ruler dial indicated parallel with the cross slide. If that does not replicate the condition that is effecting the surface finish then you need to be checking the thrust clearance on the spindle bearings.

Good Luck,
Ron

 

[Bryanbdp]

I think tooling was the issue. I played around with bits and some worked much better than others. It is hard to get a really uniform cut in this material. Surface cuts are easier than face cuts.
Thanks to all,
Bryan

 

[XD351]

Try a HSS tool with zero or even some negative rake

 

[bobden72]

My opinion is that you are all looking too deep for a none existing problem with the machine. It is just caused by not turning the cross slide handle at a constant speed, when you momentary stop to move your hand for another turn the tool drags for a sec and causes the patterns.

 

[Naiveambition]

When I first started I too produced the pattern like yours. At the time I was off center using a the cheapest carbide bit I could find and was using a candle for lubricant. It smoked like crazy plus made the room smell nice , and cut okish while producing a spiral pattern. After switching to hss and finding the true center I never have had theses issues. I used braised carbide on bearing bronze recently, with no issues, I can't remember but I'm pretty sure 660 is bearing bronze, but I may be wrong.
Although it did look really nice and I've thought a few times of trying it again for decorative parts.
I notice you said it pulls the cutter into the work, on mine if it's doing that it's either off center or the gibs are not tight

 

[mortimer]

as a thought , try a negative top rake on a HSS tool with a bull nose profile , it works on cast iron

 

[johwen]

As you seem to have tried most alternatives, I'd guess at a slack feed screw/ nut.

Maybe putting a dial mike at the back of the saddle would show the amount of slackness there

Only a guess from a distance


Norm

Johwen from Australia, Many years ago now we had this problem on some Asian lathes and it was caused by the drive belt, they were molded and had hard and soft spots and in some cases had uneven sections causing the belt to ride up in the groove as it drove the pulley. I would suggest checking and changing the belt for a quality one. This fixed the problem in these cases. Hope this helps to solve your problem Norm. John

 

[Neil Lickfold]

I am assuming that you had the saddle locked to reduce any movement there and the top slide/compound slide as well. Does the cross slide feed freely and uniformly? ie no easy and then a little resistance? The easy and little resistance can be from a slightly bent cross slide screw, or from miss alignment between the nut and the handle support. It could also be from the cross slide being slightly too loose. If you run a DTI on a straight edge mounted on the tool holder, is the dial running dead true, or do you see a very slight wobble in the DTI. Sometimes dull tools will give a better result as it has a higher tool pressure to cut and the variations are less than the tool pressure required to cut the surface. A very sharp tool can often show up machine tool irregularities that a dull or not so sharp a geometry tool would not show. Other issues like belts and vibration can also show patterns, but usually if you change the feed rate or the rpm, the pattern will often change with it. Your pattern looks to be the pitch of the cross slide screw to me.
Neil

 

[goldstar31]

No probs. John. I was merely trying to help Bryan.

However, it is certainly quite alarming.

Cheers

Norm

 

[dkwflight]

Hi
You might look at how close the tool tip is to the hold down bolt. Closer is better. Less leverage.
I have seen this type of tool flexibility in my 9 x 20 enco.
The tool geometry will have an effect too. If it digs in and tips toward the work you will get odd finishes.
These small lathes are not as rigid as would be desirable.
Get your tool as sharp as possible and take small cuts.
Good luck
Dennis

 

[john_reese]

Keep our tool sharp. Hone it until it shines. Zero or neg. rake, up to 5*. Small end radius. Keep the tool stickout as short as possible. You should be fine. You may want to rig a chip deflector close to the tool. Bronze sprays ships everywhere.

 

[trently]

Bryanbdp off topic question, I have the same lathe as yours. Mine is wired for 110v and I want to change it to 220v but I have no schematics. Is yours running on 220?

 

[Rolland]

Johwen from Australia, Many years ago now we had this problem on some Asian lathes and it was caused by the drive belt, they were molded and had hard and soft spots and in some cases had uneven sections causing the belt to ride up in the groove as it drove the pulley. I would suggest checking and changing the belt for a quality one. This fixed the problem in these cases. Hope this helps to solve your problem Norm. John

I changed my belts to link belts and the problem went away. I have a Grizzly lathe 12x36, belts were from McMasters.

 

[Bryanbdp]

Hi. Yes, I'm running it on 220v. The wiring diagram is on the motor label. I'll attach it here.
I don't know if you have the same motor or not, but here's the label.

NOTE: If you rewire the motor for 220v, you also have to adjust the connections to the transformer in the control box. Change input leads from 120v to 220v screws, note that BOTH leads are hot when using 220v.

What's interesting to me, is that the lathe works in both directions with single phase 220.
I don't know how the motor reversing is done, I thought AC motors only ran in one direction, except for 3 phase.

If there's a way to lock the saddle or top slide, I don't know how to do it. Am I missing something?
Indicating the tool holder seems like a good idea, i'll give that a try.
Thanks,
Bryan

 

[goldstar31]

Looking at the right side of the front of my saddle ie the Sieg C4 ,there is a number of a number of allen bolts and one of the rear part locks number one shear with a hexagon key

Yours may be similar. Let us know if yours is similar

Norm

 

[trently]

Bryan, to lock the saddle on ours there is a 14mm but to the right of the crosslide on the top of the carriage. Yours might be newer than mine (1981) the motor is different. I am wanting to hook up the 220 to the main panel so that the switches and other controls will still function as built. I'm not sure how to connect the 220 and not over volt them. I may not be making sense with my description

 

[Bryanbdp]

I took a few photos of my carriage assembly. I found a hex headed bolt under the DRO scale I never noticed before. It's loose and wiggly, but it does seem to tighten down and lock the carriage in the X direction.
Still can't find a lock for the cross slide, it may be under the scale as well. Perhaps I can add one to the other side.
As to 220/240 volt hookup, look at the photo I posted above, it has the wiring connections listed for both 120 and 240 volts.
Th

anks,
Bryan

 

[goldstar31]

I guess that 'your wiggly thing' is the clamp which is sort of replicated in my Sieg.

Does it need a hex key?

I would guess that all the other clamps/handles do not tighten up the saddle sufficiently. This may solve your original problem and I guess that you should now allow proper power facing without getting ' wavy' results.

Norm

 

[Bryanbdp]

That clamp has a hex head, so I can put a wrench on it...
I think it would have made a difference in the cut.
Now I have to see if there are gibbs or other adjustments on the carriage, I feel it could be snugger...

 

[retailer]

I have the exact same lathe but sold under a different name, my lathe is around 30 or so yrs old and I had a few issues that gradually crept up over a number of years, I initially put the cause of the issues down to "tool spring" but as parting off became more problematic I started looking for answers and found that the spindle end float/bearing preload nuts located on the left side of the head stock could be done up over half a turn, the locknut needs to be loosened first - I'm guessing that the bearings have bedded down over the years and allowed a very small amount of end float in the spindle. It is quite easy to check this you only need a small brass drift to loosen the lock nut I found I could easily tap the adjusting nut around almost 3/4 of a turn, you might want to check this if you haven't done so already.