Lathe

[Ronen BursteinParticipant @ronenburstein68061]

Hi There

New to the forum and to working with lath. I recently bought a Waco WM240B Belt drive lathe.

It worked well in a sense that it gave my smooth fine surface. But the other day I change gears for thread cutting, then change it back to the original setting (presumably) and ever since i got very raged surface finish even thug i am using the automatic feed. When it got to the end i disengage the cutting head and manually bring it back to the beginning. During the path back i can see that the cutting head still cutting the metal? (See attached photo). Any idea what wrong?

Thanks

Ronen

[Ronen BursteinParticipant @ronenburstein68061]

Problem with my lathe

[Chris Evans 6Participant @chrisevans6]

Have you returned all the levers to their original position ? Seems like you still have the leadscrew engaged or federate positions wrong. You should wind the tool away from the workpiece to return to the start position.

[not done it yetParticipant @notdoneityet]

Typical cutting on returning the cutter to the starting point is poorly adjusted gibs on the carriage. But you problem could also have other causes. A poor cutting edge is among the others.

[Anonymous]

Change of material? Tearing is common with low carbon steels and insert tooling if you don't get speeds and feeds correct. Cutting on the return is common. It can be caused by the work deflecting away from the tool slightly on the cutting pass and then springing back.

Andrew

[Grindstone CowboyParticipant @grindstonecowboy]

Looks like you're cutting a thread there, so it's understandable that it would cut the untouched sections when you wind back. Does the carriage move slowly or quickly when using the power feed? As others have said, check you have reset everything to how it was before.

Rob

[OldironParticipant @oldiron]

I agree with the others. Are you sure that you have set everything back to as it was?.

Just a tip:- your posts are easier found and likely to get a better response or help people searching for a similar problem if the title was a little more descriptive, ie

"Rough finish after changing settings".

regards

[Martin ConnellyParticipant @martinconnelly55370]

Back off the tool before returning to do the next cut.

Martin C

[DMBParticipant @dmb]

Hi Ronen,

Did you get a manual? If so, consult it. It may well list all wheel configurations for threads and feeds. Assuming change wheels rather than gearbox, use largest wheel available on leadscrew. You need a huge gear reduction to get a very low leadscrew speed and thus, a fine feed. I'm not au fait with Warco lathes but if all else fails, ask makers for help/advice. Have found owner, Roger Warren a pleasant and helpful  chap to deal with.

John

Edited By DMB on 30/03/2020 23:07:38

Edited By DMB on 30/03/2020 23:08:28

Edited By DMB on 30/03/2020 23:09:06

[Bo’sunParticipant @bosun58570]

What tooling are you using. HSS or carbide tipped tooling? Positive or negative top rake? I've seen negative top rake cause this before, especially if you have a longish workpiece unsupported by the tailstock. Some refer to it as "springback".

[Tony Pratt 1Participant @tonypratt1]

Thinking logically, something must have changed from when the lathe was cutting a good finish? Material or as previously mentioned are the change wheels correct for a fine feed?

Tony

[Bo’sunParticipant @bosun58570]

Too much tool overhang maybe?

[HopperParticipant @hopper]

The marks on the piece in the photo look maybe like the feed is still in screwcutting mode. Looks like one set of marks about 1mm apart going in the right hand thread direction, then another set coming back in the left hand direction.

Looks like you maybe need to check your lathe owners manual and the settings of all your gearbox levers and change gears or whatever you changed when you went from fine feed to screw cutting. Sometimes you have to jiggle the headstock spindle back and forth as you change the gear levers on the gearbox so they can move to the new position fully.

A picture of the work after one cut without winding the carriage back would give a clearer view of how the tool is cutting. The return marks are somewhat confusing the issue I think.

Edited By Hopper on 31/03/2020 09:20:18

[SillyOldDufferModerator @sillyoldduffer]

Posted by Hopper on 31/03/2020 09:18:57:

The marks on the piece in the photo look maybe like the feed is still in screwcutting mode. …

Looks like you maybe need to check your lathe owners manual and the settings of all your gearbox levers and change gears …

…

+1

Hi Ronan,

As it's a WM240, the most likely cause is the change gears. These are set up in a particular way to do fine cuts and re-arranged in various ways to cut thread pitches. My guess is the gears were put back incorrectly, and are producing a coarse spiral.

Can you post a photo of the change gears? ( Gears and belts under the cover on the left-hand side of the headstock.) If something is wrong, should be possible to see it.

Dave

[larry phelan 1Participant @larryphelan1]

Yes I think you are set up for screwcutting, not turning. Can happen, ask me how I know !!

[Ronen BursteinParticipant @ronenburstein68061]

Hi There

Thank you all very very much for your replay. I think the problem must have been because of me putting back the gears wrongly. I am not sure that i can see in the manual the original setting but i will contact Warco for that.

Thanks again for all your replay. I got a lot of tips & trics out of it.

Regards

Ronen

[Bo’sunParticipant @bosun58570]

Hi Ronen,

The original setting is probably the one for "fine feed". Likely shown in the manual, or on a plate on the front of the machine.

[JourneymanParticipant @journeyman]

The manual should have a chart like this

Or indeed there is a chart affixed to the change gear cover that shows where each gear should be. The chart above is for the WM250 but yours will be very similar. Don't forget the 3-way gear change knob on the front which also needs to be set to its slowest range position C.

John

[Bo’sunParticipant @bosun58570]

If it's any help. my WM240 came set-up with 90T, 90T, 80T, 33T & 25T (+ 2x40T fixed) change gears for fine feed. I didn't know the WM240B came with a 3-way gear change.

[SillyOldDufferModerator @sillyoldduffer]

+1 to John (Journeyman's Chart)

The fine feed settings are shown at the top, and I've ringed the set-up I'd use in red.

I think the example gear arrangement pictured on John's picture is what's needed for fine feed. The big 80 toothed gear at bottom 'L' engages with a small 20 'Z3' hidden behind the big 75, 'Z4'. That engages with the visible small 25 'Z1', which turns the big 70 'Z2' behind. The 70 toothed gear engages with the spindle hidden behind the pulley.

All my gears (for a WM280) are stamped with the number of teeth, but the numbers aren't obvious! I've written the numbers on boldly in felt tip to make life easier. (Felt tip needs a grease free surface.)

Dave

 

Edited By SillyOldDuffer on 31/03/2020 11:11:55

[JourneymanParticipant @journeyman]

Posted by Bo'sun on 31/03/2020 10:59:27:

If it's any help. my WM240 came set-up with 90T, 90T, 80T, 33T & 25T (+ 2x40T fixed) change gears for fine feed. I didn't know the WM240B came with a 3-way gear change.

Your right, the WM 240B doesn't have the extra lead screw gear change. My bad, sorry.

John

[Ronen BursteinParticipant @ronenburstein68061]

Thanks again for your reply. Fantastic.

But if I may, one more Q. Is there optimal spindle speed for fine cut in mild steel or once i set the gear for factory fine cutting it will cut fine no matter what spindle speed?

Ronen

[JourneymanParticipant @journeyman]

Ronen, once you have set the gear train to the finest feed as per your chart it remains at a constant ratio of feed to speed. The lowest I can get on my WM 250 for example is .07mm per rev, your lowest may be different but once set that's it. It doesn't matter what speed you run the lathe at the feed stays the same it just moves along quicker the higher the speed but the ratio of feed / spindle speed is fixed.

John

Edit: Typo

Edited By Journeyman on 01/04/2020 09:31:50

[SillyOldDufferModerator @sillyoldduffer]

Posted by Ronen Burstein on 01/04/2020 09:21:51:

…Is there optimal spindle speed for fine cut in mild steel or once i set the gear for factory fine cutting it will cut fine no matter what spindle speed?

Ronen

As John says, fine feed once set is constant.

I usually keep mine at 0.07mm per turn because it works on almost everything without fuss. Occasionally though it pays to use a coarser setting to either rough cut metal fast or because sometimes and counter-intuitively, a coarser feed produces a better finish.

In my experience Coarse=Better seems more likely to be true of carbide than HSS, but if you have trouble getting good finish on a difficult material, it's worth experimenting with different depths of cut and feed rate. I emphasise the finest feed recommended by the lathe maker is good most of the time though.

A point that had me confused: the Warco gear setting diagrams refer to 'H'. Just in case you've not twigged already, this is a spacer. It allows single gears to be positioned as necessary on the axle. For example, in fine feed, the gear that drives the leadscrew is positioned on the inside, but for thread cutting the 'H' spacer goes on first and the driving gear is on the outside.

Dave

[Howard LewisParticipant @howardlewis46836]

Ronen,

As a starting point, in terms of cutting speed for Mild Steel, try 100 feet per minute, (surface speed ), using High Speed Steel tools..

So if you were starting to turn a piece of 2 inch (50 mm ) diameter mild steel, the circumference is (2 x Pi ) so say very approximately 6 inches. So you would run at 200 rpm.

Replaceable Carbide tips can be run at much higher speeds, so that the swarf comes off brown or blue, if not red hot.

As a beginner, I would suggest that you stick with HSS, so that you can learn the basics of grinding tools to the correct shape. A correctly ground tool will cut nicely, a blunt one never will!

One thing which will optimise the surface finish is that the tool,must be mounted at the height of the centre line of the lathe. If the tool is too high, it will not cut properly, but will rub. Too low, and it will not be ideal. In both cases, you will leave a pip on the end of any work that you are facing.

For this, to speed up tool setting, and save a lot of experimenting each time, it is worth making a centre height gauge.

This will also give you a little practice at turning and facing, so will be a win-win for you.

To adjust the tool to the centre height, you can pack it up with pieces of tin cut from food tins (washed! ) or from biscuit tins. Cans are often about 0.010" (0.254 mm ) thick.

If you want a picture of a centre height gauge, and instructions on how to make one, PM me.

H T H

Howard

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