Show us your lathe!

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

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bulgie
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Re: Show us your lathe!

Post by bulgie »

BigDumbDinosaur wrote: Tue Mar 29, 2022 11:16 pm Some of that shaking is sloppiness in the motor mount. I have a 12" × 36" JET lathe, whose power transmission setup is very similar to yours. After changing the belt tensioning setup to get rid of slop, I got a smooth-running machine.
I think the shake I saw was coming from the plywood benchtop. I could see the entire lathe move, sort of a one-time shake when starting up, a reaction to the startup torque. Since that motion made the top of the headstock move towards the wall and away from it, bracing it in that direction eliminated it, as far as visible motion goes anyway. It seems plenty smooth now.
BigDumbDinosaur wrote: Tue Mar 29, 2022 11:16 pmAlso, examine the belt. Asian V-belts are not the best...
Yeah I replaced both belts with USA-made Gates while I had the spindle out, noticeable improvement. Not a fair comparison since the Taiwan belts were 40 years old, but the new ones grip the sheave better too.
BigDumbDinosaur wrote: Tue Mar 29, 2022 11:16 pm Also, did you use an inverter-rated motor? Conventional motors tend to overheat when run at a slow pace
I don't know if the motor is inverter-rated, but it was so cheap I don't much care. If this were a business losing money from downtime, I'd pay more attention. But I can do without a lathe for a week or a month to buy and install a new motor, no problem. (Famous last words?) I have run it for an extended period at 40 Hz (the lowest I am likely go, for now at least) and I can't detect any increase in temperature by the super-scientific method of placing my hand on it.
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bulgie
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Re: Show us your lathe!

Post by bulgie »

The spindle speeds chart in the user manual is poorly formatted, grainy and hard to read, and it doesn't have any VFD freq info (of course). Also it's cluttered with the 50 Hz numbers — not so useful to us here in 60 Hz land (USA). So I made a spreadsheet for myself, to print and post near the lathe. Screenshot here:
Enco 92010 RPM settings with VFD.JPG
If anyone with a similar-enough lathe would find any value in the spreadsheet form, let me know and I'll upload it. You can edit it for your lathe's speeds and your preferred VFD frequencies.

So far I'm limiting the VFD range on mine to between 2/3 speed (40 Hz) and 3/2 speed (90 Hz).

Mark
John Evans
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Re: Show us your lathe!

Post by John Evans »

Good job ! That will make life easier I'm sure.
www.chaski.com
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bulgie
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Re: Show us your lathe!

Post by bulgie »

John Evans wrote: Wed Mar 30, 2022 12:53 pm That will make life easier I'm sure.
Thanks! Will it ever save me enough time to compensate for the time I spent making the spreadsheet? Time will tell...

I like the quick visual though, will help with planning. Like, I see I can get 325 rpm with 5 different combos of belts and back-gears, and I can choose the one that gives me the other speeds I'll want for the other operations on the same part, without having to change belts. (All with the VFD) Or in cases where it's torque- or power-limited, choose the combo that gets me the lowest losses.

I know, not rocket science. My dad worked at Rocketdyne in the '60s designing engines for Mercury, Gemini and Apollo, but I didn't inherit those smarts.

Mark
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rmac
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Re: Show us your lathe!

Post by rmac »

Nice job on the spreadsheet!

I have that same lathe (although branded Select instead of Enco), and its speed chart matches the 60 Hz values in your spreadsheet exactly. Trouble is, they're close, but not 100% correct.

Here's what I'm talking about. When you move the spindle belt from position C to position B, the speed will increase by some multiplier that depends on (and only on) the relative diameters of the two 3-step pulleys. Likewise, when you move the belt from position C to position A, the speed will increase by some different multiplier that again depends only on the pulley diameters. None of these ratios have anything to do with the position of the motor belt or whether or not the back gear is engaged.

Now here's an abbreviated (and not nearly as pretty :) ) version of your spreadsheet that contains just the 60 Hz speeds.

ratios.png

In columns F and G I've calculated the ratios mentioned in the previous paragraph. If the speeds in the chart were all correct, the numbers in column F would all be the same, as would all the numbers in column G. But as you can see, they're not. They vary by lots more than you could explain by something like rounding error.

When I first discovered this on my lathe, I became suspicious of all the numbers in the chart. Besides the obvious problem with the ratios, I wasn't sure if the motor pulleys might have been changed by a previous owner, or even if the motor itself was running at the intended speed. So rather than driving myself nuts trying to sort it all out, I just measured the actual spindle speeds and made a new chart:

my_speeds.png

I'm not sure if any of this actually matters in practice.

-- Russell Mac
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bulgie
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Re: Show us your lathe!

Post by bulgie »

rmac wrote: Wed Mar 30, 2022 7:07 pm <snip> If the speeds in the chart were all correct, the numbers in column F would all be the same, as would all the numbers in column G. But as you can see, they're not. They vary by lots more than you could explain by something like rounding error.
<snip> I just measured the actual spindle speeds and made a new chart
Yeah, that was on my to-do list, to confirm the numbers with a tachometer. It's a little tricky to dial in an exact frequency on the VFD but I can get it close enough for hobbyist work.

I've found a couple other errors in the user manual, so this doesn't surprise me too much. Getting the actual speeds and feeds down to the Nth decimal isn't critical, but I'm curious and have time to fiddle with it. I suspect I'll end up with the same numbers you did.

Makes ya wonder how they could have gotten it wrong though, doesn't it? And not noticed the ratios were different? A simple "sanity check" to see if your measured speeds are in the ballpark.

Mark
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Bill Shields
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Re: Show us your lathe!

Post by Bill Shields »

Are you reading the manual in English or Mandarin?

For one of my machines I have both...and the numbers do not agree from one to the other...ignoring the obvious imperial to metric conversions...
Too many things going on to bother listing them.
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rmac
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Re: Show us your lathe!

Post by rmac »

bulgie wrote: Yeah, that was on my to-do list, to confirm the numbers with a tachometer. I suspect I'll end up with the same numbers you did.
It will be interesting to compare your results against mine.

Full disclosure: I didn't use a tachometer. I measured the speeds on my lathe by manually counting revolutions over a fixed time interval, sort of like taking a pulse. If I remember correctly, I was able to do this confidently for the speeds up to 242 RPM. I then calculated the remaining faster speeds based on the ratios observed among the measured speeds.
bulgie wrote: Makes ya wonder how they could have gotten it wrong though, doesn't it?
Indeed. Although Bill's suggestion of a translation error could explain a lot.

A long as we're nerding out over all these numbers, here's the feed chart from the plate on the lathe itseelf (not from a manual). Note that it doesn't match yours. I've never measured to check it. Regardless, you gotta love that they moved the last number in the chart so it wouldn't be covered up by the rivet!

feeds.png

-- Russell Mac
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Bill Shields
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Re: Show us your lathe!

Post by Bill Shields »

do avoid the rivet head....
Too many things going on to bother listing them.
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bulgie
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Re: Show us your lathe!

Post by bulgie »

rmac wrote: Thu Mar 31, 2022 7:42 am<snip>
here's the feed chart from the plate on the lathe itseelf (not from a manual). Note that it doesn't match yours. I've never measured to check it.
I only measured my fastest feed, position A-1. I didn't measure to tenths, but it matched the manual to the last .001". Definitely .118, not .132 like your plate says. You must have different gears somewhere (duh!) in the change gears, gearbox, or the apron gears. I know we will probably never find out and it's moot anyway, just mildly curious.

Oh I guess it could become a real question if one of us needed a replacement part, then we might need to know what parts are interchangeable between the various badge-engineered variants. This happened to me once already, I had one chipped tooth in one gear and I found a Grizzly part that fit with only slight modifications.

I know, assuming that just because A-1 matches the manual, it means the rest of the numbers are correct, would be too trusting. Maybe I'll measure the slowest feed as well and if it matches, then the in-between numbers will be slightly more believable. Luckily I seldom need to know my feed rate exactly.

Hah, after writing that I looked in my manual again, and one of the four feed rate charts in it matches yours exactly. It's specified for a lathe with a 3/4" feed rod and "Hand Wheel on the Left". So, does yours have a 3/4" feed rod? Mine is 5/8"

Ever seen one of these lathes with the apron handwheel on the Right? I haven't. The manual seems to say that was a thing, and gives two more charts for those, depending on the feed rod diameter.

Mark
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rmac
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Re: Show us your lathe!

Post by rmac »

bulgie wrote: So, does yours have a 3/4" feed rod? Mine is 5/8".
Nope. Mine's 5/8", too! You'd think that a riveted-on chart would match the machine it's attached to, but maybe that's too much to ask. Now I guess I'll have to measure my feeds, too. Tomorrow.

-- Russell Mac
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rmac
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Re: Show us your lathe!

Post by rmac »

rmac wrote: Nope. Mine's 5/8", too! You'd think that a riveted-on chart would match the machine it's attached to, but maybe that's too much to ask. Now I guess I'll have to measure my feeds, too. Tomorrow.
Good grief. It looks like somebody attached the wrong chart to my lathe. The measured A-1 speed matches the number in your chart for the 5/8" feed rod. And that makes sense, of course, since I also have the 5/8" feed rod.

I still need to check some of the other speeds besides (A-1) to see if they match the 5/8" chart.

-- Russell Mac
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