clausing lathe questions

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joshuaz2
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Joined: Fri Jul 04, 2003 12:30 pm
Location: central square, n.y.

clausing lathe questions

Post by joshuaz2 »

i have a 15" lathe that the previous owners removed the variable speed unit and made it direct drive. i have finished cleaning it and fixing various problems and am now left with the drive. my original plan was to put on a VFD. i have none of the variable speed parts except the actuator, hose and slave cylinder. the motor has been turned around in the cabinet and a 1 to 1 drive with the original style toothed belt installed. my question is should i go with a VFD or try to find the parts to return it to original.
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Flybynight
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Post by Flybynight »

You didn't say what model it is.
But my guess would be go with a VFD.
I would think that pulleys and everything you needed is more.
Jim
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Bill Shields
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VFD Strategy

Post by Bill Shields »

the only problem with VFD's with no gearbox is that when you get down to GRANNY GEAR range, and need a LOT of torque at low speeds...the VFD may have trouble delivering the necessary torque to get through whatever it is you are trying to cut.

I have nothing against VFDs, in fact I like / use them, but whenever possible, I don't take out the gearbox because sure as God made little green apples, you will get into a position where you need the torque created by the gear ratios available originally.

So, all things considered, I like to keep the gears there....just in case.
PAULJ
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clausing lathe

Post by PAULJ »

attached is a pdf of the countershaft with clutch and break for a 5900 series clausing Paul
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BadDog
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Post by BadDog »

It depends on the size of the motor, AND what you do with it. If you have a motor considerably larger than stock, and don't do stuff like roughing hard steel at larger diameters, then a VFD might work well.

For reference, I have an 11" Rockwell with 1hp OEM motor and reeves drive. I wanted to get rid of the Reeves Drive AND pick up some higher rpms (go up from 1500 max to 2000 max) . I have a 5HP Baldor "Inverter Duty" motor that I was going to use. Based on my calcs, and assuming a Sensorless Vector VFD could hold 100% torque down to 20%, I would have LOST a bit less 10% (from memory) of the torque the 1hp motor gives through the Reeves drive at 70 rpm. At 200%, I would have been running just under 2000 rpm with WAY more power (but you don't need it, so who cares?).

I wound up not going through with it because of problems related to the VFD. Main problem, I'm CHEAP! And a 1ph -> 3ph VFD capable of pushing 5hp (5hp rated on 1ph input) is both rare and expensive. Often over $400 even on ebay. But you don't see many rated for 1ph input in the power range. So then you wind up looking at "derating" a 3ph input rated VFD by 30-50% (depending on who you talk to). So figure a 7hp to (preferably) 10hp VFD to run a 5hp motor. I say "preferably 10 hp" becase, based on my calcs, I would be pushing it HARD at low rpms and I didn't want to frequently trip the ERR protection circuit. Now, these 10hp+ units quickly climb from $500 and generally are larger NEMA form-factors, typically the size of a small suitcase. Not the convenient little boxes I use for some of my other equipment. And they often require an enclosure (much larger NEMA for heat dissipation = more space and $$$)...

That was going from 1hp to 5hp on an 11" lathe, which I judged for my uses to be the minimal acceptable combo. It would not have looked quite so bleak if I had not been wanting more high rpm. Richard (rohamm) here did a similar conversion with (I think?) a 3hp motor but kept the stock 1500 rpm top speed. To my knowledge, he is happy, but I think I recall him saying he's not had much chance to use it since then...
Russ
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JHenriksen
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Post by JHenriksen »

A bit different ap but I have retrofit several Lagun mills with vfd's. I have replaced the stock motors with 3 hp and set the pulley rations for a 2.5;1 speed reduction and use the vfd to run the motors above normal rated speed.
I would try the same with your lathe, put a slightly bigger motor on it to give you a little more low speed torque and run the motor (a 1750rpm) up to double speed. If it is a 5900 series lathe, a 5 hp shouldn't be too big to cause problems.
To hijack the thread a bit, I have a lathe like Russ' but I added the vfd and kept the varidrive. I set the max frequency at 90 hz which lets me run the spindle over 2000 if I want to. Most times I run at 50-70 hz somewhere about 1200 rpm. I foud the starting and stopping are much smoother with a vfd than my rpc was, but the reversing is a bit slower.
joshuaz2
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Joined: Fri Jul 04, 2003 12:30 pm
Location: central square, n.y.

model #

Post by joshuaz2 »

its a 6903 serial 600827
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