Graziano sag 12 transmission removal?

Has anyone here removed the transmission and just used a motor with a vfd to run the graziano sag 12 lathe,instead of replacing the clutches in the trans?

Thanks Mike

Why is there something badly wrong with your transmission?.

I think that what you are describing has been done, but I don't know what the outcome was like. The stock transmission is a pretty fabulous machine. Running the stock setup with a VFD gives you the best of both old tech and new. Unless your trans is completely hashed, I wouldn't consider throwing it out.

Catch22,

I use to have a Sag 12 that came with the Vfd motor conversion and the original gear box out of the lathe when I bought it. I never had a problem with it and actually it was a nice feature. If I remember correctly the gear box pulley had an internal taper that was bored straight to accept the fit on the new motor shaft. Good luck

Im starting to loose speeds on it and I was told that the clutches are starting to go.
And im told its pretty expensive to replace those clutches.

catch22 said:

Im starting to loose speeds on it and I was told that the clutches are starting to go.
And im told its pretty expensive to replace those clutches.

Click to expand...

My '180 had a slipping clutch and there was a ring nut you tightened that brought it back to new. Keith Price in Australia make high quality replacement clutch assemblies including Graziano:
http://www.keithprice.com.au/ and the exchange rate would be in your favour too so it might be worth an email.

SAG 180,

In case you weren't aware, the Sag 12 gearbox is nothing like the other Graziano models. It uses magnetic clutches to change speeds and direction. No adjustments possible. However, as you say, clutch parts are available, and Gizmo Wizard has posted excellent info on how to overhaul these gearboxes. It certainly helped relieve my fears of what to do when my gearbox starts to play up.

Sometimes my lathe doesn't reverse correctly, but I will check the switching before I worry about the clutches, maybe try powering the clutches directly to rule out the possibility of switch failure?

A local machinery dealer who use to sell Graziano lathes told me that a reason that the clutches start to slip or go bad is that the oil in the gearbox after time starts collecting metal particals, with enough metal dust in the oil it acts as a conduit and ruins the clutches. He said oil has to be changed often. Just passing on some info.

backspace said:

A local machinery dealer who use to sell Graziano lathes told me that a reason that the clutches start to slip or go bad is that the oil in the gearbox after time starts collecting metal particals, with enough metal dust in the oil it acts as a conduit and ruins the clutches. He said oil has to be changed often. Just passing on some info.

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That would be in line with my experience, I had some bronze in the sump most likely from the main spindle bush and the bronze yokes that activate forward/reverse and select gears.

Peter S said:

SAG 180,

In case you weren't aware, the Sag 12 gearbox is nothing like the other Graziano models. It uses magnetic clutches to change speeds and direction. No adjustments possible. However, as you say, clutch parts are available, and Gizmo Wizard has posted excellent info on how to overhaul these gearboxes. It certainly helped relieve my fears of what to do when my gearbox starts to play up.

Sometimes my lathe doesn't reverse correctly, but I will check the switching before I worry about the clutches, maybe try powering the clutches directly to rule out the possibility of switch failure?

Click to expand...

I vaguely remember reading something about an electric transmission for Grazianos. Wasn't there some guy who rewinds various solenoids and restores them to working condition?.

It's true that there is no adjustment possible for the Sag12 clutches. They're a multiplate affair, electromagnetically activated, and running in oil.
The coil that engages it can go bad. There was a guy in the Bay Area that rebuilt them as recently as a couple of years ago. I don't have his contact info in front of me now, but could dig it up.
I had him rewind my bad clutch, and I'm as good as new now.
Also, there are six identical clutches (one for forward, one for reverse, and one for each of the four speeds) so in a pinch, you could swap a clutch from a speed you were least likely to use to one that you are more likely to. My bad one was forward, which was a big problem!
My write up, such as it is, is at www.gizmowizard.com.
Paul

Thanks for all the comments guys,I appreciate it.

Getting back to what I am guessing catch22's original question is - can a VFD-controlled motor cover the speed range of the existing four-speed 'electric' transmission?

My lathe is in storage, so I am working by the parts book and guess work so please correct me if I am wrong.

It looks to me like a VFD will cover the existing speed range by working between say 25 and 100 hz, which sounds reasonable to me. I have used VFD's over this range on other applications.

For a Sag 12 with single speed motor, my manual says the lowest spindle speed is 80 rpm and the highest is 2000 rpm.

Working from the number of teeth shown in the manual, the gearing in the headstock appears to give a 6.5:1 difference between high and low (i.e. backgear) on the spindle.

Thus the input speed of the headstock varies in four ratios between 423 rpm (lowest) and and 1627 rpm (highest) irrespective of whether high or low range is selected inthe headstock.

Assuming a 4 pole motor (i.e. 1400 rpm at 50 hz), and a 1:1 belt pulley ratio on motor and headstock, the motor would be running at about 15 hz to give 80 rpm at the spindle and about 58 hz to give the top spindle speed.

This doesn't sound ideal to me, I would guess running the motor at 25 hz at its lowest would be better, so this would mean fitting a 1.7:1 ratio set of pulleys, e.g. if the bottom pulley was 100mm, then the top pulley would be 170mm. Would this interfere with the door? Possibly, I can't go and check as my lathe is 60 miles away....

With this pulley ratio, the motor at 100 hz would give the top speed spindle speed of 2000 rpm.

It sounds do-able to me, I would even try it with the existing pulleys for a start (are they 1:1?), or use whatever reduction ratio will fit inside the covers. An 'A' section v-belt minimum pulley diameter is around 80mm/3", so possibly reduce the motor pulley to this (not sure what diameter it is at present, a little larger I think).

Further, once the four speed transmission is removed, a plate could be made to take the place of the transmission, to this the existing motor could be flange mounted (it is flange mounted already), so you have exactly the same system of tensioning the belts that exists for the gearbox.

Any comments/criticism - fire away!

As a longtime SAG 12 user (and owner) I have repaired and rebuilt several gearboxes over the years. I bought out RAM- SAG's remaining SAG 12 inventory when they finally closed up a few years ago. I have some new clutches from a different model that could probably be adapted to the 12 gearbox, but haven't had the time to work out the details.
In any case, I have rebuilt the original clutches and it was a whole lot cheaper than buying new ones (about $1200 each at the time). It requires making a spindle to wind the wire (I Believe it was 1mm thick copper) to a dimension that fits inside the clutch housing. The approximate resistance should be about 12.5 ohms for the winding. after installing the coil and connecting the wire ends, seal it up with a marine grade epoxy that is impervious to oil, let it set up and re assemble the gearbox. I did the labor myself and had an electric motor repair service do the epoxy job but he would not tell me who made the epoxy (big secret I guess). I'm sure that could be sourced out very easily today. I will be doing this again to my latest machine as soon as I can afford to have it down for awhile as I lost the 1250 rpm speed. I will post more info as find out.
BTW, a preventive measure is to turn off the main power switch when the machine is in use. Even with the motor turned off the clutch on the selected speed is still energized which is why the clutch for the most commonly used speed burns out. I hope this has been helpful.
Bill

Bill,

Many thanks for your post - I look forward to any info you can post later on re-building the Sag 12 clutches. We now have great descriptions on this forum for rebuilding the Sag 12 headstock spindle and the transmission, but not on re-winding the clutches (not that I am aware of anyway) - that would really be helpful, thanks!

ps maybe you could try the VFD idea in the post above to keep your Sag 12 operational why you rebuild the transmission??

Bill Robinson said:

As a longtime SAG 12 user (and owner) I have repaired and rebuilt several gearboxes over the years. I bought out RAM- SAG's remaining SAG 12 inventory when they finally closed up a few years ago. I have some new clutches from a different model that could probably be adapted to the 12 gearbox, but haven't had the time to work out the details.
In any case, I have rebuilt the original clutches and it was a whole lot cheaper than buying new ones (about $1200 each at the time). It requires making a spindle to wind the wire (I Believe it was 1mm thick copper) to a dimension that fits inside the clutch housing. The approximate resistance should be about 12.5 ohms for the winding. after installing the coil and connecting the wire ends, seal it up with a marine grade epoxy that is impervious to oil, let it set up and re assemble the gearbox. I did the labor myself and had an electric motor repair service do the epoxy job but he would not tell me who made the epoxy (big secret I guess). I'm sure that could be sourced out very easily today. I will be doing this again to my latest machine as soon as I can afford to have it down for awhile as I lost the 1250 rpm speed. I will post more info as find out.
BTW, a preventive measure is to turn off the main power switch when the machine is in use. Even with the motor turned off the clutch on the selected speed is still energized which is why the clutch for the most commonly used speed burns out. I hope this has been helpful.
Bill

Click to expand...

It sounds like there's a heat dissipation problem with these solenoid coils that causes an eventual burnout. With some electronics I've seen, the circuit boards would work fine until they were potted in resin which would then insulate the components and prevent air cooling and they would fail in under a year or so instead of ten years +.

Are these solenoid coil housings immersed under oil or are they in air?. Either way they'd probably last longer with improved passive cooling: You could just coat the coil with transformer lacquer and bake them (if the wire former will hold up to baking heat). Without the epoxy insulation they can radiate some heat into the housing or the gearbox oil can carry the heat away, transformer oil is close to a straight mineral oil just like gearbox oil and the lacquer would protect from any metal particles.

Long term though you want to try and wind a coil that doesn't overheat, it's not that hard to make a coil that won't overheat and still be the same strength but the time taken for the magnetic flux to build up may be slower and this may affect gearbox operation. Probably improving the cooling by removing the epoxy and some heatsinking would be easiest and not compromise mechanical operation.

I found a link that appears to be an accurate description of doing the R&R of the shafts and clutches:http://home.earthlink.net/~gizmowizard/graz/data/SAG12-main.htm .
Btw, I may have a sag 12 for sale as I found a perfect specimen and may replace mine. It is in generally good working order but the 1250 rpm clutch needs to be replaced and I do not have the time to repair it. Any interest here?

Bill
do you have any sag 12 clutch parts, thanks

sag 12 transmission for sold

i have completely transmission for sold. motor is a 550v and have 2 clutch defect. another 4 cluth is ok. the motor is ok. I'm put a vfd to my sag12.

if interested please contact me.

[email protected]

thanks

400$ for completely transmission with motor

thanks