Hi,

I have a lathe that would only go as slow as 160rpm, I would like to have it down to 40rpm.
The headstock is driven by belts and 3 planetary pullies, one on motor, one in the middle, one on the headstock. The middle one can be loosened and tightened for changing belt tracks and speed.

In the past, someone told me to make the small pullies smaller but how is that accomplished? An article on a machinist magazine introduced another way : using another motor, attached outside the headstock housing, and use it to drive the original motor pulley, the original motor is not turned on. Now the lathe go through 3 stages of speed reduction instead of 2.
This is too much fuss.

Any other easier ways to reduce speed?

Thanks

You can't put it in "back gear"?

What is backgear?

Mine is driven by pullies...?

If you can use step pullies it is relatively simple. These will work basiaclly the same way the cheap Taiwan twelve speed drill presses do. Two six groove pullies opposed to each other. These type pullies are not expensive. Mount one on the motor and the other on the arbor. I have seen this done on several lathes over the years and it works

Pyrotec---

If the lathe doesn't have back gears the best way is to buy a gear reducing motor and mount it along side the regular motor. If you build a rocker plate with a motor on each side, like a see saw, depending on which way it's set determines which motor is driving the spindle.

What lathe have you got?

Pyrotek, what kind of lathe do you have? Make and model, please. This will help all to better understand the nature of your beast.

Axel

[ 05-28-2003, 18:15: Message edited by: Axel ]

jbelk's idea is the most plausible, if you can find a gear reducer. You might try experimenting with pulley size, but it depends on how much room you have in the pulley enclosure. Sounds like a small chinese lathe like a jet, grizzly or similar, yes? There are actually quite a few options with pulley ratio and the like, it just depends on what you have available, and how much work you want to get into. Good luck

DGK

[ 05-28-2003, 20:54: Message edited by: 375hnh ]

How about a frequency drive for the motor, then you would have complete control over the speed range?? Would it be cheaper then a gear reduction motor??

I like Lar45's solution, a VFD. If your motor is already 3 phase, you can use it. If not, 3 phase motors are pretty cheap.

Thanks for you all who try to help me here. For a guy(me) who has a lathe in the garage, he's pretty ignorant about machining

My machine is actually a 3-in-1, lathe-mill/drill, marketed under the company name "ShopTask", and the machine is called "GunMaster", according to the company, their machines are made in China. I'll list the specs of the machine in a following post.

Is there anything I should do after receiving a machine, like cleaning or replacing some parts? I have been using this machine as is for a little, all I did was clean up dusty grease and spraying oil.

Where can I find a place to buy motors, and the frequency drive? I sure haven't seen one in Canadian Tires.

[ 05-29-2003, 01:26: Message edited by: Pyrotek ]

Specs of my machine :

SPECIFICATIONS
MACHINE 53"L, 19"W, 38" H
CRATE 55"L, 23"W,45" H
WEIGHT SHIPPING 800#, MACHINE 650#
MILL-DRILL SWIVEL 180 DEGREES

LATHE
SWING 17" OVER BED 8.5" OVER TABLE
DISTANCE BETWEEN CENTERS 32"
SPINDLE BORE 1.1"
HEADSTOCK TAPER MT4
TAILSTOCK TAPER MT3
SPINDLE SPEEDS 7 160 TO 1360 RPM
THREADING INCH 4-120 METRIC .2-6.0
CROSS SLIDE TRAVEL 8"
POWER 3/4 HP 110 VOLT
MILL
MILLHEAD TAPER MT3
MILL TABLE 6.25 x 18.75
T SLOT 7/16"
SPINDLE SPEEDS 16 120 TO 3000 RPM
QUILL DIAMETER 3.15"
QUILL TRAVEL 4.33"
DISTANCE TO TABLE 7.75 TO 12"
POWER 3/4 HP 110 VOLT
SPINDLE CENTER TO COLUMN 11.25"
DRILL
DRILL CHUCK 1/2"
ARBOR MT 3
DRILLING DEPTH 4.33"

WARRANTY 2 YEAR PARTS REPLACEMENT

Pyrotek

I'm sure you will find good information on this board, but you might also check out the specific 3 in 1 machine groups or the general lathe and machinine groups: This is one of the best, there are several other good ones if you do a google search.

http://www.practicalmachinist.com/cgi-bin/ubbcgi/Ultimate.cgi?action=intro&BypassC ookie=true

Roger

PS The practical machinist board has very good discussions of DC motors and variable frequency drives. Lots of info with a search. Also try the "home shop machinist" board, sorry I don't have the url handy

[ 05-29-2003, 03:34: Message edited by: N4652E ]

I think that you should be able to use the single phase motor your lathe came with.

You might do a search on freq drives

http://www.motorbuy.org/MBSalesWegVFDrives.htm

was one hit of many.

A single phase drive would be cheaper, if you can only find a 3 phase drive, then you might be able to use only one line from it, check with manufacturer first??

You might check with a local industrial electrical distributor?

Thanks for the info,

I've been doing some experiment and found out that, if I turn on the lathe, engage the 2 thread cutting latches(headstock to lead screw, and carriage to lead screw) then turn it off, without disengaging the 2 latches I can still make the carriage move forward/rearward by manually rotating the headstock, I've tried this to cut a small diameter aluminum rod but have not tried on large diameter steel like receiver or barrel.

Will this manual rotation cut threads with the same pitch as when the lathe is turned on? Any comments?

Yes

Here is whare a lot of talent resides regarding home (and comercial) machining. Lots of information abour VFD's etc.

http://www.chaski.com/ubb/ubbthreads.php

Pyrotek-Shoptask sells a low speed kit for their lathe. It requires drilling and tapping a couple of holes. Gives 32 rpm Check their Web site to see if it fits your model. http://www.shoptask.com/

[ 06-22-2003, 17:21: Message edited by: John Stranahan ]

Thanks John,

I have tried to order one before but they said it wouldn't fit. They said the description contains an error : It will not fit an XMTC 17-32(Gunmaster).

Pyrotek- I wonder if the slow speed kit would fit with only a belt size change. Send me a picture of your belt drive and I might be able to tell. Be glad to send you a picture of the slow speed kit installed on a 17-20 XMTC lathe. JohnStranahan@aol.com

160 down to 40 is another additional 4:1 reduction. Running the motor at 1/4 speed with a VFD is going to loose quite a bit of horsepower. If this is for chambering it probably won't matter since you will have excess power for that operation. You will want to watch the motor for overheating though. Particularly if it does not have an inverter rated motor on it.

Out of curiosity - are you running on 50 or 60hz power?

You said that there were 2 stages of reduction. I'm guessing that one is from the motor to the middle pulley. And one from this middle location to the headstock pulley. With 7 speeds I can only guess that one "reduction" is fixed and not adjustable while the other one has 7 steps. Is this correct? If it is could you let us know what the non-selectable belt pulley sizes are? And where it is. Motor to middle or middle to headstock?

Hi, John,

Thanks for your help, E-mail is sent.

Vibe,

The reduction steps you imagined are correct. However they all are planetary pullies. There are only 7 speeds because the way the belts are set up---the middle pully is adjustable, but its position must provide enough tension on both belts therefore not all combination of belt tracks are used. If the belts are replaced with larger/shorter ones it can provide some new intermediate speeds but just not any slower.

Please clarify what you mean by planetary pulley. Your useage of the term does not agree with my experience. Smithy offers a planetary pulley that is a pulley with a planetary gear reduction set built in - but this does not sound like what you are talking about.

The Smithy planetary pulley only offers another 2:1 reduction and is $200+

http://www.campbelltools.com/smithy/smithylathespecs.html

I've never checked what a planetary pully really is.

Intuitively I think it means a pully that has many concentric tracks with gradually smaller/larger diameters. Looks like a planetary system hence the name.....?

Those are usually refered to as step pulleys. Each reduction being located in each step. The planetary pulleys have a planetary gear system in them where there is a ring gear on the outside, a sun gear in the center and several (usually 3) planetary gears. If the ring gear is held stationary the planet gears rotate around the sun gear at the reduced RPM. If the planet gears are held stationary then the ring gear rotates at the reduced RPM, but in the other direction.

Most cordless drills have planetary final drive transmissions in them so if you have an old one, you can tear it apart to see what it looks like. These usually have the ring gear stationary.

Hydraulic driven hub motors on heavy equipment are sometimes of the planet gear stationary type.

With a step pully system you could look in a McMaster Carr, MSC, or local bearing supplier catalogue and find another step pulley or step pulley set that could replace the ones you have. Depending upon shaft length on the motor and jackshaft you might even be able to add an additional pair of pulleys that would give you the one low speed ratio you are looking for. Very small pulley on the motor, very large pulley on the jackshaft.

Vibe,

Thanks for clearing things up