Author Topic: Jack Shaft for Taig Lathe?  (Read 1904 times)

Offline Bear

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Jack Shaft for Taig Lathe?
« on: January 03, 2025, 04:37:10 PM »
I would like to slow down the spindle rpm of my Tag lathe. I have contemplated a variable speed motor; but I am more drawn to a jackshaft system. I have seen some made on the internet. But my question is how to calculate the rpm of the spindle.
The slowest speed on the Taig factory set-up is about 525 rpm. https://taigtools.com/product/micro-lathe-ii-m1015/. My intent is to purchase a pully from Taig https://taigtools.com/product/1164-6-step-pulley-5-8-shaft/. I would then mount it such that the smallest diameter of the motor pulley would go to the largest diameter of the jackshaft pully which in theory would give me approx. 525 rpm of the jackshaft pulley? If I am correct about the 525 rpm of the jackshaft pulley, what would the headstock spindle rpm be if the smallest pulley diameter of the jackshaft drove the largest pulley of the spindle?

Offline Jo

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Re: Jack Shaft for Taig Lathe?
« Reply #1 on: January 03, 2025, 05:06:16 PM »
Calculate the circumference of the driving pully and the driven pulley. The ratio of these two measurements gives you the reduction factor for the speed.

Jo
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Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #2 on: January 03, 2025, 06:30:21 PM »
Calculate the circumference of the driving pully and the driven pulley. The ratio of these two measurements gives you the reduction factor for the speed.

Jo

Thanks, Jo. Math has not been my forte in life :-[. I will try to do as you state and report back with my findings to see if I figured it correctly

Offline mklotz

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Re: Jack Shaft for Taig Lathe?
« Reply #3 on: January 03, 2025, 08:40:24 PM »
No need to calculate the circumference ratio.  Use the diameter ratio; the missing factor of pi cancels out.
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Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #4 on: January 03, 2025, 10:12:43 PM »
No need to calculate the circumference ratio.  Use the diameter ratio; the missing factor of pi cancels out.

Thanks, Marv. I have just gotten around to measuring the diameters, and will start trying to do the calculations soon.

Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #5 on: January 04, 2025, 12:00:38 AM »
Alright. I think I figured it out. I wasn't able to get exact measurements from the Taig pulley. I used the approx. figures as follows: Smallest pulley diameter (.650); Largest pulley diameter (2.15)

I divided .650 x 2.15 for a ratio of .302.

I took the motor rpm of 1725 and multiplied by .302 = approx. 521 spindle rpm without jack shaft.

I then took the 521 spindle rpm and multiplied by the same ratio of .302 for a reduced speed of approx. 157 spindle rpm with jack shaft.

If my calculation are correct, I would be fine with the reduced amounts on the various pulley speeds. Actually, I would go with the 1/2" bore pulley from Taig for the jack shaft, not the 5/8" linked above. https://taigtools.com/product/part-300-62-lathe-motor-4-step-pulley/

I would appreciate confirmation of my calculations. Thanks.
















Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #6 on: January 04, 2025, 04:17:01 AM »
On second thought, I may forego the jack shaft idea. If my calculations are correct, my highest speed would be sacrificed significantly. I guess I need to think this out further before taking the plunge. There are other options, or maybe I will just leave it as is.

Offline Jo

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Re: Jack Shaft for Taig Lathe?
« Reply #7 on: January 04, 2025, 08:57:31 AM »
The idea with an additional Countershaft is you only put the belts round it when you want to use the slow speeds, otherwise you leave it out  ::) . Don't forget one additional belt will reverse the direction of the headstock (hence the term "counter"shaft as it counter rotates ).

Jo
« Last Edit: January 04, 2025, 09:00:38 AM by Jo »
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Offline Vixen

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Re: Jack Shaft for Taig Lathe?
« Reply #8 on: January 04, 2025, 09:12:30 AM »
The idea with an additional Countershaft is you only put the belts round it when you want to use the slow speeds, otherwise you leave it out  ::) . Don't forget one additional belt will reverse the direction of the headstock (hence the term "counter"shaft as it counter rotates ).

Jo

Jo, are you sure about the rotation direction? Belt driven not gear driven


« Last Edit: January 04, 2025, 10:00:02 AM by Vixen »
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Offline Jo

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Re: Jack Shaft for Taig Lathe?
« Reply #9 on: January 04, 2025, 12:56:35 PM »
Mike is right  :facepalm:  :old:

Jo
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Offline Jasonb

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Re: Jack Shaft for Taig Lathe?
« Reply #10 on: January 04, 2025, 01:14:02 PM »
You may just need a different length belt or possibly two the same depending on the position of your additional shaft.

The images here show how the U3 does it, either direct from the motor pulley at the bottom to the spindle or via the top pulley which is on a stub shaft. So going from motor to spindle will give the speeds you already have, ones via the other pulley will reduce the speed.

https://www.ebay.co.uk/itm/284451636288

Offline ShopShoe

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Re: Jack Shaft for Taig Lathe?
« Reply #11 on: January 04, 2025, 01:39:00 PM »
I found the link I couldn't find earlier:

http://mechanicalphilosopher.com/TaigJackshaft.html

And ....I know there are other, similar installations out there.

ShopShoe

Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #12 on: January 04, 2025, 03:35:11 PM »
Thank you for all the responses. Shopshoe, I did see that link and was planning on something like that but taking up less space. However, I still don't see how I could use the motor to spindle configuration so that I don't lose so much on the spindle rpm if I were to disable the countershaft pulley, unless I were to set the motor up on a sliding system that would not be too tedious to move. The link provided by Jason might give me some ideas. Back to the drawing board  :).

Offline crueby

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Re: Jack Shaft for Taig Lathe?
« Reply #13 on: January 04, 2025, 05:38:26 PM »
On the Sherline lathe/mill they use a double pulley on each shaft, one large and one small diameter on each pulley, set up so one belt can work in either position without moving the motor position. Could something like that be done on the Taig? Or even swap out pulleys and belts to change speed range? The lower speed range pulley position gives better torque on the Sherline compared to just turning down the speed control, since the motor can run a bit faster and be in a better part of its power curve.

Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #14 on: January 04, 2025, 06:43:52 PM »
Thanks Chris. I will take a close look at a photo of the Sherline set-up to see if I can figure something out.

I am currently in the process of trying to bore a mild steel cylinder approx. 1" diameter and a little over 1 3/4" long. The bore will just be around .750". Not the size of the Webster cylinder that I referenced in another thread: https://www.modelenginemaker.com/index.php/topic,12134.msg287091.html#msg287091

I had already turned the outside dimension on the Taig a couple weeks ago with no taper. It was just sitting in the Taig 4 jaw mounted such that the jaws are clamped on a 3/4" diameter, with over 1 3/4"  stick out. I am still drilling the bore to get it to about 7/16". may try the steady rest as suggested in the other thread. If this works well at the stock slow speed of 525 rpm, I may just forego the jack shaft idea.
« Last Edit: January 05, 2025, 01:24:41 AM by Bear »

Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #15 on: January 05, 2025, 01:08:01 AM »
Update: Boring is a slow process. In any event, I am getting there. After drilling bore out to 7/16" on the Taig, I have bored it out to .535" so far. The depth of the bore is 1.9". The OD of the mild steel is .9085".
I am using the Taig steady rest (otherwise there is slight chatter at the bore entry). I am using a 3/8" boring bar with CCMT 21.51 insert (Korloy). There much more stick out of the bar than I would like. Taking a few spring cuts.
Nevertheless, I am getting no measurable taper as best as I can measure with telescoping gage. I am impressed with the capability of this little Taig with power feed.
I am aiming for a .750" bore; but, that will have to wait till tomorrow. Actually, the bore may be a little less so that I don't break through on the approximate 3/4" portion inserted in the chuck, or I may just shorten the bore accordingly. Doesn't look like the jack shaft will be neccessary, at least in the near future.
« Last Edit: January 05, 2025, 01:21:52 AM by Bear »

Offline crueby

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Re: Jack Shaft for Taig Lathe?
« Reply #16 on: January 05, 2025, 01:11:18 AM »
Excellent!

Offline Bear

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Re: Jack Shaft for Taig Lathe?
« Reply #17 on: January 06, 2025, 02:10:11 AM »
Okay, got the bore to .685". I think I will just stop here. The wall is getting thin. Final result is negligible taper of no more than .0001" to .0002" (larger at the tailstock end), if my measurements are correct with the telescoping bore gage.
The importance of this experiment   :) is that I have made a personal determination that the Taig is quite capable and accurate even with a somewhat larger steel cylinder such as the one I have turned.
Nevertheless, I still would like to reduce the speed for turning. Lapping the cylinder which would be required anyway would also need a much slower speed.
Thank you all who participated in this thread. 

 

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