Setting-up the PM 1236-T Lathe

[Z2V]

Mikey and Dabbler, thank you, that is very helpful. I was a little concerned about the appearance of the oil, a bit like liquid graphite at the bottom of the headstock, but all else looked great.

TK, my 1236 was the same. I drained it and wiped the gunk out and refilled it. All is well now. It was filthy though.
I’ll say again, thanks for the detailed write up of your build out. You have gone all out on this project, well done.

 

[Titanium Knurler]

I did the same with my headstock, hopefully it will stay pretty clear after this first oil change. It certainly should be easier to change the oil next time around.

Thanks Z2V, I appreciate your feedback. I have a few small items to go(QCTP, Taper Attachment, and Microstop Clutch Adjustment) then I will probably disappear for a while to complete the last section on Checking Specs and Adjustments. Believe it or not, I am looking forward to this section and I want to play around with it for a while. I know it has been a long slog, I am happy you have been able to stick it out.

 

[MWCurl]

TK

We corresponded through this forum a week or two ago. I am still considering the1236T. Can you tell me how to PM on this site? If not, my email address is mcurl@sextonsinc.com. Please contact me. Thanks.

Mike

 

[Dabbler]

Mike, hover your mouse over the blue "Tianium Knurler" (for example) in the left side of the thread. A dialog will appear that includes a link to "Start Conversation". This is the easiest way to start up a PM with somebody.

 

[Titanium Knurler]

V. Miscellaneous




B. Quick Change Tool Post(QCTP)- what a great invention the QCTP is! The last time I used a lathe was in high school when we had South Bend lathes and lantern style tool posts:



I am sure there are some of you that use the lantern style toolpost, and you probably use it better than I use my QCTP, but remember I am a newbie easily impressed by these things. But to be able to quickly change tools and have it rigidly held in exactly the same position as the last time you used it or to quickly make adjustments and quickly lock it in place is a wonderful thing.

I thought I would briefly go over how to measure the Lathe Center Height(LCH) and the minimum Tool Center Height(TCH) and why it is important in your selection of a tool post. It turns out that just because you have a tool holder that will hold a 1” shank tool it does not mean that it will work with your lathe. I found this out first hand. I had my eye on a tool that only comes with a one inch square shank. I thought if I ordered a tool holder that would accommodate a 1” shank it would work on my 1236-T, however, I found out that I don’t have quite enough LCH and will have to have the shank ground down to 3/4” to make it work on my lathe. After going over Center Height I will go over the 4-way tool post that comes with the lathe, the PM QCTP and finally the Dorian QCTP that I use.

To measure the LCH, one just measures from the top of the compound to the lathe centerline. The 1236-T measures just under 1-1/4”:



Here is how to calculate the minimum TCH. It is just th height of the lower lip of the tool holder + the height of the tool that you want to use:



If the minimum TCH is greater than the LCH then the tool is too tall and will be above the center line of the lathe.

Aside: American-style T-nut mounting vs. European-style threaded post. PM has accommodations for both:

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The stock PM 4-way tool post- it is attached to the compound in the American-style using a post and T-nut and has an enormous 1-1/8” opening for tools but much of it is unusable since with this holder and lathe the maximum usable tool height is 5/8”. To directly measure this I put a scribe in a collet chuck and marked it directly on the tool holders:

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The scribed line shows the minimum TCH which is the largest tool height that can be used. In this case it is 5/8”:



The PM QCTP- this is quite a bargain. You get a QCTP and five tool holders for about a third of the price of the equivalent Aloris or Dorian tool holder alone. Here are some photos of the QCTP, the tool holders and how it is attached:

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There are two similar tool holders available for square shanked tools from PM: the 250-201 that will allow you to use up to 5/8” shanks and the 250-201-XL that will allow you to use a tool with a 3/4” shanked with the 1236-T.

The Dorian SDN30BXA QCTP- this is a very nicely made piece of equipment. I originally purchased it because it’s tool holder had a 1-1/16” opening which I thought would nicely accommodate the 1” shanked tool I had my eye on, however, once I measured the LCH and the minimum TCH, I discovered that only about 13/16” was available because of my LCH. Did I return it when I found this out? Well, no, I didn’t. I will say that there is one disadvantage of the Dorian QCTP and that is that you need to machine some shoulders on the T-nut supplied. I milled the shoulder so that the top of the nut fell .01” short of flush with the top of the compound and also left .01” space between the bottom of the T-nut and the bottom of the T-slot so it would easily slide into the slot.

Isn’t she a beauty?



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The last photo just shows the PM and Dorian QCTP side-by-side and the Dorian D30BXA-1, PM 250-201 XL and PM 250-201with there respective maximum tool heights that can be used with the 1236-T.



To summarize, I would get rid of the stock 4-way tool post(how do you change the height of the tool anyway? Shims?), get a good QCTP and pay attention to the lathe Center Height when shopping. I may have belabored the lathe Center Height a bit but it is an important thing to consider, especially if you have a nifty 1” shank tool in mind...ah, but that will be the topic of another HM thread.

 

[mikey]

Dorian posts are definitely prettier than an Aloris if you get a good one.

 

[Titanium Knurler]

V. Miscellaneous
C. Taper attachment



Like most things we purchase for our shop I had a project in mind when I purchased it. The part that I wanted to make was to be made of titanium, was about 4” long, about 3/8” in diameter and had about a 1 degree taper. My order of operations did not include turning between centers and I didn’t particularly want to offset my tailstock since I wasn’t keen about readjusting the lathe every time I wanted to create a taper. I did a bit of reading and discovered that there are four ways, that I could find, to create a taper on a manual lathe. The title of this sections tells you the end of the story but let me tell you how I got there.

The four ways to create a taper on a manual lathe
1. Using the compound
2. Offsetting the tailstock
3. Tailstock offsetting device
4. Taper attachment

1. Using the compound is simple, just rotate the compound to half the angle required and cut:



This unfortunately would not work for me since it is only good for short lengths and relatively acute angles.

2. Offsetting the tailstock is much better than using the compound for longer pieces and small angles like I need but I was not planning on turning between centers and this technique requires re-adjusting the lathe every time you use this technique. So, this would not work for my purpose.

3. Tailstock offsetting device. This was getting closer; it offsets the tailstock but does not require re-setting the ailstock when you are finished. I knew I was not going to use this technique but during my research I found a beautifully made offsetting device made by Royal and purchased it. The device has a micrometer for setting the offset, a ball-nosed live center and a spirit level for making sure the device is level:



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This one, unfortunately, is no longer manufactured but there are some others available new on eBay:

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Why the spirit level on the Royal unit? Well, in every source that I read about turning a taper they all mention the importance of starting, and keeping, the cutting tool at the level of the axis of rotation or one will get inconsistent results.

Using the table that came with the tailstock offset device and Dr Jackson’s formula for calculating the error in cutting depth created by a vertical error(in this case the rotation away from level of the tailstock offset device). Let me walk through how significant this is. If you have an aversion to math just skip this and go to the next section. Here is part of the table that came with the Royal device:



If you look at the blue oval it gives directions and an example for using the chart. So, for a 2 degree taper on a 5” workpiece one offsets the device .087”. This is the reduction in the radius of the workpiece. Easy enough, but what if the offset device is not level and it raises or lowers the workpiece, say 0.1” on a 0.25” radius workpiece. Using Dr Jackson’s formula the change in depth of cut would be 0.02”((.1x.1)/(2x0.25)). So, at the end of the cut nearest the offset device you would not see the radius reduced by 0.087”, like you expected, but instead it would be reduced by only 0.067”. That is a 23% reduction in your taper at the end of the workpiece. What is even worse is that the elevation or depression of the workpiece will change as you go from the spindle, where there is minimal displacement, to the offset device, where it is maximal. Unfortunately, the Royal offset device does not work for my application because I am not planning on working between centers for this project but it is a work of art and I now know I must be very careful to make sure it is level, and stays level, when I use it.

4. Taper attachment- this turns out to be the tool that I need for my project. It can create a taper of +/-10 degrees over a length of ten inches, I don’t have to change my order of operations to include turning between centers and I don’t have to re-calibrate the lathe once I am finished. The only disadvantage is that the cross slide lead screw needs to be disconnected and the drawplate needs to be reconnected when the taper attachment is in use. The instructions in the PM Manual are very good so I will just show you a few photos from the Manual and of my installation on the 1236-T with the splash guard removed. Basically you bolt it onto the four pre-drilled holes on the backside of the carriage and zero it.



Attaching to the carriage:

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Removing the bolt to the cross slide leadscrew nut:

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Clamp and tie rod as well as draw plate are attached:



Zeroing:



The attachment comes without a reference mark on the taper guide. This is added once the taper attachment is zeroed:





That’s it for the PM taper attachment.

 

[Tozguy]

Why the spirit level on the Royal unit? Well, in every source that I read about turning a taper they all mention the importance of starting, and keeping, the cutting tool at the level of the axis of rotation or one will get inconsistent results.

That Royal tool is very nice, especially the round shape of the center tip. Curious as to why the scale goes from zero to 5 and back to zero.

Over the range of adjustment of the tool I would not be concerned at all about it slipping off level from vibration and cutting forces. The MT taper has plenty of hold to prevent that. After using a boring head a few times for offsetting the TS center to cut long slow tapers I can say that the Royal should not be very difficult to set up level and to keep it that way. It would be great to get your comments on using it since it looks like it would work like a charm.

The crux of cutting long slow tapers between centres regardless of the mechanical approach is to avoid chatter and patterning. If you ever come up with a practical follow rest for taper turning I am all ears and eyes.

 

[Titanium Knurler]

Tozguy, here is a better picture of the scale on the Royal tool:



As you can see, the zero on the left is where the tool is lined-up and the zero on the right represents a 10.

This is a photo from the box. I guess Emco Lux is a European Parts supplier. I wonder what the 244 000 represents? Probably a part no., or maybe a price?



I am not sure how often you turn a long taper and how much you want to spend on a self adjusting follow-rest but it looks like gunsmiths use a hydraulic follow rest to self adjust the rest as the taper is formed. Here is a thread that I found on the topic:

Is there a lathe that has a follower rest to allow taper turning

Do any of you have a lathe that will allow you to turn a 15 inch long taper using a follower rest? Markus

www.practicalmachinist.com

I wonder if there is a cheaper spring-type available or could be made? Sounds like a fun project to me.

TK

 

[Titanium Knurler]

For anyone interested in the PM Taper attachment I should have spent a little more time on zeroing it. Here is a photo that shows how I did this:



After removing the Draw Plate I put a magnetic based indicator dial on the carriage with it’s tip on the Follower Carriage. I adjusted the angle of the Taper Guide by loosening and then re-tightening the screws holding the Taper Guide in place(no. 3 in the photo). I then moved the Dove-tail slide back and forth, readjusted the Taper Guide, until I got zero movement on the indicator dial.

Another small thing I should have mentioned is that when the Draw Plate is disconnected it leaves the threaded holes on the Carriage open to collect debris, so I put set screws in place to plug the holes. I roughened the threads a bit before putting them in so they would not vibrate out of position and prevent the Draw Plate from moving freely and binding the crossfeed while the Taper Attachment is disconnected:

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Next I plan on posting the Adjustment of the Carriage Stop Clutch. I haven’t done this yet, so if all goes well I will post this soon. Mikey, I know you are not a fan of this mechanism, I recall you saying something like it was a “Newbie assault on a lathe”. I may find out why later today.