Setting-up the PM 1236-T Lathe

[Tozguy]

TK thanks for the link and reply re the scale, I need to have my eyeglasses tuned I guess.

 

[MWCurl]

TK

As you are aware, I am considering purchasing a PM 1236-T. The description on the PM website states this lathe comes with a 6” Economy 3-jaw Chuck. How would you characterize this chuck? Do you know the difference in repeatability and run out between this chuck and a high precision 3-jaw or 4-jaw chuck?

Also, what is your typical depth of rough cut and depth of finish cut for stainless steel and titanium?

Mike

 

[Titanium Knurler]

MWCurl, I am afraid I have not tested the stock “economy” chuck. Here is a photo of it on the top shelf of my stand. Even though it is on my “top shelf” I probably unfairly labeled it less than top shelf and purchased a Bison Set-Tru for working on good stuff:



“Bottom Shelf”:



I use exactly what Seco recommends since I use their inserts for titanium and ss. Here are their recommendations as well as a sample piece of titanium in which I tried their three recommended settings:





Hope that helps,
TK

 

[Titanium Knurler]

V. Miscellaneous
D. Microstop clutch adjustment- Well, this went more smoothly than I anticipated but was caught off guard by the forces involved. What do you think the “force”, in lbs, turned out to be for allowing the clutch to slip reproducibly but still have enough force not to trigger while turning? 100#?, 200#?, 300#? More?

This is how I adjusted the clutch but please keep in mind that these settigs may need to be modified if I find the clutch is slipping prematurely. I simply backed off on the two set screws one half turn at a time and had the carriage travel into the stop. If the stop was pushed down the way, the clutch was not slipping soon enough, I then backed off some more. I repeated this until I found that four half turns seemed to be correct. On my 1236-T this put the top of the set screw just flush with the counter sunk holes. Here are the pre-, post-adjustment photos of the clutch screws:

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I then placed a Force Meter between the carriage and the headstock and ran the carriage into the meter. It began to sound it’s overrange warning at 154lbs so I had to stop the “experiment”.

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So I rigged up a scale that has a range of 20-2,000 lbs. Surely it must be less than that!

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Next, I tested reproducibility of the carriage to stop at the same position at the setting as shown in the photo below:

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I repeated it ten times and found the carriage to stop within 0.0001” of the original position, but you must really clamp down the stop very tightly or it will get pushed along the ways at this setting of the clutch. I set it this way because I did not want the clutch slipping prematurely while I was cutting.

I also tried the stop on either side of the carriage with similar results:

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Well, that’s about it for the clutch adjustment, somewhere around 350lbs of force seems about right. I will update this in the future if for some reason it doesn’t work well. I hope this helps and I hoped it puts to rest any thoughts that I might be crazy, now you know for sure. Seriously, to me “367 lbs of force” is much better than “four half turns from the factory setting”. Who knows for sure where those set screws started on your machine?

 

[MWCurl]

TK

Thanks for the prompt response. Your comments were helpful.

Mike

 

[mikey]

I've only used the clutch when boring on one occasion and that was to test it to see if it works. It does. I happened to have my hand on the saddle feed at the time because I worried that I might have to emergently shut it off. The clutch worked but I could also feel the feed handle load up, which tells me the saddle feed mechanism is under strain. Given that I need my power feed much more than I need a stop for boring, I have personally decided that I won't use the clutch this way. Besides, I generally have my brain in gear when boring and it requires no significant effort to kick the saddle feed out of gear when approaching the carriage stop and then manually feeding gently into the stop.

Having done hundreds of blind bores without a clutch, I know I don't need it for this purpose. I need it in case I make a mistake and crash. It will slip until I can stop the lathe without stripping my saddle feed. I know PM lists using the stop for boring so I guess they intend for you to use it that way. For myself, I won't do that.

I noticed that your carriage stop is directly contacting the saddle body. My Emco lathe has a hardened dowel pin where the stop makes contact; this limits wear on the cast iron saddle, which seems like a good idea to me.

 

[Titanium Knurler]

Mikey, I intend to use it the same way. As a beginner, I still stop for a moment and ask myself “ OK, what are you going to do if this goes wrong?” I don’t have the experience or “muscle memory” yet to respond like I would like to. This is why I have changed the motor control lever knob to red like the e-stop button.

The hardened pin on your Emco is a very good idea. If I was planning on using the clutch often I would do something to protect the casting; 370lbs is a lot, especially if you are contacting that area often.

If your Emco is anything like the Royal tailstock offset device sold by Emco it must be a beauty.

 

[mikey]

My lathe is a beauty, at least to me. I pulled it apart (except for the headstock) to clean and lube it and was amazed at how precisely everything is designed and built. Everything fits, nothing needs to be forced, and the machining is top notch. Little touches, like that carriage stop dowel pin, are everywhere. Zero backlash on the cross slide and compound feeds result in reduced chatter and prolonged component life. Precision ground and hardened spindle running in FAG bearings results in zero spindle run out with little heat generated. Hardened and ground gear train with FAG bearings make it quieter at top speed than a Compact 8 running at low speed. Rohm-built lathe chucks and live centers, Llambrich or Rohm drill chucks, etc, etc.

At the time the Super 11 was built, it was their flagship. Built to a DIN tool room standard, they used top shelf components to assemble it. Those Austrians sure know how to build a lathe!

 

[Larry42]

V. Miscellaneous

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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:

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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”:

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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:

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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”:

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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.

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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.

My lathe came with the PM QCTP and 5 holders. All seem to work fine. I replaced the nut used for swiveling the tool post with a shop made lever so I don't need to keep another wrench near by. I want to get a scissors type knurling tool rather than the push in type that came with. One of the holders has a small V in the bottom for holding round tools. I've bought more tool holders mostly from Shars. The set screws are poor quality and need to be replaced but otherwise they seem fine. I can't believe anyone would want to use a lantern style tool post. I made a tool height gage similar to the one Oxtool made in one of his videos. Works well.

 

[Dabbler]

Hey, larry, I use my lantern regularly! It just depends on the work you do and the tooling you have. It is no better, nor a lot worse than other tool holders... I use mine for turning wood with HSS bits, and to reach weird places for O ring grooves, etc.

-- It is a lot slower when You aren't familiar, or don't have a height setting gauge, and is then a real pain! I was trained on Lantern tool posts, so I have some experience with them and know their weaknesses, and so I can avoid them.