Keep PM-1236T or get back in line for PM-1340GT?

[davidpbest]

I don't see myself changing chucks at lot and when using my Atlas 618, I did find myself re-chucking parts about half the time... so TIR is somewhat important to me. So far, all I've used is a 3 jaw scroll chuck.

I was not aware of a combination chuck.... I'll have to check that out.

I'll underscore what others have said - ultimately you will want a 3-Jaw scroll, a 4-Jaw independent, and some kind of collet chuck (ER40 or 5C). I have a 6" 3-jaw made in Taiwan with Set-true adjustability provided by PM - it's in the same general quality category as my Bison chucks. I also have their 8" 4-jaw which is fine, but nothing special. To me, one often overlooked aspect in selecting a chuck is to pick versions with 2-piece jaws. That gives you the flexibility to put on sacrificial jaws and makes it a lot easier to rotate them 180°.

 

[skcncx]

Well..... I made the switch... back in line for another 6-7 months. That's the only downside, well cost too but those are non issues once you get past them.

Came down to these primary reasons... (no single one, all combined aspects of the change)

• Single phase to 3 phase
  • I'll get the HITACHI-WJ200-015SF VFD as long as it supports the braking resistor option. That seems to be the "go to" for this lathe. May try out the auto stop feature when threading toward chuck (one day, some day kind of thing).
    
    
• Taller compound to center line height for greater range for tooling
  • Already have the BXA Aloris tool post.
  • 1.2" on 1236T vs 1.7" on 1340GT.
    
    
• Planned on getting a better chuck anyway... now I have to. The 1340GT doesn't come with one.
  • I'll heed the advice from others... start out with quality set-true 3 jaw and add on from there.
    
    
• Extra 4" length may come in handy one day
  
  
• Focus on getting benchtop mill for this winter and the myriad of other projects I have in the queue... while I wait.
  
  
• I won't continue to second guess my order on the 1236T

If I hadn't already started with so much tooling that overlaps with Aukai's PM-1340GT package, I'd go that route... still food for thought.

 

[skcncx]

I have a 6" 3-jaw made in Taiwan with Set-true adjustability provided by PM - it's in the same general quality category as my Bison chucks.

I'll likely land on PM's option. There's a supplier near me that has the TMX Set Tru 3 jaw for $800... but no backing plate and that's nearly a $400 extra charge. So $500+ compared to PM's option.

To me, one often overlooked aspect in selecting a chuck is to pick versions with 2-piece jaws. That gives you the flexibility to put on sacrificial jaws and makes it a lot easier to rotate them 180°.

Out of my ignorance are these equivalent?... "2-piece jaws" and "Removeable bolt on jaws can be reversed". PM's adjustable 3 jaw has removeable and soft jaws available... I assume that's the same as saying "2-piece jaws".

 

[davidpbest]

Out of my ignorance are these equivalent?... "2-piece jaws" and "Removeable bolt on jaws can be reversed". PM's adjustable 3 jaw has removeable and soft jaws available... I assume that's the same as saying "2-piece jaws".

Yes, but you might ask if they are American or Metric tongue and groove compatible. Here is where I get my jaws:

MonsterJaws Mfg - High Quality Chuck and Vise Jaws (Machinable Soft Jaws)

MonsterJaws Mfg Chuck Lathe Mill Vise Machinable Carvable Soft Jaws Aluminum Steel

monsterjaws.com

 

[Beckerkumm]

I'll second ( or third ) the recommendation for a quality combo or set tru 6" chuck. I'm primarily a used guy but don't think used is a good option for a chuck unless NOS or very lightly used. There is one exception to my rule. I have watched for a decent looking used 8" with outside jaws for the larger diameter stuff. It doesn't need to be set tru and can even be direct mount which are fairly unloved and often priced to reflect that. Putting a turned slug into the smallest part of the jaws allows you to bore out the second notch and then putting a turned piece into the second notch allows you to bore out the third and give very good concentricity for the two positions. The scroll needs to be decent to be repeatable but not a horrible risk if you are careful when buying. Dave

 

[davidpbest]

Out of my ignorance are these equivalent?... "2-piece jaws" and "Removeable bolt on jaws can be reversed". PM's adjustable 3 jaw has removeable and soft jaws available... I assume that's the same as saying "2-piece jaws".

I just checked the PM web site. This is similar to the 6" 3J I bought from them - different manufacturer, but very similar in all regards:

6″ Adjustable Ultra Precision 3 Jaw Chuck, D1-4 Mount – Precision Matthews Machinery Co.

www.precisionmatthews.com

This is the chuck they supplied for me (with depth-stop blocks I added): made by Chandox in Taiwan:

https://flic.kr/p/XU9P1r

I also own this chuck, which would be the functional equivalent to the one PM sells, although this Bison does not come with a D1-4 backplate:

6" BISON 3 Jaw SET-TRU Chuck Forged Steel 7-866-0600

 

[skcncx]

I just checked the PM web site. This is similar to the 6" 3J I bought from them - different manufacturer, but very similar in all regards:

6″ Adjustable Ultra Precision 3 Jaw Chuck, D1-4 Mount – Precision Matthews Machinery Co.

www.precisionmatthews.com

This is the chuck they supplied for me (with depth-stop blocks I added): made by Chandox in Taiwan:

https://flic.kr/p/XU9P1r

I also own this chuck, which would be the functional equivalent to the one PM sells, although this Bison does not come with a D1-4 backplate:

6" BISON 3 Jaw SET-TRU Chuck Forged Steel 7-866-0600

PM's 3 jaw adjustable is most cost effective option.... I was looking at the TMX version from ajaxtool supply https://www.ajaxtoolsupply.com/tmx6settrufo.html and their D1-4 backing plate https://www.ajaxtoolsupply.com/tobaforse6in.html. Bison is just about $100 more for backing plate and lathe on each time.

Both TMX and Bison are forged... not sure really the differnt between forged, steel and the semi-steel the make them from. PM's "balanced" seems great... maybe that's standard for forged chucks.

PM's on back order until April next year... though, no big deal, since I switched to 3 phase 1340GT.... that's not due until May/June 2023.

 

[mksj]

Semi-steel is a lower grade cast steel, as such the chuck is rated to a lower top speed, forged is a higher grade steel which has a higher maximum speed. This becomes more important if your lathe can achieve those maximum speeds, and you are spinning a large chuck. Example is an 8" semi-steel will usually be rated to 2,000 RPM, where a forged would be 2,500 RPM. Otherwise they are the same, other than semi steel is much less expensive. On a smaller chuck, say 6" you are looking at maximum speeds in the 5K range, so pretty much a non-issue. Do recall recently another HM member that bought an Bison 8" combo in semi-steel, the company (Small Tools) found they were on back order and offered him a forged for the same price.

Act Fast, this is probably one of those deals that one rarely sees. This is the Bison 8" combination chuck at 47% off ($794) from Grizzly. You can buy a Gator D1-4 back plate (about 1/2 the cost of the Bison), that is what I installed on mine.

8" 4-Jaw Plain Back Independent Chuck

The jaws on this chuck move independently, so you can use them for holding odd shaped pieces or where zero tolerance is required. Forged steel body with a large thru-hole, this chuck has heavy-duty reversible jaws, (hard top jaws and hard master jaws), and a set of mounting bolts and eye bolt...

www.grizzly.com

Link to chuck at Bison America

Bison

www.bison-america.com

 

[skcncx]

Semi-steel is a lower grade cast steel, as such the chuck is rated to a lower top speed, forged is a higher grade steel which has a higher maximum speed. This becomes more important if your lathe can achieve those maximum speeds, and you are spinning a large chuck. Example is an 8" semi-steel will usually be rated to 2,000 RPM, where a forged would be 2,500 RPM. Otherwise they are the same, other than semi steel is much less expensive. On a smaller chuck, say 6" you are looking at maximum speeds in the 5K range, so pretty much a non-issue. Do recall recently another HM member that bought an Bison 8" combo in semi-steel, the company (Small Tools) found they were on back order and offered him a forged for the same price.

Act Fast, this is probably one of those deals that one rarely sees. This is the Bison 8" combination chuck at 47% off ($794) from Grizzly. You can buy a Gator D1-4 back plate (about 1/2 the cost of the Bison), that is what I installed on mine.

8" 4-Jaw Plain Back Independent Chuck

The jaws on this chuck move independently, so you can use them for holding odd shaped pieces or where zero tolerance is required. Forged steel body with a large thru-hole, this chuck has heavy-duty reversible jaws, (hard top jaws and hard master jaws), and a set of mounting bolts and eye bolt...

www.grizzly.com

Link to chuck at Bison America

Bison

www.bison-america.com

That is a good deal. So , still figuring out the “combination”… independent and scroll type? Or is it scroll but you can fine adjust them independently… I must be dense on this.

 

[mksj]

Think off a scroll chuck and then add a screw type adjustment on top of that that acts the same as an independent chuck. Look at the previous picture and you will see the carrier that is operated by the scroll and then the jaw position with a scroll adjuster between them,

You use the scroll to get the work in/out of the chuck and for repeat work that you do not need sub 0.001" accuracy on the repeat. You can tweak opposing jaws to null out any TIR if needed. As there are slight difference in jaw torquing, this accounts for a slight variation with repeat use of the scroll. The other plus of this chuck is three-fold, first it can hold work down to 0.2" because the jaws are narrow at the tips, second is it can hold work more securely because of the opposing jaws, and third you can compensate for holding power if the work is not perfectly cylindrical.