Pm-1340gt Vs Pm-1440gt

[dave2176]

What is the advantage of the a wider bed? Less deflection of the carriage? .001" seems like a very fine feed. Is that useful for a fine cleanup pass?

The advantage would be overall rigidity improvements. I don't use very fine feeds unless I am doing something very small and fine. For most things a couple strokes with a lathe file followed by emery cloth works great. Just nice to have ability to do very fine work when the need arises.

So what your saying is, I also need a horizontal mill to cut gears?

Well of course you do, who doesn't "need" one. What I was referring to however is all the gaps or blank spaces in the threading charts. My lathe uses a 40 tooth on F and a 40 on G by default which provides all the "published" American threads from 4-112 tpi but it only gives me a couple metric threads that are useful. So if I want a 0.635mm pitch it's the same gears and position as 40tpi, one of the standard threads. My lathe didn't come with a 27tpi which is useful for a number of things so by changing gears, specifically leaving on F and putting the 60 on G I have 27 tpi on C2. So with my QCGB having 40 possibilities and 24 options of change gears I have 960 possible threads which also translate to feed rates. Any other lathe with change gears has many more possibilities than what is what is published on the charts.

 

[dogma]

My lathe uses a 40 tooth on F and a 40 on G by default which provides all the "published" American threads from 4-112 tpi but it only gives me a couple metric threads that are useful.

Is there a good reference to read up on various lathe threading gear box designs? I am completely ignorant of how they operate.

 

[dogma]

Similar to Dan, I usually do 0.050" DOC (0.100 total) in aluminum, 0.050-0.060" total stock removal in steel with no problems on the 1340GT. Type of tool holder/insert make a difference in how hard you can push it.

I'm still a bit fuzzy on the relationship between longitudinal feeds, spindle speed (obviously, linear surface speed is what maters), and DOC translate into required power (per material). I have a fancy android app that does it but if there a good resource to learn the theory?

 

[dogma]

However, I think it might be a fun project to weld up a heavy duty stand. IMS (a local metal supplier) has delivered heavy stock to the house for something like a $50 surcharge.

I've done a little bit of reading on this and it seems that gray cast iron is preferred for this sort of construction due to it's vibration dampening properties and IMS doesn't stock CI flats. Sandwiching some sort of elastomer between steel plates might work. Will have to see if I can get someone at work to do an FEA...

 

[mksj]

Cast iron is the preferred material, Meehanite cast iron used in the ERL-1340 and 1440GT is denser and has more ideal strength and dampening properties. Wouldn't chase your tail with FEA. On feed and speed, there is a lot published, I loosely use some of the manufactures recommendations for speed and feed, in general, you will be probably be at 50% SFM of published table attached (or lower RPM and faster feed), and way under those published if using inserts. Most of the feed rates fall into the 0.001-0.004 IPR. The lowest IPR on the 1340GT is 0.002, so lower RPM and slighter faster feed. Just a rough calculation, a 1" bar at 1000 RPM would have a SFM of 262, the same bar at 250 RPM would have a SFM 65. The DOC, varies on materials, IPR, Hp and cutter, working with different materials, you start to get a feel when you are pushing the DOC for stock removal. Just some thoughts, there are much more scientific formulas on all this stuff.

After awhile, you get a better feel of the cutting speed and feed, this is also affected by the cutter and the finish you need. I tend to push harder to remove material, then do a skim cut for for close to the final finish. There is minimum cut for different cutting tools, so taking like a 0.001" cut may not work very well. The cross slide feed is 1/2 the Z axis (longitudinal), when doing cut off I slow the speed down 300-450 RPM and feed manually, just need that tactile feedback. The nice thing when using a VFD, you can really find that sweet spot for the machine, I am always amazed that small changes in the RPM make a large change in the cutting performance/chatter, especially when boring/drilling.

 

[jbolt]

Matt told me this morning that the PM-1440GT is back ordered until September, so it may make this decision a bit easier.

Sounds like he has completely sold out the first batch. He said those were supposed to be finished in May. Not sure yet what that actually means for receiving and delivery. That will be about a two month slip in the original schedule when I ordered mine.

September sounds like is a "best guess". I'm sure it is a real challenge to work with overseas manufacturers who are building machines for multiple customers.

 

[wrmiller]

Matt always tries to give a "best guess" to his customers, but it is based on what information he is getting from his manufacturers. If they are overly 'optimistic' when communicating their delivery schedules...then as they say, the "big round brown ball" rolls downhill. But having said that, Matt appears to be getting better at translating his manufacturers delivery communications. Only one of my three machines I've bought from Matt over the years was delayed, and that was only a few months. That was a long few months though...

He also told me that it would be a "few months" for the cast iron stands to become available for the 1340GT, and that extras would be available for existing customers. But, I automatically translated that into 'may be available by the end of summer'. I'm hoping I'm wrong though, as he (Matt) is having these stands done here in the US.

 

[jbolt]

This got me thinking about the executive office build out I did for Hyundai corporate back in the 90's. All the cultural hoops I had to go through was nuts.

 

[qualitymachinetools]

"I'm hoping I'm wrong though, as he (Matt) is having these stands done here in the US"

Yeah we are waiting on our pattern guy for the castings, its no difference, overseas or in the US.

 

[GA Gyro]

Hey Matt,

Way to go on the cast iron base for the 1340...
Please put me down for one also!

Any rough idea of weight of the base (base alone)?

THX

John/GA