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Grizzly 4003G Speed Question

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digadv

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#1
I'm down to my final decision between the PM1236 and the Griz 4003G. The top-end RPM of the PM1236 is 1800 and the 4003G is 1400. My question is will I need the extra 400 RPM at the high end? In my research I understand that fpm is the thing to look at and I've run some online calculators - many confusing to me with all of the "knobs" to turn. My anticipated uses for the lathe range from using aluminum to stainless steel. I recall in one instance running the calculator that turning 1/2 alum alloy with a HSS insert would require over 3800 RPM - could this be correct or did I possibly mis-configure something?

As a follow up question ... have folks safely achieved higher speeds on this lathe with a VFD conversion?

Many thanks and Merry Christmas to all!
 

Bob Korves

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#2
More top speed is always a good thing, but at what cost? If you could list all the speeds for both machines, and give us an idea of what you plan to do with the lathe, we could no doubt be much more helpful.

Speeds shown on manufacturer's recommended speed charts are for production work in an environment where everything is optimized -- very rigid machines, fire hose flood coolant, etc. Tools and machines will not last as long in that environment without paying careful attention to a lot of details. In a hobby shop, dial it down some, especially at first, and see how it works for you. High surface speeds often do help the achieved finish. Good work can be done with machines that are much more humble.

Three phase machines can be sped up with a VFD, but only to a certain point without destroying spindle bearings and motor, and perhaps becoming unsafe to the operator with some components. A 25% increase (and decrease) is often quite possible and usable, but "it all depends."
 

digadv

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#3
Thanks for the reply. Here are the speeds of the two machines (from spec sheets):

4003G: 70, 200, 220, 270, 360, 600, 800, 1000, 1400 RPM
PM1236: 65-1800 RPM in 18 steps

Uses for the lathe range from small parts out of aluminum/steel to threading various fittings to eventually rechambering SS barrels.
 

Alan H

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#4
Thanks for the reply. Here are the speeds of the two machines (from spec sheets):

4003G: 70, 200, 220, 270, 360, 600, 800, 1000, 1400 RPM
PM1236: 65-1800 RPM in 18 steps

Uses for the lathe range from small parts out of aluminum/steel to threading various fittings to eventually rechambering SS barrels.
Small = Speed most of the time

Full disclosure - I am a PM fan. I like the equipment they sell and from my experience, their customer service is in a league far above that of the Griz.
 

Bob Korves

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So the PM has a lower low speed, a higher high speed, and 18 speeds compared to 9 speeds. If that is the only criterion for choosing between them, then you have your answer...

Barrels are still small diameter, and will use speeds well above the lowest -- except perhaps for power chambering with a reamer, which is a slow speed operation.
 

SSage

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#6
I got a PM1236 this year and the 1825 rpm is just adequate for CCMT tooling. If your turning round bar under 1" with carbide insert tools you need speed for sure. Grizzly models didn't compare well feature wise for the money and PM has the better warranty.

I would suggest getting a heavier model with a foot brake. I had to wait for mine, but I like my choice so far. I figured eventually I'll need that foot brake. :)
 
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epanzella

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#7
I have the Grizzly G4003G. Love the machine and never use over 1000rpm even when doing small parts despite what the books says. They come out fine. Things happen a bit to fast for my comfort level when spinning @ 1400.
 

mikey

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Speeds are a greater concern when using carbide tooling, especially inserted carbide. Most hobby class lathes cannot get anywhere near the optimal speeds unless you're turning harder materials with largish diameters - they're too slow. However, carbide will cut at lower speeds, as most hobby guys will attest so I wouldn't worry over much; the lathe will work.

On the other hand, HSS is always an option and most lathes can use HSS quite effectively. For example, you can easily turn 1/2" OD aluminum at 1500 rpm and produce a mirror finish. The only issue with HSS is that you have to grind your own or use an inserted HSS bar like those from AR Warner. My 11" lathe has a top speed of 2200 rpm and it works fine with HSS tooling for almost anything I do. YMMV.
 

Bob Korves

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#9
The carbide tooling will work better at lower speeds if you get positive rake tooling, not neutral or negative, for smaller lathes and work. Chip breakers and sharp cutting edges can make neutral rake tooling cut like they are positive tools.
 

Mitch Alsup

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#10
This seems to be a thread where the following question is pertinent::

The G4003G has 2HP
There are a variety of videos on the net concerning negative rake insert tooling.
Many of these videos suggest CNMG tooling needs more HP than CCMT, etc.

Does the 2HP the G4003G has fall into the "not enough" or the "about enough" category wrt negative rake insert tooling?
 

Bob Korves

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#11
This seems to be a thread where the following question is pertinent::

The G4003G has 2HP
There are a variety of videos on the net concerning negative rake insert tooling.
Many of these videos suggest CNMG tooling needs more HP than CCMT, etc.

Does the 2HP the G4003G has fall into the "not enough" or the "about enough" category wrt negative rake insert tooling?
Not enough for heavier work and negative rake tooling. Even those of us with 13x40 and 14x40 import machines are mostly in the same boat, at least on some or much of our work. I don't even mess with negative tooling and don't even have CCMT tooling for my 13x40 Kent lathe. Heavier lathes with lots more cast iron and 5 or more hp, or something like a 10EE in lighter lathes, sure. IMO...
 

SSage

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#12
The cast stands make a noticeable difference too, you gotta get up in size on the new machines before you see the cast iron. I use CCMT inserts because I work with tool steels 99% of the time, you can run them at say 1,000 rpm but your better off using HSS at the lower speeds. I use both, but I prefer carbide insert tools, they save me time and work much better on the hard steels. I get okay finishes at 1400 with a RH turning tool, but it likes 1800 for the last couple cuts when its say a .300 drill rod.

2 hp from one source probably is not the same from another. Look at the motor's amp rating, that may give you a better idea of the real power. Precision Mathews has a 11x27 that has the features of a lager machine in a compact size with variable speed. I almost bought one, I ended up remolding my shop to make room for a 1236. They are about the same price. I looked hard at the Grizzly offerings and kept going back and forth comparing them to the PM machines. PM has similar models with nice refinements, that 11x27 is a really nice machine if you don't want a 1200 pounder.
 

Superburban

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#13
The biggest thing I would like to see on the gunsmith lathe, is a much lower low speed. Somewhere in the 20 to 25 RPM would be nice.
 

IdiotEngineer

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#14
For what its worth, I think the G4003G has a much beefier tailstock quill and a norton gearbox which is great for inch threads- no end gear replacements required for all inch feed rates and thread pitches. When I made the decision last year that was more important than an extra 400 RPM and the longer warranty
 
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Splat

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Digadv, did you ever make a decision? I went thru the same thing but what helped me decide was local seller selling a near-mint G4003G. I've been very happy with my decision, but if I didn't have that opportunity I would've went with the PM1236 with a VFD. I think all around, including support from Matt and the PM guys, you get a better deal. D1-4 chucks are easier to find and slightly cheaper than D1-5 (tho not too bad), and for $200 you can get the heavier cast iron PM stand. The G4003G stand is now lighter steel stand and the lathe is already $100 more than PM without the cast iron stand. Wider speed range on the PM machine. The shipping is $50 less for PM. Lastly, and this ia a doozy, while both lathes are considered good machines Grizzly is only a 1 year warranty. PM's is 3 years. That's a big difference, IMO, though hopefully you wouldn't have to use it. It's better to have it and not need it....
 

digadv

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@Splat - yes, I went with the PM, but it was very close and came down to the wire on Grizzly's end of year sale. I see that Grizzly has now raised the price and I think Matt will follow soon. One thing to note is that my PM1236 came with an outboard spider so that was a happy surprise.
 
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