Mill Fever

[Alan B]

I see I'm not the only one thinking about a new mill. There are a number of "My New Mill" threads on here. Great!

I'm still in the selection phase. I like to pick out a major item like this some time ahead of the actual purchase.

At the moment I have a Grizzly G0516 combo. A very nice machine. It combines a 10x24 lathe with a Mini-Mill. I've had them for several years and cut a LOT of plastic, and a little aluminum, brass and cast iron. Mostly I cut plastic, and I do some every few days, so it gets a lot of use.

My plan is to move up in the lathe category and in the Mill category. I need to do the Mill first since when I upgrade the lathe I won't have the Mini-Mill either, since they will go together and I don't have enough space for two lathes. Even a separate Mill is going to be a crunch, so that constrains the Mill and Lathe sizes. I have basically one side of a 2 car garage, but there is also a table saw, bandsaw and a few other things. But that is a different story.

I've been following the mill selection/purchase threads. The Rong Fu looks good and has a great price. The Super X3 is a bit smaller but has more features. Which brings me to the feature I'd like to hear about.

I do a lot of tapping in plastic. 1/4 NPT and 1/8 NPT. These are large taps and not really breakable in plastic, but they take some power to operate. Right now I do this either on the Mini-Mill or with a hand drill. I used to do it by hand, but alignment is iffy and my wrists got tired and the last thing I need is to get a repetitive stress injury from tapping. When I tap on the Mini-Mill I have to reverse by hand since there is no powered reversing. Luckily in plastic I don't have to do much reversing, but it would probably be better to, and there is always backing the tap out at the end.

So I would like to get tapping capability on my next mill. I see the SX3 has it. How does this work? Is it worthwhile?? Here is the G0619 aka SX3:

http://www.grizzly.com/catalog/2009/Main/533

Another larger mill I see with tapping is the Grizzly G0519:

http://www.grizzly.com/catalog/2009/Main/535

This second unit requires 220V 3 phase, so a phase converter (or VFD?) would be required, adding to the cost.

Note that I'm not stuck on Grizzly, I'm just more familiar with their catalog than other offerings. I'd like to hear about similar stuff from other vendors that I should consider.

Thanks for your comments,

 

[Mirage_Man]

While I like the idea of a knee mill that small one only offers a max of 12" between the spindle and table. The bench top has 20"! Given those specs the table top is the one I'd go with.

That said, my next mill will be a full sized Bridgeport type mill. The round column one I just got will do just fine until then .

I can't speak to tapping as that's not something that I really have a need for.

 

[Alan B]

While I like the idea of a knee mill that small one only offers a max of 12" between the spindle and table. The bench top has 20"! Given those specs the table top is the one I'd go with.

That said, my next mill will be a full sized Bridgeport type mill. The round column one I just got will do just fine until then .

I can't speak to tapping as that's not something that I really have a need for.

Thanks for your comments.

The spindle to table space is a very important factor for me. The mini-mill is about 11" on mine, and the SX3 says 14-3/4" while the larger one is 20". I didn't see the 12", not sure where that is. So the SX3 would be a gain of about 4" on what I have. The 20 inches of the larger mill sounds amazing.

 

[Mirage_Man]

Thanks for your comments.

The spindle to table space is a very important factor for me. The mini-mill is about 11" on mine, and the SX3 says 14-3/4" while the larger one is 20". I didn't see the 12", not sure where that is. So the SX3 would be a gain of about 4" on what I have. The 20 inches of the larger mill sounds amazing.

According to the specs in the catalog page you linked to the g0519 has 20" and the one below it on the same page, the g3103 says 12.5".

 

[precisionworks]

I run a couple of contract jobs on my Enco mill-drill (almost identical to Brian's new one), probably 500 drilled & tapped holes each month. Whatever machine you buy, you'll want to purchase a separate tapping head because of two features. First is the clutch, which eliminates tap breakage when the tap is buried in the part, or when the tap bottoms in a blind hole ... without a clutch, your vocabulary will expand greatly:scowl:

The second feature is auto reverse, so that as soon as you remove down feed pressure, the tap reverses at double speed and quickly backs out of the hole.

If you have one or two holes, don't buy a head. When your motor starts smoking because you start/stop/reversed it too many times, you'll have to buy one.

My Tapmatic was auction purchased, but there are always some on eBay (X-Series). Ettco heads have auto reverse but the clutch is not adjustable ... they are still a bargain at around $50 (look for a 2B).

 

[Alan B]

According to the specs in the catalog page you linked to the g0519 has 20" and the one below it on the same page, the g3103 says 12.5".

OK. I wasn't looking at the 3103. Thanks. The G0619 is 14+".

 

[Alan B]

I run a couple of contract jobs on my Enco mill-drill (almost identical to Brian's new one), probably 500 drilled & tapped holes each month. Whatever machine you buy, you'll want to purchase a separate tapping head because of two features. First is the clutch, which eliminates tap breakage when the tap is buried in the part, or when the tap bottoms in a blind hole ... without a clutch, your vocabulary will expand greatly:scowl:

The second feature is auto reverse, so that as soon as you remove down feed pressure, the tap reverses at double speed and quickly backs out of the hole.

If you have one or two holes, don't buy a head. When your motor starts smoking because you start/stop/reversed it too many times, you'll have to buy one.

My Tapmatic was auction purchased, but there are always some on eBay (X-Series). Ettco heads have auto reverse but the clutch is not adjustable ... they are still a bargain at around $50 (look for a 2B).

I'll look into them, I'm not familiar with them. I need something that will handle large taps, the NPT taps are quite large. I have a hand tapping machine for smaller taps, but it won't take the NPT taps. I don't think I can break a 1/8 or 1/4 NPT tap in plastic. I can drive them straight through with no reversing and not break them, at least in the plastic I am working with.

So the reversing is pretty hard on these motors, then? Perhaps they do it too suddenly??

 

[Mirage_Man]

I'll look into them, I'm not familiar with them. They must have a manual reverse as well as auto-reverse. I need something that will handle large taps, the NPT taps are quite large. I have a hand tapping machine for smaller taps, but it won't take the NPT taps. I don't think I can break a 1/8 or 1/4 NPT tap in plastic. I can drive them straight through with no reversing and not break them, at least in the plastic I am working with.

So the reversing is pretty hard on these motors, then? Perhaps they do it too suddenly??

The only motors that will do instant reverse are 3-phase, I think :thinking:. Not sure though.

 

[Alan B]

The only motors that will do instant reverse are 3-phase, I think :thinking:. Not sure though.

Right, 3 phase can reverse. The DC motors can also reverse, but the single phase AC motors would have to stop first.

 

[precisionworks]

So the reversing is pretty hard on these motors

Actually, starting (whether forward or reverse) generates a huge heat input for a single phase, capacitor start motor - the motor supplied with most mill-drills & small knee mills.

NEMA allows 6 starts/hour, so if you're tapping & reversing the motor, you've used 2 starts. Then wait 20 minutes before tapping the next hole, to stay within the 6 allowed starts/hour.

Three phase motors are allowed 10 starts/minute using across-the-line starters. They are allowed unlimited starts/minute when using a soft starter or VFD. Brushless DC motors are also allowed 10 starts/minute (these are not the "universal" motor found in some small mills).

The only motors that will do instant reverse are 3-phase

Exactly. You can tap & reverse all day long on a Bridgeport, which has a 3-phase motor, as long as you don't exceed 10 starts/minute (which means 5 holes/minute, one every 12 seconds).

I need something that will handle large taps, the NPT taps are quite large.

Any of the larger Tapmatic heads with drive a 1/2" NPT, a couple will go 3/4" NPT, and one goes up to 1 1/4" NPT. With a tapping head, the machine is started and continues to run in forward until all holes are tapped, as the head provides the reversing function. My mill will often run for a couple of hours while tapping a few hundred holes.

http://www.tapmatic.com/pdfs/TAPMATICGenCatManual.pdf


Kennametal has a nice, online tapping calculator to verify that your machine has both the torque & hp needed:

http://reference.kennametal.com/Calculators/Imperial/TappingHPTorque.aspx

 

[StrikerDown]

Those Tapmatics are really slick.

http://video.google.com/videosearch...&sa=X&oi=video_result_group&resnum=5&ct=title#

Dang Barry, you have some cool tooling. I am starting to grasp what you really mean when you talk about the cost on the machine just being a small start of the $pending !

 

[Alan B]

So I would need something like the RX70 for 1/8 and 1/4 NPT.

Looks very nice. Pricey too. Probably won't fit on my current mill, either, due to the height of everything. Maybe for one hole in a flat part, but for the holes in a 5" tall part not going to fit.

 

[precisionworks]

the cost on the machine just being a small start of the $pending !

95% of the tooling in my shop is eBay or auction purchased, which really helps. If you work hard on eBay, it isn't uncommon to pay 10% - 15% of new cost for most tooling. The rest gets purchased from J&L or MSC when they have their monthly sales - usually 1/3 off retail (more or less). Enco sales can also be very good, but you have to watch what you're buying more closely - it's either awesome or awful