New benchtop mill

[asid61]

Originally Posted by Cory

RF-45 is the highest quality readily available benchtop mill you're going to find. It's pretty pain free to use and can legitimately make good parts (especially with DRO), but it is small, doesn't have much z-travel, and changing tools can be annoying.

It's well within your budget, but you could also be looking at bridgeports/bridgeport clones with your budget, if you have space.

Seconded. The RF-45 has a dovetail column, which is a must IMO for drilling and milling on the same machine (which you will do). Whatever you go for, avoid round column mills.
Make sure you bolt these down, especially if you put them on the flimsy sheet metal stands they come with. I've found that as little as turning the handles too fast makes it shake and throws it off as much as 0.005" on the spindle.

[sanddrag]

Who makes the best Bridgeport clone these days?

[protoserge]

Why benchtop when you have budget for a knee mill? Is tooling factored into the budget? A knee mill isn't much more of a footprint on the largest benchtop type.

PM-940 from machinetoolonline.com would be my recommendation if you have to get a benchtop type. Ask about getting a variable speed spindle for it. PM-935 knee mill is made in Taiwan and would be even better if you can swing it. Both are 240V.

Enco has yearly 25% off sales that include machinery with free shipping. You could get a great deal on one of the knee mills if you sign up for their newsletter. I believe the Turn-Pro brand is Taiwanese.

[JohnFogarty]

I was going to be going back through the content of these threads looking for some recommendation for 4901's new machining equipment.

One thing I have to ask is there a good knee-mill that uses single phase power? There's no way my team can get a 220V+ hookup in our shop.

[vigneshv]

Originally Posted by JohnFogarty

I was going to be going back through the content of these threads looking for some recommendation for 4901's new machining equipment.

One thing I have to ask is there a good knee-mill that uses single phase power? There's no way my team can get a 220V+ hookup in our shop.

We have the same problem, we were originally looking at knee Mills, but we found we couldn't meet the 220V power requirements.

[protoserge]

220-240V is typically single phase. 208-230V is typical three phase.

You can get static phase converters pretty cheap these days. If the motor is rated for inverter duty, you can get a variable frequency drive.

If you only have 120V available, there are VFDs for running three phase 208-230V motors, but you are limited in power.

A lot of knee mills are single phase, just check the motor nameplate.

[JohnFogarty]

Originally Posted by protoserge

220-240V is typically single phase. 208-230V is typical three phase.

You can get static phase converters pretty cheap these days. If the motor is rated for inverter duty, you can get a variable frequency drive.

If you only have 120V available, there are VFDs for running three phase 208-230V motors, but you are limited in power.

A lot of knee mills are single phase, just check the motor nameplate.

We only have 120V availible.

[protoserge]

Originally Posted by JohnFogarty

We only have 120V availible.

You might be able to get a 1-1.5HP 208 3 phase mill and run a properly rated 120V single phase to 208V three phase VFD. Your maximum current draw (I estimate 9-10A for a 1.5HP on 120V) may be closer to the limit of the common 15A 120V circuit than you'd like.

I believe most knee mills use standard frame motors, so getting a working solution (120V motor) may not be that big of a deal. If it came between making a knee mill work on 120V or getting a G0704, I would get the knee mill and live with the 0.5-1 HP compromise.

[RoboChair]

Originally Posted by protoserge

You might be able to get a 1-1.5HP 208 3 phase mill and run a properly rated 120V single phase to 208V three phase VFD. Your maximum current draw (I estimate 9-10A for a 1.5HP on 120V) may be closer to the limit of the common 15A 120V circuit than you'd like.

DO THIS. If you only have single phase 120V this is the WAY TO GO, its only a few hundred bucks for the VFD and its really easy to get a slightly larger breaker installed on the circuit you are using(go from a 10A or 15A to a 20A or 25A)

[protoserge]

Originally Posted by RoboChair

its really easy to get a slightly larger breaker installed on the circuit you are using(go from a 10A or 15A to a 20A or 25A)

Only if your wiring is rated for higher current is this a possibility (or within code). Otherwise, you are rewiring and you might as well get 240V run.

[techhelpbb]

I mirror the RF45 recommendation.
These have R8 spindles like the Bridgeport.
http://charteroakautomation.com/our-.../cnc-bed-mill/

That said, I have a highly modified Sieg X2 and have used the stock Sieg X3.
These have R8 spindles like the Bridgeport.
If you get one in good shape they can hold 0.001".
http://www.siegind.com/products_list/&pmcId=29.html
http://www.hossmachine.info/
Tool changer

I also own a ShopMaster Patriot VFD post-2012 mill/drill/lathe that I got for $4,000 with shipping used complete with CNC.
My machine takes 220V and has 1 VFD and 2 drive motors.
These have R8 mill spindles like the Bridgeport, MT3 for the lathe tailstock.
These machines support rigid tapping.
They can have sensors put on both the lathe and mill to 'close the loop' for RPM through the control PC.
http://www.shopmasterusa.com/content...-1-machine-cnc
The latest model just sold on eBay for $5,600 because a school ordered some and the funding fell through.

Also I've seen Tormachs here and there in the $5,000 range.
http://www.tormach.com/

I own both a MaxNC10 and MaxNC15 CNC min-mills with 4th rotary axis.
These are like Taig and Sherline.
They are a good tool for small jobs and could be used for jewelry making and aluminum gear making.
I wouldn't necessarily make robot sides with it because the travels max out at 16".
http://www.maxnc.net/category_s/1817.htm

You want to make sure with the Chinese mills you can get support after the sale in case you have defects.
I hesitate to buy any used, 'been laying around almost new', Chinese mills because you don't know they were ever tested.

You don't need a mill deck the length of the side of your robot: if you put a guide on the back of the deck and dowel pins at the extreme travels. You end up with some extra holes but you can then support the over-length on rollers. Just tile the operations.

[RoboChair]

Originally Posted by protoserge

Only if your wiring is rated for higher current is this a possibility (or within code). Otherwise, you are rewiring and you might as well get 240V run.

Fair point, but I think in most cases bumping it up an extra 5A will be well within what the wire is good for.

[protoserge]

Originally Posted by RoboChair

Fair point, but I think in most cases bumping it up an extra 5A will be well within what the wire is good for.

No. It is not.

[Tyson]

The set screw gibb adjusters in a sieg type minimill (harbor freight, little machine shop, grizzly etc) are an absolute non starter and not recommended.

They're horrible to adjust and go out frequently.

The stepper motor, fixed column, size, r8 collet option, available accessories are great for small parts machining. But you'll never get an accurate part with those gibbs. The spanner wrench collet loading isn't great either. Was a big mistake.

The graciously donated JET mini mill drill has been the workhorse of the shop. We lock the z stalk because switching between drill chuck and collets wears out the clamp bolts and requires rezeroing the dro, wasting a lot of time. So we just use shorty drill bits in appropriately sized collets for drilling functions.

So the RF 45 or similar would be great minimal entry for a benchtop mill.

[techhelpbb]

Originally Posted by Tyson

The set screw gibb adjusters in a sieg type minimill (harbor freight, little machine shop, grizzly etc) are an absolute non starter and not recommended.

They're horrible to adjust and go out frequently.

The stepper motor, fixed column, size, r8 collet option, available accessories are great for small parts machining. But you'll never get an accurate part with those gibbs. The spanner wrench collet loading isn't great either. Was a big mistake.

The graciously donated JET mini mill drill has been the workhorse of the shop. We lock the z stalk because switching between drill chuck and collets wears out the clamp bolts and requires rezeroing the dro, wasting a lot of time. So we just use shorty drill bits in appropriately sized collets for drilling functions.

So the RF 45 or similar would be great minimal entry for a benchtop mill.

Although I also recommend the RF45:

There are times I'd rather adjust set screw driven gibs than try to move a 700lb+ machine. Besides pretty much all the aluminum Sherline/Taigs/MaxNC machines are going to have issues on anything harder than aluminum. The Seigs X2 and below will never be as rigid as a Bridgeport or an RF45.

On the opposite end of this, we have the ShopBot style routers with aluminum parts here and there and square tube frames with ER collets on the spindles (if you are lucky).

There are times I prefer a good Bridgeport knee mill for messing around.
There are times I prefer to load 4' square plates.
There are plenty of teams running around with ShopBots banging out robot drive trains - they obviously won't be broaching with them - but they can locate and make holes and do some light work.