New benchtop mill
 

Hi,
We are looking to buy a benchtop mill in the offseason. Does anyone have any recommendations on which mills would be best for FRC use? Our budget is around $5000. Thanks!

Re: New benchtop mill
 

I'm just going to run through the standard CD checklist for mills:

1: Does it have to be a benchtop? Do you have room for a full knee mill like a Bridgeport?

2: You should probably count on spending at least as much on tooling as on the machine.

3: Do you have a mentor or a contact who knows how to use a mill? The nicest machine in the world won't do you any good if you don't know how to use it.

4: Whatever machine you get, it's probably worth taking it apart and cleaning it up. You can look up details for whatever model you end up getting online.

5: At some point, Cory might post in this thread. If he does, listen to what he says. He knows what he's talking about (much more so than I do).

6: The search feature is your friend. A quick search for "benchtop mill" produced a ton of results. Here are a few you might find relevant:

[1] [2] [3]

It's definitely worth reading through some of these old threads-- most of the info is still relevant.

Best of luck with your search!

Edit: Based on those old threads, I'd look into a RF-45. Grizzlys work but... Well, the one in the metal shop where 2667 works is pretty much perpetually broken and the Bridgeport has been trucking since probably before I was born, so make of that what you will.

Re: New benchtop mill
 

This thread and this thread should be able to help you!

Also I did a little bit of digging around and I found this

That seems to be a decent mill with a Digital Read Out for really cheap (!!!)
I don't own one so I can not attest to the quality of the mill however we have been using Grizzly tools in our shop for years and we've never had a problem.

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

Buy the most machine that you can afford and make space for, machine performance to price ratio is non-linear(eg. 2x$$$=4xMachine). If you want advice on tooling and/or buying a full sized machine used, please do not hesitate to PM me. Some people around here might say I buy too many machines >_>

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

Who makes the best Bridgeport clone these days?

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

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

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

We only have 120V availible.

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

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)

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

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.

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

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No. It is not.

Re: New benchtop mill
 

I will admit that that was a sweeping statement I made about the circuit layouts, sorry about that. You will often see smaller breakers in the panel than the wire can handle, before we had our former classroom turned shop rewired it had a LOT of 10A breakers when the wire gauge could have handled 15A.

If you have a 10A breaker, there are no problems on the part of the 14g wire upgrading it to a 15A breaker. A 2 HP(1500 Watts) Bridgeport at peak amperage being run via a VFD is 12.5A @120V even with efficiency losses you would have to be pushing that mill very hard to hit 15A (1800 Watts).

12g can be bumped to 20A (2400 Watts)
10g can be bumped to 30A (3600 Watts)

Re: New benchtop mill
 

I thought you were saying to change a 15A breaker to 20A. That would be a terrible idea. I have seen it done before and had conduit that was hot to the touch. Sorry for the confusion on my part.

Re: New benchtop mill
 

Not trying to discourage in any way, but I have a few points when buying a Mill.
Everyone is talking power so I'll leave that alone. :deadhorse:

No matter what you buy, you need to ensure you have excess in your budget for Collets, Cutters, and a Vise. Depending on what your plans are you can get a set of cutters from Harbor Freight that will do sufficiently on aluminum. Collets, here is a good portion of money you need to spend. R8 collets are pretty much the standard for most bench tops. You'll need any where from 5 - 8 depending on your cutter shaft. commons are 3/8, 1/2, 5/8 and a few more. If the mill doesn't come with digital read outs, I'd highly recommend buying a set and installing them, as the slop in the cranks is always there and only gets worse.
A Vise, for most table top mills a small vise is all that is needed. But if you end up getting a bridgeport or any type large knee mill, a decent vise will run $200-$400 or more. A full set of mill clamps (T-Nuts, studs/nuts and clamps) can also add to the budget.

Someone asked about a knee mill, Katy ISD has a JET knee mill in the STEM Center for the teams to use. I know 624 (CRyptonite) and a couple other teams used it extensively this year. I can provide further info.

Have fun and happy cutting:yikes: :)

Re: New benchtop mill
 

Shars.com for good quality cheap tooling

As for a Vise, the Kurt Scratch and Dent discount vise comes highly recommended. You will not regret your purchase.
http://www.amazon.com/D688-SD-6-inch...qid=1460749066
Two words: FREE SHIPPING

Re: New benchtop mill
 

No need for cutter sets. Buy a few HSS 1/8", 1/4", and 1/2" end mills and collet holders to support it.

I like the Shar's 4" precision vise for the price, but you can get Glacern for a great price in November (at least this past year and two years ago). Most boring heads that look like Criterions are junk. eBay the real thing if you need one.

Re: New benchtop mill
 

Common machine tool accessories you might buy for a lathe or mill:
(no additional costs to notice here...just move along :yikes:)

R8 collets (25 imperial sizes are common)
MT2 collets (23 imperial sizes are common)
MT3 collets (23 imperial sizes are common)
5C collets (64 imperial sizes are common)
Sherline/Taig/MaxNC 3/8"-16 collets (8 imperial sizes are common)
ER16 collets (12 imperial sizes are common) Note 1
ER20 collets (14 imperial sizes are common)
ER25 collets (16 imperial sizes are common)
ER32 collets (25 imperial sizes are common) Note 2
ER40 collets (25 imperial sizes are common)

ER16 tool holders and wrenches
ER20 tool holders and wrenches
ER25 tool holders and wrenches
ER32 tool holders and wrenches
ER40 tool holders and wrenches
CAT40 tool holders and tightening stand
The tool holder list can go on and on: CAT50, CAT60, Brown&Sharp
* Note 3

Note 1: ER16 is often the actual spindle for small machines like the MaxNC.
Some also use 3/8"-16 collets. The ER16 collet holder has a small
outside diameter that makes it easier to plunge into tight spaces.

Note 2: ER32 has a pretty large outside diameter, but can holder larger
diameter tools.

Note 3: Notice I didn't mention metric ;). Also there are things like ER20-GB collets.
These collets have a square in the back to engage the square on the taps.

Edge finders (mechanical or electronic)
Probes
1-2-3 blocks
Tombstones
Micrometers
Squares
Dial indicators
Dial test indicators
Feeler gauges
Torque wrenches (collets, draw bars)
Calibration rings
Granite test blocks
Gauge blocks (you know that perfectly sized test piece you just welded into the robot as scrap!)

Center drills
Square nose end mills
Ball nose end mills
Jobber drill bits
Aircraft drill bits
Split point drill bits
Countersinks
Boring bars
Carbide bars (lathe)
Indexed cutters
Punches
Fly cutters
Slitting saws
Hobs

Rotary broaches
4th/5th axis
Ball turners
Dividing heads
Rotary tables
Tool makers vises
Sine vises
Pin vises
V-Blocks
Down force milling vises
Boring heads
Taping heads
Rigid tap holders
Self-centering chucks
Independent jaw chucks
5C collet chucks
Tail stocks
Live centers

Bottom taps
Plug taps
Gun taps
Tap/drill combos

Broaches

Vortex coolers
Mist coolers
Drip coolers

CAM software
CAD software

That's just a tiny little start...this is the tool buying that never ends...it goes on and on my friend..

Re: New benchtop mill
 

What are your thoughts on used Kurts? Machine shop auctions inevitably have them go for <$150.

Re: New benchtop mill
 

Used Kurts are good if they work.

Enco sells Kurt so you can get them new at 25% off as well.

Re: New benchtop mill
 

$150 is only for the exceptionally patient bidder. But buying used is perfectly fine and is most of what we do for major items. You need to know what you are looking for and also what you are looking at, otherwise you could end up spending too much for something that is way more than you will benefit from or of poor quality for the price.

Re: New benchtop mill
 

If you are getting a VFD, watch out for the following:

• Get the VFD sized properly based on the motor's rated current (look at the motor name plate). If the VFD is rated for operation at different input/output voltages, the current rating is still the same, no matter the voltage (i.e. a VFD rated for 10A at 480V is still rated for 10A at 240V).

• If the VFD you are buying is rated for operation with a single-phase source, you are good to go. If it is only rated for operation with a three-phase source, you will have to get a VFD rated for 173% more output current or you may blow out the input rectifiers.

• If your budget can handle it, get the next larger VFD to have a bit more margin. Many are built down to a price and have very little margin.

• Install the VFD where metal dust and shavings cannot get into it, otherwise, it can be permanently damaged. The same thing would happen to the Jaguar's of several years ago but VFD's store much more energy and can sound like a shotgun blast when they die. If you can see through slots in the VFD's enclosure and see circuit boards and other components, it can be damaged this way. A good place to mount a VFD would be up high on a wall above the mill. Most VFD's have inputs so that you can connect start and stop switches and mount those next to your mill. If you must mount it where metal dust/shavings can fall on it, install it in a sealed metal box with a stirring fan. The box needs to be large enough to dissipate the heat generated by the VFD. The VFD vendor should be able to help you select a box of appropriate size (based on the VFD's heat output, the dimensions of the box and the sides that are exposed to the air). If they cannot help you, PM me and I will get the formulas from our Applications Department.

• A motor does not have to be VFD-rated to be used with a VFD. VFD's generate high voltage spikes that speed up the break down the insulation in a motor over many years of continuous use. VFD rated motors are manufactured with stronger/thicker insulation to resist this and are usually a bit more expensive and may be a bit harder to get. A mill for an FRC team will probably not see enough use for this to really matter. Many of our customers (my employer is a VFD manufacturer) do not use VFD-rated motors.

If you are setting up a home shop where you usually have only one person operating only one piece of equipment in the shop at a time, you may want to consider putting an appropriate in-line receptacle on the VFD output. You can then convert some other pieces of equipment to run on the same VFD and control the speed with a 10-turn pot. Drill presses run on a VFD are really sweet to use. No more swapping the belt around when going from a 1/8" bit to a 1" bit.

Re: New benchtop mill
 

This California bay area auction just went up.

http://www.westauction.com/auction/m...hine-shop-1474

If you PM me I might be willing to proxy for some of the more shippable items, inspect specific items, or pick up stuff if you are too far to drive. If you register to bid on anything please make your user name obvious that you are a robotics team (eg. FRC1678), don't want to get in bidding wars with other teams.

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Can someone tell me if this looks worth looking into?

https://www.govdeals.com/index.cfm?f...d=1055#me dia

Re: New benchtop mill
 

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.

Re: New benchtop mill
 

Kent
Having a local distributor in orange county is a benefit I suppose.
http://www.kentusa.com/mills/

Re: New 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.

Re: New benchtop mill
 

It definitely looks to be worth taking a closer look at it. Call them and schedule an appointment to inspect the Bridgeport in person, it has a lot of good features on it but I can't see any detailed pics of the ways. If you can see the flaking marks on the ways and it feels mostly smooth up, down, left, right, front, back, quill up and down, DRO functional. If that all looks good then it would be a great machine.

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Generally any government surplus machine that makes it to public auction is a piece of junk. Every federal agency and then state agency had a Crack at it and passed. Tons of govt surplus material sits outside completely unprotected from the elements as well. This mill doesn't look like it had that problem, but be wary.

Kent is the same rebadged Chinese/Taiwanese machines as every other brand. They are by no means a premium brand.

From everything I've heard, Sharp is the best Asian clone (the high end Acras are the same as Sharp).

New benchtop mill
 

Just saw this auction. What are the worthwhile items for an FRC team? Does that Haas VF-1 have any use in FRC? That and the manual mill particularly perked my interest.

Edit: Here is the link for the Haas

Re: New benchtop mill
 

FRC11/193 has a Haas TM-1P mill and a TL-1 lathe.
Fine machines but probably overkill only for FRC use.

You definitely want to make sure you know that VF-1 is in running order also notice the mill table size:
http://www.haascnc.com/we_spec1.asp?..._VMC#gsc.tab=0

It's big, it's heavy, and if there's something seriously wrong with it any money you save might be a drop in the bucket compared to the repair cost.

Re: New benchtop mill
 

It is a fantastic machine, my work has a VF-0 of the same year. It will be costly to move, require 3 phase wiring routed to it with a fat breaker, and I doubt it will go for very cheap. You are better off getting a CNC router first if you don't have one already. It was running code in a demo video, but it is a lot of machine and it is old making parts and support harder to find.

Re: New benchtop mill
 

The manual machines, tooling for them of machines you have already, bandsaws, hand tools, and various power tools. Bench tools such as grinders, drill presses, vises, and saws are usually pretty solid. Tool chests can be nice especially when sold with contents.

In the end it all really depends on what you have, what you want or can use, and what you can accommodate in the space/power/skills you have at your disposal.