Bench Top or Turret Miller ?

[JQ_Quint]

Need help guys..

I wish to purchase a miller to enable me to rework/modify my own cast iron cylinder heads (austin mini).
Basic spec = 500mm X axis travel, 130mm Y axis, Power feed in X, Z axis DRO.

I need a good tolerance spindle (min run-out) to enable accurate valve seat machining & good fine power feed in axis to enable head skimming.

I have a budget of about £900.00

The issue I have is I'm worried about the typical bench type mill i.e. Sieg type (not sure big enough anyway) not being "man enough", but when I start to look at the older "sturdy" turret type mill (bridgeport etc) i'm way off with price.

Another consideration is that I would at some point like to cnc mill the combustion chambres and therefore wish to either convert the machine or buy cnc now (again price a major issue).

Any advice will be appreciated!
Anyone who uses a machine for simialar use?
Anyone with views on bench mills?
Anyone with views on most suitable m/c to convert and typ costs?

Thanks in advance
Jamie

[Robin Hewitt]

I bought a bench mill and it has two drawbacks.

The column bends, not a lot, but it does bend, you have to go real light on the final pass if you want it accurate, especially when cutting uphill.

If you discover you need more height under the quill you lose your X,Y position as well as the Z.

With the economic downturn turret mills aren't selling at all well. If your business is going down the tubes you may have to take what you can get so it's definately a buyers market at the moment.

There are absolute bargains to be had on ebay, well within your budget, helps if you can collect. I'm trying to hang on for a bit to see when it's going to bottom out. What's the scrap value for 1.7 metric tons of iron?

[ataxy]

If you discover you need more height under the quill you lose your X,Y position as well as the Z.

Well this apply to those rf30 type mill/drill but not to benchtop mill that have square column.

Need help guys..

I wish to purchase a miller to enable me to rework/modify my own cast iron cylinder heads (austin mini).
Basic spec = 500mm X axis travel, 130mm Y axis, Power feed in X, Z axis DRO.

I need a good tolerance spindle (min run-out) to enable accurate valve seat machining & good fine power feed in axis to enable head skimming.

I have a budget of about £900.00

The issue I have is I'm worried about the typical bench type mill i.e. Sieg type (not sure big enough anyway) not being "man enough", but when I start to look at the older "sturdy" turret type mill (bridgeport etc) i'm way off with price.

Another consideration is that I would at some point like to cnc mill the combustion chambres and therefore wish to either convert the machine or buy cnc now (again price a major issue).

Any advice will be appreciated!
Anyone who uses a machine for simialar use?
Anyone with views on bench mills?
Anyone with views on most suitable m/c to convert and typ costs?

Thanks in advance
Jamie

It depends on what type of precision you intend on having and how fast you want the part done, keep in mind that you will need much more stronger motor and might have to go with servo if you want good performance with a bridgeport type mill wich are going to cost you alot more.

[TOTALLYRC]

Need help guys..

I wish to purchase a miller to enable me to rework/modify my own cast iron cylinder heads (austin mini).
Basic spec = 500mm X axis travel, 130mm Y axis, Power feed in X, Z axis DRO.

I need a good tolerance spindle (min run-out) to enable accurate valve seat machining & good fine power feed in axis to enable head skimming.

I have a budget of about £900.00

The issue I have is I'm worried about the typical bench type mill i.e. Sieg type (not sure big enough anyway) not being "man enough", but when I start to look at the older "sturdy" turret type mill (bridgeport etc) i'm way off with price.

Another consideration is that I would at some point like to cnc mill the combustion chambres and therefore wish to either convert the machine or buy cnc now (again price a major issue).

Any advice will be appreciated!
Anyone who uses a machine for simialar use?
Anyone with views on bench mills?
Anyone with views on most suitable m/c to convert and typ costs?

Thanks in advance
Jamie

Hi Jamie. In the USA I would suggest that you take a hard look at buying a Bport type mill that is already cnc with a bad control. Bought mine for $1k usd. Add in a nice cnc controller, ~$1500 and you have one heck of a machine. I recomend this because these machines have a nice spindle, ball screws, servo motors, and all kinds of stuff that you won't have to add on later. Mine has a 24 position tool change that I will be interfacing this winter.

I am not sure of what a similar machine would cost in the UK.
If that kind of budget is beyond your means right now, then by all means by get a manual machine to get started. You could even do what I suggest at a later date and then sell the manual machine.

The cost of ball screws to convert my manual bport was going to be more than I paid for the entire cnc ready machine.

If you are going benchtop mill, get a square column machine.

Mike

[MIKE JEFFERS]

jamie have a look for a bridgeport interact if you've got the space they can be picked
up cheap (£1000 or so ) easy to program and sturdy too the interact 1 is a bit smaller
than the others with a 450x300 x/y travel, the bigger ones are about 760x 360

[JQ_Quint]

Thanks Robin,

That is my concern, yes they do look a bit weak on the Z column. I did spot one though on Chester UK website the Lux bench top mill. At 330kg it seems quite sturdy but at £1200 its a gamble if it will do what you have suggested (bend at column).
I would prefer the turret type, i'm a little put off with the 3 phase issue though. Wouldn't I have to buy an expensive invertor?

Thanks
J.

[JQ_Quint]

Well from a precision point of view I would need a spindle run-out of less then 10 microns if possible, otherwise valve & guide cutting will be difficult. Also squareness of spindle to table would also need to be within probably about 10 to 15 microns otherwise i'll risk run-off off valves to rockers..
I'm not concerned about speed. Head skimming would be done very slowly for finish but stability is essential. Any table drop off at full extent would be disastrous.
So really I need accuracy over power.
Are you Pro then bench mill ?

Thanks
J.

[JQ_Quint]

Thanks Mike,

I like the Bridgeport idea. Like I said in a post earlier though is 3 phase an issue?
I got drawn into a web page last night offering cnc conversion kits but never really got all the data. What would be the typ costs to convert a typ bridgport or Tom senior type turret machine?

Thanks
J.

[JQ_Quint]

Thanks Mike (jeffers),

Another Bridgeport suggestion, looks like a common solution.
I would need the bigger one though. Would need at least 490mm in X.
I'm going to start the hunt for one of these. When I looked specifically the other day for B-Ports they were well expensive though...

Thanks
J.

[JQ_Quint]

Just been looking at a Bridgeport Series 2 cnc, which is plenty big enough but had an air line fed slideway lube system (i think). Being a garage based machine can this be converted into a hand pumped system?


Thanks
J.

[TOTALLYRC]

Thanks Mike,

I like the Bridgeport idea. Like I said in a post earlier though is 3 phase an issue?
I got drawn into a web page last night offering cnc conversion kits but never really got all the data. What would be the typ costs to convert a typ bridgport or Tom senior type turret machine?

Thanks
J.

What I use is a Hitachi single phase in, 3 phase out vfd. Works great on my 3hp btc-1.
You can go into the rest of the wiring and convert to single phase, only the motor is truly 3 phase in the original setup.
For the accuracy that you are looking for, the ball scres will be $1k+usd. Thats just for the screws. Then you have to do all the other stuff.
Search the Zone for vince's bridgeport conversion for a well done and well documented conversion. It is what made me decide on a old cnc that just needed new controls.
As far as the head to table alignment so the valve guides are lined up to the seats, that would be part of the setup as far as i am concerned. I would use a pin in the valve guide, then use a tenths indicator and line it up as you go up and down the pin to get as close to zero as possible. It will be as close as you are patient.

Of course you could just get a used valve seat reconditioning system which if I remember is a self contained unit that doesn't need a machine to use. Then a used mill with power feed to surface the heads.

If you really need that much accuracy, don't stretch a machine to get the travels, buy the machine that you need upfront. It will be much sturdier and have much less flex if it is designed large in the first place.

If you have to go bench top, the industrial hobbies mill gets my vote. It may be out of you price range, but then what isn't these days?

Best of luck with your search.
Mike

[JQ_Quint]

Thanks for the advice mike,

I've had a quick look at the industrial hobbies mill and yes it does look like one of the better bench mills.

Those cnc convert costs look scary. I really do need to see if I can get an old cnc to "tart up" I guess.

In these difficult times I am hoping to benefit from getting a bargain..

the search continues..

Thanks J.