Concrete base for small mill?

Hi, all

I'm going to be buying one of the HF 'mini-mills' in the near future and I'm considering casting a concrete base for it (as opposed to building a wood bench). I'm thinking of something like a flat-topped obelisk with a hollow core, reinforced with rebar and mesh. Anyone ever done this?

I thought about welding up a bench, but getting it in the basement would be a nightmare.

-Carl

Reply to
Carl Byrns
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First off let me suggest that this is shooting from the hip and not from a personal experience or an engineering analysis, but I would not waste the effort on a HF cheapie. These machines have problems that bolting to a concrete are not going to fix. I would bolt it to the table and learn it's limitations and then machine within them.

Reply to
Roger Shoaf

Roger-

I'm not picking on you personaly, but this is the reason I don't bother with RCM very often.

You admit upfront that you have zero experience with these machines, and yet you freely criticize them.

FWIW, the bulk of the work I'll be doing will be such that a Sherline is too small and a Bridgeport is overkill. Even is someone gave me a Bridgeport, it would cost a ton to get it into my basement and make it operational. My friend has a full size mill if I need one. Despite what you hear one this NG, there are a lot of folks out there who do nice work with the HF mill.

-Carl

Reply to
Carl Byrns

Sounds like getting it *out* of your basement might be really hard if you ever had to move the mill. How much do you figure it would weigh?

That seems like a lot of work to me, but then again maybe you're more comfortable than I am working with that stuff. I'd just weld up a heavy table, as strong as it needs to be. I used to build Navy ships and every machine on the whole ship is mounted onto a welded steel base.

GWE

Reply to
Grant Erwin

Well, you know, there's a considerable body of shared experience with HF equipment on this group. You don't have to have bought every piece of the stuff they sell to have a pretty good idea of what to expect.

Don't get your thong all knotted up. You came here to ask a question. You got one answer. Bank it up against other opinions you hear here, bounce it off the experience of all the other experienced machinists that you happen to know personally, and make up your own mind. But don't go all finger up the nose when someone takes the time to respond to your question with an answer that you don't want to hear.

And of course I mean that in the nicest possible way.

Best regards, Tom Dacon

Reply to
Tom Dacon

Sledge it to manageble chunks.

I like the idea of a concrete base- it would be stiffer than wood and quieter than steel. I've seen it done for telescope mounts.

I'd love to weld up a bench, but unless I did it in place (not gonna happen), getting it in the basement would be a job and a half.

-Carl

Reply to
Carl Byrns

I've never had a thing to do with H.F. machines but as a general rule setting machine tools involves mounting them on some surface that is completely stationary. Once the machine is mounted it is "leveled", i.e. adjusted by shimming, or otherwise moving the mounting feet, until the ways are parallel over their entire length. This is usually checked by use of a precision level, thus the term "leveled".

Ensuring that the ways, the surfaces that the various parts of the machine move on, are parallel and/or at right angles ensures that the machine will be as accurate as possible, always considering the in built accuracy of the machine itself.

Bruce in Bangkok (brucepaigeatgmaildotcom)

Reply to
K4556

I was not trying to suggest that you can't do accepable work on the small mill, I was suggesting that the machine bolted to concrete is not going to be much better than the machine bolted to a sturdy woden bench.

While I have not used HF made in China machines, I have used small scale machine tools and you need a different technique with the less rigid machines than with the solid machines. The lighter machines you need to make lighter cuts and sneak up on critical measurments as the machine flexes mor under a heavy cut than it does with a light cut

Reply to
Roger Shoaf

Waisted money and time. If it would be a big lathe OK. But a small mill doesn't need that.

Nick

Reply to
Nick Mueller

Yup... done it. My 6" Atlas is on a "honeycomb" concrete table top on a roll-around wooden cart. It's not _always_ dead-level (although I trim it up for close work), but it's always "true" front-to-back and end-to-end.

It's not exactly convenient; the table-top weighs about 120lb -- more than the lathe. But it really has served me well over the thirty years it's been set up like that -- not a sign of any warp, and probably none will ever occur.

LLoyd

Reply to
Lloyd E. Sponenburgh

"Tom Dacon" wrote in news: snipped-for-privacy@corp.supernews.com:

So... if someone responds all xyz company products suck but I've never used any XYZ products you don't see any problem with that??????? So I guess the OP's opinion of that poster's response was something you didn't want to hear so it got your 'thong' all knotted up and you had to make sure you slammed him down... in the nicest way.....

Bill

Reply to
Bill

Bill, HF is a seller of bottom price-point tools. While they provide (usually) decent value for the buck, they are what they are.

Spend the $40 or whatever HF wants for the steel stand and be done with it, it'll work just fine, and you won't be here later asking how to fit a 38 inch concrete plinth out through a 36 inch door.

You new to usenet? You seen a little quick to get wound up. Best not to, as the thrashing attracts the sharks...:-)

The advise was good, as far as I am concerned.

Cheers Trevor Jones

Reply to
Trevor Jones

Lloyd sez: "> It's not exactly convenient; the table-top weighs about 120lb -- more than

Great idea. It addresses one other aspect of mounting machine tools - combined weight of tool and mount also contributes to rigidity. If there is any possible way to get a mill-drill down to his basement, Carl should consider pouring the round column full of concrete.

Bob Swinney

Reply to
Robert Swinney

Weighting down the bench is a time honored tradition for light machines. Many wood lathe users just drape sand bags over the cross pieces of the lathe stands.

I have a Shoptask 3-in-1 and have made the bench as heavy as practical by adding shelves to store accessories. It helps cut down vibrations in my opinion.

I think a concrete bench would cut out a lot of the 'buzzing' that can plauge a light machine.

Reply to
DT

Trevor Jones wrote in news:8V9Mh.113844$Du6.24982@edtnps82:

At what point did you think I got wound up???? I respounded to a post with a point of my own and now I'm accused of being a newbie and told to shut up. My point is valid reguardless you like it or not. A person asked a specific question relating to a workbench and he gets a poster telling him "harbor freight stuff is lousy and oh by the way I've never even used their products." I know what HF sells and the quality of the stuff, I even have the mill he is talking about but back to the original point he did not ask about the merits of the mill but about a bench to put it on. Some people in this group start frothing at the mouth if you even mention HF. I'm surprised that we haven't seen the posts about old iron being the best and just wait and look and you'll find the perfect used machine.

Bill

Reply to
Bill

I bought a Central Machinery mini-mill at auction recently. It weighs around 500 pounds. It came with a base and an oil tray.

While the mill weighs plenty, the base couldn't be more than 75 pounds. Yet it is sturdy enough to handle the mill just fine.

I think the base is the one in the HF catalog sold as an accessory to the mill for $200.I can't imagine it being "a nightmare" to get into a basement.

Gary

Reply to
grice

Well, Bill, the old iron IS the best, and once you work on it, you wonder what all the chinalloy machines are really good for. The new stuff has all the 'toys', but the old behemoths just run, and run, and run, and.....

But on the other hand, you probably couldn't drag a Cincy #2 into your basement without jacking the house up off the foundations!!

(hey! YOU brought it up )

Seriously, a concrete top could be made substantially lighter than I did mine. When I cast it, I had no practical information on how strong the concrete would be, so I distinctly over-did it. Thinner webs and a thinner top surface would have saved - probably - fifty of those 120lb.

The only concession I made to making the top more usable was to saturate the top and sides with a heavily-thinned urethane paint. It sealed the surface against oil and swarf without adding any significant film thickness to the surface that might squirm under the shims when the lathe was bolted down. 'More like a stain than a paint, the way I did it.

LLoyd

Reply to
Lloyd E. Sponenburgh

"Lloyd E. Sponenburgh" wrote in news:460156de$0$24736$ snipped-for-privacy@roadrunner.com:

I agree with you my point was there are people in this group that poo poo a small mill, especially one from HF. I built a wooden bench with a 8 inch thick top because I had access to a bunch of 2 by 8s and wanted as heavy a bench as possible. It helped alot with vibration. The only other thing I thought of doing to dampen the mill some more is filling the empty column with lead shot, just haven't gotten a roundtoit yet. :)

Bill

Reply to
Bill

That was the idea- lots of dead weight in the right place. While my first thought was a flat-top obelisk, a length of sonotube with a table on top would work as well.

I really like Lloyds' comment about painting the concrete as chip and oil barrier.

-Carl

Reply to
Carl Byrns

I see some of the Rong Fus used in some of the smaller shops..and what a lot of guys do is put bags of readi mix concrete on a shelf below the mill. Adds a fair amount of weight, yet is readily removable for moving etc. Seems to aid in removing some vibrations too.

A few hundred pounds of bird shot would work nicely too.

Gunner

"Liberalism is a philosophy of consolation for Western civilization as it commits suicide"

- James Burnham

Reply to
Gunner

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