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View Full Version : New to the site with a newbe question.



housedad
10-27-2009, 02:55 PM
Hi everyone.

I operated a small gunsmithing shop for 15 years. The Shop was shut down due to health reasons. All those tools and my lathe is now in my garage.I never used much in the way of a milling machine at work, just a Mill/Drill during that time.

However, Now that the kids are mostly grown, I have the Happy fortune to be able to buy a new Tiawanese mill in about a month. I've always wanted to make the ideas I had, just never had a machine that could do it.

I have been looking at the 9X49 Birminghams and GMCs at a dealer near here. I have had the opportunity to try them both.

This machine will see fairly light garage duty, mainly doing one-offs, protoyping, and repairing and modifying guns for friends, family and my collection. I need the long table for the work I will be doing on 50 caliber bullpup barrels, if nothing else. Ultimately, sometime in early 2011, I will be ableto afford a Centroid CNC conversion for it.

A couple of questions:

Do you recommend a variable speed head with a VFD to provide 3 phase, or a Belt drive head with a VFD? I can get either head at the same price.

It is crazy, but I find that I can afford either the 9X49 or the 10X54. I have just barely enough room to fit the 10x54 with adequate maneuvering room around it. Would there be any advantage in accuracy in going to the 10X54? Any other advantages? Any disadvantages other than the obvious weight on the floor, and taking up more room?

Thanks for your time. I look forward to being on here a lot in the future.

Bion Rogers

SGW
10-27-2009, 04:51 PM
Based on nothing except personal opinion, I'd select VFD and belt drive. The VFD will give you variable speed, and the addition of a variable-speed head seems to me redundant and extra complexity you don't need. But others who know more than I do may feel differently.

camdigger
10-27-2009, 05:03 PM
Hi everyone.

It is crazy, but I find that I can afford either the 9X49 or the 10X54. I have just barely enough room to fit the 10x54 with adequate maneuvering room around it. Would there be any advantage in accuracy in going to the 10X54? Any other advantages? Any disadvantages other than the obvious weight on the floor, and taking up more room?

Thanks for your time. I look forward to being on here a lot in the future.

Bion Rogers

My experience is that my projects always grow to a size possible, but only just, on whatever equipment I have at my disposal....:o

I can't see accuracy being affected simply by machine size, BUT I can see a CNC of a larger machine being a bit more $ because the ball screws would be longer and possibly larger...

Something you've not mentioned is how machine size will affect the ease of installation... Dimensionally, the 10-54 machine has to be larger, but is likely significantly heavier.... Will this affect your ability ot spot the machine? Will it cost more to install. Just how bad do you need the extra table room?

hardtail
10-27-2009, 05:35 PM
I take it the VFD issues are to provide residential 3 ph? If you have to run a VFD you may as well go belt drive, the varispeed heads can be noisier at times than a straight belt and more expensive to replace.......the only drawback could be resale but doubtful.

I would go with the 10x54, unless those machines have know problems it's bound to be more rigid, you'll find this out when performing operations out on tables end........

Have you tried Quality Machine Tools?????

housedad
10-27-2009, 07:29 PM
hardtail- your signature line tells it all about this choice. :)

I jsut checked with a couple of dealers. The GMC 9X49, whick I am leaning toward, is only available in the vari speed drive. Oh, well.

Yes, the VFD is to provide residential 3 ph. They seem to do it a lot better than the other solutions out there. I guess I would just leave it at the stated RPM of the motor and then just use the Varispeed head unless I need the lower or higher frequencies, which I doubt. It is just as well, since I would probably be replacing the motor soon as it is not VFD spec.

As to putting the machine in place, it would be slighly more difficult with the 10X54. It is about 600lbs more. The ceiling hight in the garage is 11 feet, so that is not a problem. It pretty much will require the same machine, a forklift, to place it. Have to rent one with a operator for that. As it is, I intend on putting down some wide feet of 1/2" or 3/4" plate to spread the weight on the floor. The concrete is only 4 inches. I miss my shop. I had that floor poured to 6 inches with rebar in anticipation of a heavy mill. sigh.

9X49 or 10X54? This will be the machine I keep for many years. I guess it comes down to whether it is TOO big. That is, does it get to be cumbersome to use.

hardtail
10-27-2009, 07:56 PM
I doubt you will encounter any problems with the original motor supplied with the mill running off a VFD, we did a major retrofit of about 30 fans to run off VFD's at work mostly ranging from 5-40hp, the good ol cast frame motors which did 15 yrs service were tossed for hi eff VFD motors, most a pile of crap.........frown.

I would go with the larger machine, it will likely take more power consumption having a larger motor but I would think if your doing work out on the table ends it will be beefier.......you make not be doing heavy cuts but it should be more rigid for accuract. You will know what type of machining requirements you expect to encounter better than I........

Fasttrack
10-27-2009, 08:21 PM
I would go with the 10X54 with the belt drive head and VFD. The varispeed heads tend to be louder than the belt drive. This may not seem like an issue, but when you run a small endmill and crank the rpm up and have to run the machine for a few hours ... well your ears will thank you if you choose the quieter mill ;)

Plus, I can't tell you how many times I've needed just a tiny bit more travel out of the 9" Bridgeport at work... I think you will appreciate the larger mill.

lane
10-27-2009, 08:56 PM
I own a Birmingham with variable speed head and run off a static phase converter. The 10 by 50 is ok but too hard to work around > I`m 6' 2'' with long arm`s but do not like operating one . Ran 10x50 at last place i worked a new ACRA just too hard to reach around . Have a 10x50 Vectrax and a 9x49 Vectrax at shop I work in now hate the 10x50 9x49 a lot easer to use . If you go the vdf rout get the belt head but get it cheaper than the variable speed head . No way they can be same price . If they are go with the variable speed and leave the vdf out of the system. Their is nothing wrong with variable speed heads people just do not understand them. and how to make them last a long time Been running them for well over 40 years and never had a problem I could not fix. I love my Birmingham. Sold a super nice Bridgeport to buy it .

darryl
10-27-2009, 09:51 PM
I have no experience with either machine, but I'd lean towards the larger one for its extra weight and rigidity, if it is so. The main thing that would concern me is if the range of speeds leaves something lacking for the various jobs you might do. Secondly, if the larger machine isn't in as good a shape as the smaller one, I'd probably go with the one in better condition, as long as I wasn't missing features that I needed.

housedad
10-27-2009, 10:06 PM
Sorry, I see that I missed stating that this will be a factory new machine. If I'm gonna keep it for a long time, I might as well buy new.