I am about to buy a combined lathe/mill and need to know how accurate it needs to be for gunsmithing tasks like rechambering a barrel.
I have spoken to a sales rep who admittedly seemed to know less them me about these machines, (which is very little) and he said that this was capable of machining to within 0.1mm which is about 0.039 in inches.
I find this hard to belive for two reasons; 1.he just gave this arbitraty figure which with no mention of spindle, chuck or cross table and two, well, because you wouldn't brag about that kind of machine...

Just how accurate does a machine like this need to be? I'll be using it mostly for simple tasks like making small modifications, maybe a few scoipe bases, .22lr adaptors, and the most delicate jobs might be reaming a .45-70 to .45-120 reaming .45HP to .45 ACP threading for a muzzle break or squaring and re-threading actions to barrel threads.

What are the rightquesitons I need to ask these people?

First of all .1 mm is .004 and not .04.....a millimeter is about forty thousandths!

Any mill that can't work to .001 (assuming skilled operation) isn't worth having IMO!

Most any lathe will perform accurate enough for most gunsmithing.....the skill of the operator can make up for a lot of wear!

If the best the lathe is capable of is also .004 then it too is junk and not worthy of your money!

I suspect that both pieces are much more accurate than the salesman said however!

If you are in Italy just get one of the Austrian made EMCOs. (not E N C O) They are very high quality but a bit pricey.
If not in your price range compare the specifications of the EMCO to your eventual choice. Finally get an experienced machinist to give you an opinion after he has seen the machine.

I will 2nd the Emco.
Heres one for you to look at

http://cgi.ebay.com/Emco-Super-11-Lathe-Best-Accessorie...QQrdZ1QQcmdZViewItem

Thanks for the replies. I am waiting on a reply from the company with some more accurate information, I am quite sure that the salesman was just mouthing off and doesn't have a clue what a tenth of a millimeter is.
This is my first such machine, and I'd say that regardless of what it is capable of doing, I won't be able to achieve so much accuracy for a little while anyways. If I find I get along well, then I may upgrade to a seperate high quality lathe and mill but for now and the circumstances I find myself in, this seems like a good choice for me.

here is a link to the machine.

www.damatomacchine.com - look under lathes / metal working / HQ500

don't forget error is cumulative. along with a accurate machine, you need an accurate chuck etc. I'd suggest you go out any buy a copy of the machinists handbook (worth having anyway) there's a lifetimes knowledge within.

quote:

Originally posted by vapodog:
First of all .1 mm is .004 and not .04.....a millimeter is about forty thousandths!

Wrong! A millimeter is indeed .03937... (.04) not .004!

B.Martins

quote:

Originally posted by b.martins:

quote:

Originally posted by vapodog:
First of all .1 mm is .004 and not .04.....a millimeter is about forty thousandths!

Wrong! A millimeter is indeed .03937... (.04) not .004!

B.Martins

Do the reading again.....my post is correct albeit rounded six tenths!

quote:

Originally posted by b.martins:

quote:

Originally posted by vapodog:
First of all .1 mm is .004 and not .04.....a millimeter is about forty thousandths!

Wrong! A millimeter is indeed .03937... (.04) not .004!

B.Martins

.1mm is .003937 in inches. (it has a decimal in front of it and he/vapo rounded it to .004 inches, then made a statement that 1mm is about 40 thou which is correct) Express actually has it wrong at the very beginning.

Anytime you want to convert, multiply or divide depending on which way by 25.4 for the answer/equivalent. (25.4mm = 1 inch)

quote:

Originally posted by gsp:
I will 2nd the Emco.
Heres one for you to look at

http://cgi.ebay.com/Emco-Super-11-Lathe-Best-Accessorie...QQrdZ1QQcmdZViewItem

I never heard of EMCO before this, but hat lathe looks, to my eyes, like it was made in China.

This old EMCO may have been made in Austria:
http://cgi.ebay.com/Emco-MAXIMAT-10-x-24-LATHE-MILL-COM...ryZ633QQcmdZViewItem

EMCO Lathes

Emco has been building lathes a long time.
I always check them out at the IMTS in Chicago.
The EMCO looks like a LeBlond or Monarch quality lathe only smaller. Chinese and Taiwan machine tools look like crap by comparison. However you have to pay for the EMCO quality.

>>>>>> http://www.mini-lathe.com/C6_lathe/C6/c6.htm

Extract from above link:
"...Runout is measured using a sensitive dial test indicator (DTI) on the inner surface of the spindle taper. I was pleased to find the runout on the lathe I am reviewing to be about 0.00016", or less than two ten-thousandths of an inch, as measured by a good-quality Peacock brand DTI calibrated in divisions of "tenths", or 0.0001". Runout measured at the surface of the raised spindle boss was also under two tenths. Not bad for a lathe selling for less than $1000...."


....and at the other end of the spectrum, HARDINGE....sure is nice to dream.

My old Walker/Turner woodwoorking lathe is old enough to be my grandfather and has less than .001" runout on the spindle.

I can't imagine that even the cheapest of Asian knock off would be as innaccurate as your salesman suggested.

I don't put much stock in what that reviewer has to say. He is measuring a less than premium machine with a less than premium test indicator, and claiming both great accuracy and resolution. I am not questioning his sincerity, merely his ability. When you get down to measuring in a few millionths of an inch, few indicators do it well, and far, FAR fewer users can actually get meaningful and repeatable numbers. Nothing I read on his site led me to believe he can.

He seems like a nice guy who is trying hard, but I think he has made some honest mistakes and put out bad data.

In the article the run out measured does not attribute it to bearings or the spindle.
If the bearings are good the spindle bore run out would only affect a collet holder.
With good bearings the OD run out would only affect a 3 jaw chuck and most 3 jaws are not that good anyway. The OD run out has zero effect on a 4 jaw which is used for the most demanding work.
One thing he did not measure is the facial run out of the chuck mounting shoulder. This error would be magnified on a long work piece unless you tap it into running true.

When we wanted to buy a lathe, we looked at several makes.

Eventually deciding to get an EMCO. We never regretted that decision, despite the cost.

And when we wanted to get a CNC lathe, we decided to get am EMCO too.

We are very happy with both machines.

quote:

Originally posted by Saeed:
Eventually deciding to get an EMCO. We never regretted that decision, despite the cost.

Certainly cheaper than a ski resort.