Lathe critical parameters?

6

6.5x47lapua

Guest
Guys,

I'm just a beginner with zero experince in gunsmithing.

I'm trying to understand how to choose the right lathe for top acuurate chambering abd barrel work..

Its clear, that it should be some ~16" x 40" with support screws for outboard part of the spindle.

What are other critical parameters to make a TOP accurate gunsmithing?

- Spindel center runout? (0,0003" or less?)
- Difference in center height spindel-tailstock?
- Parallelism of center line of tailstock spindel to longit. motion?

Can a "regular" lathe be upgraded to top class machine for precision barrel work? Some super precision bearings? gearbox? or tunned spindel?

I understand of course, that 99% of success is a man behinde the machine...

My logic is to invest in hardware "theoretically" allowing making top accurate rifle.


Thanks,
 
Well, a lot of guys have looked at this post and not responded. If you truly understand that the man is more important than the machine, the question is already half answered. Any new quality machine will more than do for your use, because until you know how to adjust to and "read" the work, any machine is better than you are. All the super bearings and gears versus belts, is mostly hype. Good machine practice and experience are the keys to making good rifles. Sorry to say, but 20 years of experience trumps a great lathe any day. Get a reasonably good lathe and start working - then you will be able to assess what you "really" need.

scott
 
shevelin said:
Well, a lot of guys have looked at this post and not responded. If you truly understand that the man is more important than the machine, the question is already half answered. Any new quality machine will more than do for your use, because until you know how to adjust to and "read" the work, any machine is better than you are. All the super bearings and gears versus belts, is mostly hype. Good machine practice and experience are the keys to making good rifles. Sorry to say, but 20 years of experience trumps a great lathe any day. Get a reasonably good lathe and start working - then you will be able to assess what you "really" need.
Click to expand...

Scott,

Thanks for answering.

As I understood, dialing the barrel is extremely important for chambering.

PTG and Gordy Gritters say 0,0001" is necessary.

How its possible if machine's spindel tolerance (center runout, if I
understood correctly) is 0,0003"? For example on Grizzly professional
gunsmith lathe.

Is there some top gunsmith's conspiracy .... :confused:

I'm in Europe and unfortunately we do not have such a wide selection of ready-to-go lathes for gunsmithing.

So, my only way is to understand which lathe parameters to pay attantion and buy the machine, which is "theoretically" not limiting accuracy.

Russ
 
6.5x47lapua said:
Scott,
PTG and Gordy Gritters say 0,0001" is necessary.
How its possible if machine's spindel tolerance (center runout, if I
understood correctly) is 0,0003"? For example on Grizzly professional
gunsmith lathe.
Russ
Click to expand...

G'day Mate..

To answer the above questions simply is that yes the spindle nose and the internal Morse Taper can have some runout and for what we are doing it's not realy important. What is important is that the bearings are good quality and should have zero play. If there is zero play in the bearings then there will be an imaginary point on the bearing axis that has zero runout, this will allow you to dial up a job to run perfectly true (or as close as we can get it).
Where the spindle nose rinout is noticed is when turning between centers or using a precision 3 jaw chuck.

Does that make sense?

Cheers
Leeroy
 
Leeroy said:
G'day Mate..

To answer the above questions simply is that yes the spindle nose and the internal Morse Taper can have some runout and for what we are doing it's not realy important. What is important is that the bearings are good quality and should have zero play. If there is zero play in the bearings then there will be an imaginary point on the bearing axis that has zero runout, this will allow you to dial up a job to run perfectly true (or as close as we can get it).
Where the spindle nose rinout is noticed is when turning between centers or using a precision 3 jaw chuck.

Does that make sense?

Cheers
Leeroy
Click to expand...

Leeroy,

Yes, its almost clear now!

What is the lathe's tolerance parameters saying about bearing quality and no play in spindel? :confused:

Fro example on Grizzy's gunsmith lathe tolerance certificate:
http://cdn7.grizzly.com/specsheets/g0509g_ds.pdf

- Accuracy of outside round cutting (Roundness): 0.0001"
- Cam action of spindle 0.0003"?
- Spindle nose runout 0.0002"
- Spindle center runout 0.0003"
 
Russ,

Reading the machine specifications won't help you much except to tell you the "quoted" accuracy of the machine. What is more important is to understand what .0001" means when you are doing the work. Any man who can turn work to .0001" with a single point lathe tool gets my great respect - more likely he is turning to .001" with grinding/sanding/lapping making the final "tenths". Aligning a barrel in the 4 jaw chuck or spider to .0001" with a good indicator is good and not really all that difficult (but it is time consuming). WhatIi said earlier about experience is understanding the relative difficulty in obtaining the different tolerances. For instance, if you can measure to .0001" on a piece of 1" stock in a cold room, then hold the piece in your hand or raise the temperature 30 degrees or so and see if the stock has not grown a tenth or two in size justdue to thermal expansion. Understanding these kinds of tolerances will not come to you quickly, as machinists of great experience have trouble working in this range. When reaming a chamber you need to do everything to get the barrel running true to the spindle center and you need to push the reamer as close to center as you can get, but there are a lot of variables of huge proportion that you will not understand until you do some actual work. It is harder than you think to do precision work and only is vaguely involved with the quality of the machinery. Tolerances on the .0001" level "get lost in the noise" for most gun work. Opinions will vary, of course.

Scott
 
6.5x47Lapua
For chambering you need a lathe that can handle your barrel in the headstock and has excellent headstock bearings. The ways can be worn out! They are only in use turning the tenon and threading.
Now most of us cannot have a chambering lathe and another that is not worn out for precision turning. If you really know your worn out lathe, you can still turn good parts.
Butch
 
Not A True Statement

"99 percent of success is the man behind the machine".

Not really true. I have been in the Machine Shop Business for most of my adult life, and I can say that a man is no better than the machine he is running.

Just like a Benchrest Shooter cannot make a Rifle that is locked into a .300 agg shoot a sub .200 agg.

That being said, the little Grizzly Machines, such as those seen in Gordy's video, are suitable for doing any sort of work involved in extreme accuracy Gunsmithing..........jackie
 
jackie schmidt said:
"99 percent of success is the man behind the machine".

Not really true. I have been in the Machine Shop Business for most of my adult life, and I can say that a man is no better than the machine he is running.
Click to expand...

Thats true, the best machinist in the world can't compensate for a sloppy spindle or a spindle thats out of alignment with the ways. Usually by the time your a good machinist you have a good lathe to match.
 
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