...

I think it would be hard to find hardened and ground off the shelf. If you said .750 it may be easier. That is awfully thin for the length. How about .625? Have you checked with Dave Kiff at PT&G?
Butch

Have you tried Thompson linear shaft. Order it right out of the McMaster Carr site. If you really wanted to get fancy. You could get an ejector pin from DME. Stuff is hard as a whores heart and straight as an arrow.
Let me know if you need a link to a item or a site.

DME
PCS
any dia you want any length hardend and ground and strait....I can sell you one or a hundred

Kerry and Ted I need to remember you guys.
Butch

...

soooooo .001 per 12" isn't good......OK

I have never run a lathe in 25 years that would hold tenths.....but I'm not done yet I spose

...

...

and .0003 in 4" is not good? You are chaseing casper my new friend.

Gotta go with Ted on this one. Ideal is one thing, but real is another.

Doug,
I think you've read too much on the internet from keyboard machinist, gunsmiths.
What type receivers are you doing, Remington?

Butch

quote:

Originally posted by butchlambert:
Doug,
I think you've read too much on the internet from keyboard machinist, gunsmiths.
What type receivers are you doing, Remington?

Butch

What Butch says is "spot on".

If he ain't got some of these he is adrift in troubled seas.



Hope we are not heading in the direction of another 50 Millionths Man discussion!

I will stay out of the sandbox from here on.

The top one looks like my Interapid, The second is my Mitutoyo, and last looks like my Brown & Sharpe.
Butch

...

Nice rifles! I learned a few years ago that you can buy a custom[Remington clone} for the price of a properly [blueprinted] machined factory receiver. Now if I were having to do a receiver I would borrow my Bud's tools. No use having a perfect mandrell if you don't ream the receiver bore first. If I needed a mandrell I would go to the tool grinding shop that sharpens my tools and have them grind a mandrell between centers. MCC Tooling in Garland, Tx.
Butch

...

There's no secret at all. Now depending on your indicator and I will use the two that I have as an example they are tenth's indicators but read the instructions and they are only accurate to within .0002" and repeatability is only .0001" so your thenth's indicator is not as accurate as you might think.
Read the specs on your indicator and find out just how accurate it really is.
The other thing is .0005" over the length of the chamber is way better then it needs to be depending on its intended end use. But within a half thou is damn close and borderline over kill.

You could have a gauge pin custom ground but it would be very expensive. And not really worth it if you don't have a machine that is capable of that kind of accuracy. Read the specs on the lathe bet you it is not as accurate as you think either.
Everything has a variance a degree of uncertainty, knowing what that uncertainty is the key.

...

Sounds like you have found all of your answers,no thanks to us, and you are good to go.
Good luck with your project.

Have you priced an indicator that will repeat with in .00005"??? They are not cheep nor easy to find. And just because you pin is dead nuts straight doesn't make the reading you get on you indicator correct. I'm not sure you understand the inherint hysteresis in an indicator.

Kerry,
He has solved his problem. He knows what he wants and thinks he has found it.

quote:

Originally posted by butchlambert:
Kerry,
He has solved his problem. He knows what he wants and thinks he has found it.

Yeah I know i should just walk away after he made a statement like that. Shaking my head no less.

I deleted a longer post out of a waste of breath

Kerry,
You have been doing very precision machining for many years, what do you know?

quote:

Originally posted by butchlambert:
Kerry,
You have been doing very precision machining for many years, what do you know?

Now that was funny Butch
I know which hill I want to die on and this ain't it.

The German in me can't let this die without one last comment though.

Take your finest resolution indicator. set it up on a grade A or better surface plate. then get a Joe block in X dimension and on the is one tenth larger or smaller. Then get out the sheet that calls out it's absolute dimension traceability to the NIST record the actual dimension of each Joe block subtract one from the other. This is your absolute Delta. Then slide one block under the indicator with minimal deflection as to avoid error from upsetting it's natural position.
then slide the other one under it. and see if the readings match your math.
Then do it again about ten times and watch the Delta change. not much but it will change.

BTW all this needs to be done in a temperature controlled environment. At the same temperature that the Joe blocks were calibrated to with in +/- 1 degree F. and completely clean and free of dust and debris to a level consistent with a class 1000 clean room.

No machine shop in the world is set up that way. not even a German one.

Come over an have some coffee with me in my shop and we can talk Angstroms if you like. Not you Butch, Doug....
But Butch you are free to come over to my place anytime you like for a glass or cup of anything you like from coffee to Scotch

your all black smiths

I used to work to better than tenths in wood.



Tenths of an inch that is.

...

That was not the issue.

The point I was making was that you had said

quote:

I have looked at Thompson linear shafting.
"Straight within .001" per foot cumulative when shipped from the factory."

That didn't seem straight enough to indicate to 0.0001??

You have it in your head that you can use a tenth indicator to indicate to a tenth meaning to with in .0001" or +/-.00005" which most "tenth" indicators can not do.

Not to mention you made no mention of the lathe you are using and there are few machines out there that the spindle is accurate to better then .0001" not to mention where it is when it's running or after the bearing warm up. Most people don't think about this because they are working to with in +/-.005" or a little better. Move the decimal to the left one digit and things begin to change very fast.

My issue was and is that I don't believe that you have any experience working that close as you are ignoring a great many variables that will affect your readings. That's why I went into my statement on Joe blocks and proper setup.
When working that fine you have to be willing to accept variables and understand where they are coming from. It's also why I tried to inform you for indicator hysteresis. As most do not understand it and do not know how to apply it when working that close to your indicator's ability.

See the real thing is that a person that has experience doing this kind of work and I mean just indicating a part in that close, nothing else. Should not be here asking how it's done. You should be able to look at the set up and make your best judgment. Based on that you r statements ring "Novice"
Forgive me if I'm off base or If I've insulted you. I'm only stating my perspective.

...

I did respond but deleted it as I felt it was a waste of my time since you had this all figured out.
There are tools out there specifically designed for this type of work. If that doesn't suit your needs you make it or have it made.
I also feel that is the reason Westpac and Kobe have not chimed in.

...

Home made jigs and fixture. I'm a toolmaker so I don't buy things that I can make unless it's just inefficient to do so.

I use an Brown and Sharp anvil and a Suburban 0 to 1 hammer

Doug,

The first three posts gave you answers to your question of where can you get 1/2 inch, hardened and ground bars. I'll summarize them below:

Dave Kiff at PT&G
Thompson linear shaft. Order it right out of the McMaster Carr site
Ejector pin from DME
DME
PCS

The reason you're not getting meaningful answers after that is that the next question you came up with gave your criteria that you want it to allow indicating to an accuracy of .0001".

The answer that all the rest of the answers are skirting around is that your desired "accuracy" is not realistic in the real world, so there is not a meaningful answer that will satisfy your criteria.

I personally have used pre-purchased mandrels from Brownells or turned my own to true actions. That's what I use. It will not meet your criteria of accuracy to .0001", so it's not a meaningful answer to you. My equipment has some real slop in it, so I'm pleased if I can get everything within .001" or .002", and can lap it in true from there! If I was to indicate a perfectly true shaft, the repeatability of measurements just on the wear in my timpken bearings on the headstock would probably read .001". Add in the lathe chuck, live center bearings, lathe bed wear, cross slide, compound, tool holder, heat distortion of the machine as it works, heating of the work, and .001" in 12" on a hardened bar gets lost in the noise.

That's not representative with everybody, there's many here that will do infintely better than that with their work.

To answer your question for everybody, (not that I can really presume to speak for everybody): NONE OF US ARE USING A MANDREL OR FIXTURE OR ANYTHING TO TRUE ACTIONS THAT WILL ALLOW INDICATING TO AN ACCURACY OF .0001. Using anything that gives you data to this level is just giving you an illusion of accuracy, nothing else.

dave

quote:

Originally posted by ted thorn:
I use an Brown and Sharp anvil and a Suburban 0 to 1 hammer

Those Suburban hammers are expensive

...

At break today a couple other toolmakers here at the shop read over this thread. Lathes and tenths don't go together was the opinions of most....

...

...