Newbie Lathe Help

[scott63]

So I have cleaned and oiled my lathe and read the owners manual, which is a model of brevity. I was able to get it set up for the speed/rotation I wanted and was actually able to turn it on!

 

The first thing I want to do is true the face of some receivers. I have receiver mandrels, and a three jaw and four jaw chuck. But when I put the mandrel into the four jaw chuck I can't help but think it is going to be difficult to have it secure the mandrel evenly as each jaw tightens separately. If it was like a drill chuck, all four jaws would tighten simultaneously. So how do I get it centered?

 

I tried to get it eyeball close (which I know is not close at all) with a Turk receiver on a mandrel. If you are familiar with this action it has a handguard retaining lip the is normally taken off when the face is trued. I began cutting and took off about 2/3 of the lip, stopped and checked with a small machinist square and then with a depth micrometer. The amount taken off was suprisingly uniform all the way around. I don't understand how that can be when the mandrel can't possibly be centered with any degree of precision

Any light you can shed on these issues would be greatly appreciated..................Thanks scott

[Limpid Lizard]

Facing cuts, which you do to true the face of the receiver, do not require the same amount of precision in centering to axis as do other cuts.

 

The easiest way for you to figure out how to center the chuck is to put the mandrel close to your bit. Turn the lathe over by hand and you will see that it comes close and then moves away from the bit. Turn it until it is farthest from the bit and then loosen that jaw. Now turn the opposite jaw in until the distance is halved.

 

Rotate the chuck by hand again. Repeat the centering operation. See how it works? If yours eyes are good, you can come within a couple of thou. in this manner. To get better than this, you need a dial test indicator. With this, you measure the distance the mandrel is out of line with the spindle rotational axis. You center in the same way, however it is often easier to indicate the high side and tighten it. There generally is less reaching over the chuck to do so.

 

No DTI (dial test indicator)? Use a piece of chalk. You can get suprisingly close by just spinning the chuck while holding the chalk close to the material in the chuck. Tighten the high spot, wipe, use the chalk again.

 

Dialing in becomes a matter of minutes after you have done it a couple dozen times. The 3 jaw is rarely needed. The 4 is more precise, and it takes less time to dial in than to change chucks. LL

[Clemson]

Congratulations, Scott!

 

Using the receiver facing mandrell is a great "first project" for your new lathe. There are a couple of things that you need to do before starting to cut:

 

1. Check the alignment of your tailstock with your headstock.

2. Run the mandrell between centers.

 

The alignment piece is crucial. First, center drill a round bar on each end. This will be your alignment bar. You can use the three-jaw chuck to hold the bar for drilling. If you do, just leave that chuck on the machine for the subsequent steps. You can use a four-jaw if you want to, but there is really no need at this point.

 

Next, you will chuck up a piece of round stock. I normally use 1" scrap. Set your compound rest to cut a 60 degree center.

 

You could use a faceplate and a dead center in the headstock of the lathe. Using a chuck and cutting a center is pretty common practice, and it avoids having to change out chucks.

 

Now take the bar that you drilled for centers, and swing it between the center that you just cut and a live center in the tailstock. Use a lathe dog to drive the bar.

 

Take a light cut on each end of the bar. This is much easier to keep precise if you go ahead and take a heavy "hogging" cut down the center of the bar, leaving a "pad" on each end to take the measurements from. Close examination of the photo above will show you that the center is a smaller diameter than either end. Use your micrometer to measure each end of the bar. Adjust the alignment of the tailstock to take out all the difference between diameters of the ends. Once you have equal diameters on each end, your tailstock is aligned with your headstock!

 

Now use the procedure below to face your receiver:

http://www.sporterizing.com/index.php?showtopic=1865

 

Good luck, Scott!

 

Clemson

[scott63]

Congratulations, Scott!

 

Using the receiver facing mandrell is a great "first project" for your new lathe. There are a couple of things that you need to do before starting to cut:

 

1. Check the alignment of your tailstock with your headstock.

2. Run the mandrell between centers.

 

The alignment piece is crucial. First, center drill a round bar on each end. This will be your alignment bar. You can use the three-jaw chuck to hold the bar for drilling. If you do, just leave that chuck on the machine for the subsequent steps. You can use a four-jaw if you want to, but there is really no need at this point.

 

Next, you will chuck up a piece of round stock. I normally use 1" scrap. Set your compound rest to cut a 60 degree center.

 

You could use a faceplate and a dead center in the headstock of the lathe. Using a chuck and cutting a center is pretty common practice, and it avoids having to change out chucks.

 

Now take the bar that you drilled for centers, and swing it between the center that you just cut and a live center in the tailstock. Use a lathe dog to drive the bar.

 

Take a light cut on each end of the bar. This is much easier to keep precise if you go ahead and take a heavy "hogging" cut down the center of the bar, leaving a "pad" on each end to take the measurements from. Close examination of the photo above will show you that the center is a smaller diameter than either end. Use your micrometer to measure each end of the bar. Adjust the alignment of the tailstock to take out all the difference between diameters of the ends. Once you have equal diameters on each end, your tailstock is aligned with your headstock!

 

Now use the procedure below to face your receiver:

http://www.sporterizing.com/index.php?showtopic=1865

 

Good luck, Scott!

 

Clemson

 

 

Thank you both for your help, this info is exactly what I was looking for.............Scott

 

[gun nutty]

The example that Clemson is showing is one of the easiest and most accurate ways.

 

You're essentially using the headstock as a "live-center". Keep a 1" diameter piece of scrap steel around; every time you need to put thungs between centers, mount the piece of steel in the headstock (I prefer the 4 jaw) good and tight, set the compound rest to make a 30 degree cut, and take a light skim cut on the scrap, creating a fresh surface.

 

Do this EVERY time you remove the scrap and re-insert it. It sure beats dialing-in the mandrel every time.

[Limpid Lizard]

Most chucks will open enough that you can slip a dead center into the headstock when you want to turn between centers. As long as the depth of the chuck is not a problem, open the jaws, slide the center in, close the jaws as much as practial and begin turning.

 

Your receiver mandrel should be between centers to to turn the receiver face anyway.

 

One point that is kinda picky, but important as you become more involved in intricate work, when you align a tailstock with the headstock, not just as Clemson showed, but any way you do it, it is only aligned at that distance, that torque setting and tailstock barrel extension. Every other setting is close. LL

[milsurpcollector]

Scott,

 

If you are going to do much lathe work, I would pick up a few books on it. also Kuhnhausen's mauser gunsmithing book.

 

Do a seach on amazon to see whats out there. I dont have a list because im at work otherwise i would list a few that helped me

 

The books will give you an idea of what tools you need.

 

Ebay is a great place to find quality tools for less than new.

 

Buy american or japanese tools if at all possible.