Chambering Short Barrels

M

mpatti

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I recently purchased the Grizzly 4003G. I noticed that barrels that are around 20 inches are too short to make it through the headstock to the spider gear. On this site, I have read that some people chamber in the steady rest between centers. I am curious how you chamber between centers because I feel limited that my lathe can only work on longer barrels ,24 inches or so, through the headstock.
Can anyone describe this or recommend a good book on this??
 
I do all of my barrel work between centers and thru the steady rest. Mainly because the lathe I have setup for barrel work doesn't have a spindle bore large enough to accept a barrel thru it. I start by setting the barrel up between centers. (a live center in the the tailstock, and a face plate and lathe dog on the headstock.) then I turn my shoulder and thread for the action. I usualy leave my barrels a touch longer than finished length, and turn down the muzzle end to make it concentric with the bore. Then I take it down, and install a 4 jaw chuck and grab the muzzle end that I trued up, and place the steady rest just behind the tenon. then I indicate the bore until I get it where I want it and then you are setup to start chambering. I'm sure some of the benchrest smiths will shudder when reading that, but I build hunting rifles, and it's worked for me so far. John Hinnant has a book out that gives in detail various ways to chamber.
 
mpatti said:
I recently purchased the Grizzly 4003G. I noticed that barrels that are around 20 inches are too short to make it through the headstock to the spider gear. On this site, I have read that some people chamber in the steady rest between centers. I am curious how you chamber between centers because I feel limited that my lathe can only work on longer barrels ,24 inches or so, through the headstock.
Can anyone describe this or recommend a good book on this??
Click to expand...
Many long headstock lathe users start by putting the barrel between centers and turning a portion of the muzzle OD to where it is concentric with the muzzle bore.

Then they make a bushing that is a snug but still running fit with the spindle bore on the bushings OD. Then on that bushings ID they make it to fit the spot they just turned on the barrel muzzle.

Then slip that assembly into a cleaned spindle bore to where you can use a 4-jaw chuck or a tru-adjust 3/6-jaw chuck to indicate and machine the breech (tenon, cone and chamber.

There are variants of this process but that is the basic method to chamber through the spindle on a long headstock lathe.
 
mpatti

Are you using the 4 jaw chuck? If so make yourself another spider to use on the inboard side. I was probably the first to do it years ago simply to shorten up the distance through the headstock.

Dave
 
Dave

The internal "spider", is it just a cylinder that will just slide inside your spindle bore and it has 4 alignment screws at 90 degrees to one another?

How tight of fit to the spindle bore. Any pictures. What did you make the spider out of?

Hal
 
I believe that the 4003G lathe has D1-5 tooling. Get a D1-5 backing plate and bolt a piece of aluminum to it and turn. Put it in your mill and drill and tap 4 holes for your spider. I had to do this on my Clausing. Dave has posted photos of his setup and I can email photos of mine.
Butch
 
Butch Lambert said:
I believe that the 4003G lathe has D1-5 tooling. Get a D1-5 backing plate and bolt a piece of aluminum to it and turn. Put it in your mill and drill and tap 4 holes for your spider. I had to do this on my Clausing. Dave has posted photos of his setup and I can email photos of mine.
Butch
Click to expand...

Butch
I had thought I had seen photos of Daves setup and did a search but couldn't find it.
Could you post a link to them.
You are correct that it has D1-5 tooling, it also comes with a backing plate.
Thanks
James
 
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mpatti, even with the front end spider that Dave and Butch use to replace the 4-jaw chuck you may still come up "short" so to speak. eg Depending on your lathe design and barrel length you may still have to run an internal bushing on the muzzle end while you are chambering the other end.
 
Here we go again

Take a backing plate for a chuck, Turn it down as much as possible, then add 4 screws. Photo attached
No need to add an attachment to it. That's a D1-5 in the picture.
There is also a block added to drive lathe dogs

Dave
 

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I did almost the exact sam ething as Dave Tooley did. The difference betweenhis and mine is that I used a face plate that was laying around. It works just the same. I can do barrels down to 18 1/2" long
 
I am glad to hear there are some solutions. I will be starting on some longer barrels at first but I will keep all these ideas in mind. Eventually I will want to work on some shorter stuff as well. Thanks.
 
For those of you who use that spider arrangement on both ends of the spindle, I'm curious if you ever have any problems with the barrel slipping?
 
I can't say it's never happened but only when I was turning down the tenon at 1250 rpm's and taking .050" off on a pass. Then it was just a few thousandths. Checked it internally with an indicator and it might have moved the bore a couple of tenths.
I face off the end of the stub, set my travel indicator on the saddle to my shank length, turn to the diameter I want stopping .001" short until the last pass, feed in about .020" to relieve the corner of the tenon and shoulder, pull it out which faces off the shoulder, then go back to my shank length number and face the end of the barrel again. I always end up taking a few thousandths off there because of expansion from the heat. If the barrel slipped I would catch it then.

Dave
 
Dave Tooley said:
Here we go again

Take a backing plate for a chuck, Turn it down as much as possible, then add 4 screws. Photo attached
No need to add an attachment to it. That's a D1-5 in the picture.
There is also a block added to drive lathe dogs

Dave
Click to expand...

When I went to gunsmithing school 25 years ago, we used 9" swing SB and turned between centers using a drive plate and lathe dogs. After buying a used 12X36 a few months ago I've been looking for a lathe drive plate in D1-4 configuration and been unsuccessful. This looks to be a viable alternative with additional capability. :)
 
Dave Tooley said:
Here we go again

Take a backing plate for a chuck, Turn it down as much as possible, then add 4 screws. Photo attached
No need to add an attachment to it. That's a D1-5 in the picture.
There is also a block added to drive lathe dogs

Dave
Click to expand...

Dave - really liked your idea, so today I went ahead and did the drawings for a "stepped" back plate that fits directly into the D1-5 spindle. It will be one piece cast iron with brass tipped screws for the spider and the normal studs on the back to fit into the spindle. Also did one for the larger lathe that has D1-6. Should be commercially available from us in about four or five months.
Thanks.
 
Shiraz
Please let us know when it's available.
But then of course part of the enjoyment of having a lathe is making some of your own tooling.:D
Also it sure is nice having someone who is responsive to the customers needs. Thank you Shiraz
James
 
Shiraz

I was going to talk to you about that and a couple of other things at the Shot Show. See you and Gordy at the show.

Dave
 
In a hurry?

"when I was turning down the tenon at 1250 rpm's and taking .050" off on a pass."

Wow, that's getting the job done! :)
 
Wayne

Time is money. I've slowed down to 800 RPM's now. Seems reasonable now. I don't have the eyes I used to have so I've had to slow down some.

Dave
 
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