Chambering short barrels in the headstock

[LVLAaron]

Every inch counts when you're sticking out 10 inches from the spindle bearing The less pressure on the machine and bearings the better.

6" ALUMINUM 6061 ROUND ROD 12" LONG T6511 Solid Extruded Lathe Bar Stock New | eBay

This is extruded bar not sanded or polished and may have scratches from handling.

www.ebay.com

Get some good boring bars, large drill bits, and heavy duty trash bags. I filled 3 large bags with chips

 

[Jake P]

Every inch counts when you're sticking out 10 inches from the spindle bearing The less pressure on the machine and bearings the better.

6" ALUMINUM 6061 ROUND ROD 12" LONG T6511 Solid Extruded Lathe Bar Stock New | eBay

This is extruded bar not sanded or polished and may have scratches from handling.

www.ebay.com

Get some good boring bars, large drill bits, and heavy duty trash bags. I filled 3 large bags with chips

Thanks!

Yep, it's a mess making enterprise for sure! This is one reason I am very glad that I was lucky enough to happen upon a 1440GT, the large chip pan! It fills up fast!

So I believe that Ken had mentioned he made his fixture about six inches long and would make it 7 again if he were to redo it. How did you end up making yours?

Edit: I see that it's a six inch piece that you ordered.

 

[LVLAaron]

6 inch round, 12 inches long. I cut off 4 inches of length off the raw stock.

I essentially have this on the inboard part of the fixture. Give me a day and I can make some measurements. I had to allow for an inch of thread engagement from the backplate into the aluminum fixture

 

[Jake P]

DUH.... Yes, that was diameter not length

 

[Ken226]

Put a witness mark on your lathe and on your new back plate. Be sure to turn the face of the backplate true. Mine was out 5-8 thou. (cheapo plate from grizzly)

Get some big aluminum from ebay and get turning. I posted another thread with some links to a counter bore and tools I used.



Here's another fixture that's similar. Really nice design. I was going to skip the back plate on mine but was worried I wouldn't be able to accurately cut the cone shaped register.

I agree. My spindle has 1 mark, and all of my chucks and spindle mount fixtures get a mark. Yea, the runout doesn't really matter on spider chucks bet I'm kinda OCD.

That's another interesting take on the same basic design as Ken, but looks to be aluminum instead of steel as Ken used.

Here's another design for holding the barrel between the two ends of the headstock, obviously for longer barrels.

View attachment 401319

The longer the arm between the two points of adjustment the greater the finesse one can attain in micro adjustments in bore alignment.

Obviously if the barrel will not reach through the spindle bore then a fixture as you are making is necessary.

My thought is why not make a backplate that can have both of these fixtures swapped out depending upon the length of the barrel to be worked on?

I have a similar set of spiders for barrels. The fixture that is the subject of this thread is primarily for blueprinting receivers (though it can be used for barrel work), but I use a dedicated set for barrels. The d1-4 spider obviously goes on the front of the spindle, the other spider goes on the tail end:

I dont think you'd want to be swapping out back plates. In my mind, once a backplate is attached to something, it's married to it for life.

Some guys like an inboard spider like you just posted, some just use a 4 jaw chuck. I like a 4 jaw because that's what mostly lives in my machine anyway. But with in inboard spider you do work a couple inches close to the spindle.

I treat my backplates like my rifle Scopes. Each chuck gets its own, and it pretty much never comes off. It's not necessary, and I wouldn't presume to call someone who swaps them out wrong, it's just the OCD thing again.

Every inch counts when you're sticking out 10 inches from the spindle bearing The less pressure on the machine and bearings the better.

6" ALUMINUM 6061 ROUND ROD 12" LONG T6511 Solid Extruded Lathe Bar Stock New | eBay

This is extruded bar not sanded or polished and may have scratches from handling.

www.ebay.com

Get some good boring bars, large drill bits, and heavy duty trash bags. I filled 3 large bags with chips

Absolutely. Rigidity is a inverse cube function of length. A little more stickem out = alot less rigid.




You'll love that fixture.

My FN SPR was built on these tools. The Action was blueprinted on that fixture, and the Kreiger 7.5 twist 5r was chambered in that fron/back spider setup. It shoots like a champ.

And there's a spare Kreiger 7.5 twist 5r blank in the safe, waiting for this one to lose its mojo..






I'm kinda proud of my magnetic quick detach adjustable cheek rest too. Brake pressed 1/8" aluminum sheet, Tig welded to pillars fit into sockets epoxied into the stock. The sockets have neodymium magnets pressed into the bottom.

 

[LVLAaron]

I like the cut of your jib.

 

[Jake P]

Ken, do you see a need to make the fixture of steel vs. aluminum?

Any pros and cons in the ultimate use?

 

[Ken226]

Ken, do you see a need to make the fixture of steel vs. aluminum?

Any pros and cons in the ultimate use?

Not really. I used steel because I got a great deal on the chunk I used. 50$ for a 5" diameter x 6" long round.

Maybe my steel one will outlast his aluminum one, but not In any way that will matter to either of us. Perhaps in 5000 years some future archeologist at a dig site may be comparing them side by side and note that mine is slightly less worn, and alot more rusty than his.

 

[Jake P]

Not really. I used steel because I got a great deal on the chunk I used. 50$ for a 5" diameter x 6" long round.

Maybe my steel one will outlast his aluminum one, but not In any way that will matter to either of us. Perhaps in 5000 years some future archeologist at a dig site may be comparing them side by side and note that mine is slightly less worn, and alot more rusty than his.

I take it then that rigidity with something with this mass is not enough of a difference then to worry about. Thanks!

 

[LVLAaron]

I chose aluminum due to cost and ease of machining. Turning that much steel seemed like a pain in the ass. Aluminum "should" absorb more vibration than steel. Does that matter? Probably not. If I like the style of fixture I'll probably make one out of a513 steel if I can find a piece, and I find a bag of cash in a ditch - because it's probably 500 dollars of raw stock right now.