Boring Bars to Rough Cut Chamber

[tclaunch]

Gentlemen, do any here practice using a boring bar to remove material pryor to chambering? If this is a good practice please advise a good boring bar for this to use mainly in 6mm barrels, Tim.

I was looking on E-Bay and see .180" minimum hole diameter and there is a maximum hole diameter listed. Please help me understand.

 

[Cigarcop]

Tim,

I believe most using this method are predrilling, then cleaning the hole with the boring bar to just under the reamer size so they have a straight hole to follow with the finish reamer & less wear on it.

 

[jscandale]

Old end mills make great boring bars. Just grind the face on an angle and use one of the flutes for the cutting edge and that's it, you've got yourself a boring bar.

JS

 

[pdhntr]

The two main types of boring bars that I know of are the fixed cutter and the replaceable type cutter.

The typical fixed uses a carbide cutter permanently attached to the bar, and the replaceable uses a carbide or high speed steel (hss) triangle bit that attaches to the boring bar with a small screw.

To prebore a chamber, you must open a hole somehow that will allow the boring bar to enter. I use a common drill. If you drill a 3/8 hole, the boring bar used must have a minimum diameter of less than 3/8.

I then follow with a boring bar using a hss insert. I like the hss tooling from Warner, but the sky is the limit on the tooling you can use. Often it is dependent on the lathe and the desires of the machinist.

Realistically, you can use just about anything to get the hole large enough to get your boring bar into. The boring bar will straighten it out. That is the idea. You want a straight hole for the reamer to follow.

Jim

 

[tclaunch]

I did some digging since my last post, and is turning out to be very helpful. Thanks for the great replys, I too use Warner tooling, I may give this a try very soon, I have a set back barrel indicated and threaded in the South Bend right now.

 

[hammerjack]

Kit # 13 from Arthur R. Warner should do the job.

 

[X Ring Accuracy]

Is using a finish reamer with coolant / cutting oil thru the pipe out of the question? Just askin'

 

[Hal]

TC

Over on the benchrest forum there were a series of pictures showing how Jackie chambered a barrel by first drilling, to remove the bulk of the chamber, than boring , to align the chamber , and finaly using a reamer to finish the chamber.

Hal

 

[tclaunch]

I have had this lathe since April 15th, 4 1/2 months, tooling came several weeks later, so I feel like I have been doing well just starting out and a cooant pump can be put in the plans as thats a great way to do business. I feel like I spend quite a bit of time clearing chips and re-oiling the flutes, and the wear factor on the reamer has to be considered. I would like to try this once or twice as I now have about 15 chambers and 10 or so muzzle brakes under my belt. I think pre drilling and using the boring bar has merit.

 

[tclaunch]

TC

Over on the benchrest forum there were a series of pictures showing how Jackie chambered a barrel by first drilling, to remove the bulk of the chamber, than boring , to align the chamber , and finaly using a reamer to finish the chamber.

Hal

I`ll do more digging and look that over, thank you Hal.

 

[butchlambert]

I use solid carbide boring bars. Remember for PPC and BR cases you are preboring a small diameter hole. I use short stiff carbide boring bars.

http://travers.com/product.asp?eaprodid=31726-21-101-114&r=s&n=||Cutting%3A+H.S.S.+%26+Solid+Carbide||AttribSelect%3DBrand%3D%27MICRO+100%27||Boring+Bars+-+Solid||UserSearch1%3Dblock+id+31726+and+class+level3+id+30273

 

[tclaunch]

Thanks Butch. I have an opportunity to try this on a seating die. I have a Wilson blank needs opened up. You guys are a world of help and I truly appreciate it, thanks Tim

 

[Clark]

I draw up a plan for each chamber and reamer.
I have to decide the minimum pilot purchase into the bore.

Typically, I drill 1/2" deep.
Then I boring bar 1/2" deep.
Then I ream 1/2" deep.
Then I drill 1" deep.
Then I boring bar 1" deep
Then I ream 1" deep.
Ect
I hang that plan over the lathe.

Working backwards, I want the reamer to clean up .015" of the drill hole.
I want to chose a drill that is the next size below .015" below the reamer.

Often I will set the compound to the angle of the reamer.
The 1 degree marking of the compound on my lathe are not accurate enough for gentle angles.
I dial in the angle using something ground in the tool holder and cranking the compound handle.

DRO helps a lot.

I have to get all the chips out of the bore before I put the reamer in the bore.
I have to get all the chip off the reamer before I put the reamer in the bore.
To do this I first use a vacuum cleaner on the reamer and the bore. Then there are a series of brushes.
Finally, I have to get cutting oil all over the reamer.
My reamers do not get dull, but it takes me 3 or 4 hours to cut a 300WM chamber.

This is a plan for a 7mmRM, but you get the idea.

Finally, I head space a 7mmRM, 300WM, or 338WM at .215", not .220", because that is the largest brass I can find.