Previous Drilling of Chamber

[swd]

I guess I'd rather be lucky than good with 100+ chambers I've drilled and cleaned up with a boring bar prior to chambering that averaged .0002"or less run out.

 

[ridgeway]

The comment was in response to someone questioning my statement that enlarging an existing hole with a twist drill was a bad machining practice.

Try to keep up guys, no one ever said anyone needed to use a carbide drill on a gun barrel. The fact is a drill will not follow an existing hole or bore, as has been stated here many times and it destroys the drill in the process, . That Info is available from just about any drill manufacturer. It's fact, not just my opinion.

How do you figure it's bad machining practice to use a twist drill to enlarge a hole? Because it wears a little more? Sharpen it. Holes are enlarged all the time with twist drills.

The drill will follow the existing hole...In what way are you saying it won't?

 

[butchlambert]

How do you figure it's bad machining practice to use a twist drill to enlarge a hole? Because it wears a little more? Sharpen it. Holes are enlarged all the time with twist drills.

The drill will follow the existing hole...In what way are you saying it won't?

Remember, you are reading what tra posts. I guess the prices he is putting on solid carbide tooling has greatly greatly increased the last couple years. I think I might list mine for sale.

 

[ridgeway]

Without doubt, carbide drills are expensive, especially when you are using coated coolant through drills that utilize special geometry all over. It's not unheard of spending $300-400 or more on a carbide drill. Crazy geometry endmills are another story, lol

 

[swd]

How do you figure it's bad machining practice to use a twist drill to enlarge a hole?

Apparently we can't use a drill or a boring bar. Maybe make a fixture to hold the barrel and plunge mill it? Cold chisle and a scraper??

 

[TRA]

How do you figure it's bad machining practice to use a twist drill to enlarge a hole? Because it wears a little more? Sharpen it. Holes are enlarged all the time with twist drills.

The drill will follow the existing hole...In what way are you saying it won't?

That's right it will not, I don't care who tells you so, ain't gonna happen especially when some sharpening wizard gets done with it.

 

[TRA]

Remember, you are reading what tra posts. I guess the prices he is putting on solid carbide tooling has greatly greatly increased the last couple years. I think I might list mine for sale.

Lambert, read it and weap. These are not even the specialty drills that are application specific.

https://www.mscdirect.com/browse/tn...Bits?navid=12106186#navid=12106186+4287558951

 

[ridgeway]

LOL...OK. Please explain to us what a drill does when you say it does not follow an existing hole. In your mind, what does it do?

Every hole I enlarged with a larger twist drill in SS, inconel, aluminum, plastic, carbon steel, brass, bronze or whatever followed the existing hole.

Maybe you are talking about something way different, so please explain what you mean...

 

[swd]

Unless he's just trying to trip up the OP it just doesn't make any sense at all. I've never seen such a simple operation made to look so hard. Drill a hole and clean it up with a boring bar. Rocket science.

 

[Cloudrepair]

Ok drill a hole through a 1" piece of steel with a hss .250 drill measure the distance from the edge were it broke though. Then move part .010 of in x plane or .02- .05 even .125 then drill a letter f .257 were you moved to the measure again at the place were they broke through the distance will be about same because the drill will try to follow first hole. And your hole were it broke through will probably be a little big but it will come out same place.

 

[TRA]

Unless he's just trying to trip up the OP it just doesn't make any sense at all. I've never seen such a simple operation made to look so hard. Drill a hole and clean it up with a boring bar. Rocket science.

I'm not trying to do anything. The OP did not seem to understand that what was being stated as boring is not the same as drilling. I attempted to point that out and you smart a~~es took it and ran with it. You guys need to be specific when you give your poor advice. Stop referring to drilling as boring. What kind of machinists are you anyway? I think most of you are not at all. Talks cheap.

 

[TRA]

Ok drill a hole through a 1" piece of steel with a hss .250 drill measure the distance from the edge were it broke though. Then move part .010 of in x plane or .02- .05 even .125 then drill a letter f .257 were you moved to the measure again at the place were they broke through the distance will be about same because the drill will try to follow first hole. And your hole were it broke through will probably be a little big but it will come out same place.

Now that's funny, I don't care who you are. That's blacksmith talk. One things for sure the hole is not .257 anymore and it is no longer perpendicular to the workpiece.

because the drill will try to follow first hole

You are correct, it will try, but that's pretty crude thinking for chambering a rifle chamber.

When you do this experiment stop about .25 from the exit and look into the hole, then tell me it followed the hole. Then try to run a chambering reamer through that hole.

 

[Riesel]

Got some thought provoking comments here.
Thanks for all the input.

 

[ridgeway]

You are the one with the attitude. You are the one making the claim you can't run a twist drill in an existing hole to enlarge it. And a twist drill won't follow an existing hole. Please explain instead of the trash talking.

I don't think anyone is referring to drilling as a boring operation using a boring bar.

 

[Cloudrepair]

Now that's funny, I don't care who you are. That's blacksmith talk. One things for sure the hole is not .257 anymore and it is no longer perpendicular to the workpiece.



You are correct, it will try, but that's pretty crude thinking for chambering a rifle chamber.

When you do this experiment stop about .25 from the exit and look into the hole, then tell me it followed the hole. Then try to run a chambering reamer through that hole.

Now your putting words in my mouth.

 

[TRA]

You are the one with the attitude. You are the one making the claim you can't run a twist drill in an existing hole to enlarge it. And a twist drill won't follow an existing hole. Please explain instead of the trash talking.

“WARNING: TWO FLUTED DRILLS SHOULD NOT BE USED TO ENLARGE PRE-EXISTING HOLES.”
-Triumph Twist Drill

All drill bit manufacturer's support this fact, and it is the reason that they make reamers, core drills, counterbores and multi-flute drills. In their 10 page flier: Technical Information Guide on drilling that Triumph Twist Drill prints, they state the quote above in bold, at the top of page one. Another respected manufacture, Precision Twist Drill states on their website “one of the rules broken most often ... Never use a two flute drill to enlarge or open a hole."
While the practice of “pre-drilling” isn’t uncommon with 118° drill bits (*see below) you will find that most all of the drill bits that we sell are 135° split point and will self-center, and start drilling immediately upon contact with the material. If you must enlarge or "finish" an existing hole, then we suggest any one of these acceptable type of tools:

1.) Three or four flute drills
2.) Three, four, or five flute Counterbores
3.) Three or four flute Core Drills
4.) Reamers - (hundreds of styles and flute patterns)
(All the tools in this list have more than two-flutes and are designed for enlarging and finishing holes exclusively.)

Trash talk you say????? You can do anything you want to do but when you are making statements or claims, try to be accurate.

 

[Cloudrepair]

However your set up or dialed in if your going to predrill I would drill it small enough to bore it .005-.010 per side under shoulder diameter before reaming because your drill will follow the bore of the barrel.
so it will not be true to the dialed in points without boring it to the final pre ream diameter.
I usually aim for .014 under shoulder diameter

I guess I just assumed people operating machines would understand that I was referring to boring with a boring bar when I said ( enough to bore it ) sorry I talk to people here like they understand machining and the common practises

 

[Cloudrepair]

If I was doing a run of a 1000 or more parts it may be cost effective to have and use these multi flute drills.
Fore the accuracy I want and the few barrels that I need my set of drills I already have are no worse for the wear.

I have little trouble keeping mine within .0002 now that is with pre drilling and boring with a boring bar to .014 under reamer shoulder diameter. And short .020-.050
Then reaming

 

[Cloudrepair]

And the fact is most of them are not and don't, then you blame me for your error.

If you are talking to me I can take the blame for Any errors I make.

My apologies to the op for Any troubles.

I was trying to help

 

[ridgeway]

Copy and paste from a website? Come on guy....

Still doesn't answer my questions, lol

Trash talk you say????? You can do anything you want to do but when you are making statements or claims, try to be accurate

I suggest you heed your own advice...