Oh No......

[PIKELAKE]

I need some help, please. There I was drilling a hole in the barrel to install a White LIghting liner. I have done this at least two dozen times. Not an expert, but real comfortable in doing this task till now. Everything on track till the drill bit fractured and by the time I got the drill press shut off and the drill bit out of the barrel I now have a ragged hole in my barrel.  I was going to install a 5/16 liner in my Rice 40 cal barrel which has a 1 inch breech.  Now I have thought about 2 fixes. Drill the hole larger and round and install a 3/8 liner which will be very very close to the edge of the next flat, or drill out the existing hole, with the next size drill, find the next size tap,  tap the nice new hole , make a liner out of something and procced that way. If I go to the 3/8 size liner I have visions of more trouble in drillin out the "I" drilled hole with a "Q" size drill. I can not aford another ragged hole. I have always been able to think thru my problems but this has me upset and scratchin my head. The rifle is done and  this was to be the last detail. I'm so mad. Thanks in advance for any help.    JZ

[omark]

if it was me, i would go to the next size liner rather than bush the hole. putting in a bushing you have just as much chance of it going bad again as putting the next size liner and you have 2 sets of threads. twice the chance of failure when drilling or shooting. jmho  mark

[Joe Stein]

John,
I would first check to be sure the ragged hole isn't already too big to drill out for the 3/8 WH liner.  If it's OK, I think I would use a center cutting end mill in the drill press to cut it out to a size as close to that needed to thread for the 3/8 liner, then drill or ream to the proper size.  It might take a few days to get the end mill if you don't have one, but that's better than ruining the barrel.

-Joe

[Cody Tetachuk]

OR, you can order another barrel, fit your breechplug to it (so the tang still fits the inlet) install new barrel tennons & sights and install the 5/16 liner as planned. Then, cut the offending part off this barrel, rebreech and use the now slightly shortened barrel on another project.

[billd]

I like Joe Stein's idea best, but be careful with an end mill in a drill press. If not clamped down it could grab and make matters worse.  If you have access to a Bridgeport or similar milling machine, that would be the way to go.

Bill

[Acer Saccharum]

Once an endmill grabs there is no telling where the barrel will end up. Either on the floor or climb right up the shank of the endmill until the mill hits the other side of the bore. Bad idea unless you have a real rigid setup.

Tom

[ehoff]

I don't like using endmills to drill holes, especially using a drill press one grab and it will make the problem much worse. Take it to a machinist or someone with a milling machine who has a boring head. After it is centerd the the hole can be trued using the boring head and then finished drill or bored to the proper size.

[Nate McKenzie]

Hope you took out the breech plug before drilling. Nicking the plug can break tools.

[bluenoser]

I'll bet you already checked this, but just in case you haven't.  Is it possible your ragged hole is under sized and can be cleaned up?  Whatever you do, I recommend using a sharp high quality drill turning at the proper RPM and cutting fluid.  A machinists reference manual should give the proper RPM for the size drill you are using and the type of steel.

Laurie

[Birddog6]

Well, I would cut the barrel & rebreech if you don't have the underlugs on it. If you do I would get another barrel & use a 1/4" vent liner in a .40 barrel. I feel a 5/16" one is too large for it & you are really gonna feel that liner when your patch & jag gets to it.
Save the other barrel for a dif. project.

[Joe Stein]

Once an endmill grabs there is no telling where the barrel will end up. Either on the floor or climb right up the shank of the endmill until the mill hits the other side of the bore. Bad idea unless you have a real rigid setup.

Tom

OK......  Thanks for setting me straight on that, Tom.

[frogwalking]

Bluenoser,

For those of us who only occasionally build something, can someone give the rpm for different common drill sizes in the type of steel barrels and locks are made of?  I am not likely to buy a machinist's manual, and may not be the only one.

Thanks

[jwh1947]

Add this to the list of complications associated with liners.

[coutios]

  Normally common sense will tell you when a drill is running at a good speed. The feed rate or pressure is what will cause most people problems. If you have little experience in these matters get some scrap material and do a little trial and error before moving to the real deal...

Ragards
Dave

[Cody Tetachuk]

Add this to the list of complications associated with liners.

And which 'list' would you add it to if it happened while drilling a straight touch hole?. How about the list of complications that can be remedied by the installation of a liner .

[bluenoser]

Small machinist’s bench manuals are inexpensive and chock full of useful information.  Mine is “Machinist’s Ready Reference” by Prakken Publications.

I am afraid I cannot agree with Dave.  Before I took a night school course in machine shop, I had a very poor notion of what the proper RPM was for a given drill size is.  Now I know just enough to be dangerous. 

Cutting speeds are typically expressed in surface feet per minute.  Think of the circumference of your bit in terms of being a fraction of a foot.

For high-speed drills, the following cutting speeds are recommended:
Mild steel (.2 carbon to .3 carbon) – 80 to 110 feet per minute
Steel (.4 carbon to .5 carbon) – 70 to 80 feet per minute
Tool steel (1.2 carbon) – 50 to 60 feet per minute

The circumference of a 1/8 bit is .3925” or .0327 ft. (pi x dia. Where pi is 3.14)
For the circumference to turn at 80 feet per minute, the RPM would be 1/.0327 x 80, or 2446 RPM.

That’s doing it the hard way.  The easy way is to flip to the table for the drill we are using (fraction, number, letter or metric) and look up the size and FPM.  At 80 FPM, a 1/8 bit rotates at 2445 RPM.

Here are the figures for some common diameters @ 80 FPM:
1/16” – 4889 RPM
1/8” – 2445 RPM
3/16” – 1630 RPM
¼” – 1222 RPM
# 20 – 1898 RPM
# 29 – 2247 RPM
Shoot for something close to the recommended RPM.
The larger the diameter, the slower the RPM.
One can extrapolate for higher or lower FPM.

Feed rates also vary with drill size.
For drills under 1/8”, the feed rate is listed as .001 to .002 inch per revolution
1/8” to ¼” - .002 to .004
¼” to ½” - .004 to .007

If you would like information for other sizes, just post your question and I will look it up.

By the way, I am strictly amateur when it comes to machinist work, so don’t be surprised if a real machinist steps in and sets me straight!

Laurie

[billd]

What Laurie says is correct.  I've been a machinist all my life, longer than I care to remember. I shocks me when we hire someone who claims they have "experience"  yet can't understand that the smaller the drill, or end mill, the faster it has to rotate.  Sort of like putting 12" tires on your pickup. Go down the road at 55mph and those little tires will be rotating way, way faster than the 17 inchers you took off.

Download a catalog from a drill manufacture such as Precision Twist Drill or Cleveland. The technical section has all this info in it. Get it for free.

As far as feed goes. If you're using a hand drill press you can't set feed. A mill with a power feed usually only has a few set feeds. A CNC mill is infinitely variable but most people don't happen to have one in there garage. You just have to get a feel for the feed. If you can set a power feed, a good rule of thumb is 1% of the drill diameter in inches per revolution.

Bill

[billd]

Just a quick example of my above post. I run .028 carbide drills in a CNC drill/mill at 20,000 rpms (yep, thousand) in 1215 steel. That's as fast as my machine will go, they should be running about 35.000 rpms. Feed is .0002 IPR.

Smaller the drill, faster speed, slower feed.

If you want info on tapping, Geenfield Tap and Die, or GTD, has great tips in their catalog. I think their web site is linked to Kennametal too.
Bill

[coutios]

  I agree with Laurie 100% if you have zero knowledge of speeds and feeds you should do some reading to understand the basics for the different types of materials you will come across.  Power tools I use building long guns are a five speed drill press and a variable speed hand drill. Allways regreted not buying a Bridgeport and a South Bend back in the late 70's when everyone was dumping them for automatics. After 33 years in a machine shop I guess I can tell by eye and feel when things are right. Sorry if I over simplified..

Regards
Dave

[Scott Semmel]

Okydoky I'm gonna display my ignorance, I've drilled more then a few holes in various metals and never fractured a drill with a drill press, broke more then my share when using a hand held or when I did not properly secure the object being drilled in the press. When I have broken a drill the biggist issue was getting the broken part of the drill out of the hole and getting a new bit. I am having a bit of trouble wrapping my mind around a bit breaking in a manner that would have the fragments create a hole too large for the appropriate tap. Would you folks with more experience tell me what causes such occurrences and how frequent they are. Thanks

[billd]

Scott, usually this happens when the drill grabs upon breaking out the other side of the part being drilled.  Very common on brass.

Bill

[California Kid]

Jwh, back to the bunker. Hopefully the Dr. will be there soon! HA! HA!

[Daryl]

Boys!

[California Kid]

Just kidding!

[Pete G.]

I learned something that I never knew before. I had always run the drill press at the lowest speed because I felt that it gave me better control; only going to a higher speed when polishing or sanding. Thanks for the info. I will print it out and tape it to the top of my press.