Reamer chatter

[eww1350]

Here is a brain burner for you guys that chamber rifles...I have a good friend and gunsmith that is chambering up a Shilen 6.5 caliber S/S barrel in 6.5x55 using a new PTG solid pilot reamer.
He cut the chamber and had major chatter in the finished chamber..now keep in mind he has been chambering rifles for 20+ years and uses a quality lathe made in the late 60s..he sets up the barrel in the headstock with the muzzle riding on a 60 degree center in the rear of the headstock just like "Jackie Schmidt" he uses the best sulpurized cutting oil etc..never experienced chatter "ever" when chambering barrels...he called me and asked what I thought...I could not find anything in his setup...I recommended he use my floating reamer holder for the second chamber attempt (he cut off the the threaded shank to start over) he started to cut the chamber about .050" an stopped to check it with an indicator...it looked good and measured almost "zero" runout...so he proceeded to cut the chamber..as he neared the correct depth for headspace...he stocpped and checked the chamber at the neck portion with a long reach indicator and I couldn't believe it...the indicator was jumping up and down like it was riding over the lands and grooves..!!!
He was understandibly frustrated..and decided to polish the chamber with some 400 grit paper and assemble the barrel and shoot it to check the effects on the brass...he later called me to tell me the neck of the fired brass was eliptical and was going to stop and call Dave Kiff for help...Dave recommended he send the reamer back for inspection...but did not offer an explanation..we are both at a loss on this one...by the way the reamer never cut on all flutes...anyway this has been a real brain teaser for us...have any of you experienced anything similar???


Eddie in Texas

 

[RonAKA]

Way over my head, but here is an article with Dan Lilja's thoughts on chambering reamer chatter.

http://www.riflebarrels.com/articles/barrel_making/chatter_chambering.htm

 

[Rustystud]

Reamers always get the blame for chatter. In my 40 plus years of reaming chambers, I have come to the conclusion sometimes it is the barrel and not the reamer. I have had reamers that cut true chambers then chatter with another barrel and then follow by cutting another true chamber all on the same lathe and set-up.

Nat Lambeth

 

[Greg110]

Could be what Nat said. Different steel lot or alloy also. So not NECESSARILY the reamer.

 

[clowdis]

I don't necessarily agree with Nat on this one. I've had reamers from one particular reamer grinder chatter more than other grinders, so much in fact that I believe that the geometry of the grind he puts on the reamer has something to do with it. Yes, speed and feed are critical and so is a good fit of the pilot bushing in the bore (which you probably didn't have with a solid pilot). You can stop the chatter with cleaning patches in the reamer flutes and other methods (search topic) but it sounds like it's too late for you now. You may have to cut off the shank of your barrel and start over to get a good chamber unless your 'smith is very careful restarting your chamber with the new reamer. Hopefully he gets one with interchangable pilots so he can fit a pilot bushing to the bore. That will really help.

 

[Rustystud]

I had this vary conversation with Dave kiff two days ago. Dave goes back to old school reamer grinding. Dave said because of changes in metal, and machining that reamers have had to change with the times. Dave told me he had to replace grinders because thay would not cut reamers with the needed geometry. Dave said some of the best reamer makers have not kept up with the modern technology and their reamers will not work with highspeed and high pressure reaming. Their reamers are still made with highspeed steel and not M7 tool steel.
This may be a little off topic but more and more gunsmiths are now using high speed reaming and high pressure flush systems. It is like running a quarter inch drill bit at 250 rpms it grinds to a halt, work hardening the stock being drilled. Drilling it at 900 Rpms and it goes through like a hot knife in butter. Then again run it at 1200 rpms and the bit just burns up.
I find less chatter when high speed reaming with sharp reamer. I was reading Chad Dixon's post where he is reaming at 400-600 rpms.
If you have the set up then it works.
Nat Lambeth

 

[fdshuster]

Nat: Question? Do you think there is any advantage to a spiral fluted reamer, over conventional straight flutes, to stop, or at least reduce chatter?

 

[clowdis]

Nat,
Just to sort of confirm what you said, a couple of the reamers I had chatter problems with I solved the chatter by speeding up the speed and feed on the reamer. Sort of bassackwards to what you might normally do to solve a chatter problem. Go figure. Found another reamer supplier anyway.

 

[Rustystud]

I have both straight and helical reamers. I prefer straight as I use a high preasure flush system. I don't want coolant spraying all over the shop at 125 psi.
Nat Lambeth

 

[wnroscoe]

The chamber reamer I had chatter was at 70RPM with no muzzle flush system in place. Now, I ream at 200RPM with a muzzle flush system and all is good. Better chamber finishses and quicker chambering times.

The last reamer I had chatter was during a 338 Lapua Mag build. I flooded the chamber with extra oil and slowed my feed, worked out great. Try wrapping wax paper around the reamer and try to remove the chatter this way. Loose parts/tools promote chatter in the work piece.

 

[DCRYDER]

I agree with clowdis for the most part. I've only had 2 reamers chatter and they were loaners from a fellow local smith and they were from the same maker, I also won't mention the name (but it starts with a "C" and ends with a "R"). I only buy PT&G reamers and have NEVER had any chatter with them.

They chattered early so i sanded it as smooth as i could, SHARPENED reamer just a little with an Arkansas stone, lubed with crisco, added a little extra feed pressure at 70 RPMs and turned out fine.

Hows about a 10% discount on next order Dave??? lol

 

[kjcpoint]

Sent a .243 reamer back to PTG to inspect cause I had the same chatter problems with a top quality barrel. Got the reamer back yesterday and started fresh with the same barrel and still had the same result. Next I used a Howa and a Rem take off barrels and no chatter.
This is the 3rd barrel of the same make we have had chatter?

Very interesting and open to all thoughts.

Thanks
Kyle

 

[D.Kiff]

Eddie , one resone I dont like solid pilot reamers is the solid pilot is ground to the small side of barrel tolerance , a one size fits all problem. If the bore is large the reamer will not only have a chance of chatter but also the slop can let the cutting flutes shift to one side and only one or two flutes will do all the work. Folks send reamers to us made by the other four chamber reamer makers and instaling a removable bushing on the solid pilot takes care of the problem most of the time. I have a nice stagger on our tools so most of the time if one of our tools chatter it is pilot to bore fit or the tool is to sharp for a barrel with a softer heat treat. The reamer that will cut some barrels clean with out chatter an then a barrel comes along and that same reamer starts to chatter I find these barrels are either gummy and soft or have hard spots. If any one ever has one of our tools that chatters just send it in and we will find out what the problem mite be and If its a reamer made by some other tool grinder send it in and we can fix it also. I put removable pilots on all reamers made by other companies all the time Thanks Dave

 

[wapiti25]

Plus one one the pilot fit to the bore. I was told by Dave Manson that it is nearly imposible to get the cutting angle correct on spiral flutes. I just completed a light weight hunting rifle in 7mm rem mag using one of Dave's reamers and it worked fantstic. Shooting 1" groups at 300 yds, I'm very happy.

 

[LongRiflesinc]

When I first got to Nesika threading/chambering was done on a bench top import lathe that Glen Harris's wife Lisa bought for him 12+ years before I started working there as a present when he first started tinkering with benchrest actions. It took awhile, but we cut some mighty nice chambers on that thing. One thing I can promise you all is we didn't hold onto the reamer with a tap wrench. A genius ol timer back in Poulsbo ginned up a process that worked very well using the carriage to hold the tool. (HINT)


Speaking in broad general terms:

Tool chatter is a function of rpm, feed-rate, work holding rigidity, and tool rigidity. If for instance I'm in the milling machine or on a lathe chewing on a piece of stock and my cutter starts squealing like a pig I do this:

Ensure I have a solid hold on the part
Ensure my tool is secure by either the tool holder, collet, spindle, whatever. (notice I didn't say "hand")
Increase the feed-rate
Reduce RPM

Sometimes both on the last two.

SO if I were to experience chatter with a reamer I would first reduce the RPM. Since most gunsmiths seem to chamber at very, very conservative spindle speeds I would then look toward being more aggressive with the feedrate. This is surely going to raise the hairs on the necks of many as the tap wrench method of reamer holding is likely the most common method. This would then point to the first two items I addressed. Part work holding and tool rigidity.

Chambering one barrel to the next doesn't mean much. The bigger barrel companies try to buy their steel in as large a quantity as they can. "A pour at a time" as it was put to me once. This saves them money in the long run because drills and reams only need to be set once because the material is much more likely to be consistent this way during the stress relieving process. If your using a variety of barrel brands on different customer guns then it's unlikely they are all buying steel from the same lot or "pour". Not surprising at all that the material condition changes slightly. It may also be an indication that your consistently running on the ragged edge of work holding/tool holding if your getting chatter.

Be that as it may it doesn't change the fact that tool chatter is still a function of work holding, Tool rigidity, RPM, and feedrate.

That's it, no voodoo or fancy cutting fluid is ever going to solve that. FWIW I pull my feeds/speeds right out of any of the published charts scattered all over internet land: 40-85 SFM. I use the largest diameter of the ream when computing the formula. This generally puts me in the 400-475 RPM range. I have the luxury of using a very nice CNC turning center for my barrel work. It wasn't always like this. Once upon a time I too used a manual machine. I still used the same feeds/speeds. That should hopefully encourage at least someone to take a long/hard look at the process. Big heavy machines with zillion dollar bearings certainly help, but I've done this same stuff on 15+ year old import lathes that should have been turned into fish habitat.

The reamer is an easy item to blame. Bear in mind chatter is going to wear that tool out that much faster. Your shock loading the cutting surfaces and this is going to erode them faster. Just like it does on a mill or turning insert. I have reamers that have cut hundreds of chambers just like I have chucking reamers that have scoured out hundreds of holes. They still cut very well.

Just a few things to consider.

Great topic, hope this helped, and good luck!

C

 

[butchlambert]

Wrap the reamer flutes with wax paper. Don't laugh, a lot of experienced smiths do this when having a chatter problem.
Butch

 

[22XC Guy]

There is several differing opinions as to what machinability really is. Some are interested only in the speed at which a material can be cut, others consider tool life at a reasonable speed to be most important, while others rate machinability on the surface finish produced. Obviously, all factors are important — cutting speed, tool life, and surface finish — and all are considered in rating the machinability of a metal.

The machinability of stainless steels is substantially different from that of carbon or alloy steels and other metals. In varying degree, most standard stainless steels are somewhat more difficult to machine. That is why there are enhanced or free-machining stainless steel types. In fact, stainless steels are routinely machined on high-production equipment. The best way to get maximum machinability, wherever end-use conditions permit, is to specify a free-machining stainless steel. The 400 series stainless steels are the easiest to machine, but they do produce a stringy chip that can slow productivity.

The 200 and 300 Series, on the other hand, are characterized as being the most difficult to machine, primarily because of their gumminess and, secondarily, because of their propensity to work harden at a very rapid rate. However, the difficulty is not so great as to be a deterrent to selecting a stainless steel for a machined part.

Certain alloying elements in stainless steels, such as sulfur, selenium, lead, copper, aluminum, calcium, or phosphorus can be added or adjusted during melting to alter the machining characteristics. These alloying elements serve to reduce the friction between the workpiece and the tool thereby minimizing the tendency of the chip to weld to the tool. Also, sulfur forms inclusions that reduce the friction forces and transverse ductility of the chips, causing them to break off more readily. The improvement in machinability in the free-machining stainless steels — namely Types 303, 303 Se, 203, 430F, 416, and 420F.

 

[butchlambert]

I think he wanted help with reaming a 416R SS barrel, not a lesson on different stainless steels. We don't get to pick the metals that the barrel makers use.
Butch

 

[22XC Guy]

Here are a few guidelines recommended from a few shops. This may be useful when working with stainless steels:

1. Machine tools should be rigid, modern, and as much “overpowered” as possible. Best practice is to use the machine up to about 75 percent of its rated capacity.
2. The work-piece and tool should be held rigid. Tool overhang should be minimized and extra support used when necessary.
3. Tools, either high speed tool steels or carbide, should be kept sharp, preferably being sharpened at regular intervals rather than only when necessary.
4. A good lubricant is required, such as compounded sulfur-chlorinated mineral oil plus fatty oil for high-speed tools, and heavy duty emulsifiable oil for carbide tools.
5. Positive cuts are necessary. Care should be exercised to avoid dwelling so as not to work harden the material, especially the austenitic (300 Series) stainless steels.

 

[butchlambert]

OK, what is the next chapter of the book are you going to give us next?
Butch