Breaking Reamers

MilGunsmith

MilGunsmith

Member
I have had a recent rash of broken reamers. All in .260 Rem, three were HSS and on was Carbide. I have been using the same methods for the past 12 years, barrel dialed in headstock. Floating reamer holder. Pre boring chamber. Running HSS at 90rpm and Carbide at 185rpm. All lubed with Tap Magic/Dark Sulfur oil mix. The HSS reamers have broken off a piece of flute and the Carbide shattered completely. These are all PTG reamers. I used the same setup to run 6.5 Creedmoor with a JGS reamer and did 10 barrels without a problem. The reamers appear to have the flutes cut very deep with only about .1875" of solid materiel in center at the base. Has anyone else experienced this?
 
MilGunsmith said:
I have had a recent rash of broken reamers. All in .260 Rem, three were HSS and on was Carbide. I have been using the same methods for the past 12 years, barrel dialed in headstock. Floating reamer holder. Pre boring chamber. Running HSS at 90rpm and Carbide at 185rpm. All lubed with Tap Magic/Dark Sulfur oil mix. The HSS reamers have broken off a piece of flute and the Carbide shattered completely. These are all PTG reamers. I used the same setup to run 6.5 Creedmoor with a JGS reamer and did 10 barrels without a problem. The reamers appear to have the flutes cut very deep with only about .1875" of solid materiel in center at the base. Has anyone else experienced this?
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I have never broke a Chambering Reamer, but at our shop, we tried the "offshore" brand of large HSS end mills (Chinese), for cutting large keyseats in shafts. They were junk. Would just shatter. We had the same experience with large drills, (1 inch diameter and larger).

I do not know who is the source of PTG's HSS or Carbide. There is a possibility they got a inferior lot of material for blanks. This can happen, often a manufacturer is at the mercy of his supplier.

I do know this. PTG has a fine reputation. I have used their reamers for years with very few problems.

Give them a call. Discuss the problem. I'm sure they are interested any any issues customers have with their product, regardless of the origin of the problem.
 
MilGunsmith said:
I have had a recent rash of broken reamers. All in .260 Rem, three were HSS and on was Carbide. I have been using the same methods for the past 12 years, barrel dialed in headstock. Floating reamer holder. Pre boring chamber. Running HSS at 90rpm and Carbide at 185rpm. All lubed with Tap Magic/Dark Sulfur oil mix. The HSS reamers have broken off a piece of flute and the Carbide shattered completely. These are all PTG reamers. I used the same setup to run 6.5 Creedmoor with a JGS reamer and did 10 barrels without a problem. The reamers appear to have the flutes cut very deep with only about .1875" of solid materiel in center at the base. Has anyone else experienced this?
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I have had trouble with several PTG reamers. I rough drill and taper bore my chambers leaving about .005 per side for the reamer. I go by feel on the tail stock to determine when the flutes or starting to load up. When I feel it is time to clean reamer I stop the lathe first then pull it out. A few of these reamers seem to crowd even though continue to cut. When this has happened I have had to pull the reamer out under power. No,I am not being ham fisted when this has happened. As I said earlier I think it is a relief problem and if I were to force the reamer I can see how you might break one. After sending them back they solved the problem but did not elaborate as to what happened.
 
If broken reamers is a new occurance, I'd relook the process or the current barrel material machanibikity.

Go to pure dark cutting oil.

Retract and clean more frequently.

Slower rpm. Just things to consider.

Were all the reamers broken on the same workpiece?

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No, they were in different barrels. This last was on the third barrel for that reamer. All 416R 5R barrels by a reputable manufacture. Just last week I did 12 .308win barrels and two .300 Norma Mags with same setups and had no problems. I wonder if the design of the .260 reamer is like a 6-32 tap, just prone to breakage.
 
There's no way to sugar coat this. I chamber a lot of barrels, a lot of barrels and there's one company I won't buy reamers from. Too many surprises over the years. Lead times are bad enough without having to start over waiting on a new reamer. HSS I get from Manson and carbide from JGS. Nothing wrong with JGS HSS just that I've bought from Manson for decades. Good friend.
 
I have been using a Manson floating reamer holder and the chambers are coming out to spec. Thinking maybe a method with more give might be better. I measured the flute depth on the broken .260 reamer and they are at .141", the 6.5mm Creedmoor is at .119" for the same diameter.
 
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MilGunsmith said:
I have been using a Manson floating reamer holder and the chambers are coming out to spec. Thinking maybe a method with more give might be better. I measured the flute depth on the broken .260 reamer and they are at .141", the 6.5mm Creedmoor is at .119" for the same diameter.
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"more give" will just make an oversize chamber if you are talking about lateral give. Reamers breaking are generally caused by torque. Too heavy feed pressure or a chip jam up. A reasonably sharp reamer, given not too much pressure will simply cut sideways like an endmill thus an Over size chamber.

Go with the sources Toot reccomended.

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MilGunsmith said:
I have had a recent rash of broken reamers. All in .260 Rem, three were HSS and on was Carbide. I have been using the same methods for the past 12 years, barrel dialed in headstock. Floating reamer holder. Pre boring chamber. Running HSS at 90rpm and Carbide at 185rpm. All lubed with Tap Magic/Dark Sulfur oil mix. The HSS reamers have broken off a piece of flute and the Carbide shattered completely. These are all PTG reamers. I used the same setup to run 6.5 Creedmoor with a JGS reamer and did 10 barrels without a problem. The reamers appear to have the flutes cut very deep with only about .1875" of solid materiel in center at the base. Has anyone else experienced this?
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Double check the setup to make sure nothing has worn or loosened up.

One of the down sides of carbide tooling is that less than solid setups can produce loads that shatter it.

And the finer the grade of carbide the thinner the bonds between the actual grains of carbide are.

Carbide for interrupted cutting is NOT the same as solid cutting.

The crystal structure of steel vs. aluminum's uniformity are a big deal.

And 'high carbide' aluminum is a special nightmare.


One of the long term 'tricks' to aluminum manufacture has been carefully controlled cooling of the melt to allow carbide formation.

When cooled correctly, etched, and polished you can produce a carbide wear surface in aluminum.

The methods are considered proprietary by the manufacturers.

I worked for one of them designing the equipment to allow control of the cooling process

It was a nightmare (at that time) to control the heater current for the controlled cooling.

The power levels where at the limits of triac technology at the time.

More than one 'puck' packaged triac exploded from overheating.
We had a box made from very thick polycarbonate to confine the debris.
 
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Lost a 22 Hornet from PTG of all things and pushing it easy. The flutes were cut so deep there was not much of a solid core left to it and where it failed. But on the other hand I have several of their reamers of the highest quality and no complaints.
 
I might add this was a set back and re-chamber from a washed out throat in the Hornet so possibly there was some hardening of the chrome moly in that area?

JLouis
 
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