Broke my first reamer

M

Mram10

New member
Frustrating part is, I’m not sure what I did wrong

Carbide 300wm reamer (used. 1st time using it)
Standard floating reamer holder
205 rpm
Barrel Flush at about 1/2 power
Stainless Rem varmint contour
Pre drilled 1.5” in with .390 bit
Boring bar first half inch to .450

Reamer was feeding extremely well then the cutting oil spray changed a bit and before I could stop it, the reamer broke off in there with about half inch left to go. My guess, it hit the end of the pre drilled section and grabbed??? Chips seemed to be clearing out well. Ideas?

I only have 2 carbide reamers and my 308 has never given me problems. First time using this 300 wm reamer. Used from a friend and seemed to be doing great .... until it wasn’t? Point is, not sure of nuances to carbide v hss reamers. Ideas?

Also, tried to tap out with cleaning rod and no luck. About to part the first 1.5” and start over.
 
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did you predrill and clearance the neck and taper bore so there was good solid body cutting/centering ?

I HAVE NEVER DONE carbide, hss and 140rpm with flood( not flush)

Mram10 said:
Frustrating part is, I’m not sure what I did wrong

Carbide 300wm reamer (used. 1st time using it)
Standard floating reamer holder
425 rpm
Barrel Flush at about 1/2 power
Stainless Rem varmint contour
Pre drilled 1.5” in with .390 bit
Boring bar first half inch to .450

Reamer was feeding extremely well then the cutting oil spray changed a bit and before I could stop it, the reamer broke off in there with about half inch left to go. My guess, it hit the end of the pre drilled section and grabbed??? Chips seemed to be clearing out well. Ideas?

I only have 2 carbide reamers and my 308 has never given me problems. First time using this 300 wm reamer. Used from a friend and seemed to be doing great .... until it wasn’t? Point is, not sure of nuances to carbide v hss reamers. Ideas?

Also, tried to tap out with cleaning rod and no luck. About to part the first 1.5” and start over.
Click to expand...
 
In short, no. I pre drilled then only used the boring bar for part of the chamber to get it started out centered. I haven’t tried it this way before and definitely won’t again.

Another mistake I think I made was using a screw on a flat from the reamer to holder. It couldn’t spin when caught and broke
 
I chamber at 80 rpm and hold the HSS reamer with a tap wrench. I've had them grab and let go of the tap wrench letting it spin, but have never broken a reamer. I drill and bore out most of the chamber. With the dimensions that you are saying, I would have drilled the hole for 1.5" at .390" in diameter, then bored for 1.450" to .010" under shoulder diameter. Then would have bored out the start of the hole to shoulder diameter to where the shoulder of the reamer will just slip into the hole for about .050 to .100" long. I'll push with a dead center until I'm about .125" from full depth and then switch over to a pusher to finish the chamber. I feel that the dead center gives the reamer more support as it reams most of the hole and the pusher lets the reamer cut on diameter to finish the hole. The dead center needs to be in line with the lathe centerline, but pretty easy for it to be just a little off. The pusher is a tube that clears the reamer shank by about .010" and pushes against the tap wrench. I keep my hand behind the tap wrench just in case it does grab and break loose from my hand. The few times that I've used commercial floating reamer holders, I've cut the biggest oversize chambers that I've ever cut. The pusher works similarly to the Bald Eagle reamer holder. If I was going to use a reamer holder, that is the one I'd use. It's hand held and keeps your hand away from the flutes of the reamer in case the reamer grabs. I've only used a couple of carbide reamers and those were customer furnished reamers for their barrel. I've never seen the need for a carbide reamer over a HSS. Most gunsmiths don't cut enough chambers of a particular caliber to justify the extra expense of a carbide reamer. I've chambered more 6 PPC barrels than just about any other chambering and even then I don't see the need for a carbide reamer. The speed that you are using with the carbide reamer sounds about right for what I understand carbide needs. That's about the speed that I thread with carbide inserts.
 
Thank you for your response Mike! I too use the same speed as you and the process is somewhat similar as well and I have yet to break a HSS reamer and they are the only ones that I have used.
 
Thanks for the responses guys. Carbide reamers are so darn fragile that I am wondering if it already had a crack or chip and it decided to give while it was in there. I definitely was not feeding it too fast and I had plenty of oil pressure to push out the chips. Luckily it popped out after cutting off the tenon and giving it a few taps with a cleaning rod. I am back to HSS for now. Always learning .....

After parting off the tenon, I turned it into a 25” 300wsm ;). Guess there is always a silver lining.
 
Retired,
When you say “flood not flush “ are you setting the oil flow aimed into the reamer/tenon area? I’m easily confused
 
Gotcha. Thanks. Did a 6.5 creed like that today cause my reamer is still stuck in my floating holder. No barrel Flush was painful.....
 
Louis.J said:
What speeds do most of you folks chamber at I am not one who turns a barrel that fast.
Click to expand...

That does seem a little fast on the RPM.

What was the feed rate or was it manual?

Carbide reamers are very brittle (like pretty much everything carbide).

Changing loads on a carbide cutter are often a problem.

Interrupted cuts are NOT a good idea with carbide inserts.

HSS that is correctly heat treated is adequate for a lot of applications.

Carbide tooling demand very solid support and solid setups.
Chatter will destroy carbide tooling in the blink of an eye.
 
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