Gunsmithing Chamber Reamer Wear

[Praeger]

I'm looking for some opinions regarding the wear showing on a PTG 6 Creedmoor finishing reamer.

The PTG reamer has 6 flutes, each flute has two facets (primary and secondary relief angles). The wear is visible on the cutting edge at the case mouth and shoulder sections (shown with yellow arrows in photos) below the junction of the primary relief angle and the cutting edge. The reamer has cut 2 chambers, using low rpm (90), high sulfur cutting oil (generously applied), fed into the bore about 0.050" per pass (reamer and chamber cleared of chips each pass), mounted on a floating reamer holder. On all my chamberings I've gone slowly, following mainstream processes.

Is this wear typical? Is it some type of build up residue from SS barrel? The reamer was purchased new - I didn't notice anything unusual, but wasn't specifically looking at these areas. The surface finish of the chamber walls are perfect, but the shoulder has fine striations corresponding to the wear areas. Photos are of the same reamer, rotated to show different flutes. I wanted to get some feedback before trying to stone it or otherwise restore.

 

[smoooth1]

Looks like material build-up more than wear. Those areas are subject to the most direct cutting action and pressures. Wear would be on the very edge and reducing the diameter of your reamer.

 

[mcfred]

Do you pre-drill and single-point bore before running the finish reamer in?

 

[Praeger]

Do you pre-drill and single-point bore before running the finish reamer in?

No pre-boring.

@smoooth1 I ran a fine point brass pick over the area and think you may be correct. It feels like very slight deposit. Under magnification the primary cutting angle looks clean. Might try a fine oil stone slip - carefully run it along that side of the flute.

 

[Hateca]

That’s build up. As for pre boring and or roughing reamer prior to finish reaming, don’t believe everything you read or hear, learn from experience. Unless you are cutting hundreds of chambers your finish reamer is all you need. I’ve cut many chambers with nothing but finish reamers and have yet to wear one out or need it sharpened. Good cutting oil, the correct speed and feed, and watch heat build up. If the barrel and or the reamer is getting hot to where you can’t touch it stop and let it cool. This will also help to lesson build up.

 

[lariat]

That’s build up. As for pre boring and or roughing reamer prior to finish reaming, don’t believe everything you read or hear, learn from experience. Unless you are cutting hundreds of chambers your finish reamer is all you need. I’ve cut many chambers with nothing but finish reamers and have yet to wear one out or need it sharpened. Good cutting oil, the correct speed and feed, and watch heat build up. If the barrel and or the reamer is getting hot to where you can’t touch it stop and let it cool. This will also help to lesson build up.

Agree on the oil and speed/feed. What do you do for peck depth?

 

[Hateca]

Agree on the oil and speed/feed. What do you do for peck depth?

Depends on the caliber but a good rule of thumb is until the flute channels fill up with chips or heat starts to build or I feel a change in resistance. When I first start the chamber I keep feeding until I feel heat build up in the barrel, most of the reamer is outside the barrel and chips will just fall and don’t fill the flutes.

I use a floating holder and feed by the tail stock and can actually feel the change in feed resistance. Once you start to feed do not stop or break contact with the barrel unless you are going to withdraw the reamer to brush off. If you start and stop you are in danger of rolling a chip. Some stop rotation to withdraw the reamer, I dont stop rotation it‘s easier on the reamer and barrel. Magnums and big calibers will build heat faster simply because they are bigger and cutting more barrel so my technique will change.

If I wasn’t invested in tooling and did more barrels per day I would invest in a flush system. This setup allows for faster chamber jobs. Pretty much non stop from start to finish.

 

[lariat]

Thanks for the explanation. My shop is all cnc so I think in that context. Looking at his reamer it looks like he ran out of oil before the retract or didn’t have enough, which is causing the build-up. At least that’s what I have experienced when I have tools that look like that. It’s notable that it isn’t occurring on the reamer but on the drill portion of the tool, which is taking the majority of the cutting force.

 

[Hateca]

Thanks for the explanation. My shop is all cnc so I think in that context. Looking at his reamer it looks like he ran out of oil before the retract or didn’t have enough, which is causing the build-up. At least that’s what I have experienced when I have tools that look like that. It’s notable that it isn’t occurring on the reamer but on the drill portion of the tool, which is taking the majority of the cutting force.

Yes or he is letting the reamer and or the barrel get too hot during the cut.

 

[Praeger]

Looking at his reamer it looks like he ran out of oil before the retract or didn’t have enough, which is causing the build-up. At least that’s what I have experienced when I have tools that look like that. It’s notable that it isn’t occurring on the reamer but on the drill portion of the tool, which is taking the majority of the cutting force.

Yes or he is letting the reamer and or the barrel get too hot during the cut.

I can't imagine going any slower or with more oil. Each plunge is about 0.050", fed very slowly at 90 rpm with no pause during the plunge. After each pass I remove the reamer from the floating holder and clear chips from the reamer and the chamber. The reamer isn't hot, not even warm to the touch.

Before making the next plunge, I coat both the chamber and the reamer with high sulfur cutting oil - enough oil that it is dripping off the reamer. The chips are drenched in oil when I retract the reamer at the end of a plunge, so I don't think it is a lack of oil. That's what I find perplexing. I have threaded/chambered about a dozen barrels over the last year - mostly Kreiger and Bartlein - and I didn't encounter this buildup. This is a Hart barrel (the 2nd I've chambered this year) and am wondering if it a difference in the metal itself. Thus far it has been machining nicely, good clean cuts and thread form has been crisp. Perhaps this material is simply more prone to leaving deposits.

I was able to remove virtually all the build up with a oil slip stone, and under magnification the cutting edge appears well defined and I don't feel any catches when I run my fingernail down the cutting edge. I'll resume chambering and check results.

 

[Hateca]

I can't imagine going any slower or with more oil. Each plunge is about 0.050", fed very slowly at 90 rpm with no pause during the plunge. After each pass I remove the reamer from the floating holder and clear chips from the reamer and the chamber. The reamer isn't hot, not even warm to the touch.

Before making the next plunge, I coat both the chamber and the reamer with high sulfur cutting oil - enough oil that it is dripping off the reamer. The chips are drenched in oil when I retract the reamer at the end of a plunge, so I don't think it is a lack of oil. That's what I find perplexing. I have threaded/chambered about a dozen barrels over the last year - mostly Kreiger and Bartlein - and I didn't encounter this buildup. This is a Hart barrel (the 2nd I've chambered this year) and am wondering if it a difference in the metal itself. Thus far it has been machining nicely, good clean cuts and thread form has been crisp. Perhaps this material is simply more prone to leaving deposits.

I was able to remove virtually all the build up with a oil slip stone, and under magnification the cutting edge appears well defined and I don't feel any catches when I run my fingernail down the cutting edge. I'll resume chambering and check results.

You might have said but is this a carbide reamer? If it is try increasing your speed to about 120. Carbide likes to cut at faster speeds. Like I said it‘s a learning thing. You could absolutely be cutting a barrel that is a little different. I’ve cut a few stainless barrels over my time that’s seemed to be soft and gummy feeling on the reamer and left more build up on the reamer. Not all barrels are created equal.

 

[Praeger]

You might have said but is this a carbide reamer? If it is try increasing your speed to about 120. Carbide likes to cut at faster speeds. Like I said it‘s a learning thing. You could absolutely be cutting a barrel that is a little different. I’ve cut a few stainless barrels over my time that’s seemed to be soft and gummy feeling on the reamer and left more build up on the reamer. Not all barrels are created equal.

No, it's the standard PTG fare - HSS. I've tried all the low gear speeds; 90, 135, 205 with no visible change in finish - just cutting faster. I'm about done chambering this particular barrel and after removing the build up I'm still not thrilled with the finish on the shoulder but it is better than before and I was able to polish it out.

 

[1moaoff]

Are you manually oiling the tool? Flush is really the best way. At higher speed if finish is the same the question is do you still get the build up.

 

[lariat]

I’m going to go put on a limb and say it is the HSS tool. I did some research on it last night and they offer a carbide tool as well. Personally I hate using HSS in stainless, especially uncoated. But if it’s done with no burrs bad spots in the chamber then good to go.

 

[Praeger]

Are you manually oiling the tool? Flush is really the best way. At higher speed if finish is the same the question is do you still get the build up.

I am manually oiling the reamer and the chamber before each plunge. From 90-205 rpm no noticeable difference in the shoulder surface finish. I haven't had the issue of built up on other reamers. A flush system would be ideal, and it would certainly speed the process up, but other than this barrel my results have been very good. For the volume of barrels I turn, I just can't see investing in a flush system.

@lariat The reamer is the standard PTG HSS.

 

[Killswitch Engage]

i dont think i could go back to reaming a chamber that wasnt pre bored and not under flush. its just too damn nice and way easier on the machine in terms of stop and start. reamer and barrel stay constantly cool and lubricated. start to headpsace on a typical .473 case in 10 min.

 

[1moaoff]

Do you stop rotation before removing reamer?

 

[Praeger]

i dont think i could go back to reaming a chamber that wasnt pre bored and not under flush. its just too damn nice and way easier on the machine in terms of stop and start. reamer and barrel stay constantly cool and lubricated. start to headpsace on a typical .473 case in 10 min.

I know, although I tried pre-boring and it didn't speed things up much if any. I think pre-boring is more for those who inidcate with pocket DTI's to get the stylus further into the area ahead of the chamber.

 

[Praeger]

Do you stop rotation before removing reamer?

No, and yes. I don't in the first inch of boring, then do stop the lathe before retracting the reamer after the first inch to avoid possibility of rolling a chip.

 

[Supersubes]

I can't imagine going any slower or with more oil. Each plunge is about 0.050", fed very slowly at 90 rpm with no pause during the plunge. After each pass I remove the reamer from the floating holder and clear chips from the reamer and the chamber. The reamer isn't hot, not even warm to the touch.

Before making the next plunge, I coat both the chamber and the reamer with high sulfur cutting oil - enough oil that it is dripping off the reamer. The chips are drenched in oil when I retract the reamer at the end of a plunge, so I don't think it is a lack of oil. That's what I find perplexing. I have threaded/chambered about a dozen barrels over the last year - mostly Kreiger and Bartlein - and I didn't encounter this buildup. This is a Hart barrel (the 2nd I've chambered this year) and am wondering if it a difference in the metal itself. Thus far it has been machining nicely, good clean cuts and thread form has been crisp. Perhaps this material is simply more prone to leaving deposits.

I was able to remove virtually all the build up with a oil slip stone, and under magnification the cutting edge appears well defined and I don't feel any catches when I run my fingernail down the cutting edge. I'll resume chambering and check results.

Maybe I missed this but who’s blank are you chambering? This could be a combination of that steel, your oil, the reamer. Some blanks seem positively gummy to cut.


One other thing. I find that near full reamer depth, .050 plunge is too much in one pass. The reamer flutes fill with chips quickly and the reamer starts to bunch up. I’m down around .015 per pass at the end. I’m not power flushing.

 

[Praeger]

Maybe I missed this but who’s blank are you chambering? This could be a combination of that steel, your oil, the reamer. Some blanks seem positively gummy to cut.


One other thing. I find that near full reamer depth, .050 plunge is too much in one pass. The reamer flutes fill with chips quickly and the reamer starts to bunch up. I’m down around .015 per pass at the end. I’m not power flushing.

It's a Hart barrel. I do follow a similar reduction in plunge depth towards the end, and try to be sensitive to any increase in resistance from the tail stock hand wheel as the chips begin to compact in the reamer flutes.

Like a lot of other guys, I started turning my own barrels about 2 years ago out of frustration with long lead times and several botched barrels. I've completed about a dozen in the last year and they've all turned out well but I'm still picking up on nuances as I get more experience.

I mention this as early on I was focused on getting threads right (not crashing the lathe) and following steps from the Gordy Gritters DVD. As I began to turn barrels to tenon print specs without the host action, I began to more fully understand the measurements and paid more attention to how the reamer cut. So, I'm looking much more closely at chips and surface finish that I likely did a year ago. I don't recall seeing this much build up on a reamer, but most of what I've worked on have been Bartlein and Kreiger barrels. Maybe it was just this particular barrel.

 

[Hateca]

HSS is not ideal but will work. Start paying a little extra and get the carbide readers you will thank yourself. I think you just got a barrel that is soft and gummy. It happens and I‘ve experienced the same with some stainless barrels. Call this a learning experience and keep moving forward.

 

[__JR__]

do all your flutes look like they are filling equally?

 

[Praeger]

do all your flutes look like they are filling equally?

On balance, yes. Except when taking the final passes where the plunge is .010" - .020" when one or two of the flutes had a very fine steel wool fill and other have a slightly more coarse cut/curl.

 

[lariat]

Second picture, bottom flute: is it chipped at the radius? It looks like it.

 

[Alan Warner]

First off, Dave kiff cant put a good edge on a reamer edge if his life depended on it. And, his heat treat is all over the map

Prebore in steps to reduce reamer
work.
Should not take more than .3 or
4 of forward travel to finish.
And,
God gave us
Arkansas, ruby and diamond hones and stones for a reason
Learn how to use them.
Use a good forced oil flow from the front end.
Reamers vary in life cycle
Some better than others.
Hugh hendricks still makes the best imo.
If you can wait for him.
If you are doing production, go carbide.

 

[__JR__]

First off, Dave kiff cant put a good edge on a reamer edge if his life depended on it. And, his heat treat is all over the map

Prebore in steps to reduce reamer
work.
Should not take more than .3 or
4 of forward travel to finish.
And,
God gave us
Arkansas, ruby and diamond hones and stones for a reason
Learn how to use them.
Use a good forced oil flow from the front end.
Reamers vary in life cycle
Some better than others.
Hugh hendricks still makes the best imo.
If you can wait for him.
If you are doing production, go carbide.

That's a broad statement. But I do have a jig set up to fix the fixable. If I specificlally order 'up sharp'after coat, chances are better.

 

[Praeger]

Second picture, bottom flute: is it chipped at the radius? It looks like it.

No, it is an artifact of the photo. All the reamer edges are intact and clean.

 

[Praeger]

That's a broad statement. But I do have a jig set up to fix the fixable. If I specificlally order 'up sharp'after coat, chances are better.

Is the jig you mentioned the Gre-Tan/PTG Reamer Stoning Jig?

 

[__JR__]

Is the jig you mentioned the Gre-Tan/PTG Reamer Stoning Jig?

View attachment 7516501
View attachment 7516504

I've got that one, it's truly handy even without the CD instructions. But I learned how to make reamers from Dan Green, formerly of Forgreens. so my mileage varies how I eyeball evaluate and work in a reamer before presenting to a match bore..

 

[HellcatActual]

That’s build up. As for pre boring and or roughing reamer prior to finish reaming, don’t believe everything you read or hear, learn from experience. Unless you are cutting hundreds of chambers your finish reamer is all you need. I’ve cut many chambers with nothing but finish reamers and have yet to wear one out or need it sharpened. Good cutting oil, the correct speed and feed, and watch heat build up. If the barrel and or the reamer is getting hot to where you can’t touch it stop and let it cool. This will also help to lesson build up.

cutting oil improvement will help with the buildup on the flutes.

I would suggest the pre bore isn't always a way to reduce wear on the reamer, as its still cutting no matter what. I think most guys cutting pipes (at least in my case) pre bore so we can get a long reach DTI and take a direct reading immediately where the bullet starts its life.

at least in my case thats why I pre bore.

 

[Hateca]

cutting oil improvement will help with the buildup on the flutes.

I would suggest the pre bore isn't always a way to reduce wear on the reamer, as its still cutting no matter what. I think most guys cutting pipes (at least in my case) pre bore so we can get a long reach DTI and take a direct reading immediately where the bullet starts its life.

at least in my case thats why I pre bore.

Didn’t say it was, in fact I see no difference In reamer life. Dial in the barrel at the lead on throat you will almost always need to pre bore to guarantee the chamber isn‘t out of round at the chamber mouth.

 

[HellcatActual]

Didn’t say it was, in fact I see no difference In reamer life. Dial in the barrel at the lead on throat you will almost always need to pre bore to guarantee the chamber isn‘t out of round at the chamber mouth.

we are on the same page... on the same book. drinking the same scotch

 

[Hateca]

we are on the same page... on the same book. drinking the same scotch