Floating reamer holders:

imho,
just the opposite.
the reamer is following the taper bore. straight true no stress.
the bushing will try to follow the bore..which is not straight, creating stress and
attempting to pull the reamer off the intended path.

to no bushing is if you use oil through the bbl. Alot more oil goes by the reamer and keeps the chips flushed out.
I can finish the chamber in two "passes" with the reamer doing it this way. If every thing is dialed in perfectly I have seen no difference between bushing vs no bushing. Looking through the the bore scope both methods work equally well.

Richard

Can I ask if you have successfully chambered 5 grove barrels using a 6 flute reamer without the bushing?

If so what do you consider success in terms of TIR at the throat and chamber mouth?

In theory I agree that if your pre-bore is true and you get the reamer in half way you should have enough contact area to keep everything straight without the bush but so far Ive never had the confidence or spare piece of barrel to try it out myself.
 
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All I have done

is 4 and 6 groove, so I can't help with 5 groove bbl's. TIR on the 4 and 6 run from nothing to .0002

Richard
 
is 4 and 6 groove, so I can't help with 5 groove bbl's. TIR on the 4 and 6 run from nothing to .0002

Richard

When you say tir is nothin to .0002 this is reading what and where? Just the chamber itself ?
or neck to aft of chamber? Or throat to aft of chamber?
 
to no bushing is if you use oil through the bbl. Alot more oil goes by the reamer and keeps the chips flushed out.
I can finish the chamber in two "passes" with the reamer doing it this way. If every thing is dialed in perfectly I have seen no difference between bushing vs no bushing. Looking through the the bore scope both methods work equally well.

Richard

That's a clear explanation of one reason for "no bushing". However, I have no oil flush but I do use a lot of oil & clean chips frequently.

Why I don't understand the "no bore is straight, so don't use a pilot" argument is simple:

The pilot is maybe 1/8" ahead of the throating portion of the reamer. How much can a match grade barrel run out in that 1/8"?

The pilot, at the closest, is .0002-.0004 smaller than the lands, and the pilot runs on a oil film the lands that takes .0001-.0002 of that space. So the reamer is following the lands pretty true to the lands at the throat, which is the goal of a good chamber.

No doubt you can do a good job either way, but I'll still use a pilot every time until I get an explanation that convinces me otherwise.

Regards,
Ron
 
no,
it depends on how much material is removed behind the throat.
it all influences the stress on the reamer.
some of the posts say get a 1/2 of taper reamer fit....that leaves about
an inch of reaming on the bushing BEFORE the throat
if you pre-bore as close as jackie does, it is a non-issue,
but starting 1/2 into a 1 1/2" chamber is plenty of room for stress.

again just an opinion form my collection of pennies

The pilot is maybe 1/8" ahead of the throating portion of the reamer. How much can a match grade barrel run out in that 1/8"?

The pilot, at the closest, is .0002-.0004 smaller than the lands, and the pilot runs on a oil film the lands that takes .0001-.0002 of that space. So the reamer is following the lands pretty true to the lands at the throat, which is the goal of a good chamber.
Ron
 
Pilot or no?

I guess the indicator is the judge here and rather than opinions we should be able to deal in facts, surely this same principle would also separate out the different chambering methods?.
 
Need to make my ealier post a little more clear about why I use the bushing and starting the reamer.

All of my chambers are first drilled then taper bored to within .004 to 008 (some Less) wall thickness and as close to the shoulder as I fill comfortable .025 to .050. No matter if 6PPC or 338 Laupa Mag. The reason I say ½ inch is when talking about 6PPC, that is the least amount the reamer with a fitted bushing can be started at and make contact with both pre-indicated points. As said earlier ever since I have been using the PTG floater and a close fitted bushing all of my cut chambers (6PPC to 338 Laupa) have TIR of .0001 or less at the base. :rolleyes:

Base TIR checked with a .0001 Brown&Sharpe 7023-3, Mitutoyo 503-504, and Interapid 312-3
Neck throat TIR or as far as I can reach with a Interapid 312-15, Mitutoyo 513-512, and Brown&Sharpe which are all long needle reading at .0005 can see Very little or no movement of the needle.
Way less than .0005.:rolleyes::rolleyes:
Chet
 
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From someone who actually DOES this............

The reason we do it this way is to avoid the reamer pilot following and wallowing in "runout ahead of the throat."

That area, from the ogive FORWARD about an inch is specifically the area which is dialed into alignment. From this parallel section, the metal behind it is bored/single-pointed away and the area ahead of it is allowed to run wild.

The way I do it, the pilot enters the bore just before the reamer starts to cut and it's only function is to eliminate chatter generated (IMO) be reamer wrapup. It doesn't "guide" anything nor does it make any marks of any sort.

It works well.

It's repeatable,

and since the amount of barrel runout is generally many times greater than the resolution of the measuring method it becomes an elementary matter to point the barrel wherever you want.

My method is to bring things into a straight-back track with a small muzzle-upward bias.
 
One last remark as to using the bushing. I have and do check each bore in front of the throat where the bushing is on the reamer with a Hawkeye bore scope and have never seen any kind of a mark indicating that the bushing might be touching the barrels bore. Like a good South Bend heavy 10 spindle bearing it lets the spindle float under a load with a fine film of oil and I believe that is what is happening with the piloted reamer bushing riding on a light film of oil.
Just my point of view. :rolleyes::rolleyes:
Chet
 
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One last remark as to using the bushing. I have and do check each bore in front of the throat where the bushing is on the reamer with a Hawkeye bore scope and have never seen any kind of a mark indicating that the bushing might be touching the barrels bore. Like a good South Bend heavy 10 spindle bearing it lets the spindle float under a load with a fine film of oil and I believe that is what is happening with the piloted reamer bushing riding on a light film of oil.
Just my point of view. :rolleyes::rolleyes:
Chet

I've never found any marks either, since I got my Hawkeye about 6yrs ago.....which is AFTER I started using my current method. I went to this method because of chatter I've experienced in the past. With my current method chatter is just a distant memory, as are scratches/ridges/rollups/burrs/eccentricities in the throat/leade area.

In other words...."I couldn't agree more" :)
 
If posters review my thoughts on this subject, I have presented a way to check your work. This is standard practice in machine shops every day.

The customer demands that you have a verified method of checking, and verifying your work. Always be aware that a flawed testing method will produce flawed results.

I have also stated that when presented with an imperfect part in the beginning, (in this case, the straightness of a barrels ID with its self), then you are automatically faced with a compromise. How you deal with this compromise determines the final outcome.

As a professional, (how's that for a high fallutin term :cool:), I have to deal with these problems every day as varied jobs com through the door. It is sometimes difficult to discuss these things with those with limited knowledge of what I call "basic machine shop practice".

Always be cognizant of what you are trying to achieve. Develop a set up that allows you to reach this goal with the machinery you have on hand. And always remember that is just as important, perhaps more important, to be aware as to WHY you do things a certain way as well as knowing HOW to do things.
 
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