I thought that I had a handle on this then when making two attempts at a reamer that were soft I near gave up not really

Third one worked but I would love to have someone experienced walk 'us' through the process.


oh yes what the project required was a long reamer made to open the barrel to just past the transfer port and then give a nice 5 degree leade to the rifling.
What made all this tricky was the barrel is in the receiver of a B51 BAM PCP and I did not want to remove that barrel.
pellets loaded very rough and showed major smears on the skirts. Kodiaks loaded real rough.

So reamed the free bore to 0.228" then made up a tapered reamer with a 5 degree nose and a 0.2275" straight guiding section.

If I make another go at this it will be an all in one piloted reamer.

Walter....

Access to a surface grinder and either
a Harig head or a decent indexable
5C collet fixture?

If so, I will make a drawing for you for a
reamer that will do the job for you.

I can save it as a jpeg and post it here or
as a pdf and e-mail either to you.

Since you are removing very little material,
I would make a two flute reamer.With pilot
as you wished.

I do need to know how deep you need
to reach since you are not removing the barrel.

Edit 1;
Sorry, read your post again, and saw that you were able
to get what you wanted cut.

What are you having problems with?
the heat treat of the reamer?
Was it a cutting edge relief, rake angle or an edge clearance
issue?
I would like to help.

Edit 2;
Usually drill rod, ( oil hardening tool steel)
is easy to get hard, and would more than likely not require tempering.

I am sure you must have been able to get the tool hard,
because it sounds like you got the breech end cut.

I am curious if it was not cutting properly,
if it was not just a cutting edge geometry
issue?

On the first tries, was the cutting edges breaking down?
I can tell allot by looking at a tool after it is used
as to why it is not cuting properly.

Like I said I would just like to help here.

I was getting a 'soft' cutter and so it would fold over when used.

The problem I think was the reamers were not hot enough nor heated long enough to affect a good treatment.

To get the form I turned it and polished the shape I wanted. Setup in mill dividing head and milled in four flutes. Then slipped it 10 degrees or so and cut a relief leaving a land about 0.050" wide. Hand filed that relief back to leave a margin of say 0.015" and then hardened it. Stoned the cutting lips after hardening but the first attempts pushed over whereas the last attempt held up fine.

I guess I need practice getting it hot enough.

A file of that would help me know what direction to go for better cutters. Yes I would like to get that from you.

Walter...

It sounds to me like you know
how to cut a reamer and finish it.

It does sound like a lack of heat problem to me.

If you have some small scrap pieces of
oil hardening drill rod available, experiment
with it a little.
I have found that it needs to be hot enough
to where the surface just starts to form a scale,
it almost looks like a blister forming
on the surface.

I have heard people use the term "cherry red"
this is not hot enough. It needs to start
going from a red to yellow. And then quenches in oil.
This is for oil hardening steels, air hardening steels
need to go from yellow to almost white.
I have oil quenched air hardening steels,(S-7) I found
that they tend to harden better.

Just heat it up slowly, moving the flame
off of it so that you can see what the surface is doing.

Concentrate the heat more on the cutting edges,
this will allow the center of the tool to not
get as hard as the cutting edges and be less likely
to be too brittle.

You obviously have the skills to cut a reamer.

Hardening is however a "try it until you get it"
kind of thing, like sharpening a twist drill
on a bench grinder. Once you see what works,
you will be succesfull 98% of the time.

hope this helps, heat treating a reamer is unfortunatly
something I cannot send a file on.
Cause it is not cut and dry, or as some would say black or white.

The best test to see if you got the steel hot enough is to touch it to a magnet. If the steel sticks, it needs to get hotter. Once the steel does not stick to the magnet it has reached the transformation point. Heat it another 50 degrees or so (another 15 - 30 seconds is probably enough time depending on your heat source)and then quench in oil. Should do the trick.