K&M chamfer tool use?

[JustinP]

Hey guys

Recently bought a K&M case mouth chamfer tool. Either it didn't come with destructions or I've lost them in a recent house move :,

Anyway, I basically set it by inserting the tool into a case to the point where the case mouth meets the chamfer blades and then setting the stop to touch the top of the case mouth.

I then tried chamfering a couple of cases as a test and I ended up with a deep but very shallow chamfer cut. Looking at it through a loupe, I can't even tell if I've managed to put a tapered cut in.

Does this sound about right? I'm used to using a 45deg forster chamfer tool by hand, where I can easily see the slight cut - so that's all I have to go on for comparison purposed.

Any users of this tool that want to chime in, I'd be appreciative.

Thanks, Justin

 

[Winchester69]

...a deep but very shallow....

 

[Forum Boss]

Justin,

The K&M deep-angle cutter, IMHO, is tricky to use for the reasons you've described. The three prongs or fingers that are supposed to stabilize the tool on the case mouth usually rock a little bit.

It's VERY easy to remove a LOT of brass if you just set the tool a bit long. Those blades are very sharp. I suggest you experiment with some old, not-match-grade cases while you experiment with the cutting depth.

Personally I went back to a 45-degree chamferer because it seemed to do the job and I didn't run the risk of ruining case necks by cutting too much.

 

[nonliberal]

I agree with the Moderator on being careful with setup and taking a little time to get familiar with the tool. However, I have been looking really closely and experimenting with bullet run-out lately and found less loaded round run-out when using the K&M over the regular hand held 45-degree chamferer.

I used 20 virgin pieces of lapua brass that I sized and neck turned and purposely didn't chamfer, then I fire formed the brass and measured brass run-out to be within .0005. Then I neck sized all the brass with the same die, and grabbed 10 of the cases at random and used the K&M tool, the other 10 were done on a basic 45 degree tool,I believe its a Forrester).

Doing every step the same way except the chamfer tool used and all brass and bullets,Berger 108BT) were taken at random.

I took readings of every loaded round at the same place on the bullet and averaged each side. The average of the K&M was .002 and the average with the 45-degree was .004.

I'm not going to pretend to know the reason for this, I guess there could be many possibilities but since it convinced me and makes me feel good, I will use it. Results may vary but those were mine.


PS. when shooting all the rounds I didnt see a noticable diference on paper between the groups.

 

[GermanS1]

I've always used the K&M as a second-step deburring tool. First I use a 45 degree tool, then chase it with the K&M which takes off the burr,yes) that the 45 degree tool leaves. Go easy with the K&M, look at the results of a two-step process with a magnifier and I think you'll like what you see.

 

[flatlander]

The latest version of the K&M chamfering tool includes a longer stem with a very small pilot that indexes the tool off the case's flash hole. This is intended to keep the tool aligned with the case's longitudinal axis, and if it works as intended, should insure that the tool is held square with the case, thus avoiding neck damage caused when the cutter is off-axis. Of course, if your cases have off-center flashholes, you're screwed.

I've owned & used one of the original K&M tools for over 10yrs., and have no doubt that cases chamfered with it will do far less damage to bullets as they're seated than a case chamfered with the old standard 45* deburring tools. However, it's always been kind of a bugger to use, even when held in the 3-jaw chuck of the old Atlas lathe I use for most of my case prep work. If the case isn't aligned very closely to the axis of the cutter, you wind up shaving brass from deeper inside the neck, not just out at the mouth. The new tool with the pilot stem should address this problem.

 

[nonliberal]

I use the newer style with the pilot that goes through the flash hole. I was thinking that it keeping me straight was part of the reason for less run out. Im a little off center anyway so anything that can help me out with that is a good thing.

 

[Bullydog]

...a deep but very shallow....

I think what he means is that the cut extends far down the neck,towards the shoulder) but doesn't take off much material- i.e. the case neck walls don't get thinned down that much.

 

[Winchester69]

Thanks for the interpretation.