D bit reamer form tool

[mu38&Bg#]

Has anyone had any luck with a stepped D bit reamer? I make a turned aluminum part with a flat bottom hole. The hole is fairly deep so a boring bar is tricky. 5/16" diameter and up to 1.5" deep. For the sake of simplicity, I had been using a 5/16" endmill. Sometimes it worked nicely and other times chatter made for a poor finish on this bore I'm trying to seal with an O-ring. There is a slightly larger diameter (T letter drill) counter bore on this hole that equals half the depth. I was thinking that I could make a D bit reamer with both features and sink it into a drilled 1/4" hole to remove much of the material.

I was messing around with a D bit reamer made from a 1/4" HSS drill blank and was pretty surprised by the cutting ability and smoothness of the resulting bore. I've never tried them before. It's not exactly a high speed procedure, but I'm sure the way I make it now is slow.

I also hadn't had much of a need to turn drill rod before, but since I was experimenting I gave it a go. C6 brazed carbide tools did a wonderful job, I was quite surprised.

 

[steamer]

Yup!

http://www.homemodelenginemachinist.com/index.php?topic=3951.45

Used one to make the bore for the carb on my engine.

Dave

 

[mu38&Bg#]

Doh, Dave I did see your photos last week in the thread. It must have taken a while to creep into my head and discover it on my own :

This is a definite go. I have to get a couple pieces of drill rod and try it out.

 

[steamer]

Dieselpilot,

I'll get a shot of the far side of that tool.....there was some creative relief grinding on it...freehand of course.

You'll want to see that.....

Heat treating is pretty straight forward though....

Dave

 

[steamer]

Hi Dieselpilot,

some photo's of the cutter....

The front of the tool was not cut back as it is a pilot for an existing hole...honestly I could have omitted it all together, but I offered a way to center the work for the cut, and lead the initial cut of the 10mm bore

The 10mm bore with a .531 spotface was the "meat" of it

Cut the diameter back to d/2 + .005" and she will cut smooth and chatterless right to size

You'll notice the relief I put on behind the cutting edge with the corner of the grinding wheel by hand.

Don't grind off the leading edge obviously!

I did not draw the temper, but left it full hard then ground the relief. Enough heat is put in during grinding to draw the temper sufficently. Remember to slow way down with carbon steel cutters....can't go at it like HSS or carbide

Stone the flat side after hardening for a keen edge.

Dave

 

[mu38&Bg#]

Dave, Thanks for the photos. The reliefs are needed to provide clearance for feeding the tool.

I'll get some drill rod today and maybe try it over the weekend. It's finally warm around here, so I have other things I need to take care of. I want to put a chamfer at the top of the smaller hole, so we'll see what happens.

Greg

 

[mu38&Bg#]

Ah, it turns out the guy down the street didn't have stock on the drill blanks I wanted. So I wait.