Help me make a D-reamer

Ian

Notorious member
New territory for this machining newb, need some help from the experienced please. I want to make some fixed-pilot D-reamers for altering H-dies into nose-first sizing dies, maybe alter the shape a little to fit various throats. Need a material that I can turn and polish with my mini-lathe, grind the D and the relief, sharpen, harden, and possibly draw.

What material should I buy for the reamers?
Any tips on hardening/tempering temperatures?
Any tips in general to get me off on the right foot?
 

KeithB

Resident Half Fast Machinist
1. O1 or A2 or 4140 in that order of preference.

2. Harden at 1450 to 1550 F for any of the above. If you don't have a high temp furnace and plan to use a torch then use a slightly carburizing flame. This limits surface oxidation and decarburization. Keep a magnet handy and don't quench until the magnet won't stick to the part. As soon as the part loses any magnetic attraction then quench. Use oil for O1 or 4140 and air for A2.

As soon a spit won't sizzle you need to temper. You can use a regular oven for this, I have many times. For a cutting tool where hardness is more important than toughness temper at 400-500 F for about a half hour. I usually just shut the oven off after 20-30 min and let it slow cool to room temp.

After that you can hone, polish, etc. to your heart's content.

I would probably go with O1, it has a lot to recommend.
 

Brad

Benevolent Overlord and site owner
Staff member
Any suggestions for cutting angles, etc?
Is a D remedy essentially a round part with half milled away then the backside ground some for clearance?
 

Brad

Benevolent Overlord and site owner
Staff member
He also is a hell of a backyard machinist with unbelievable stick-to-it-ness and desire.
If Ian can find a way to make it happen he will. Make do is his middle name.
 

Ian

Notorious member
Thanks Keith! Quick 'n' dirty with all the info I need.

Brad, that's how I understand it. The relief part is what looks to be the tough part for me, will have to use Dykem and grind away as much as I want for depth of cut, I figure at least .005".
 

Ian

Notorious member
If I had a rotating tailstock chuck with four independent jaws, I could offset the reamer at the correct point and cut the relief on the back side to just almost meet the cutting edge, then finish with a stone.... but I don't.
 

smokeywolf

Well-Known Member
Ian, try to use/acquire an oil with a very high flash point for your quenching.

Steer clear of motor oils and ATF, as they have additives that when heated, you might not want to breathe. If you don't want to bite the bullet and spend some do-re-mi on quenching oil, canola or mineral oil will do.
 

KeithB

Resident Half Fast Machinist
That's probably the safest choice for a lot of reasons. Water hardening steel is fine except it tends to crack more frequently when quenching. Air hardening is fine but if you have to anneal any of it later (forgot to tap a hole or cut a feature?) good luck. 4140 won't last long cutting harder steels but is a fine material for one-off tools to cut aluminum.

The secret to heat treating steel is to be sure it has turned into 100% austenite, that is the stable phase at 1400+F, and using a magnet will guarantee that since austenite is nonmagnetic. You want to end up with tempered martensite, and the proper quench followed by oven tempering will do that IF you start with 100% austenite.

Do you have a regular four jaw chuck? All the cutting tools I have made have been cantilever type, supported only on one end by the spindle or tool holder, i.e. mold cherries, form tools, etc. I have thought that making a D reamer would be sort of like making a crank, with the center of the pilot offset from the center of the reamer form. With a four jaw and dial indicator it is easy to cut the reamer form and then offset the part the desired amount to cut the pilot. When you mill/file/grind away the excess to make the D shape you index the part to be sure you are cutting the material away from the correct side. The offset between the pilot and the reamer form gives the clearance behind the cutting edge. I hope my crude quick drawing gives a little clearer explanation. The final D shape is straight line across the center of the pilot and the curved line toward the bottom, more than half the reamer form is cut away.

If the tool is so long you need to use your tailstock then you may need to drill one center hole, cut the reamer form, and then offset the piece and drill a second center hole to cut the pilot.

A crude drawing but its the best I can do right now.

D-reamer_xsect.jpg
 

Ian

Notorious member
Brilliant solution, Keith, perfectly clear and I can work that out easily. Since this is a piloted tool and tolerances have to be as near zero as I can manage, support on both ends seems the best way. Cantilevering should work if I can keep the pilot short and hand-finish it to final size, I'll keep that in mind too for shorter reamers that don't need a long, true, parallel pilot.
 

KeithB

Resident Half Fast Machinist
If your centers will be very close together on the end you may have to make it a little long and drill one center, cut the part, and then face the end off to length and drill the 2nd pilot hole. Also will have to cut a little rake clearance on cutting edge(s) on front of tool but you probably already figured that out.
 
  • Like
Reactions: Ian

Intheshop

Banned
O1... heated with the gas axe,which is stuck in a vise.The part is in a drill motor turning in the flame.Use a magnet and I've been using canola oil from the kitchen. They're pretty easy to make.
 

JSH

Active Member
Ian, you get this done throw a picture up. I am trying to wrap my mind around this.
Jeff
 

Pistolero

Well-Known Member
Hmmmm. I basically THOUGHT I understood what a D-reamer was, but now with Keith's
explanation I am totally confused. I have absolutely no doubt that it is because I am missing
some key, super basic piece of the puzzle, in my ignorance.

I'll just sit and watch and learn.

Bill
 

Ian

Notorious member
Drill rods arrived this morning, first project will be to make a uniforming/sizing H-die and ejector punch for my MX3 .22 bullets, so I need a reamer for that. I also need a two-diameter .22 sizing die for my 75-grain silhouette bullets to ensure reliable feeding when powder-coated. I'm pretty sure one die can be made to work for both if a nose punch is made for each bullet.

Basically I'm looking for a .2265" parallel section, a 1.5° per side taper, and a .218" portion the rest of the way through with a .217" or so ejector rod. The silhouette bullets won't touch the taper, I'll just set the depth so the leading edge of the front band kisses the start of the taper.

The reamer will have a pilot that rides the ejector bore and D-shank that includes the taper and body diameter. I'll relieve behind the pilot slightly and bring the cutting edge straight in to slightly under pilot diameter. For this small reamer, the plan is to relieve the back side by hand and also relieve the cutting edge with a hand stone. The tricky part will be getting a sharp edge with correct relief but without changing the reamer form.
 

Pistolero

Well-Known Member
From what I have read, if you feed slowly no relief is needed, even though that sounds
odd.
OK, I understand this, sound straightforward, but didn't grasp the offset centers in Keith's recommendation.

Again, I have no doubt that Keith is right..... but I am still baffled as to why there would need to be two
centers. Seems like the pilot and reamer and reamer shank are all on the same centerline.
 

KeithB

Resident Half Fast Machinist
My suggestion is merely a way to create a little radial relief at the cutting edge instead of trying to hand file/grind relief. I have read about 0 degree relief D reamer tools and yes they can cut, sloooowly. I have ground planer tools (metal planer) with 0 degree relief behind the cutting edge. That gave the max strength when cutting hard materials, and the actual tool flex provided the little relief needed. But you couldn't take big bites.

I looked at every reamer and cutter and form tool in the shop and they all have some relief behind the cutting edge. And when they get dull and wipe out that relief they stop cutting well and stick/jump into a cut. I have a .257 Roberts AI multi-flute piloted reamer that I used when rebarreling a Turkish Mauser. It has relief behind the cutting edge of all the flutes.

Lets say you want 3 degrees relief behind the cutting edge. Look at the drawing below to see how to lay that out and what to cut away. By using two centers you end up raising the cutting edge up to center with your relief already included. This doesn't help the face/front of the cutting edge.

Lets see what Ian comes up with and how it works, he's a very talented person with lots of original ideas.

(Sorry, photo is a little twisted, as is the photographer at times)
Dreamer2.jpg