Making D Bit Reamers

I make them by FIRST hardening a piece of drill rod and drawing it to a light brown color. THEN I grind a long angle of about 30º on the end of it. I grind after hardening because the hardening process can,and usually will warp the reamer a bit,because there is a different amount of surface area on either side of an already ground reamer. The reamer is just fed into the hole,and will cut very cleanly and nicely. Don't try REVERSING the reamer when withdrawing it. This can jerk a chunk out of the angled cutting edge. You don't reverse modern reamers either,for that matter. Keep them rotating in the same direction as before while withdrawing them.
 
Hi George. Thanks for the clear description. So, this is what we are looking for? Sorry about the poor graphics, but I am not too familiar with this drawing program.

ream.png
 
You should have at least 5 degrees relief on the cutting edges, your picture shows no relief at all
 
Actually,the reamer as shown will cut just fine. I have made and used them. I grind mine all the way down to a sharp edge at the front. Bt,the one,as drawn,will work just fine.

I have gotten a lot of info that has been useful,from studying 19th. C. books on machining. Back when I had little money,home made reamers and D bits were very useful. And still can be.
 
shooter123456 said:
I have a spin index for my mill so I may try one with multiple flutes. Is there anywhere I can find the math for the angles, flute sizes, and the like? For the moment, I want to ream a .250" hole 1.5" deep. But if I can figure it all out, I would like to make a set of reamers to do the standard holes I do a lot such as .156, .375, .1875, etc. Tolerances aren't critical here, +- .003 would be fantastic. Hopefully just a straighter, rounder, better finished hole than I can do with a standard twist drill. If I can learn more about machining in the process, thats a bonus.
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There is info on reamer making in machinist handbook that will help with deciding what amount to mill into the stock to leave a certain center mass(size). Other than that just mill .001 or .002 less that center and then grind a secondary angle till only .010 or so is left of the primary angle. I don't think I actually ground a primary angle the outside dia of the stock was that edge and the secondary angle ground to leave the .010-.020 . So the secondary angle is just the relief.
Like everything else there is much more to it...Cutting edges offset to make it chater less etc. etc.
The reamers you list are standard size and inexpensive. the amount of work to make a standard size reamer is not worth it.
I got the reamer set to 1/2 and the over under set from CDOC and use the heck out of them.
Check out this dovetail cutter this guy makes and how he makes it.
 
Rgray
How do those reamers from CDCO work? Do they size accurately and do they leave a good finish? Also, do they last well? I've been considering buying a set but did not know what to expect from the cheap set from CDCO.
Thanks.
-Randall
 
Randall Marx said:
How do those reamers from CDCO work?
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I've had good luck with them. They cut good and to size. I've had them for a couple of years and haven't had opportunity to use all of them but have used about half of them. I damaged a small one somehow (my fault) and cut it back a 1/4 inch and still use it.
 
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