Making D Bit Reamers

Do I have a setting wrong? for the pics
 
I think I fixed the pics. Let me know.
 
HERE IS THE STRAIGHT DOPE: YOU MUST MAKE A HOLE the SAME SIZE as the D bit to enter before trying to use it,or indeed,it WILL skip around. And probably never get around to drilling the hole. Make the entry hole depth at least the same depth as the diameter of the D bit.

I always made this entry hole by single point boring in the lathe. I wanted the entry hole to be EXACTLY the same diameter as the D bit. Otherwise,I'd be inviting the D bit to take an off angle right at the get-go.

Best get rid of that angular cutting edge you put on the outside diameter of your D bit. It is not necessary,and might cause problems. Your front edge angles are o.k.,though I suggest that you give the front cutting edge a bit more clearance angle. And,your D bit has hardly any length of half round to store chips while drilling. You may be extracting that bit every 1/16". Chips pile up very quickly. Even with more than 1" of half round length,I was extracting my bit frequently. Can't recall how deep it would drill as it has been a few decades!!:)

I made a 9/16" D bit,and drilled the 18" length of 2 flintlock pistol barrels. The D bit exited the other end of the barrel less than .002" off center. They do drill exceedingly accurately if frequently cleared and not pushed too hard,and,of course made properly. And that was on a Jet 10x24" bench lathe! In new condition.

BY THE WAY: D bits are DRILLS,not REAMERS. You CAN make a real nice reamer,as someone mentioned,by putting an angle on the end of a hardened piece of drill rod. They work very well,and have been in use for centuries. I use about a 30º angle when I make one. DO NOT reverse the lathe when extracting this reamer from a hole. I pulled a chunk out of the cutting edge of the first one I made by doing this. But,that was nearly 50 years ago. I have gotten better!:)
 
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I didn't find it,Ericc. And,I don't understand your question or description. Sorry.

I'll clarify how I make my "D" bits. I forget where I learned how. Out of a 19th. C. book,probably. Back when they had to get along with what few tools they had,or could rig up.

BTW: They used to drill pipe stems made of amber with D bits.

Looking at the OP's D bit from the top,the slight angle towards the cutting corner is fine. From the SIDE view,I'd grind just a little more clearance. BUT NOT MUCH MORE. Maybe a degree.

I left the foremost corner square and slightly rounded it.(He has ground an angle on it. NOT NECESSARY,OR WANTED. )I just slightly rounded the leading corner with a small India stone. This was to help eliminate cut marks from inside the hole being bored. And,make sure that when you stone the leading corner,that you still have a relief angle under that rounded corner,or it will not cut.

I hope this is clear. About the slightly rounded cutting edge: This is exactly like making a lathe tool with a slightly rounded cutting edge ; It helps make the turned surface smoother. Make your D bit on the same principle.
 
george wilson said:
HERE IS THE STRAIGHT DOPE: YOU MUST MAKE A HOLE the SAME SIZE as the D bit to enter before trying to use it,or indeed,it WILL skip around. And probably never get around to drilling the hole. Make the entry hole depth at least the same depth as the diameter of the D bit.

I always made this entry hole by single point boring in the lathe. I wanted the entry hole to be EXACTLY the same diameter as the D bit. Otherwise,I'd be inviting the D bit to take an off angle right at the get-go.

Best get rid of that angular cutting edge you put on the outside diameter of your D bit. It is not necessary,and might cause problems. Your front edge angles are o.k.,though I suggest that you give the front cutting edge a bit more clearance angle. And,your D bit has hardly any length of half round to store chips while drilling. You may be extracting that bit every 1/16". Chips pile up very quickly. Even with more than 1" of half round length,I was extracting my bit frequently. Can't recall how deep it would drill as it has been a few decades!!:)

I made a 9/16" D bit,and drilled the 18" length of 2 flintlock pistol barrels. The D bit exited the other end of the barrel less than .002" off center. They do drill exceedingly accurately if frequently cleared and not pushed too hard,and,of course made properly. And that was on a Jet 10x24" bench lathe! In new condition.

BY THE WAY: D bits are DRILLS,not REAMERS. You CAN make a real nice reamer,as someone mentioned,by putting an angle on the end of a hardened piece of drill rod. They work very well,and have been in use for centuries. I use about a 30º angle when I make one. DO NOT reverse the lathe when extracting this reamer from a hole. I pulled a chunk out of the cutting edge of the first one I made by doing this. But,that was nearly 50 years ago. I have gotten better!:)
Click to expand...

This gives me a lot of questions.

1. When working on the mill, is there a good way to make the starting hole for the d bit to enter?

2. When you say it has "hardly any length of half round to store chips" are you referring to the cut made on the shank side of the cutting edge?

3. What makes them a drill bit vs a reamer? Im not saying you are wrong, im just not well versed as to why.

4. Where would that angle be cut to make a reamer out of drill rod?

Thank you for all the info, I have already learned a lot.
 
rgray said:
Ok. I'll attempt photos. Haven't put a photo on hear since the site switched platforms. Also my trusty old digital camera died so this is a first for my to use a phone camera to get an image on the computer.

I'll attempt to insert a pic and write the description under:
View media item 955463 drills. Bottom is a commercial gun drill. The carbide is chipped but you can see the shape. Middle one is a D-reamer I made. The cutting edge on the front extends past center. it's made from 5/16 0-1 and the shank is not relieved(mistake). The top one is .375 with a 22 cal pilot that was made to follow the bore in a 22 pistol barrel. It's 0-1 and has the shank relieved.

View media item 95547Side view of all 3. Of note is the relief under the cutting edge of the one in the middle. I made that reamer to finish the unreachable center portion of a 22 cal barrel that was to long for the purchased barrel lining drill to reach from both ends. It is 17 inch and the barrel lining drill is 14. It only needed to enlarge a couple of inches of barrel and it worked even though I did not relieve the shank.

View media item 95548Back side and you can see that the cutting edge is now at the top and that it leads all other surfaces. The top one is .375 with the remaining shank turned down to .360. I didn't relieve the underside of the cutting edge. It is more a drill than reamer.

View media item 95549This is the reamer I made to finish the .375 drilled hole to .380 for the liner. It's 12 1/2 inches long so will do most pistol barrels. More difficult to make than the others as you must start with larger stock and reduce to the size for the cutting edge and reduce the shaft even smaller. Made it on the mill with a spin index and made the mistake of not supporting the end so you can see the flute is wider at the end where it flexed away from the end mill Didn't seem to bother it much diameter was cut first of course. Not sure if any of this is helpful. Other than the commercial gun drill these are basically roughing tools as all they must do is make the hole large enough for the liner that gets either Loctite, solider, or fiberglassed in place.
Not sure what kind of hole or tolerance your working for but I have heard that a simple angled cut on round tool steel that is then hardened makes a nice finish as a reamer. I have yet to try that. I believe it needs to be close to hole size.
Click to expand...

Thats a lot of info, I really appreciate that.

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.
 
Shooter: Answers: #1- D bits are really designed for use in lathes.

#2- The longer the half round portion of the D bit,the more room for chips to be stored before you must withdraw the bit to empty it.

#3.- Reamers enlarge holes. Drills do not. They just drill the hole. D bits just drill the hole also. Then,a reamer might be used to enlarge the hole.

#4.- I don't understand your question. Please re word it.
 
george wilson said:
...

BY THE WAY: D bits are DRILLS,not REAMERS. You CAN make a real nice reamer,as someone mentioned,by putting an angle on the end of a hardened piece of drill rod. They work very well,and have been in use for centuries. I use about a 30º angle when I make one. DO NOT reverse the lathe when extracting this reamer from a hole. I pulled a chunk out of the cutting edge of the first one I made by doing this. But,that was nearly 50 years ago. I have gotten better!:)
Click to expand...

Hi George. For some odd reason, the quote feature gave me the wrong text. I noticed that it pointed to some other website.

I was asking about the 30 degree angle you referred to for the reamer. I was wondering if this meant a 30 degree angled point at the tip of the (half-section) bar.
 
george wilson said:
Shooter: Answers: #1- D bits are really designed for use in lathes.

#2- The longer the half round portion of the D bit,the more room for chips to be stored before you must withdraw the bit to empty it.

#3.- Reamers enlarge holes. Drills do not. They just drill the hole. D bits just drill the hole also. Then,a reamer might be used to enlarge the hole.

#4.- I don't understand your question. Please re word it.
Click to expand...

Thanks for the info.

Regarding question 4, you said "You CAN make a real nice reamer,as someone mentioned,by putting an angle on the end of a hardened piece of drill rod. They work very well,and have been in use for centuries. I use about a 30º angle when I make one." I was asking for clarification on how that reamer would be made or where I can find more info.
 
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