Drill Geometry

I hope I used the correct word Geometry. I simply want to know the dimensions of a drill. I have a Darex Drill Grinder M5. Purchased new with all the drill chucks including the one needed to grind drills over 3/4" (up to 1-1/4" I think). Managed to get 2 more from HGR quite cheap but in surprisingly great shape. One had the stand missing but I was able to find it on ebay, a guy was parting one out. It also has the top of the right side holder missing (lower part is complete) that's used for split pointing and other point modifications. I didn't care since I want to make one to do point modification on drills larger than 3/4", it's not possible with what is supplied for grinding the large drills. The other is complete.
Also missing was the drill chucks for both grinders. I really don't need them having all those available except the left hand drill type. Seen them on ebay but the price was ridiculous.
However I want to make a few chucks and thinking about using 2 small ER Type or similar collets. I'm hoping to find a type that has a smaller OD than the ER-25 for a 5/8" drill. I have a customer that I grind a few drills for so I want very accurate holder for only a few sizes. I have ground 0° rake on drills above 3/4" using my surface grinder using a 5C 7/8" collet however I've found the 5C collets don't hold drills on the flute side well. To get the drill to align properly I made a bushing that was screwed into the collet stop threads. Worked enough to grind the rake.
I know the diameter is tapered, large side nearest the point. Where does the taper end so that the shank is straight?

"Where does the taper end so that the shank is straight?"

Your micrometer can answer that question for whatever bit it is you mean. I suspect the answer will depend upon the bit size, type and manufacturer.

Larry

Does that mean there is no standard? I have been grinding 100's of drills made by Michigan Drill, I have to look back but it seems they purchased another drill company, drills came from them with another name might have been Federal. From what I understand they are being made in Florida. I have received a batch of drills all in Michigan labeled cardboard tubes that were different, seems there were 4 different grinds. They were completed (50 total 5/8" drills) Next batch was again different but all seemed to be the same. I do have 5 to play with, I want to check dimensions and looking for a way to hold the shank to insure concentricity and straightness. Maybe boring soft chuck jaws?

Harig used to sell a Steptool grinding fixture that had 5 C collets with 4 slits instead of 3 and perhaps longer bearing surfaces to grip the drills more accurately than the regular ones .
Hardinge probably made the collets for them and if I remember Hardinge called them 5C -4ST or something similar.
harig Step Tool drill grinding fixtures - Google Search
I have an older version of the machine shown here with the collets (scroll Down ) that are double ended and have four splits up to 3/4" dia. to grip the drills accurately over the margins.
https://www.novatechonline.com/products/mega/MEGA_blue_USA.pdf
I have a feeling that one collet might be quite costly though .
I can maybe post some pictures and measurements later.
Jim

Here is a very basic drill information site.

michiganbuck said:

Here is a very basic drill information site.

Click to expand...

I tried clicking on what looks like a small square tag but get nothing. Can you post the address?
Quite some time ago I had a Black Diamond Drill Grinder, it had 5C collet but can't remember if it was special. Also provided were bushings to reduce the 5C collet size to all the drill sizes. If my memory is correct larger sizes used 1 or 3/4" Collet and as drill size got smaller collet size was also smaller.

http://www.nachiamerica.com/content/training/Basics of Drilling.pdf

Drills taper smaller away from the point perhaps .0002 per inch (or more) so they don't stick in the hole often back to the end of the flute. Reamers taper back but less per inch than drills.

Drills, reamers, and all end feeding cutting tools nee 10 to 15* primary clearance..much because the feed spiral take away some clearance. A 5* primary and a fast feed rate might act like just a spin grind with no clearance at all and so would not even cut at all.

It is not uncommon for a drill to make a slightly out-of-round hole.