D Bit Question

[edan]

Hello,
I have a question about a D bit fixture but first a little background if I may.
I have not yet made or used a D Bit. Actually the more I check into this the more I am confused so I figured I had just better jump in and find out for myself.

I understand that a D bit is not that complicated and fairly easy to make without a fixture, but I would like to be able to reproduce as close as possible a design that works for me.
The pictures below I hope will give you a good idea of what I have in mind.

The fixture is designed to sit in a vise.
First I would (after clamping the drill rod in place) mill the bar to slightly over half with a bull endmill. This is with the fixture level.

Next I would sit the fixture on the 10 degree angle and clamp it in a vise. Then set the angle I wanted by rotating the top portion the desired amount. This should cut the angle and also undercut it for clearance.

Now the question.
For those who have made these before, does it look like I understand the general principle of making a D bit?

Please don’t be shy if I have done something stupid in my design. I have been married for 32 years and I am use to getting criticized.

Thank you.

 

[Blogwitch]

Personally, I think you are using a sledgehammer to crack a nut, and you really need to understand the concept of a d-bit.

D-bits can be one of your saviours when it comes to making not only straight holes, but all sorts of shapes.

This bit of a post of mine shows just what sort of shapes can be made and used, and with a little care, none of them require a fixture to make.

http://madmodder.net/index.php?topic=2312.0

Then follow the link on the second line down.

Cutting reliefs are usually just hand filed on the end before hardening.

Also just down a bit on this post (to be finished off very soon)

http://www.homemodelenginemachinist.com/index.php?topic=8194.msg86752#msg86752

Hope this explains things a little.


Bogs

 

[New_Guy]

the best most handiest thing to learn in the work shop is probably hand grinding drill bits hands down get yourself a black book it has a gauge and shows you the defects and problems from incorrect grinding but once you ace it you wont lose it and it will help latter when learning to grind reamers and endmills .....what you dont think it would ever be as accurate? just try it

 

[steamer]

YES ....sledge hammer for a nut is a good analogy........a big one.

Dave

 

[Omnimill]

First off, thats a nice looking jig edan!

Second, when anyone mentions "D" Bits I always think of those used for reaming as here:

http://www.homemodelenginemachinist.com/index.php?topic=5251.0

Are you thinking of D bits to cut odd shaped holes or for reaming?

Vic.

 

[edan]

Hello,

Thanks everyone who replied.

“Personally, I think you are using a sledgehammer to crack a nut, and you really need to understand the concept of a d-bit.”

This is actually funny to me because it describes how I generally approach a subject…I do have a tendency to go overboard.

Due to medical issues and the fact that I am getting older, I do not have the ability with a grinder that I once had. When I first started metalworking I could grind a split point on a 3/64 drill with no problem. The last time I tried, and this was a 3/8 drill, I could not get it centered.

I will be making a set of off size reamers for myself and a friend who has just started in metalworking. Both of us share a passion for “odd” small engines.

I think I understand the basic concept and will probably go ahead and see if this works for me. I like to have a couple of projects going at the same time in case I get tired/frustrated with one of them. This way I always have something to do in my shop.

Thank you again everyone who took time to give an opinion.