D bits

Hi all.

In the Emma Victoria construction series there are several references to using a 'D' bit for making a flat bottom hole.

Is there such a thing as D bits commercially available or does this fall into the 'home made' category (I assume silver steel)

Would a milling slot cutter do the job?

Regards and happy Christmas to all.

Bill D.

Bill,

I purchased a set from Tracey Tools.

You can make your own if you want to.

Dave

Bill,

I'd be cautious about using a slot cutter. I've done it many times but the set up needs to be rigid: it works on a milling machine or from the tailstock of the lathe if the job is held in the chuck. The problem is that the milling cutter has a greater tendency to cut on the sides than a D bit so if the job isn't held properly the hole gets enlarged and everything starts to wobble. Don't even think about it in bronze, the cutter will almost certainly grab and mayhem ensues. I have learnt all this from experience

HTH

Rod

hi rod,

if you use the old fashioned slot drills (of which i seem to have quite a few) then i would disagree. they are basically 2 sided 'D' bits with straight sides.

'D' bits, pin drills. counter bore cutters etc can all easily be made out of silver steel and make the life of building the smaller locos much easier, and easily made in the home workshop and will last a life time. i dont know what i would do without mine even though ive a dore westbury mill etc. as a simple example it is much easier to make the knuckle joints of 2 parts coupling rods with a counterbore cutter. ive made a whole set of special 'D' bits for making unions of all sorts of ME sizes that you wouldnt get commercially in any event.

cheers,

julian

G'day.

A detailed technique for making accurate D-bits and slot drills that actually cut very well was published in Model Engineer 18 Feb 1977 by Rowland Harman. I tried this technique a few years ago and although a bit fiddly, the resultant tools are excellent and well worth the effort.

Regards from the land of the kangaroo

(105º today but cooling for Xmas so have a great one wherever you are)

* Danny M *

Hi Bill,

You can also find description on how to make D-bits on the web:

** Link**

**Link**

They are not difficult to make and work well.

Thor

Slot drills are designed to cut on the side so they will tend to cut oversize. If you need an accurate size use a D-bit. They are easy to make from silver steel. Many people recommend making the cutting part D/2 but then they can still cut oversize. Make it a few thou over half diameter and it should only cut on the end and give an accurate size hole.

Russell.

Edited By Russell Eberhardt on 21/12/2013 09:48:42