[Asfar]

I need to drill with the place very accurate. . I tried dril many ways but all methods were bit offset. so please advice me your suggestion. i have given some details about work part.

Mildsteel
Dimention: 31x16x110 mm

Need to drill D13mm

thanks.
Asfar Sri Lanka.

Attachment 335736

[ERUS]

A straight flute won't walk as much if that is the issue you're having. Its also important that the drill is ground fairly accurately. A drill that cuts on one flute is going to walk.

Attachment 335748

[Asfar]

thanks for your details. what is the name of that tool. where can i buy that?

[hanermo]

Picture tool is a reamer.You use it to finish last 0.2 mm of hole. Not to drill.

You cannot drill it accurately with common basic tools.
A drill press will walk- 0.1-0.2 mm or (much) more depending.

A mill might get you a bit better - if you use good industrial drill bits.
Carbide drills - much better. Expensive. 200-300$.
13 Mm Solid Carbide Drill | MSCDirect.com

You need to bore the hole to get it straight.
Use a boring head on a mill. You will need to do from both ends, and locate accurately.

Drill about 0.1 mm undersize.
Finish with a reamer.

Or, ..
on a lathe, its possible to bore from both ends, and the bores will be very straight.
Bore 12.9 mm, finish with reamer.
On a lathe, you could drill to 12 mm first, and then bore to get it straight.
Finish last 0.1 mm with reamer.
When the workpiece rotates, the holes stay straight by nature.

On a decent lathe, about 0.01 mm tir *and* accuracy is possible.
About 0.02 mm is easy, with experience.
0.01 mm size and straight is not easy, for such a long hole.
0.01 mm true is hard.

True means the location is accurate from both ends, and the hole is round (tir) and straight, throughout.
There are 4 different concepts.
Size, roundness, straightness, and location on both ends.

HTH or Hope This Helps.


Bore it in stages, first with very short boring bar, with only 1:3 overhang or less.
3 x 13 mm = 39 mm deep.
Then do the last 110/2x39=31 mm /2 = 15.5 mm with a longer bar.
The first bore will be better, and will guide the reamer.

It will work well, to 0.02 - 0.01 mm, on a 12x lathe.

This is a difficult job, if both ends need to be accurately located.
If only one end must be accurate in location, it is easy.

[Asfar]

brother hanermo, thanks a lot for your information and spending your short time to comment for my post. really I got few points from your comment. Actually I don't care diameter of bit because i can manage with the male part. It must be very straight. that is very important for me. According to your advice tomorrow i will try to do from both end. what machine is better for this process? Radial drilling machine or lathe machine?///

[hoecken]

If you have to make a lot of these holes then you should look at a gundrill setup.
Ray Behner on the Practical machinist Forum had a posting about a gundrilling setup he made himself.
Many machineshops have them and not for gundrilling , just for deephole drilling.

[AARONT]

Hanermo,

That is indeed a straight flute drill, NOT a reamer.