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drilling problem

M

mumtaz

Plastic
Joined
Dec 1, 2015
Hello Everyone,

I need to ask question about drilling operations which follow each other,
I have a workpiece which's length is around 250 mm. and and i need to drill from its back side but the problem is different diameter drills needs to work(dia=4,dia=5,dia=6,=dia=7,dia=8,dia=9,dia=10,dia=11,dia=12) in same center.If i start drilling operation from dia=12.After dia=10 or dia=11, i can't find enough lenth center drill for other diameters, and if i continue drilling operation without center drill.At the end i have a hole which is eccentric from center.

If i start drilling operation from small diameter(dia=4) and continue without center drill. The result doesn't change , i have a hole which is eccentric again.

So is there any advice regarding this issue or is anyone encounter this kind of process, if it is "yes" please share your experience with me.
 
Can you share the approximate diameters and their respective lengths? Maybe you can drill them all a bit undersized and then clean them up with a long em?
 
Form drill?
10" long and a weird shape, so I don't know how well it'd work. Well, 250mm is the overall length. How deep is the hole overall?

Maybe a few different form drills and a way of guiding or supporting them. Like an old school jig near the workpiece surface. Perhaps a way of piloting or supporting them with the hole from the previous drill. Perhaps a combo of form drills/ then form reamers to increase the accuracy.

What type of are machine are you using?
 
mumtaz said:
Hello Everyone,

I need to ask question about drilling operations which follow each other,
I have a workpiece which's length is around 250 mm. and and i need to drill from its back side but the problem is different diameter drills needs to work(dia=4,dia=5,dia=6,=dia=7,dia=8,dia=9,dia=10,dia=11,dia=12) in same center.If i start drilling operation from dia=12.After dia=10 or dia=11, i can't find enough lenth center drill for other diameters, and if i continue drilling operation without center drill.At the end i have a hole which is eccentric from center.

If i start drilling operation from small diameter(dia=4) and continue without center drill. The result doesn't change , i have a hole which is eccentric again.

So is there any advice regarding this issue or is anyone encounter this kind of process, if it is "yes" please share your experience with me.
Click to expand...

What I would do is spend a bunch of money and time, making damn sure the Smallest diameter is Drilling straight. 250mm isn't too long. but I would need to know what the Smallest Diameter Drill you need, to point you in the right direction to get it straight (concentric). If it's smaller than 6mm it'll get more expensive, but it's very possible.

We have no idea what Material you are working with, what Machine you are using, what Tooling you have access to, so it's just guessing for now.

R
 
mumtaz said:
Hello Everyone,

I need to ask question about drilling operations which follow each other,
I have a workpiece which's length is around 250 mm. and and i need to drill from its back side but the problem is different diameter drills needs to work(dia=4,dia=5,dia=6,=dia=7,dia=8,dia=9,dia=10,dia=11,dia=12) in same center.If i start drilling operation from dia=12.After dia=10 or dia=11, i can't find enough lenth center drill for other diameters, and if i continue drilling operation without center drill.At the end i have a hole which is eccentric from center.

If i start drilling operation from small diameter(dia=4) and continue without center drill. The result doesn't change , i have a hole which is eccentric again.

So is there any advice regarding this issue or is anyone encounter this kind of process, if it is "yes" please share your experience with me.
Click to expand...


12 to 4 mm through 10" long shaft - yeah, it will prolly walk.

Common practice for gun barrels is to start with oversize material and turn the OD between centers after the hole is in.


You could farm it out to a gun-drilling shop, and let them at least put the 4mm hole through, and then you could open it up from there? The actual gun drill and right machine will likely make a decently strait hole, so maybe you wouldn't need to turn the OD.


---------------

Think Snow Eh!
Ox
 
Ox, I didn't know that was common practice for Barrels. I do it for other stuff, but I would think Straightness of the Hole would be an issue. You know with the Bullets needing to go straight and all. :D

R
 
Doesn't mean the hole aint strait, just not 100% strait with the OD is all.

The ones that don't come out strait are used for Urban Warfare - for shooting around corners....
Just gotta index the receiver so that it's not shooting your hoof off.... :o

I don't make'm. I've modified oodles of them, but I have always been told that's how they make'm.

I'f I'm wrong - I'll just push the blame back upstream....


----------------

Think Snow Eh!
Ox
 
Yikes...I misunderstood the OP and had VMC on my mind. Can you drill undersized a bit and use a boring bar to finish? Maybe you could modify the boring bar itself to have steps in it to minimize deflection instead of having a super skinny bar 250mm long.
 
If there is any kind of quantity, I would go with some kind of custom stepped drill and do it all at once. On a lathe, alignment has to be perfect. It might be easier to hold the part stationary and use a rotating drill (machining center). Then you could turn the OD last, like Ox said.
 
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