A boring question

[robin]

Yes, both tedious and about boring...

I need to bore a hole of 4.0-4.5mm but the tool needs to fit through a hole of 2.9mm. Can't see a way round this at the moment. Is this possible on my Myford Super 7 or am I being unrealistic?

I'm new to lathework so don't blind me with science!!

[jackrae]

Do you mean you have a job - in the chuck - which has a 2.9mm hole in it. On the backside of which you need to produce a counter bore.

What do you mean 4.0mm - 4.5mm. Is this dimension diameter or depth. Why the "loose" dimension.

If it's not an obvious question why can't you bore from the other side - or are you trying to make a recess part way along a deep 2.9mm hole.

By now you will gather that what you see and think is not always obvious to convey in words - the engineers perpetual problem. Hence the old saying "a picture is worth a thousand words".

Failing a picture, a description of the actual task in hand may elicit various ideas from readers.

Oh, and what's the material

good luck
jack

[Tel]

I interpreted it that way Jack - a 2.9 hole with an expanded section somewhere along its length, certainly doable but, as you say - more details needed.

[robin]

Sorry, should have been a little clearer

Let's hope this works:


Marvellous. The 4.5mm dimension is not that critical, which is why I said it could be 4 to 4.5mm. The whole assembly is 1/4" diameter (6.4mm) and I'd be holding it in a collet probably.

As you can see, there is a hole either end of the 4.5mm bore (although the hole to the left may be only 2mm by the time the piece is finally designed).

Whole piece is in stainless steel - probably A2 (although again, not critical - any free machining grade will do)

[greasemonkey]

Hi Robin
How about boring it out to 4.5mm and then pressing a sleeve in to reduce the bore to 2.9mm where necessary

Andy

[jackrae]

Robin

Forget your boring problem
Just please advise how you managed to get a sketch onto the system
ie instruction for dummies please
jack

[robin]

What tolerances would I need to make the two parts for in order to stop them falling apart (or would I use some glue as well)? The reason for the 2.9mm hole is to tap it for an M3.5 thread. You've set me thinking, though - I could press the left hand bit with the 2mm (or smaller) hole in - that might work.

[jackrae]

If you're not operating at high temperatures >100C then the usual superglue type product (Loctite) will suffice with a clearance fit (0.001" or there abouts)
However if steam or whatever is involved then a press fit is required.
Alternatively you could leave the left hand bush/hole until the last operation, having bored the 4mm recess in the body you then silver solder in a blank disk and finally drill the 2mm hole.
Half the fun of doing a job is spending countless hours of thought on working out how to do a five minute complex operation.
Out of curiousity, what is it you are making - or should we open up a "guess-the-job" quiz
regards
jack

[greasemonkey]

Hi Robin
As Jack has said Loctite would do the trick at low temperature or silver solder at high temp. Interference press fits are usually truned at 1 thou per inch of diameter. For example if you were to make a steel tyre for a locomotive and the wheel was six inches diameter then the inside diameter of the tyre would need to be 6 thou smaller or 5.994 inches.
You would need to work the sizes out for your aplication but if you get it wrong and the diffrence is to large, then the item you are squeezing in acts like a punch.
regards

Andy

[steammadman]

Can't see a problem!,make the whole thing up in two peicies, then as already suggested either loctite it , or press fit it.

[steammadman]

Yes guy's i've turned up again, got grounded by the domestic director, had to do some painting. So remember when you make a good job of painting your model DON'T SHOW THE WIFE.

[robin]

Thanks for the replies, guys. Can't really say what I'm making, although:
a) You're welcome to guess
b) It's nothing to do with steam

As for putting sketches up here, I've got some free webspace with my ISP. I just found the address of the picture that I uploaded there and bracketed it with [/img]

I might press fit it, but it might be subject to some vibration so perhaps a dab of Loctite might be in order

[greasemonkey]

Hi Robin
Remember that Loctite require a small clearance of about 1 thou to work! The ideal way is to make some small groves for it.

Andy

[Tel]

Hmmmmmm.......... I'm gonna guess - SOME SORT OF BURNER NOZZLE?

[robin]

Wrong!! High temperature not involved... guess again

[Tim Bayliss]

Let's see what clues we have!
It's stainless so it has either to be corrosion/erosion resistant, easy to clean or look pretty. Probably a combination.
It has a chamber in it. This can only be for liquids or gasses to produce a pressure drop and/or create turbulance or disrupt a flow.
As it doesn't involve heat I'd quess it's something like a spray paint nozzle.
For ease of machining I'd make it out of 303 grade.
Regards,
Tim

[Tel]

As it doesn't involve heat I'd quess it's something like a spray paint nozzle

Aw shoot! That was gonna be my next guess

[steammadman]

Come on Robin , put us all out of our misery!!!!
we're all inquisitive buggers you know

[robin]

It's not a nozzle... no fluids involved.

It's a new tip design for a fencing foil

[donofnelson]

Hi Robin, well that answer has shut us up, New tip for a fencing foil, sound energetic to me.
The fencing that is.
If my past experiance with these group members on a previouse board is anything to go by, you will find them a great bunch and extremly helpful.