[AMCjeepCJ]

I know it's for the boring tool.

lol, sorry, I knew you knew, I was still wound up when I wrote it... I kind of wonder why I even care but it bugs me he keeps insinuating everyone is a liar because he can't do what we can... lol and we can do it on crappy ass equipment if need be~

[dapoling]

How familiar are you with using near zero clearance bushing with oil or grease in them? You can get a virtual 0.000" clearance with the lube included but then again you're talk of "slip fits" makes you the expert here... Do you have any experience with making a bushing actually undersized by a few tenths and basically pushing the larger diameter through the hole thereby creating a slow steady feed rate in the negative Z direction?? Yeah, it's only good for one part but it works great... I do not know if Geof did that or not but I do know first hand how well it works...

Let's just be straight up... Answer this with a yes or no and I'll drop it...

Is Geof lying about making that hole the way he did and to the tolerances he specified??

AMC you really believe this don't you.
The idea you are talking about of making a machining a bushing underside by a few tenths (known as an interference fit) using this there would be no room for lubrication and with the spinning of the tool into this would generate heat increasing the tool size faster then the the bushing being mounted in the table thus binding and stopping the tool from rotating.
And yet you think you can control the rate of decent to a level of accuracy to allow for +/-.001 hole.

If one was to make a busing with in .0002 larger then the tool size and lubed and with oil grooves this would provide some resistance on the z travel and still you have to contend with the cutting forces of the tool and the rigidity of the equipment you are using.

I know you keep looking for that mythical land that you can beat the laws of science but you're not there yet.
You make outrageous statements and expect others to believe!

You already know my position on the tolerance which I have stated clearly before, and you know what Geof has claimed, get over these school girl games and deal with facts.

[dapoling]

lol, sorry, I knew you knew, I was still wound up when I wrote it... I kind of wonder why I even care but it bugs me he keeps insinuating everyone is a liar because he can't do what we can... lol and we can do it on crappy ass equipment if need be~

A typical statement by those uninformed, I bet you can drill a hole smaller then the drill size being used.

[dapoling]

Man don't you guys have jobs, I am retired whats your excuse lol

[AMCjeepCJ]

I quit, you win......but just so you know, it is possible for a common twist drill to drill an undersized hole in metal... I'm looking for the technical write up on it but until I find it, let's just chalk it up to fantasy...


Until then, I just wrote a poem for you...using your zone name:


Damn..........I'm super-duper smart,
And Geof, you didn't build those parts!
Please tell me I'm the best,
Only ignore that I'm a pest...
Lies are what I find
In the posts you leave behind
Now bow before my throne,
God...........why am I alone??

L8R T8R

[AMCjeepCJ]

Man don't you guys have jobs, I am retired whats your excuse lol

We own the companies and I'm kind of semi-retired at age 31~

[dapoling]

You are a sad child aren't you? lol

I have heard many claim that they can drill a hole smaller then a drill they are using but when confronted to prove it they are unable to and don't know why?

This will happen while drilling in Bronze if you do not deliberately lengthen one flute to have it drill oversize the drill will seize up before you get very deep do the material.
This is the only material that I have found this to occur in thus far.

[Geof]

I quit, you win......but just so you know, it is possible for a common twist drill to drill an undersized hole in metal... I'm looking for the technical write up on it but until I find it, let's just chalk it up to fantasy...


Until then, I just wrote a poem for you...using your zone name:


Damn..........I'm super-duper smart,
And Geof, you didn't build those parts!
Please tell me I'm the best,
Only ignore that I'm a pest...
Lies are what I find
In the posts you leave behind
Now bow before my throne,
God...........why am I alone??

L8R T8R

Very good!!!!!!!!!!

Although nit-picky me is going to pick you up on something. Your drill doing an hole under the drill size: Is it a round hole or is it what I have seen called a constant diameter hole? I have seen these, I have done these: They are kinda multi-lobed holes and one cutting edge of the drill kinda goes out into a lobe so the opposite cutting edge is cutting below the drills nominal diameter; the drill sort of wobbles its way down the hole. But because the drill has a helix the lobes are not parallel withn the axis of the hole they follow the helix. The net result is that, provided you are not dealing with a big drill, the wobbles are very small and not really noticeable among the rought surface normally left by a drill so the drill appears to have drilled an undersize hole.

And how come I claim to have seen and done this? I made a fixture once that was intended to clamp some 5/16 material in a hole about 1-1/2" long. The two halves were faced nicely and tightly bolted together and the hole dilled carefully down the joint line; first using a 17/64" pilot hole. The 5/16" hole came out 'undersize' and when the two parts where separated it was possible to see the helical pattern on the walls of the hole.

So I figured it was because I had the joint line causing some deflection, and made both halves too thick, drilled the holes under the same conditions but this time in solid metal and then faced off the excess to expose half a hole in each side.....virtually identical!!!

But the fixture worked.

I'am not retired, yet; what's my excuse for spending time here? It is fun even if some people are irritating beyond comprehension, and anyway most times my machine(s) is (are) doing something. That is the TL2 and SuperMiniMill I have in a workshop behind my house for developing prototypes and building tooling. I work here for peace and quiet and because the production machines are pretty well tied up all the time.

[Geof]

...I have heard many claim that they can drill a hole smaller then a drill they are using but when confronted to prove it they are unable to and don't know why?...

Try practically any plastic and a dull drill; but that is kinda cheating however, it serves to show how you make all encompassing claims which when considered in detail are not entirely accurate. So now in what way are you going to come b ack with a retort? Read carefully, I already admit I am cheating.

It is also possible to drill a hole undersize in aluminum. Get a dullish drill that does drill right on size, heat the aluminum up two or three hundred degrees F, be careful doing this you don't want to anneal it, drill the hole at this temperature and then let the aluminum cool, bingo, you have drilled an undersize hole.

[AMCjeepCJ]

You are a sad child aren't you? lol

I have heard many claim that they can drill a hole smaller then a drill they are using but when confronted to prove it they are unable to and don't know why?

This will happen while drilling in Bronze if you do not deliberately lengthen one flute to have it drill oversize the drill will seize up before you get very deep do the material.
This is the only material that I have found this to occur in thus far.

I've never drilled a hole smaller than the drill size as far as I know at least... See, I learned another new thing from you today I've only read a technical article on it once and it was interesting to me because it doesn't make sense how it could occur...

I thought I was going to drop it but I guess I'm like a stupid dog that keeps coming back for more...

As for the 'interference fit', thanks, the name had temporarily escaped me, I think you were assuming you have to use metal for the bushing?? I never said this but it was probably implied... I have used metal to do this before and at extremely low rpm's it works fantastic in the right situation... We used this trick quite often when my dad and I used to build plastic injection molds... This is kind of related but off topic:

Another thing you can do if you are reaming a taper is use the straight flute reamers or preferably the ones that are right hand cutting but left hand spiral and very slowly run them down an undersized sprue hole making sure the flutes DO load up with chips... It acts like a big buffer and gets rid of ALL the chatter if you're good... The only problem is if you get to excited and snap that baby off, you're screwed...

Dapoling:

Do you just like to fight or something?? I guess I really ought to drop it from here on out but we'll see... I like this website but I do not like your attitude on here though... I guess if you deflect blame again or continue to not answer questions directly, I'll have to shuttup... Someone on here called me a troll a little over two years ago and I've never quite fully recovered... My lawyer told me two days ago, if you give someone enough time, they'll feed themselves enough rope that you won't need to do anything~

I guess I get to test that theory in two arena's...

Geof, I was thinking the same thing on the plastic idea or really any material with enough spring and self lubricating properties could possibly do it~

[dapoling]

Geof if one cutting edge is lengthen then it will cut oversize do to the stress invoked by the longer cutting edge thus cutting a larger hole. This is why a drill point must be equal on the angle and length of the cutting edge.
These lobes by creating these would oversize the hole as the flutes would have to enter and exit the designed hole diameter to create what you call is lobes.

Oh your imagination when it comes to making this hole smaller, cutting off material on two pieces which you no longer have a round hole, or heating the material first would be the closest to having this happen but using a dull drill in aluminum give me a break, why not just freeze it afterwards?

The example I gave was at room temperature with coolant and yes with a round hole with out tricks but you must resort to have you have to I guess.

I can see that plastic may end up with a hole smaller then orginally put in do to temperature changes, heating of material during drill operation.

[Mitsui Seiki]

A typical statement by those uninformed, I bet you can drill a hole smaller then the drill size being used.

I shouldn't be saying this but ,yes. A hole drilled with 7mm drill measured 6.983.In Stellite.Engine mounts for Airbus.Actually several holes.

[Geof]

I shouldn't be saying this but ,yes. A hole drilled with 7mm drill measured 6.983.In Stellite.Engine mounts for Airbus.Actually several holes.

Stellite? Kinda like a hard bronze? Or should I not be saying this.

Actually a very hard bronze to be picky I think. Do they actually make the entire engine mount in Stellite?

[dapoling]

Did somebody say BRONZE ! HMMMM lol

I have not cut any of Stellite products, thanks for the info.

http://en.wikipedia.org/wiki/Stellite paints a different picture of this material.

Is this the same stuff ? http://www.stellite.com/

Nope says nothing about Bonze!

[Mitsui Seiki]

Stellite? Kinda like a hard bronze? Or should I not be saying this.

Actually a very hard bronze to be picky I think. Do they actually make the entire engine mount in Stellite?

I think it's a cobalt-chromium alloy.Pretty hard material.
The whole mount is in Stellite.We're not talking A380's,these are for the smaller planes.The material is a b***h to work with.Not that it's difficult to mill or drill,it has a lot of tension.

[BobWarfield]

Once you realize a Troll will say anything to piss you off, will change the subject constantly, will try to make it personal, and above all doesn't care what people think of them, just that you got pissed off, you realize they aren't worth the time of day. It's a schoolyard bully/control thing for them that reflects something is missing from their day to day lives. Pity them, and move on.

The forum has a nice option to permanently ignore such people. When you find one, add them to your list and enjoy the peace and quiet.

Meanwhile, interesting thread Geof.

Cheers,

BW

[Geof]

I think it's a cobalt-chromium alloy.Pretty hard material.
The whole mount is in Stellite.We're not talking A380's,these are for the smaller planes.The material is a b***h to work with.Not that it's difficult to mill or drill,it has a lot of tension.

What am I thinking about then? How the **** do you know unless you are a mind reader? Cobalt-chromium is going to be well up there in melting temp and I recall using a bronze-like hard facing alloy to build up the teeth on a motorcycle sprocket when I was a teenager; using an oxyacetylene torch and the sprocket was cast steel. The alloy could be filed but only barely; I spent hours filing an acceptable tooth profile on a lot of teeth; it was the rear wheel sprocket. And they say as you get on in years the short term memory goes but the stuff you did decades ago is clear as a bell....b******t.

I know stellite is difficult to work with; how about manual lathe threading 1-1/4"-3 tpi acme in aluminum bronze, dozens of operating screws 30 inches long for big water valves per shift.

[Geof]

.....The forum has a nice option to permanently ignore such people. When you find one, add them to your list and enjoy the peace and quiet.

Meanwhile, interesting thread Geof.

Cheers,

BW

Thanks for the sanity Bob.

[martinw]

Dear Geof,

That's really neat. As someone who has only a "really cheap" drill press, and no way of turning a guide bush, I cannot follow in the footsteps of Giants, alas.

Anyway, without wishing to hi-jack, cound you possibly advise on this drilling problem for undersized holes...?

I recently needed to build a test rig for testing PCBs. It involved putting 40 sprung-loaded electrical test pins into a 10mm thick piece of sheet. The sheet is effectively a very thick glass/epoxy PCB but without any copper on it... i.e just the core insulator stuff.
The test pin manufacturers recommended a 2.00mm hole for a press fit. I drilled the holes using a 2.0 mm dia, stub drill (12mm cutting thread length), and to my great surprise, the pins were impossible to insert, despite the cheap nature of my drill press.

Next step was to try 2.10mm standard length drill (stubbies are not available at 2.1mm dia), and the holes are too big. 2.05mm dia are not available either.

Do you think that taking some emery paper to the 2.1mm bit is the way to go. BTW, I am way too lazy to be doing with the co-efficient of thermal expansion stuff, and cannot use a grinder to save my life.

Best wishes,
Martin

[Geof]

....I recently needed to build a test rig for testing PCBs. It involved putting 40 sprung-loaded electrical test pins into a 10mm thick piece of sheet. The sheet is effectively a very thick glass/epoxy PCB but without any copper on it... i.e just the core insulator stuff......
Best wishes,
Martin

Uggh, double, triple, quadruple uggh. Could you possibly find something nastier to drill holes in please? (Do I need to tell you this is a sarcastic comment.) Oh, uggh, uggh, uggh. Maybe you are getting a small hint that I am not enamoured of the material you are dealing with.

That stuff is horrifingly abrasive; with a HSS drill before you get all the way through the drill will have worn appreciably. I would not be surprised if on the first hole your pin pushes in fairly freely a short distance, but not any other hole.

Can you get carbide drills, or are you using carbide in which case I am shot down. Carbide should do several holes.

Whether or not you have HSS or carbide I think you need to go with slowish rpm, down in the few hundred range. Can you tolerate lubricant? It may help a bit.

Another approach is freeze the stuff as cold as you can get it. Deep freeze at minus 18 C may be enough to get an effect. The idea is to take advantage both of the thermal contraction and the greater stiffness in the material; the tendency to flow around a dull cutting edge is reduced.

If you can tolerate it being exposed to isopropanol, also known as rubbing alcohol, and have a source for dry ice you could dip the parts in a dry ice alcohol bath; this gives you better than minus 70 C. Careful here!!!! Instant frost bite, or pretty close to instant, if you dip your fingers in. In some ways more hazardous than liquid nitrogen because you do not get the Leidenfrost effect and the alcohol wets your skin very effectively.

Or better still take up aniother line of work.

EDIT: As you see I ignored your reticence re coefficient of expansion, making the assumption you do want something to work and it might.