Problems with Steel

[Steamchick]

Thanks for the tips. I'll try and figure out where the predictive text is coming from... (I have the same problem with my 10 year old phone!).
So when I spout "rubbish", I am always appreciative of the feedback - some quite amusing. But I apologise for sending the rubbish in case it is misleading. (If you find a wolf in the fence that's a "little red riding-hood" moment!).
K

 

[Steamchick]

Ok... I cried "Wolf" - But I am of the Chicken family, and we are paranoid about anything with such big nasty teeth, that eats meat.
But back to drilling: What are the time honoured and approved methods of accurately locating and drilling holes?

1. At school I was taught - scribe lines, centre-pop, hit the centre pop by eye with the centre drill and drill until the second cone is formed, Then use the final drill.
2. Then I was taught (in a machine shop) to draw circles using the centre-pop as the centre for the compass, and after starting drilling the first hole close to the first circle, adjust the drilling position by centre popping on the side of least cut to move the drilling across to centre it in the next circle. Maybe with further adjustments as the taper of the drill makes the circles bigger until is starts to cut at size. (after which you can't move the hole!).
3. But an aeronautical mechanic advised - "don't centre-pop, as it isn't that accurate. Use a miller-driller with an accurate location cross slide table, to get the correct spacing of holes and position from the datum. Centre drill, then final drill without moving ANY slides between the drills. (All common sense?).
4. But then I read that the centre drill should only be taken to the first taper, as a location for the main drill, not as deep as the first parallel part.. Thus the taper of the final drill will locate correctly.
5. More recently, I heard that one should drill with the centre drill until the parallel part has a little depth, then the final drill will centre on its own taper, not screw around on the "blunt" tip in a small tapered hole.

Seems logical to me? - but what do the professionals do? e.g. people who make machine tools and gauges? aeroplanes? Rockets? Watches? or other high precision manufacturing?
The only precision drilling I have been doing is drilling 0.25mm holes in gas jets. - Any watch-makers with advice?
Thanks,
K

 

[BaronJ]

Hi Steamchick, Guys,

Apart from using an optical center punch, I use a triangular center punch, the tip is ground like an inverted pyramid. This provides a sharp point that easily locates in a scribed junction or line. A spotting drill will then make a dimple that the drill point fits into.

A lot of things have altered for me since I built John Morans four facet drill grinder. I get accurately sized holes that don't wander off.

Though I do note though that one of the reasons that holes drift off as they get deeper is drill pressure. Basically since a blunt or poorly cutting drill needs more pressure to cut, the drill flexes and bends ever so slightly, larger drills less so, but the bending causes the drill to run off to one side or other resulting in a hole coming out in the wrong place. This of course gets worse the deeper the hole.

I now regrind all my drills four facet, even new ones. Unfortunately small drills, less than 3 mm are much more difficult to grind, simply because of the amount of stick out. This is where a TCG wins out.

 

[Steamchick]

Great information! I haven't heard all that before. I'm without a precision drill grinder, but do have a cheap jig/holder on the side of my bench grinder. I then finish dressing and levelling the drill bit with a Black & Decker plastic hand holder I bought in the 1970s.... which I use on a flat sheet of Carborundum, or emery. This gives drills that hardly wander - well no more than part used newish drills. But as "the job" is usually worth more than a few drills, I like new drill bits for the best jobs.
I have modified my auto-punch by using a reground broken drill stub as the punch metal - High-speed drill steel is much better for a fine point than the original bit of case-hardened steel. I will try grinding it to a triangular pyramid now for better accuracy!
But your 4-facet grinding info sounds to be one step better for drill bits!
Thanks.
K

 

[Steamchick]

Ian, Any chance of a copy of your drill grinder tool plans - mentioned a while back and I can't seem to find a link?
I've been searching the web and got confused with all the different styles of drill grinding fixtures, so haven't found what I was looking for there - yet. Maybe there is a website/link someone knows?
Ta,
K

 

[goldstar31]

I

But your 4-facet grinding info sounds to be one step better for drill bits!
Thanks.
K

Really, there is little difference between regrinding end mills and ordinary drills, I am surprised that no one has commented Again there is discussion elsewhere that the good old Quorn can do MOST things in refurbishing worn tools. In fact Chaddock actually made his 1/10th diameter end mills on his-- but had job re-sharpening them. As others have said 'Read the Manual' It was 1973 when the first Quorn emerged and there seems to be little to compete. The only thing that spoils is, is setting up time.

So I'm reducing my many bits and making a Worden as displacement therapy but once finished( when???)
it will not only do lathe tools, 4 facet drills, end mills------- and sharpen the tips on slitting saws.
All sort of in one envelope.

Meantime, I am wondering what all the fuss about drilling holes is all about. My father used a 'Bob and Aunty' jig to make 'tubs; which were small wheeled wagons to bring coal from the coal face to the surface for sorting and thence to larger wagons to the shipping staithes- pulled by wire ropes--- which my father 'socketed' He was on 'piece work' and then in the colliery holidays, re-bed the steam locomotives- with out welding them. These old guys were 'the tops' and would give little to these 'newbies' who spent time talking endlessly. He drew what he wanted on the dirt floor with a stick and he and his striker at the anvil simply got on with the task together.

Then in. my world, there was the smoothes and levelled rivets on unarmed photo recognisant Spitfires to get that few MPH out of trouble.

And, in case you doubt me, 'ours' is still flying in Canada . Thev old fitter from those days has jut died at almost 90. Hec was a boy of 18/19 then. So was I and at Hendon

I'm afraid but that is history and the old war bird is SL-721 and was the private aircraft of Sir James M Robb-- boss of RAF Fighter Command.

 

[goldstar31]

Ian, Any chance of a copy of your drill grinder tool plans - mentioned a while back and I can't seem to find a link?
I've been searching the web and got confused with all the different styles of drill grinding fixtures, so haven't found what I was looking for there - yet. Maybe there is a website/link someone knows?
Ta,
K

see GadgetBuilder.com and work from there

 

[BaronJ]

Ian, Any chance of a copy of your drill grinder tool plans - mentioned a while back and I can't seem to find a link?
I've been searching the web and got confused with all the different styles of drill grinding fixtures, so haven't found what I was looking for there - yet. Maybe there is a website/link someone knows?
Ta,
K

Here you are !
John Moran of gadget builder will Email you his notes and plans if you ask him.

You can see my build near the bottom of the page.

http://www.gadgetbuilder.com/
look down the left side for the article.

 

[goldstar31]

I've just worked through a largev quanity of alcoholo as thee guest of good friend for dinner. He's a wonderful both Chinese and European cook. Well, before all this, I had just discovered that I CAN use a 25mm diameter ER32 tool holder on my original Mark One Quorn -- because, I had made split collars which would hold the suggested Mark3 set up. my pet parrot says-- 'Who is a clever boy then'
So my ancient Mark One can move into the ethereal realms of the rather expensive Mark 3-phew!

Meanwhile-- back on the ranch- I've got a Worden which is going to be a lot simpler and less expensive but will not only do lathe tools but drills, end mills and sharpen slitting saws. In other words, ignoring everyone else.

So that's me- others may be different

Cheers

Norman

 

[awake]

Ok... I cried "Wolf" - But I am of the Chicken family, and we are paranoid about anything with such big nasty teeth, that eats meat.
But back to drilling: What are the time honoured and approved methods of accurately locating and drilling holes?

1. At school I was taught - scribe lines, centre-pop, hit the centre pop by eye with the centre drill and drill until the second cone is formed, Then use the final drill.
2. Then I was taught (in a machine shop) to draw circles using the centre-pop as the centre for the compass, and after starting drilling the first hole close to the first circle, adjust the drilling position by centre popping on the side of least cut to move the drilling across to centre it in the next circle. Maybe with further adjustments as the taper of the drill makes the circles bigger until is starts to cut at size. (after which you can't move the hole!).
3. But an aeronautical mechanic advised - "don't centre-pop, as it isn't that accurate. Use a miller-driller with an accurate location cross slide table, to get the correct spacing of holes and position from the datum. Centre drill, then final drill without moving ANY slides between the drills. (All common sense?).
4. But then I read that the centre drill should only be taken to the first taper, as a location for the main drill, not as deep as the first parallel part.. Thus the taper of the final drill will locate correctly.
5. More recently, I heard that one should drill with the centre drill until the parallel part has a little depth, then the final drill will centre on its own taper, not screw around on the "blunt" tip in a small tapered hole.

Seems logical to me? - but what do the professionals do? e.g. people who make machine tools and gauges? aeroplanes? Rockets? Watches? or other high precision manufacturing?
The only precision drilling I have been doing is drilling 0.25mm holes in gas jets. - Any watch-makers with advice?
Thanks,
K

Let me preface everything below with, "as I understand it" - I've only been doing this for about 15 years, and make no claim to being an expert!

With that disclaimer in place, it's all about the degree of accuracy required. If you are drilling clearance holes that are .030" larger than the bolt or screw going through, you theoretically only have to be within +/- .015" or so of the exact placement - easily doable with careful use of scribe and punch. If you need greater accuracy, then you will do better to locate and spot drill on a good mill - but keep in mind that 1) it would not be at all unusual to have a .001" or more of error in the average hobby-shop manual mill, and 2) drilling is never a high precision operation. That's why they make reamers (to help get closer to on-size and round, but doesn't help with placement). If the hole is large enough to allow it and with proper technique, boring will generally give the most accurate results as far as placement and roundness, but then the issue will be the accuracy of setting the boring head to get on-size.

In a commercial shop, spending twice the time to be more accurate than is actually needed is a poor use of time. In a hobby shop, the calculation may be different - the measure being what we enjoy spending time on, rather tfhan on $ / hr.

 

[Steamchick]

Fair comment - but when parts need to be dowelled for alignment, drilling positional accuracy comes to the fore. I usually cheat and either use a spigot for alignment (As with cylinder heads in a bore) or assemble and align - then drill through mating parts for the dowel pins or fitted bolts.
Thanks for comment.
K

 

[BaronJ]

Hi Guys,

This jig had the 3 mm dowel pin holes drilled and then tapped M6 holes drilled based on the mill dial readings. The clearance holes for the cap screws were drilled 6.1 mm, whilst the dowel pin holes were spotted through. I did cheat and bored the 19 mm hole on the lathe based on a 12 mm through hole.

If you look carefully the large hole is very slightly off to one side, simply because the pop mark should have been opened out with a small drill first.

This is a die used for punching 5 thou Teflon sheet for bearing preload washers used in a grinding spindle that I'm currently making for a TCG. These are punched to suit the inside hole. They will be placed on a mandrel and turned down to 21 mm diameter.

 

[awake]

Fair comment - but when parts need to be dowelled for alignment, drilling positional accuracy comes to the fore. I usually cheat and either use a spigot for alignment (As with cylinder heads in a bore) or assemble and align - then drill through mating parts for the dowel pins or fitted bolts.
Thanks for comment.
K

Yes, exactly - that is a perfect example of when positional accuracy is paramount.

Though I have to say that in my limited experience, if I want to get absolute alignment of dowels, I assemble first (clamp, bolt, spot weld - whatever is appropriate), then drill and ream through at the same time. If the dowels are to be a press fit in one side and a slip fit in the other, the above is obviously done at the press fit size; then the parts are separated and the piece into which the dowels should slip are reamed for a slip fit.

In the above scenario, absolute positional accuracy may not be essential, since the two parts have very high relative positional accuracy.

 

[fcheslop]

The way I was shown at Smiths was to use an eye glass and a spade drill bit in an Archimedes drill to spot the hole
The hole would be near sized after drilling with a cutting broach and finished with the polishing broach on brass to harden the hole
We had to make the drill bit first.
Now I use the mill and work from coordinates and spot with a spotting drill
see attached for some basic clock work
Lesson 1

 

[L98fiero]

Though I have to say that in my limited experience, if I want to get absolute alignment of dowels, I assemble first (clamp, bolt, spot weld - whatever is appropriate), then drill and ream through at the same time. If the dowels are to be a press fit in one side and a slip fit in the other, the above is obviously done at the press fit size; then the parts are separated and the piece into which the dowels should slip are reamed for a slip fit.

And if you still get the position wrong you can call it foolproofing so the parts go together correctly

 

[holmes_ca]

When we made fixtures that needed a slip fit on the top plate we ground 3 120 flats on the top portion of the dowels leaving a thin portion on the dowels OD for contact in the hole

Edmund........Alberta

 

[holmes_ca]

And if you use tapered dowels for location if the alignment is not exact you can always re-align and use the taper reamer to re-align, can't do that with a parallel (straight) dowel?

 

[SmithDoor]

I have Word 2000
There is spot you can add new words

Dave

More on the spell-check. Ignore if you want.

In one of the early versions of Word, my wife's name "Debbie" kept being changed to "debauchery."

--ShopShoe