# pre drilling for holes



## Luiz Fernando Pinto (Sep 30, 2019)

Hello, i made a hole with 10 mm diameter them the final diameter 11mm, my tool became like this and i didnt made the final hole, obviously. Is that because the relation of the diameters was too small?


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## Tim1974 (Sep 30, 2019)

Cheep drill bit ? 
What material where you drilling ?
And what speed ?


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## Luiz Fernando Pinto (Sep 30, 2019)

It´s not a cheep drill bit, it´s a dormer A002. And i thought that was a fake Dormer but it´s not. I alread taltked to Dormer and my outfitter.

So, i´m not sure what material it is, but it is a low carbor, i think. It´s a shame, but the previouly drill that I made were ok, for example, 8mm diameter.

It was about 500 rpm.


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## Luiz Fernando Pinto (Sep 30, 2019)

Look why i thouth it was a fake Dormer tool, but it is not.

3 reasons.

1 - The chip that came whith the tool.





2 and 3 - A bad ending, at the chanfer edge and blurred letter.





Despite the photos, it's not a fake or cheap drill.

So, after all, that's why i am thinking it was the large pre drill hole
Or my lathe is too small... vibration, low robust, etc,... contributed to this.


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## Tim1974 (Sep 30, 2019)

Yer looks like it grabbed , I wouldn’t normally drill out so little (when possible)


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## TonyM (Oct 1, 2019)

That does not look right even or especially for a second cut. It does not look overheated as I would expect with hard material which in any case would have shown with the 10mm drill. It definitely looks like a faulty drill bit.


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## Tim1974 (Oct 1, 2019)

yer your right tony looking at the pic agan on a bigger screen its not right at all ! unless the first drill work hardened the material ???  but yer you would see more heat , hmmmm wish i could run a file over the drill bit and see if its  hard !


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## Luiz Fernando Pinto (Oct 1, 2019)

Thanks a lot for the discussion. I will send the drill for my supplier,
he requested to send to him. Any new information i´ll post it here.


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## Nick Hulme (Oct 1, 2019)

10mm pilot for 11mm final? 
That's most of your problem right there, running it at 500rpm with 0.5mm engagement compounds the mistake as it will rip the edges off a drill bit more often than not, a 5mm pilot would be better.
This is not a case of a drill fault, it's tool abuse ;-)


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## tornitore45 (Oct 2, 2019)

> 10mm pilot for 11mm final?
> That's most of your problem right there, running it at 500rpm with 0.5mm engagement compounds the mistake as it will rip the edges off a drill bit more often than not, a 5mm pilot would be better.
> This is not a case of a drill fault, it's tool abuse ;-)



What a ridiculous statement!

Holes are reamed with 0,3 mm diameter difference.
Holes are enlarged by a trifle all day long by the thousand, in hard material without any problem.
500 RPM for a 10 mm is actually a bit slow, which eliminates overheating.
Low carbon steel does not work harden appreciably, an can almost be drilled with a screwdriver.
The drill may be a fake after all, faker can print brand logos.
The ugliness of the end is a good case for a fake.
The drill may have slipped through the hardening process.


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## Nick Hulme (Oct 2, 2019)

tornitore45 said:


> Holes are reamed with 0,3 mm diameter difference.



The only relevance of that statement is that a reamer is not a drill.


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## mcostello (Oct 2, 2019)

Do it all the time with no problems. Don't buy extra fancy drill bits either.


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## tornitore45 (Oct 2, 2019)

Nick you need to learn how to learn from those that know more than you.
Mountains of experience say you are wrong, why do you insist in defending something wrong?
By the way, from the point of view of the reamer cutting into the hole the geometry is essentially the same and that is why a drill bit can cut into a hole slightly undersized just like a reamer.  The difference is that a reamer has multiple flutes keeping a better center and cutting a rounder hole, something a drill bit may not do because is allowed to wander, but that difference is meaningless to the issue at hand.


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## Nick Hulme (Oct 2, 2019)

I am endlessly amused by you, please do keep it up


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## tjwal (Oct 2, 2019)

I agree with Nick. The pilot hole shouldn’t be much bigger than the web of the final drill.  Whether that caused the problem or not I don’t know.
John


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## tornitore45 (Oct 2, 2019)

Yes I am a funny guy.  Please tell me what evidence you have to support your rambling about drilling.  Again people drill with little stock removal all the times, you seems to be the only one incapable of doing so. Because... you are too pompous to learn.


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## tornitore45 (Oct 2, 2019)

> 1 - The chip that came whith the tool.


The picture shows flute that look like were machined with an hatchet.
What could possibly be additionally wrong with that tool.


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## TonyM (Oct 3, 2019)

Tornitore is absolutely right. It's common practice to double drill for a better sized finished hole and certainly 1mm is not too little to remove for a finishing cut.
That drill has the cutting edge and the rest of the surface removed exactly as if the material being cut was harder than the drill. It is not burnt which indicates to me that the drill is not hard and I would hazzard a guess is not even HSS.


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## Richard Carlstedt (Oct 3, 2019)

Late to the party, but I have seen similar drill damage to the flutes when the drill
was accidentally run in reverse. 
Enlarging holes with minimal increases is common in industry, but feed rate 
becomes more critical as the drill wants to pull due to the helix angle
Rich


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## Luiz Fernando Pinto (Oct 3, 2019)

Richard Carlstedt said:


> Late to the party, but I have seen similar drill damage to the flutes when the drill
> was accidentally run in reverse.



It was not reverse mode, i never use this way.


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## john_reese (Oct 3, 2019)

I think the diameter difference is the root of the problem.  The larger drill probably screwed itself into the pilot hole destroying the cutting lips on the drill.  For a pilot drill pick one just larger than the web thickness of the larger drill.  If you are enlarging a hole by 1mm or less the proper  tool is a reamer.


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## Cogsy (Oct 3, 2019)

1mm is about double of what I would normally leave for a reamer to remove but it is less than I normally leave for a drill to remove as well.


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## BaronJ (Oct 4, 2019)

Hi Guys,

If I'm reaming a hole I try for about 5 to 10 thou, much more than that, upto a millimetre or so and I go for a "D" bit.  Most metric drill sets seem to come in 0.5 mm increments anyway so only 20 thou between sizes.


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## Charles Lamont (Oct 4, 2019)

I can't make sense of the shape of that tip. Did you check that the drill had a correctly ground point in the first place? Sometimes the grinding can go completely haywire and the drill escapes inspection. I often drill a few thou under size before putting the final drill through. Never had a problem.


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## goldstar31 (Oct 4, 2019)

I'm raising several questions.
The first is  whether today's drills need lubrication to avoid damage. I keep seeing warnings about this
Again, about reamers, I always understood that new reamers were machined oversize so that a subsequent re-grind was 'on spec'

Thirdly, I 'm ancient but recall the tale- possibly an old wives one about the competition  BEFORE  WW2 between the UK and Japan drilling holes and then getting another smaller hole and then another and so on.
Again, my copy of Sparey, the Amateurs lathe book and reference to drilling and then finish drilling. Was Sparey wrong as he made a lot of designs -- which you are all copying.

Lastly,  drills heat up without lubrication and I recall that with long carbon spade drills in very hardwood wood that they both expanded and burned and -- went soft in consequence.

I doubt that my recollections are correct. Please comment

Norm


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## tornitore45 (Oct 4, 2019)

Self-feeding or grabbing happen with plastic, brass, or at the breakthrough.
It happens when feeding with the lever, you are pushing and all of a sudden supposed to reverse your force direction.
The problem can be eliminated by feeding with a "screw mechanism" like raising the knee or using the fine advance.
The lever feeding has other shortcoming. In some particular conditions it allows the bit  bounce up and down like when trying to dill out a broken tap with a carbide burr. The bouncing ruins the cutting edge.


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## Charles Lamont (Oct 4, 2019)

Phosphor bronze is particularly bad for grabbing. If resources run to it, it is a good idea to have some drills dedicated for 'brass' work, with the top-rake ground or honed off at the tip. Straight fluted drills are supposed to exist, and I think I may even have seen one once.


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## Deholby (Oct 4, 2019)

Whats the chance you drilled through part and hit a hard steel parallel under it on the edge ?


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## tornitore45 (Oct 4, 2019)

> Whats the chance you drilled through part and hit a hard steel parallel under it on the edge ?


That would not explain the flutes "superior" finish.
By the way, I know how a parallel look like when something like that happens. The parallel is the rack and the drill is the pinion.


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## mcostello (Oct 4, 2019)

I have drilled 52 holes to tap 5mmx.8. Material is 304Stainles steel.  The tap drill chart said to use a #19 drill, .166", tapping was horrendous. Increased the size to #18 ,.169" now doable without taking butt bites out of the chair. This is taking .0035" out of the hole or .00175" per size, theoretically. No problems so far.


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## xpylonracer (Oct 5, 2019)

Tapping drill size for M5x.8 is 4,2mm (for metric tap size drill deduct the thread rate from the diameter) is the reason for poor tapping performance with a #19 drill.

xpylonracer


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## mcostello (Oct 5, 2019)

If I have typed correctly, Google says 4.2mm is .1654,  #19 is.166, not much difference.


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## petertha (Oct 5, 2019)

I've purchased a few regular HSS Dormer's to fill in worn drills & they were decent quality. Can we see the cutting edge?
On your one pic, is the coating coming off, or that is remnant of swarf?


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## xpylonracer (Oct 5, 2019)

Perhaps the drill lost some diameter drilling so many holes in 304 stainless ? or the tap got blunt ?
As you say #19 is almost the same size as 4.2mm.
You didn't state thickness of the material but many people drill slightly up on the tapping size and rely on 60% engagement.

xpylonracer


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## mcostello (Oct 6, 2019)

.350 deep.


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## tornitore45 (Oct 6, 2019)

Stainless steel is not tap friendly, for that reason a 50% tread is usually done.
A M5 screw into a 0.350 (0.25 engagement) is plenty strong. the screw will break long before it strips.


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## Ozwes007 (Oct 6, 2019)

Drills and drilling. Today’s drills usually come in 5 flavours.
1 cheap and nasty - Carbon steel.
2 cheap - M02 (straight HSS)HSS with or with out coatings- coating only lasts as long as the moment you wear through it, then it’s just a M02 HSS drill.
3 M35 HSS ( 3-5% cobalt HSS) with or without coatings.
4 M42 HSS (5-8% cobalt HSS) with or without coatings.
5 Carbide Drill bits. 
Most people will buy #1 or #2 drills.
Stainless is a soft material, except if you overheat it! Then it becomes super hard and will destroy the chiselpoint and lands on all #1 and #2 drills and some #3 drills.
Slow down your speed and it will cut it like butter. I mean really slow it down. 
Tapping stainless is best done with sharp taps, check your taps if you can see a reflection from the edge they are blunt and throw them away. Use gun taps or spiral taps for stainless and you will have no problems. Make sure they are at least M35 grade HSS.
The general rule of predrilling is to make the predrill slightly larger then the chiselpoint. Chiselpoint thinning can remove the necessity to predrill upto about 25mm drills. When drilling  brass, bronze, thin steels etc, just run a fine grind or hone along the lip of the cutting edge parallel to the drill to produce a neutral or slightly negative rake angle will help greatly.
Metric taps use the rule diameter minus pitch to give you the tapping drill size for an 82-85% thread profile. The #19 is perfectly fine for drilling a M5 tapping hole, the problem will be twofold in stainless if you are having issues:
1. You overheated the steel and hardened it.
2. Your tap is blunt(usually this one)shiny edge, bin it! (Yes they can be reground)
Also lubricant is always used for tapping Stainless(make sure it’s a high pressure one suited to Stainless), never for brass or bronzes or cast iron. 
Kerosine or lard kerosine mix for Aluminium.
Just from my 50years in the trade this is what works.
Wes


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## Luiz Fernando Pinto (Oct 6, 2019)

petertha said:


> I've purchased a few regular HSS Dormer's to fill in worn drills & they were decent quality. Can we see the cutting edge?
> On your one pic, is the coating coming off, or that is remnant of swarf?



It is a remnant of swarf, definitely.

Look at the cutting edge.... it's almost identical to the photo you posted.


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## petertha (Oct 6, 2019)

The cutting edges (red) look a little ratty. Degradation? Or maybe just picture resolution.

But the (green arrow) silver stuff does not look good. I assume that is not the drill coating coming off but a smear of metal buildup. That can happen on gummy sticky alloys like certain grades of aluminum. Usually some combination of cutting fluid, speed, feed & cut depth is required. But regular carbon steel I cant say I have seen similar, myself. Strange. Is it making regular spiral chips? Are the chips silver or blue/tan? Assume the chuck is true & work is solid mounted, all the fundamental stuff?


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## Harry. (Oct 8, 2019)

I would have used a spiral reamer like these: https://www.accu.co.uk/en/1125-machine-reamers The flutes on spiral reamers tend to work better in my experience.


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## tornitore45 (Oct 8, 2019)

There is some seriously wrong with that drill bit.
The cutting edge are ragged
The flutes have a terrible finish.
The metal smear behind the lands indicates the they were not releaved for clearance. And that is the worst offense because rubbing and galling generate heat more than rough edges and flutes.
Let's face it Dormer of fake, whether it missed several manufacturing steps by accident in a quality plant or is a cheap imitation of a drill the result is the same.  A poor drill like that may work on some plastic or Styrofoam but should never come near metal or wood.
I am really curious to see what the response from Dormer is.


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## tornitore45 (Oct 8, 2019)

Harry. said:


> I would have used a spiral reamer like these: https://www.accu.co.uk/en/1125-machine-reamers The flutes on spiral reamers tend to work better in my experience.



Odd, the company is in the UK but prices are in $


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## Harry. (Oct 8, 2019)

It shows in pounds for me because I'm in the UK, so it must change to $ for people in the USA.


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## goldstar31 (Oct 8, 2019)

I can't see a firm as big as Dormer bothering about one bad drill which is only worth a few dollars.

I would send the guy an apology and a generous sample of drills-- and start living again.

I got mixed up with a rather large problem- a damned sight bigger than this - and my bank sent me a couple of vouchers worth £50 in all to buy my grandchildren some pizzas.

For the record, I'm a shareholder of the bank and if I had played awkward had access to the  bank's annual general meeting!

Life if I may remind, isn't the dress rehearsal it's the once only affair so let's move on.

Norm at almost 90!


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## ALEX1952 (Oct 9, 2019)

If the knee of the machine is to be used as a method of feed as suggested previously, lock the quill as it can still pull it through.
I think this method is a terrible and potentially dangerous idea, as it can bring your face nearer the work piece if you have to bend to do the feeding. I have never seen this used in a professional environment. Discuss!


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## chrsbrbnk (Oct 9, 2019)

Drilling with the knee is a reasonable approach just really sorta slow,    might want to clamp the work down , might want to wear safety glasses,  and of course clamp the quill. might want to keep your hair out of the fray too. Drilling under power feed is ultra common in the professional shop  and for all intents and purposes the same as cranking up the knee or the tailstock on the lathe.   just easier to keep the feed constant.  its pretty easy to give too high a feed rate when drilling out  very small amounts  leading to tip failure.
while I was working we would find brand new drill bits  with  messed up cutting  angles    once in a while you would get a whole dozen  that were soft .
best test sharpen the messed up bit and try drilling again   that will show if its the bit or material or practice


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## tornitore45 (Oct 9, 2019)

The method suggested was for special situation where the manual feeding can not guarantee a constant feed rate.
Specifically it was suggested to remove a broken tap with a carbide bit.
The irregular fracture and the tap flutes will bounce the drill or end mill chipping the fragile carbide edge if the operator arm is all that define rigidity.
In that case one has to proceed at glacial speed anyway.

My mill has no knee, the head moves down, the practice is safe but is used only when the alternate feeding method is troublesome because of the bouncing.

Knee type milling machine usually have a fine feed crank operating on the quill.

As anything in life danger and risk can be controlled or pursued.


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## Wizard69 (Oct 10, 2019)

tornitore45 said:


> Nick you need to learn how to learn from those that know more than you.
> Mountains of experience say you are wrong, why do you insist in defending something wrong?
> By the way, from the point of view of the reamer cutting into the hole the geometry is essentially the same and that is why a drill bit can cut into a hole slightly undersized just like a reamer.  The difference is that a reamer has multiple flutes keeping a better center and cutting a rounder hole, something a drill bit may not do because is allowed to wander, but that difference is meaningless to the issue at hand.


I’ve have had this issue happen to me and have seen other suffer in the same way.   If you don’t like the term tool abuse we can call it something else.   In general drill bits will tear up the margins when you try to drill close to size.   Yes drills made with better steel might tolerate it better but the fact remains it is hard on the drill.  

As for the steel I’m not certain it is low carbon.  It could be structural steel with a hard spot for all we know.


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## Wizard69 (Oct 10, 2019)

I learned this approach from an old tool and die maker.   In the right materials you are at a greater risk of shattering a diol or damaging it from Quill feed as you can control for cork screwing and other effects.  With the quil clamped and feed coming from the knee a drill bit would have to grab enough to lift the knee before anything bad happens. 

Frankly using the knee for drill feeding can be ideal in the right situation.    There ware problems though, the lack of feedback being one, so maybe not a widely used technique. As for your face where is your safety glasses and shielding.  



ALEX1952 said:


> If the knee of the machine is to be used as a method of feed as suggested previously, lock the quill as it can still pull it through.
> I think this method is a terrible and potentially dangerous idea, as it can bring your face nearer the work piece if you have to bend to do the feeding. I have never seen this used in a professional environment. Discuss!


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## xpylonracer (Oct 11, 2019)

Not all mills have a quill on the vertical function, the first mill I had was a Victoria U1 universal horizontal machine, the vertical head fitted to the rear dovetail and was driven from the 3MT horizontal arbor drive, this gave double the spindle speeds of the horizontal function.
The vertical head was a hefty lump but had no quill although it could rotated either side of vertical.
To drill or add DOC when milling it was done by using the 10" handle on the knee drive which was low geared and raised 1/8" per rev of the drive, the movement was silky smooth but tiresome on the arm when multiple holes needed drilling.
The Victoria also had a slotting head that was fitted in place of the vertical head, useful and used to slot some gears for my Colchester Bantam lathe.
All of the milling and drilling to make my avitar 5 cylinder radial engine were done on the Victoria.

xpylonracer

http://www.lathes.co.uk/victoria/


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## larryg (Oct 11, 2019)

ALEX1952 said:


> If the knee of the machine is to be used as a method of feed as suggested previously, lock the quill as it can still pull it through.
> I think this method is a terrible and potentially dangerous idea, as it can bring your face nearer the work piece if you have to bend to do the feeding. I have never seen this used in a professional environment. Discuss!



As said above on a HZ mill the knee has to be used if one wants to drill with the vertical head on.  On my HZ mill I have power feed on all three axis  so powering up to drill is not a problem.  I also have an old index #40 mill with only a hand wheel on the quill, no quick handle.  There is a lot of back lash in the quill drive so the spindle can drop ~.200" when breaking through or self driving.  I use the knee at various times if some precision is needed.  In a recent vid from Abom79 he also used the knee for some precision drilling.  So it is used at times by various people amateur and professional alike.

lg
no neat sig line


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## awake (Oct 12, 2019)

It sounds like some of you are using a power quill feed when drilling - ? I'm curious about this, as on my Bridgeport it specifically says not to use the power quill feed for drilling - it is to be used only for boring. Presumably, other types of mills do not have this limitation - ?


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## mcostello (Oct 12, 2019)

Bridgeport says 3/8" capacity when drilling.


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## tornitore45 (Oct 12, 2019)

I recall reading somewhere that there is weakness, like a pin, in the quill power feed drive chain that limit the allowed force/torque.
I can see that boring on a BP will always have a DOC  less than 3/8" so boring is safe.


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## awake (Oct 13, 2019)

mcostello said:


> Bridgeport says 3/8" capacity when drilling.



I could have sworn that the manual said not to use it for drilling, but when I checked, sure enough, the limit is no more than 3/8".

I'm thinking now I must have picked up the "no drilling at all" from reading on the PM forum ... maybe in response to comments about people messing the quill power feed by trying to drill too large a drill? Or something like that. Not sure if someone there said "no drilling," or if that was my interpretation.

In any case, thanks for catching  the mistake!


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## petertha (Oct 13, 2019)

Some discussion on another forum. I was wondering the same question on my BP clone.
https://www.***************.com/threads/drilling-using-quill-feed.76997/


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## petertha (Oct 13, 2019)

petertha said:


> Some discussion on another forum. I was wondering the same question on my BP clone.
> https://www.***************.com/threads/drilling-using-quill-feed.76997/



edit ...and it looks like no cross links allowed. Sorry. Do a google search under 'Bridgeport drilling power feed', some links quantify the clutch kick out value.


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## Badhippie (Oct 13, 2019)




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## Badhippie (Oct 13, 2019)

Sorry I am new to posting on this site. It looks like to me this drill bit has been spun backwards. If you look at the pic. The burr I circled would not be facing this way also I circled the relief cut. I can assure you that this bit was spun backwards everyone of us has done it at sometime. The burr is the proof it’s going the opposite direction.


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## chrsbrbnk (Oct 14, 2019)

in the way back days in the shop if you left your machine running unattended,  the jokesters in the shop would off then  turn on the quill on backwards so that when you came back and started using it , it would wreck the tool just like that


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## MachineTom (Oct 20, 2019)

When I was 14 years old our neighbor put in a swimming pool. Every day I watched the progress, digging the hole pouring cement etc. It being summer I had all day to watch the work progress. Now it came time to install the water slide it was mid August 95 degrees and humid.
I watched the worker drill holes for the anchor bolts, the first bolt hole went fine, but the second made no progress. Thinking the bit was dull the worker replaced it, still no joy. Back to the truck, rummage around, and brings back another. This goes on for 20-30 minutes, the guy is sweating like crazy, and cussing a blue streak. As he seats there looking at the hole with No progress, I walk over and ask why is not using left hand drills for the hole. It's over 50 years since that day, but I still recall the look on his face when he realized the drill was in reverse.


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## awake (Oct 21, 2019)

Running the drill backward - I'm happy to report that I've never done anything like that. Never. Honestly. You can believe me. Really!


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## kwoodhands (Nov 1, 2019)

goldstar31 said:


> I'm raising several questions.
> The first is  whether today's drills need lubrication to avoid damage. I keep seeing warnings about this
> Again, about reamers, I always understood that new reamers were machined oversize so that a subsequent re-grind was 'on spec'
> 
> ...



Norm as far as spade drills heating up in hardwoods , you are correct. Not sure if the bits will be annealed and
go soft. I used to get some jobs installing electric hinges  and fire exit devices ( panic bars) on wood slab  doors where long drilling was required. I kept a 5 gallon bucket 3/4 full to dip the spade bit in to cool it.
Every 3" or so the bit was extracted and dipped into the water. I spun the drill a few seconds to dry the bit before re-entering the hole. I'm guessing that a bore was about 44" or more in length and on an angle from the top hinge mortise to the device near the lock side. The spade bits probably expanded too as sometimes they were hard to extract. Often had to wait several minutes before removing the bit.
I tried various spray lubes , WD-40, BoShield etc. None worked for me. Just cooling the bit with water worked. The bore was started with a 5/8" x 6" auger, then switched to a 1/2" x 6" spade bit in an 18" extension.  Finally a machine shop made extension was used to finish the bore. 
Nerve racking  and tedious job as the set up to bore a long hole on an angle was not easy.
I wound up doing this job for various contractors from Rhode Island to Florida when it was known this job could be done at all. I heard that some attempts wound up with bits going thru the side of the doors. 
That is why I never considered using a lamp bit. Much too flimsy for precise work.

mike


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## goldstar31 (Nov 1, 2019)

kwoodhands said:


> Nerve racking  and tedious job as the set up to bore a long hole on an angle was not easy.
> I wound up doing this job for various contractors from Rhode Island to Florida when it was known this job could be done at all. I heard that some attempts wound up with bits going thru the side of the doors.
> That is why I never considered using a lamp bit. Much too flimsy for precise work.
> 
> mike



My long drillings were in woods like cocobolo, kingswood, African Blackwood and Lignum Vitae but my drills were  far narrower and possibly longer than  yours. Mine were up to 13 inches and never more than 7mm in diameter. Hence, I spent a lot of time extracting and then drilling after flicking the turnings off the silver steel/ key steel rods.
In passing, I should mention that these exotic hardwoods were naturally oily.

Thank you for the input incidentally

Norm


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## tornitore45 (Nov 1, 2019)

> Again, about reamers, I always understood that new reamers were machined oversize so that a subsequent re-grind was 'on spec'



That can't be true for 2 reasons

1) Reamers are meant to "size" a hole precisely after drilling so a pin or a dowel can slide with minimal play or be pressed in reliably.  
2) A reamer has cylindrical ground margins like a drill bit.  A reamer cutting action is limited to the small chamfer on the front.  If any sharpening need to be done it should be done there.

Drill bits heating up in wood.    Spade bits are not usually made with High Speed Steel, therefore overheating can permanently soften them.

Twist drill made of HSS can turn blue and keep hard.   Is normal to silver braze a bit of HSS to a shank to make a internal boring/threading bar without affecting the HSS hardness.


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## goldstar31 (Nov 1, 2019)

[QUOTE="tornitore45, post: 330085, member: 781

Twist drill made of HSS can turn blue and keep hard.   Is normal to silver braze a bit of HSS to a shank to make a internal boring/threading bar without affecting the HSS hardness.[/QUOTE]

If I recall my 'wood boring' days, I recall that drill bits were extended by boring the end with another hss drill and silver soldering a mild steel extension.

As I have done it repeatedly, I must assume that the drill was so- and clearly, that I must entirely disagree with you. 

Who also disagrees is the late Leonard Sparey who was the designer of many of the many engines which still appear on this web. 

On a lighter note, I recall ex Napoleonic bayonets being used to do the taper bores on The Great or Highland and Half Long bagpipe chanters!  You do know that the Irish sent bagpipes to the Scots as a joke-- and the Scots haven't seen the joke yet.


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## ALEX1952 (Nov 1, 2019)

Contrary to a previous post reamers are not parallel but very slightly tapered for some of its length and does cut on the flutes or you would struggle to get a finish, this is especially so for hand reamers as you would have difficulty starting them, that's why you are able to enter the reamer into a pilot hole and still end up at size or if desired for a fit slightly under.


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## ALEX1952 (Nov 1, 2019)

tornitore45 said:


> That can't be true for 2 reasons
> 
> 1) Reamers are meant to "size" a hole precisely after drilling so a pin or a dowel can slide with minimal play or be pressed in reliably.
> 2) A reamer has cylindrical ground margins like a drill bit.  A reamer cutting action is limited to the small chamfer on the front.  If any sharpening need to be done it should be done there.
> ...


on the contrary to a reamers are not parallel but very slightly tapered for some of its length and they do cut on the flutes or you would struggle to get a finish, this is especially so for hand reamers as you would have difficulty starting them, that's why you are able to enter the reamer into a pilot hole and still end up at size or if desired for a fit, slightly under.


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## goldstar31 (Nov 1, 2019)

In fairness, probably Torniture.  is thinking about machine reamers.
I'm in the School which believes that a properly honed boring bar creates a better finish any way

A comment  to Tourniture,  I make my boring bars from solid HSS but believe that the best finish is still achieved  with carbon steel.

As an aside, I have just resurrected my old Mark1 Quorn tool and cutter grinder as I've got sort of excited and a bit concerned with the introduction of the new Mark3.
And then a kind Scottish gentleman posted me an almost complete set of castings for the Mark 1.

Which all brings me back to drills and Professor Dennis Chaddock who designed the Quorn- from the Deckel to make end mills for his ? V8 and also 4 and 8 facet drill grinding.

Back to topic?

Norm


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## Cogsy (Nov 1, 2019)

goldstar31 said:


> If I recall my 'wood boring' days, I recall that drill bits were extended by boring the end with another hss drill and silver soldering a mild steel extension.
> 
> As I have done it repeatedly, I must assume that the drill was so- and clearly, that I must entirely disagree with you.


Drill bits (and often even reamers) are not normally hardened on the shank. This would be the only way (in my mind anyway) that a HSS drill bit could drill another HSS drill.


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## goldstar31 (Nov 1, 2019)

Sparey writes in his 1996  print of his book 'The Amateurs Lathe'  thusly

It is not generally appreciated that the shanks of drills, even high speed steel on
es are left soft, so that they may, in consequence, be turned down to fit small chucks

*********
Another advantage is that they may be turned down for insertion into a drill rod to make extension drills.

As far as I am concerned, I'd be happy to see the matter closed

Thanks to all

Norman


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## tornitore45 (Nov 3, 2019)

Given the title of this board contains "machinist" I thought it was implied that the reamer I talked about was a machine reamer or chucking reamer as they are called.

Another reason why drill bit shanks are left soft (well not hardened) is that they are usually held by chuck with hardened jaws.  Hard on hard does not grip well at all.

End Mills are hard all the way, but they are held in collet or end mill holder with a positive keying feature.


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