Squaring off the bottom of a blind hole

[ALEX1952]

In respect of drilling holes in bronze etc that tend to grab, it is entirely possible that the drill is at fault, if for arguments sake the drill is used mainly on steel or worse cast iron the cutting edge Dia. can be smaller than the flutes through wear, therefor exacerbating the problem of grab. I agree with comment 3 pages ago learn to flat bottom a drill, it will stay size as the previously drilled hole will act as a drill guide, it is also very cost effective.This method was, and maybe still is widely used in industry. a fixture with a bush to support the drill which if large would have a thinned point, followed by a flat bottom drill. You realy do need this skill otherwise how will you produce a falt bottom on a very deep hole, without special and very expensive tooling. I'll shut up now as I tend to waffle on.

 

[Ramon]

Alex, this is a phemomena of the material - most definitely not the drill. Whilst I agree that a dull or poorly ground drill will not be ideal to say the least and really lead to difficulties anyone familiar with this material would always sharpen the drill before using - such is it's properties. I know for some sharpening a drill (by hand) is a skill they may not possess but it's one that anyone with an interest in model engineering should try to acquire. Just this afternoon I broke and resharpened a brand new 1.05 mm drill by hand. Was not as good as bought but it did continue to cut and get the job done.

This is definitely the one time a person can blame the material and not the tool

Regards - Tug

 

[ALEX1952]

i WASN'T SAYING THE DRILL WAS BLUNT OR THE CHARACTERISTICS OF THE MATERIAL WAS NOT A FACTOR, THE POINT I WAS TRYING TO MAKE WAS THAT IT IS ENTIRELY POSSIBLE THAT THE DRILL DIA CAN BE SMALLER AT THE END THAN UP THE FLUTES, THEREFORE EXAGGERATING THE KNOWN CHARACTERISTIC OF THE MATERIAL BINDING,
Please excuse caps didn't realise untill the read through of my comment.

 

[Engineeringtech]

I've been machining for a living here in the USA for 21 years, and haven't encountered the terminology "slot drill". The cutting tool suppliers sell "endmills" and "center cutting endmills". You use the latter if you're plunge cutting unless you're following a pilot hole. And if you're expecting a fairly accurately sized hole or slot, you use a three or two flute cutter, and plenty of coolant or cold air else the chips don't evacuated fast enough. They pile up, prevent the removal of heat, and the hole is oversized. I've never had any exposure to bronzes except phospher bronze springs which didn't require machining, but I suspect plunging a center cutting endmill or slot drill at the correct rate to prevent work hardening and using plenty of coolant would help.

 

[Steamchick]

Thanks Engtech... I think that has explained why 2-flutes or more flutes. 2= Better swarf clearance? More flutes = more accurate diameter? ("Hole-following"... or stiffer?) - but less swarf clearance? - Please correct me if I mis-understand this.
Can you explain when to use helical flutes and when to use straight flutes? Thanks,
K2

 

[Ramon]

Engtech ,K2

Here is a link to Tracy Tools in the UK please note they list in the left hand menu 'Slot Drills' and 'EndMills' as two separate items. Tracy Tools
A visit to either will confirm the visual difference. If you refer to my post #58 - I do say this terminology is correct for the UK and explain how they are used.

I guess after a long time of workshop machining with these two distinctly differing cutters maybe I need to start referring to them as 'centre cutting endmills' so that it makes sense to every one else. Crescent and Monkey wrenches mean little over here though but a shifter and a pair of Stilsons certainly do

Next thing someone is going to ask what HSS is - I put in slot drill in 'Google' and nothing but carbide comes up. Yep I'm a dynasaw all right but hanging on in there in true fashion

Regards - Tug

 

[Steamchick]

I never get tired of these discussions. But my car has tyred wheels.
Rainwater is collected in my butt, and traditionally, butter is churned in a butt. I could sit on one, but it isn't part of my body. The bottom of a hole is not the same as the hole in my bottom. If the bottom of a hole is not blind, is it a bottom hole?
I shall go and wash-up the pots and pans in the kitchen, before this is mis-understood.
K2

 

[Steamchick]

Sorry - mis-typed. Should have read... "if the bottom of a hole is not blind, is it a bottomless hole?"
K2

 

[Ramon]

Well I'm pleased to hear you know your 'bottom' from your 'bottom' K2

Keep smiling

Tug

 

[Steamchick]

Well I'm pleased to hear you know your 'bottom' from your 'bottom' K2

Keep smiling

Tug

Sorry, I seem to have hit the "Bottom of the Butt" - or "Barrel" if you prefer - with these puns... No-one was meant to be the butt of my jokes. I am smiling, even if others are not. Life is too short to miss every happy moment or thought! My Grandfather was especially amused by puns, as I am. So happy thoughts abound. Sorry if you find it sad Norman, though you have seen and been in some situations that you may prefer not to remember, I guess. and have experienced a lot my life than I have - yet.
I'll go back in my corner and chuckle happily to myself.
K2

 

[nealeb]

I gave up about the time I discovered that on one side of the pond you pay a bill with a cheque and on the other side, a check with a bill.

I suspect that even in the UK these days, the term "slot drill" is used more amongst model engineers than industrial users, certainly going by the online tool suppliers and model engineering magazines (which is where a lot of model engineers learn and so tradition lives on). My understanding is that they are used for slotting as they have less tendency to cut oversize. With two flutes, as one edge is entering cut, the other is leaving and the sideways forces are balanced, so the cutter stays central to the slot. With four flutes ("end mill" in old speak) two opposite edges are doing that, but the "leading" cutting edge is moving sideways across the cut, thereby deflecting the cutter sideways and leading to an oversize slot. And a three-flute cutter? Search me!

 

[Steamchick]

Hi Nealeb. What a concise explanation. Very clear to me. Can you explain why I have some helical cut end mills and slot-drills, and some straight cut? - Seems to me the straight cut may be to avoid any axial thrust that would occur with the helical cut - that could draw the cutter deeper than intended if there is any play in the Quill or column? (Depth of cut "Not locked")? I am just learning when to use which tool (where I have a choice in my limited collection). Also, I was taught to use an undersize tool, then finish to size (Gauge) where possible - as tools "never give a true size"... But I agree that "within tolerance" and for mass production to cut once with a true sized cutter is preferable.
Thanks.
K2

 

[goldstar31]

Well folks, as you will see-- I gave up literally in disgust at what was heading for pedantry and my suggestions of how to deal with 'holes of one form of metal another left me cold. I was never an engineer and consequently never had the confines of having to earn a crust in front of a machine or whatever people here do.
As I explained I was sufficiently bright enough to retire at 55- whatever that I was doing and again sufficiently able to retire for longer than I ever worked. For the last part of my so called working life, I made more money in my brief lunch break having found a slot that others didn't know how to fill.
This is what it is all about. IAs Model engineering is only a hobby for me, it matters not whether I buy a milling cutter or buy a new one or regrind one- or simply go and say 'Bugger it, it is +3C outside and it is pissing down' I've had9 illegally) a wonderful morning drinking coffee and tonight, like last Friday, another millionaire friend( Oh Yes) another millionaire friend that filled a slot or niche will start on a bottle of malt and how far down the bottle is a matter of pure conjecture.
OK, I'm an honest broker and suggested that for a very modest £10( a fraction of what we will sink tonight) and a heap of scrap, one could quite simply make a cutter grinder which would 'Do' drills of whatever one fancied-- and the whole thing was met with a devastating lous silence.
So, quite frankly, my beliefs are such that I should also help mankind as well as family and friends- and in this case that I in what I regard a shortlife time feel that if help is ignore d, I don't want to wate my time or theirs.

Looking at the topic, it has been dealt with with by people who sadly have had to continue to work.
Clearly, they have missed the slot that is actually available to all- if they can stop to see it.
Somehow, I doubt that slots of whatever source here are the answer.
My thoughts before I go and enjoy what is left of my life.
As you will perceive, I'm rather annoyed having wasted what I offered- freely and for nothing.

 

[L98fiero]

Can you explain when to use helical flutes and when to use straight flutes?

About the only place to use a straight flute end mill is in reinforced plastic to prevent fraying.
As for drills, straight flute carbide drills are typically used for drilling hardened steel and chilled cast iron but they are also be used for a variety of non-ferrous materials including wood and laminates to produce clean walled holes without pulling through and to prevent 'grabbing' in brass. They're obviously not good at deep holes unless using high pressure coolant through the drill.
I've used a 3/32" HSS single flute, straight flute to drill 1" deep in aluminum. It was used as a gun drill so the hole would be accurately positioned on the far side and because of the straight flute they had to be started with a stub drill and then use 0.03 pecks with complete pull out each peck and lots of coolant.

 

[Ramon]

Well we are all entitled to an opinion but I can't say I share yours Goldstar

Someone without the knowledge came on here to ask a basic question. As did some others I replied specifically to that question based on personal experience of being shown the technique some 40 years ago and in order to help that person. That lead as forum topics usually do to further discussion

To me that is what a forum is about - helping others where you can and accepting help from others when you need it. Disagreement is not about being disagreeble - well certainly not in my book.

I don't have millionare friends to share malt with but I do have malt to share - maybe we should take a closer look and consider the reason we're here - Home Model Engine Machining. Some will not have even made a wobbler - others will have just finished a radial - most will be somewhere in between.

Some will have no engineering skills or knowledge but are so very keen to acquire them - others will have more than enough of both, though, it has to be said, not always willing to share them. Those that do however - if their reason is the same as mine - is to help someone whenever they ask - if that's a crime then I apologise.

I too ceased working early and have enjoyed every day of it since. I approach 76 spending best part of the day most of the week in my shed working, believe it, or not on an actual engine (theres that reason again) and loving every minute of it. I'm quite happy to share some part of the day with others in a friendly exchange of views to further this outlook but not, it also has to be said, not if it promotes such churlishness

Now, I'm off to the shed to work on that engine - with luck it will be finished in a week or so.

Stay safe and keep on smilin'

Regards - Tug

 

[Cogsy]

I never get tired of these discussions. But my car has tyred wheels.
Rainwater is collected in my butt, and traditionally, butter is churned in a butt. I could sit on one, but it isn't part of my body. The bottom of a hole is not the same as the hole in my bottom. If the bottom of a hole is not blind, is it a bottom hole?
I shall go and wash-up the pots and pans in the kitchen, before this is mis-understood.
K2

Well if you want to get really technical (and speak in the language of true geometry) a hole cannot have a 'bottom'. A drinking straw has only one hole and a drinking cup has none. If we drill or bore into a piece of material we don't make a hole unless we go all the way through. Language is weird...

 

[goldstar31]

There is an ld and accurate saying'Never look a gift horse in the mouth'. Studiously it is insulting not to acknowledge help from whatever source- and it hasn't happened. It costs little to say Thank you or indeed 'I don't agree or don't understand.

Over the years, and check my llikes, I have noted the horrendous number of number of people who have asked and left the site and worse still the valuable contributors who are no longer here anty more.

It would seem that my point is borne out by the loss of free help.

I recall the note that the late Don Ashton -author of valve gear definitive works on valve gear which he actually published at his own expense remarking somewhat bitterly that people were asking the same silly questions-- and getting the same silly answers.
Don died recently and it took weeks for someone to acknowledge his contribution to model engineering though NOT an engineer . He repaired musical instruments and wrote music.
He wrote music for my wife also sadly missed but Don and I were friends. Don was an unassuming World Authority on many things. He would have wholly agreed but saddened by the fact that he got so little recognition from this forum.

 

[Steamchick]

About the only place to use a straight flute end mill is in reinforced plastic to prevent fraying.
As for drills, straight flute carbide drills are typically used for drilling hardened steel and chilled cast iron but they are also be used for a variety of non-ferrous materials including wood and laminates to produce clean walled holes without pulling through and to prevent 'grabbing' in brass. They're obviously not good at deep holes unless using high pressure coolant through the drill.
I've used a 3/32" HSS single flute, straight flute to drill 1" deep in aluminum. It was used as a gun drill so the hole would be accurately positioned on the far side and because of the straight flute they had to be started with a stub drill and then use 0.03 pecks with complete pull out each peck and lots of coolant.

Thanks Fiero for explaining that one.
K2

 

[Steamchick]

Goldstar: I humbly apologise if I have offended you with my lack of knowledge, or daft comments, but having a lot of hand-me-down tools and second-hand tools when that was all I could afford, (re-ground under-size by the tool-maker who owned the shop), I have a variety of patterns of milling cutters without the knowledge to know when to use which type. This thread has helped greatly - including your contribution. For that I thank you all.
K2

 

[goldstar31]

Ken,

Beware of even well intentioned information. Many thousand engraving machines have been produced in England, in gernany and China as clones to make 'flat engraving cutters' Amongst my assorted miscellany, I have a 'Chinese'. It may well be capable of grinding lathe tools to a high degree of precision and can alter fluted tool blanks to twist drills, end drills, mill drills and whatever- in essence that is what it is-- and the original Deckels and Alexanders are or were astronomically priced, the Chines ones are only slightly less breathtaking. Reminds me that I could utilise a lot more 5C collets for mine.
thinks it is possible to buy a se t of plans for an adequate tool and cutter grinder using the scrap box for less than ONE 5C collet

best Wishes

Norman