If I were going there…

[Robin GrahamParticipant @robingraham42208]

I wouldn't be starting here, I seem to hear… but

I've been asked to upgrade a cheap (Lidl, Parkside) drilling machine by making a longer column for it – at present the column is 430mm, and the 'customer' wants it extended to 750mm, whilst still being able to go back to the original length when necessary. Personally I think he should just buy a bigger drill, but not my call.

I've made the flanged collar to fix to the drill's base plate, and 'first stage' column from solid bar. My thought is to make a threaded recess and female register at the top of this to mate with a similar (male) arrangement on the 320mm extension. Sort of like how a Myford chuck mounts, not that I have one. So my questions are (a) is this a reasonable plan, and (b) if so what sort of dimensions might be appropriate? I was thinking of maybe a 25x2mm thread and a 35mm diameter x 10mm deep register, but these numbers are just plucked from the air really. I'm thinking of the deep register in case it's necessary to bung in grub screws radially in the top piece to stop it loosening in use.

Any thoughts welcome, would like to get this done and dusted tomorrow!

Having 'upgraded' to a bigger lathe I feel I'm back to square one again!

 

Regards, Robin.

 

 

Edited By Robin Graham on 30/05/2015 22:38:27

[Robin GrahamParticipant @robingraham42208]

[Sam StonesParticipant @samstones42903]

Beam (column) stiffness is proportional to length cubed, not to mention further losses at the screwed joint.

Or did I get it wrong?

Regards,

Sam

[Sam StonesParticipant @samstones42903]

Oh! – And the fourth power of the diameter.

[steveteeParticipant @stevetee]

My cheap pillar drill , bless it's heart, bends like crazy when you press on a bit . I don't have the maths to prove it but, I would have thought that with a longer column, it would twist like the Cavern Club back in the 1960's

[Capstan SpeakingParticipant @capstanspeaking95294]

My thought is that if you charged a commercial rate it would be more than a new drill !

To compensate, I hope you enjoy doing the work…. a lot

Silk purse and sow's ear applies.

[BikepeteParticipant @bikepete]

Sorry if I'm missing something but why are you even considering a joint in the column? Surely you (or he) just needs to buy a new 750mm length of column material. If he wants to revert back, he fishes the old shorter column out from under a bench and refits it….

Edited By Bikepete on 31/05/2015 09:23:57

[Neil WyattModerator @neilwyatt]

I think you meant stiffness is inversely proportional to length cubed

At some point I will do a test on my pillar drill – I need some way of measuring the force accurately – you need about 50 to 70lbs) but a bathroom scale won't fit on the table. Perhaps I can find a valve spring and measure its length, or just measure deflection while drilling a hole for a rough and ready but practical test?

Neil

[BikepeteParticipant @bikepete]

Neil – String pulling horizontally, pulley diverting it to vertical, (known) weight on end of string…

(edit) …for a column deflection test, anyway. Wouldn't capture flex in head and table as your schemes with a force applied betweeen the two will.

Edited By Bikepete on 31/05/2015 09:47:44

Edited By Bikepete on 31/05/2015 09:48:10

[RobboParticipant @robbo]

Thought the same as Bikepete, ie just get a longer length of column tube and swop one for t'other.

If you have to have a joint then a good plain socket without the thread should do for this quality of machine.

Whey not tell him to mount the drill at the edge of his bench, then he can swivel the head round over the edge and fix drilling tables wherever he wants down the side of the bench.

[john carruthersParticipant @johncarruthers46255]

Mine has a 46mm column, I assume the Aldi machine is similar? not a common size for tube but usually available as solid bar.
Parkers (Canterbury) stock it.
Scaffold tube is 48.3mm diameter with a 4mm wall thickness, could be turned down?
I had to increase the daylight on my little drill to accomodate an x/y vice.

Here's a similar modification;
http://mikesworkshop.weebly.com/drilling-machine-improvements.html

 

Edited By john carruthers on 31/05/2015 10:25:27

[Gordon WParticipant @gordonw]

My cheap bench drill is similar, the column was undersized, on diameter, so made a new one from scaffold tube, mean to fill with concrete to improve stiffness but does not seem like much point. I use a scissor jack under the table when pushing anything bigger than 5mm drill.

[mechman48Participant @mechman48]

Much more viable to get the correct length thick wall tubing or solid bar… not worth the time, effort, energy usage costs….

George.

[IanTParticipant @iant]

Robbo beat me to it – apart from changing the pillar for a longer length or inserting an extension piece – mounting the drill over the edge and rigging the table lower is a usable bodge for one-off jobs.

For anything much more than that – I'd get a better/larger drill.

In fact – I purchased one of these small drills from Lidls a few months ago (wanted a smaller one for the inside workshop) – took it home, had a brief look at it and took it straight back for a refund (which I got no problems). OK for drilling holes in lumps of wood maybe but it wasn't going to even meet my (admittedly low) standards. The quill was really loose, it had the roughest chuck I've seen and the motor very, very noisy (really awful!)… So no – not the basis of a tool I was going to spend any time with – let alone 'improve' or try to modify. There are much better starting points…

But the thread is "If I were going there" – and fortunately most of us are not….

IanT

[Peter G. ShawParticipant @peterg-shaw75338]

There's nothing new here. Alex Weiss in Model Engineer (07 April 1995) described how he extended a Nu-Tool DIY13 bench drill by 100mm using a length of scaffold tube as his tube was a nominal 48mm.

I have also extended my Nu-Tool CH10 bench drill by using a 150mm solid length of steel turned down to a nominal 46mm with 50mm further turned down to form a spigot which was then glued into the existing column using Araldite Rapid Steel. The reason for doing this was because of the non-availability of thick-walled 46mm tube.

I cannot comment of stiffness: suffice to say that the machine itself even when new was hardly a paragon of accuracy (although better than the B&D drill stand it replaced) but it does what I want.

Regards,

Peter G. Shaw

[Michael Cox 1Participant @michaelcox1]

It always surprises me when manufacturers choose odd sizes for components.

In the case of small drilling machines 46 mm for the support tube seems to be common to a number of manufacturers. But why iuse a non standard size? A standard size like 45 or 50 mm would seem much more logical. I did think that maybe 46mm was a metric conversion of a common imperial size but it works out as 1.13/16" which does not sound particularly common either.

Mike

[Sam StonesParticipant @samstones42903]

Neil said … I think you meant stiffness is inversely proportional to length cubed

You are absolutely right Neil – SORRY LADS AND LASSES – MY MISTAKE!!!

Sam

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Cox 1 on 31/05/2015 18:32:41:

… I did think that maybe 46mm was a metric conversion of a common imperial size but it works out as 1.13/16" which does not sound particularly common either.

.

Entirely reasonable, Mike … if it was originally designed for the American market.

MichaelG.

[Robin GrahamParticipant @robingraham42208]

Thanks for your myriad replies – too many to address every one individually, but all read, digested, and appreciated.

Concensus seems to be that doing this borders on lunacy – I too thought it mightn't be the best way of getting to where the customer wants to go (hence the thread title), but I took it on because it gives me the opportunity to try some new things out, so customer gets what he wants, I learn summat, win-win. As Capstan says, if I charged commercial rate for this the guy could have got himself a new drill… Meddings probably, time it's taking me.

The column is indeed 46mm and I sought far and wide (but not so far as Canterbury – thanks John C) for tube or bar, but found none to size locally, so worked with 2 inch stock.

Scaff tube was my first thought, but it would have ended up too flimsy by the time, with my limited skills, I'd got it round and straight (the stuff I blagged off local builders was neither).

Should say that this is for woodworking, so maybe it'll work….

Anyhow, I'm learning stuff, so thanks again,

Regards, Robin.

[Michael GilliganParticipant @michaelgilligan61133]

Robin,

A perhaps non-intutive, but entirely practical, approach would be to extend the column with a box-beam made of decent quality plywood.

You could cut the steel column into two 'halves' and cross-drill as appropriate … Your woodworking customer could then make the box-beam to fit.

MichaelG.

P.S. … Some re-design of the table [if it has one] would also be required, of course.

Edited By Michael Gilligan on 31/05/2015 21:26:42

Edited By Michael Gilligan on 31/05/2015 21:29:32

[Jesse Hancock 1Participant @jessehancock1]

Interesting choice of word Stiffness instead of say rigidity. Or is it just me?

Anyway it all becomes a bit obvious when viewing a box of twist drills… there is a reason why they don't make foot long 0.5mm drills well not to my knowledge anyway.

I extended my cheap bench top drill press using 45mm solid bar and cutting it by hand to suit the lathe between centres. (turned to suite the tube) I think it was about 400mm in length but I wasn't fussed as long as it raised the head to accommodate the rotary table.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Jesse Hancock 1 on 01/06/2015 06:57:56:

Interesting choice of word Stiffness instead of say rigidity. Or is it just me?

.

It's just you, Jesse

MichaelG.

[Sam StonesParticipant @samstones42903]

Hi Jesse,

I tried to find where I had first used (heard of) stiffness as a property in Beams and Bending. No luck there, but here are another couple of terms I remember from years ago.

Slenderness ratio – The ratio of the effective length of a column to the least radius of gyration of its cross section.

It’s why it will be difficult if not impossible to find those long, small diameter drills.

Best regards,

Sam

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 01/06/2015 08:03:39:

Posted by Jesse Hancock 1 on 01/06/2015 06:57:56:

Interesting choice of word Stiffness instead of say rigidity. Or is it just me?

.

It's just you, Jesse

MichaelG.

.

Jesse,

A more useful answer:

In engineering; a rigid body is one with infinite stiffness

… i.e. no amount of force will deflect it.

Rigid is therefore an absolute; you can't have have degrees of rigidity.

MichaelG.

Edited By Michael Gilligan on 01/06/2015 22:06:20

[Robin GrahamParticipant @robingraham42208]

Michael G -that works for me, I come from a physics background, but the same terminology is used – when setting exam questions, when one says rigid one means inflexible…

Tonight this project taught me several things, the foremost being that I shouldn't clutter the mat on the headstock housing too much – experimenting with feeds and DOC, as one does, I got a chatter at some speed which dislodged something off the mat and sent it chuckwards with a BANG. It went past my left ear (it turned out to be steel rule) – if I'd been a foot to the left it'd have had half my face off. Really – it ended up embedded in a chunk of wood. So I I need to be tidier. Or maybe I should put the chuck guard back on which gets in the way mostly? It's scary how fast bad things happen when they do – no point in clenching buttocks, it's all over before you know.

Don't try this at home I guess,

Regards Robin.

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