Adapting a pillar drill for vertical milling - new chuck

[MRA]

Hi folks

I have an old Elliot Progress No1 bench drill which is clamped up to a small 3 axis table - which looks like it came from an equally ancient small milling machine. The drill is quite good - heavily made cast iron body, large spindle for a small bench drill, very little run-out.

At the moment, it's great for positioning holes for drilling, but not much use for milling since holding cutters in the 1/2" drill chuck creates too much chatter for anything but really light cuts. I'd like to make a more suitable chuck for milling cutters and perhaps a fly cutter.

The spindle is solid - so no possibility of using a draw bar without a strip down and attempts at boring / modifications - and at the business end rather than female MT2 there is a male 6JT taper with a length of 3/4 x 26tpi thread above, which normally takes the knurled ring which is used to push the chuck off its taper, if one wants to remove it.

I wondered about making a milling chuck with an internal 6JT taper on the back, but also with a 3/4-26 thread to do up on the spindle - since I doubt a taper alone (with no draw bar) will hold for milling. I'd have to put substantial flats in it to help screw it off, since the idea would be for it to be a rather good fit...

What do folks think? And any ideas for the kind of chuck I might need to make, for a variety of small cutters?

cheers

Mark, Manchester, UK

 

[Blogwitch]

Mark,

After trying to modify a friends drill press into a small mill, all I can suggest is, don't bother.

We tried for about a month to sort out each problem as it reared it's head, and eventually had to give up.

I came to the conclusion that although the drill press might seem rigid, it just won't have the quill support to carry out any decent milling, and you have already come up with the problem of not being able to have a drawbar. Well on ours, we did manage to get one in there, but it was still a failure.

Drill presses are designed to go straight down without having any side loads.


Bogs

 

[GLCarlson]

Hi folks

I have an old Elliot Progress No1 bench drill which is clamped up to a small 3 axis table - which looks like it came from an equally ancient small milling machine. The drill is quite good - heavily made cast iron body, large spindle for a small bench drill, very little run-out.

At the moment, it's great for positioning holes for drilling, but not much use for milling since holding cutters in the 1/2" drill chuck creates too much chatter for anything but really light cuts. I'd like to make a more suitable chuck for milling cutters and perhaps a fly cutter.

The spindle is solid - so no possibility of using a draw bar without a strip down and attempts at boring / modifications - and at the business end rather than female MT2 there is a male 6JT taper with a length of 3/4 x 26tpi thread above, which normally takes the knurled ring which is used to push the chuck off its taper, if one wants to remove it.

I wondered about making a milling chuck with an internal 6JT taper on the back, but also with a 3/4-26 thread to do up on the spindle - since I doubt a taper alone (with no draw bar) will hold for milling. I'd have to put substantial flats in it to help screw it off, since the idea would be for it to be a rather good fit...

What do folks think? And any ideas for the kind of chuck I might need to make, for a variety of small cutters?

cheers

Mark, Manchester, UK

Your concern about the safety of a typical drill setup for milling is well-founded.

DO NOT hold end mills in drill presses! Or use a drill press for milling. This is a very serious safety issue. The chuck (actually, the male taper holding the chuck) is unstable when exposed to the side forces encountered in typical milling jobs, and the chuck and tool WILL come loose. How badly that ends depends on speeds, materials, and luck... Don't even think about a fly cutter or interrupted cuts.

Yes, I'm aware that people do this all the time, and often (usually, in fact) get away with it. Doesn't change the inherent danger. Getting hit anywhere with a sharp tool weighing several ounces will really ruin your day. There is a drawbar on that R8 collet in the milling machine for a very good reason.

Use collets (the ER20 is common in mill tooling). With a drawbar or equivalent, either an internal or external taper connecting the collet chuck to the spindle should be tolerable.

All that said: converting a drill press to a light duty mill can be done, but it's probably cheaper and in the long run better to spend the same amount of money on a light mill (a Sherline or some such).

 

[MRA]

I know what you mean - in its last incarnation (using a really spindly top off a more ancient drill) the thing was really unhappy and developed all sorts of resonances which meant I had to cut very slowly. But - since it's this or nothing - I think I'll persevere for a bit.

I've greased the spindle bearings this afternoon and there's no play in it. I also lapped the chuck onto the taper and now it's pretty true, though the taper had obviously picked up at some time in the past.

Apart from increasing the torsional rigidity across the quill bearings, which would require some kind of bolt-on framing - not impossible, but creating a real Franken-machine! - the other obvious problem is that there's chatter on the long keyway cut all along the spindle, through which power is applied. I think I can take this out - just when the spindle is fully 'up', which should be OK as the table rises and falls - with an extra gizmo to lock the protruding spindle top to the drive pulley.

A bit of browsing reveals cheap-ish Chinese JT6 ER25 collet chucks - but with no draw bar. But since I have this 3/4" 26tpi thread on the spindle above the male JT6 taper, I guess I can make a really big hollow nut and press-fit the cylindrical, hard, collet chuck into it.

After all this, I'll come and tell you all how ****e it is

 

[MRA]

A bit of progress - having got the quill apart, it seems the spindle has a conventional deep-groove ball race at each end - dealing with side loads, perhaps - the lower one being backed up by a thrust race. The hope is I can persuade the thrust race to transmit thrust 'up' - as in normal drilling - but also 'down' - as when a milling cutter takes a big bite and tries to drag the cutter out of the chuck. I _think_ with some careful shimming, and perhaps some minor spindle modification, this might be made to work.

 

[Wizard69]

I really wouldn't bother with this!

 

[MRA]

Nor would I if I had the funds and the space for a decent milling machine Everything has to happen inside a 10'x12' shed with no access other than what I can carry in by hand (including the Progress drill - all 115kg of it - for a short distance!) , and to cost approximately nothing. I enjoy looking around and remembering the folks who have donated things / skips my legs were poking out of - It's OK if you approach it as an exercise in personal growth...

 

[bazmak]

I agree,it will work but have limited use but the fun is doing it.I posted a thread on converting a wood lathe to metal purely to see if i could.It worked got, little use and was then converted back.I then reused parts for other things
IE the T slot carriage became an angle plate for the new mill.I have said it before and will say it again you get more pleasure from making tooling and using it than making engines

 

[Wizard69]

Nor would I if I had the funds and the space for a decent milling machine

Believe me I understand I've yet to put a shop together that I really want. However I've actually tried this, that is using a drill press as a milling machine. I can say without reservation that actually using a drill press in this way is an extremely dangerous approach to machining.

Everything has to happen inside a 10'x12' shed with no access other than what I can carry in by hand (including the Progress drill - all 115kg of it - for a short distance!) , and to cost approximately nothing. I enjoy looking around and remembering the folks who have donated things / skips my legs were poking out of - It's OK if you approach it as an exercise in personal growth...

 

[barnesrickw]

There is a DVD somebody is selling about milling on a drill press. I'm assuming you've already searched the subject though.

 

[MRA]

Well, I take folks points entirely about the danger inherent in trying to mill whilst using a drill chuck on a taper - and I have a collet chuck on order, and a means of retaining it positively to the spindle.

I also understand that I may well create a god-awful finish, mill extremely slowly, and maybe break an endmill or two if I am not careful. Well, OK.

If it offends your sensibilities, folks, then perhaps I can assuage your reservations about my crimes against machinery by saying that if makes a fine mortice-cutter, and is handy for reducing the cheeks on tenons too. Not model engine work, but hey, at the moment I am building fitted cupboards!

I wonder if any US reader with time to spare, might like to spend a moment's googling to enquire whether imperial-sized taper roller combo A6075/A6162 is available there for less that I have been quoted here in the UK, land of the almost-metric? Here the best I can do is £25 each (for a full set), delivered - which seems rather steep when one is contemplating buying two sets.

Thanks for your interest, folks - Mark, Manchester UK

 

[barnesrickw]

If nothing else, you will learn something. I unsuccessfully tried it, but ended up with a accurate drill press. So Good luck.

 

[Cogsy]

I wonder if any US reader with time to spare, might like to spend a moment's googling to enquire whether imperial-sized taper roller combo A6075/A6162 is available there for less that I have been quoted here in the UK, land of the almost-metric? Here the best I can do is £25 each (for a full set), delivered - which seems rather steep when one is contemplating buying two sets.

I'm not in the US but I'm a fairly good googler so I had a look around. For a decent brand that price isn't too bad at all. You could get generic Chinese for a bit cheaper but I wouldn't use them. Best I could find quickly was about US $27 for the two (individually) for NTN brand, plus shipping x 2 so would probably end up around the same price but take longer to get to you.

 

[MRA]

Thanks Cogsy

I did some more Googling too, and eventually the light dawned that that set of rollers can come with two different cups - I need the smaller OD, and they're (even) more expensive than my £25 option. The part numbers I put on here are correct, and the best price I can do has gone up to £40 a set, which rather makes your find look competitive! I did find some much cheaper from a Canadian outlet, but the listed postage was wild. Well, I've contacted them, and we'll see.

I like your sig, by the way. I also need to work on patience and skill, but fortuitously my perfectionist sense of harsh self-criticism is already up and fully functional

 

[Nick Hulme]

It's an interesting project which will leave you with a beefy pillar drill with co-ordinate drilling capability when you reach the limitations of it's milling capacity and upgrade to a dedicated milling machine.
Don't forget that a lathe with a vertical slide also provides very capable if dimensionally limited milling capacity,

- Nick

 

[MRA]

Well, this is moving along a little. A Chinese ER25 collet chuck is now fitted to the spindle, press-fit into a holder which engages with a 3/4" 26tpi thread on the OD of the spindle. There's very little run-out on the spindle, and not much on the chuck now I've cleaned up the JT6 taper on which it locates. Bearings are the original deep-groove and thrust race types - there's no play, so I'll use it for a while to see how they stand up before fitting taper-roller types which I bought from USA - about 50 quid all in, so rather blowing the budget. Moving us back in the right direction, an elderly 'NECO' 1/2hp brushed dc motor and speed controller just came my way for nowt, which should slow things down nicely.

 

[MRA]

Well, that 18 months went quick!

to recap - I'd attached an ER25 collet chuck to the spindle of my old Elliott Progress No.1 bench drill. The spindle has a JT6 taper on the end, and I'd bought a chuck with a JT6 bore in it. This I had press-fit into a steel carrier, and together they screw on to the fine 3/4" OD thread which normally takes the chuck ejector nut.

Even with the old 1/2hp DC motor and speed controller which came my way, it wasn't (as folks here predicted) a great success. There was a lot of chatter, I could only put really small cuts on, and now and again it would grab a great big hand-full, bend and grab some more, and break a tooth off an end mill.

Lately I started looking at it again, thinking about the small Chinese verticals which folks have success with on here, and thinking about the Bridgeport at work. It stuck me that there were some obvious places where the bending stiffness of the thing was not great, and that I could experiment with stiffening it up while not doing anything which would not be completely reversible - so I would not wreck my drill.

Next post, I'll add some pictures.

 

[MRA]

Here's a picture of the spindle. You can see the JT6 taper on the end, and the fine thread above it which I've used to retain my collect chuck. What you can't see is that up the middle of all this is a female MT1 taper! This leaves a pretty thin section of tube, which is strong enough in torsion to take whatever torque is asked of it but is pretty ****e in bending.

Where the shaft thickens up, it goes from 3/4" to 1". In my toolbox there was a metric bearing with a 25mm inner race (6205? I can't remember) and 47mm
OD. I thought perhaps I could turn .4mm off the shaft diameter, add the bearing, and make some kind of truss to pick up the end of the quill. So, here goes.

 

[MRA]

Here, you can see what happened when I put the chuck and adaptor on the spindle, and the bearing on too. There was a gap between them, where the thin 'tube' spindle was only 3/4" OD. I thought I could do better than this by making a thick washer to take this gap up, and so stiffen it all up some more - so I measured the gap (by poking drill bits into it as feelers!) and made one.

Then I set the thing up and had a go with it. It worked much better - and this was with nothing holding the outside of the new bearing, just with a stiffened spindle.

In the pics you may be able to make out the general arrangement. The 3 axis table is off what I imagine was a small horizontal mill, but the drive, arbor and overarm are missing (I never had them). Maybe I'll make all that too one day, perhaps from a lathe headstock if one comes along cheap.

I've stiffened things up using the moving table from the drill, which is turned upside-down and bolted to the top of the column which holds the 3 axis table. This casting is bolted to a really thick lump of bench top, next to the base table of the pillar drill. The top of the drill spins around its pillar, so you can rotate it (like on a radial arm drill) to a position where it is 'right' for the milling table, or you can spin it round a bit and use it over the base table (perhaps this might be called the foot) of the pillar drill itself.

 

[MRA]

And finally, to the truss required for my floppy spindle (oooh, nurse, the screens! ).

The last pic shows a rather unlikely parting operation on my small lathe - I had a big lump of bar which I could have cut up at work, but it was my girl's 12th birthday and the house was full of giggling 12-year-olds listening to horrible music.

Since this is the internet and one never knows who is reading, I ought to add that the idea is to stop parting while there is a 1/2" or so remaining, and finish off with a hacksaw. So that's what I did.

Common sense then prevailed, and I left the rest until tonight after work. There is a large lathe there, drill bits up to 2", and the Bridgeport which provided some of the inspiration for all this. So I made the truss in one piece, drilled and tapped it for clamping screws, and then cut it it half on the large, powerful and not-very-accurate Wicksteed power hacksaw we normally use for cutting up large RSJs. This was rather a scary operation as it would be easy to scrap it all at the finish - but I was lucky and got it near-enough in half that I could relieve the edges of the cut with an angle grinder, and it fitted well.