Basic(?) Milling question

[paulmichael1084Participant @paulmichael1084gmail-com]

Now, this will doubtless have some people shaking their heads in despair. Old timers sat around the kettle at my first engineeeing job, I’m looking at you!

But the rest of us, I have no doubt, are wise enough to know that in engineering (and many other fields of human endevour) there is no such thing as a stupid question, just people too stupid to ask questions.

I have recently aquired a Wabeaco F1200 mini mill, which is rapidly becoming my new obsession. Yesterday I encountered a scenario where I wanted to mill a low profile billet directly on the bed, but the head would not go low enough. The only way I could see to do it would be to extend the….. quill? or is it the spindle? Anyway the spinny bit thay holds the tool, to extend that down as if I were drilling, then lock it down and then mill by moving the table in the traditional manner.

However I have never seen this done, and wasn’t sure if it was a REALLY bad idea or not. I read the manual several times, but no mention is made of this style setup\technique.

I’ve attached some pics and I would very much appreciate comments.

To those who want to know how this story ends I lifted the billet up on paralells to lift it up

[John HaineParticipant @johnhaine32865]

Quill. Perfectly fine to do what you did. I tend to work by setting the work in a vice or clamping to the table then bring the quill down to just touch the surface and lock it. Then set the Z dro to zero and use the Z feedscrew to put on the cut. Best to minimise the amount of quill feed for maximum rigidity.
<p style=”text-align: left;”></p>

[JAParticipant @ja]

I have a similar Wabeco mill but with a larger table.

I would lift the plate to be machined on to, let us say, 1″ high steel blocks. just as you have done. The clamping pieces look like Myford parts, just like what I would use. I would make sure that the clamping end was lower the the supported end (your fine photos do not make this clear). Obviously lock all the slides you are not using prior to machining. Machining a “T” slot is a brutal introduction to milling. It took me years to pluck up the courage to cut one in steel. Only a visit to a Myford’s open day convinced me that I could and I then did so without any difficulty.

As soon as you can get a good 3 axis DRO. Milling machines need DROs. On lathes they are just nice to have.

JA

[paulmichael1084Participant @paulmichael1084gmail-com]

<p style=”text-align: left;”>Thanks very much for the feedback.</p>
3 axis DRO on order, due Monday.

1. @ja cutting a slot in steel would have been preferable. I didn’t have a proper Ali cutter  so used one for steel which kept getting fouled up!
   Anyway got there eventually and it did the job

[PeteParticipant @pete41194]

No despair at all, if your not sure it would be foolish to not ask. Depending on the tool diameter, depth of cut and feed, it may not be a real issue. As a general practice, it would still be better to have the milling heads spindle retracted and locked while making your Z axis elevation changes by lowering the whole head for a few reasons. And cutting tee slots would in my opinion be definitely one where I’d do so. You already have a fair amount of collet chuck and tool length below the spindle bearings. And secondly, doing it that way moves the head down on the column which also helps with increased rigidity. The trade off I suppose is the head obstructs seeing the cut a bit. For parts like your doing, the common 1″,2″,3″ or 25, 50, 75 mm blocks are a handy and reasonably priced accessory for raising any part for clearance etc.

Unless there’s good reason for using the spindles Z axis such as a protruding feature on the part or caused by the part clamping. I keep my spindle retracted and locked and make any Z axis moves using my BP clones knee. Drilling, tapping, boring, reaming are about the only time I make use of the spindles Z axis movement. You also did a good job of moving the tee slot bolts as close to the part as possible. 👍

[VicParticipant @vic]

Many years ago I was told by an experienced machinist that the quill should be firmly locked in place for milling operations so that’s what I’ve always done on my Warco VMC. Only my personal opinion but I think the OP did the right thing by raising the workpiece.

Edit: My VMC has a drilling handle for the quill and also a fine feed wheel for the quill. I took the wheel off years ago.

[JasonBModerator @jasonb]

Alway preferable to have the quill retracted where ever possible as it is a more rigid setup. Plus if the tram and parallelism between head and quill are not what they should be you can end up with things not being quite where they should . I won’t say I don’t do it but generally only for light cuts not anything heavy like a tee slot.

 

You also look to be using a Woodruff cutter to form a tee slot which is not ideal as the narrow shank is not straight and can rub. It also limits the depth of the tee slot that can be cut and results in what you have there with very little material at the top of the slot, which will easily distort under the typical loads put on a tee nut.

Also usual practice is to run a straight sided cutter through first that is a bit deeper then the bottom of the tee which helps with clearance of swarf and less for the tool to rub against.

[bernard towersParticipant @bernardtowers37738]

Sorry Jason but I disagree with your last paragraph, the usual practice is to cut a slot a few thou less than the finished depth and when the T slot cutter is used it cleans the bottom of the slot up. If you look at comm T slots they have no witness mark at the bottom of the slot.

[bernard towers]

On bernard towers Said:

……If you look at comm T slots they have no witness mark at the bottom of the slot.

Here is a picture of the T-slots on my Bridgeport vertical mill:

Clearly as per JasonB; my Adock & Shipley horizontal mill is the same. In contrast my commercial, but not industrial, CNC mill does not have the central relief.

I also vote for not milling with the quill extended. I use the quill for drilling, reaming, tapping (hand and power) and boring. At all other times the quill is locked.

Julie

[egaParticipant @ega]

Interesting thread but is it possible to switch off the code eg “<ptext” in OP post?

I realise it may be a function of my browser (Firefox) and would be grateful for a helpful hint.

[JasonBModerator @jasonb]

Thanks Julie, that saved me having to take a photo.

With the less than rigid hobby machines anything that will reduce the loading helps so not having the cutter clearing up the bottom is one of those. You can always go back and take a second slightly deeper pass if you want a smooth bottom.

As the OP was cutting aluminium the deeper central pass also means that if you run a stud through the tee nut and into the table it does not chew up the surface a loose nut slides on so easier to place your nuts.

Ega. I’ve cleaned up the original post. I think is sometimes shows up when the text is copied and pasted rather than a problem your end

[egaParticipant @ega]

Thanks, Jason; good of you, particularly as posters can use the edit feature to do the cleaning.

As has been pointed out by others, tee nuts should be centre punched to stop the stud protruding.

[BazyleParticipant @bazyle]

For readers with round column mill the option of lowering the head to increase depth during the job is not so viable so using the quill is the only way but needs to be kept to the minimum, and of course locked after each move. In this case lower the quill, lock, then back wind the handle so that slack in the rack is taken up to help prevent cutting forces (from the spiral on the cutter) pulling the depth down a bit. Actually this apples to all mills with quills.

Back to the first post. This was a good question because I don’t recall it being asked before in years of the forum but there are some stupid questions – namely ones where ten seconds searching provides the answer tenfold. How I hate the facebook jockeys who make no effort at all but just expect everything to be handed to them on the ‘phone screen.

[paulmichael1084Participant @paulmichael1084gmail-com]

Thanks to everyone who contributed, very much appreciate your input. My takeaway is “don’t do it unless you have no alternative”

The slot I cut is actualy a test peice to test a proposed ali extrusion and clamp method, pic of a trail run attached. It is indeed a woodruff cutter as that was recomended. What is the alternative?

I did mill a vertical slot deeper than my first pass with the woodruff, then cleaned it up with a second pass. The depth to the too of the slot is 2.5mm from the top of the peice because that is how the potential extrusion is designed.

 

[JasonBModerator @jasonb]

I tee slot cutter is probably a better option. As I said earlier the reduced diameter part above the cutter is parallel and often more substantial than that of a similar size woodruff cutter, making for a more rigid cutter. There are no doubt some subtle differences in the geometry of the teeth too with a tee slot cutter cuttng on the top and bottom not just the side like a woodruff..

[Julie AnnParticipant @julieann]

Woodruff and T-slot cutters:

Woodruff cutter at the bottom, T-slot cutter on the top. The Woodruff cutter shank needs to clear a round shaft, hence the curved relief on the shank. A T-slot cutter only needs a small amount of parallel clearance so the relief on the shaft only needs to be small and parallel. The T-slot cutter will be much more rigid. Note that the T-slot cutter is much wider than the Woodruff cutter. Woodruff key widths are on a par with square and tapered keys and tend to be narrower than the depth of a T-slot.

I chose the metric side of the rule in case anyone had an attack of the vapours seeing imperial measurements.

Julie

[Clive FosterParticipant @clivefoster55965]

Working with minimal quill extension is best practice and will become second nature with practice.

However in general it’s not a good idea to run things will adjustable movement and locks butted up against the mechanical end stops. It’s possible for things to slide back under the influence of forces and jam up against the end stops. Particularly worrisome if the axis in question doesn’t have proper stops. Just coming up to the end of travel with enough solidity to notice on the hand control. Unsticking that sort of issue can be fraught.

Leaving a touch of quill movement, 1/2 inch or 10 mm will be fine, so position is held only by the locks has no serious effect on rigidity and gives you a chance to spot trouble if things do slide before anything serious happens.

If things do slide against the locks you are either overloading or there are mechanical issues with the lock.

In over half century I’ve only ever seen this or an equivalent effect cause significant trouble twice. Sorting without further derangement was a nightmare. I have seen older machines with damaged ends to feed racks where things have been pushed a bit too far. Not the sort of thing you want to happen to your pride and joy.

Clive

[Author]

Posts