First Time Milling Cutter Issues Help Needed Please

[Jamie JonesParticipant @jamiejones42723]

[Jamie JonesParticipant @jamiejones42723]

First time Milling Issue Advice Please

Lined up some Steel in the Vice (25mm Thick) and trying tidy up the edges and straighten them up.

Using a 20mm End Mill with the advancing cutter blade facing the top of the work piece as it rotates.

Using the metric speed calculation Steel 100 x 100 = 10,000 / cutter size 20mm = RPM speed of 500

The edge being end milled is not level. The cut on the right is starting to address the un-evenness of the material. I have gently feed the cutter in… Too fast causes the cutter to smoke and jam. Trying a bit slower and there is very little in the way of a cut… Splinters…

I have then tried running along the work piece in a thinner cut, ie the left third with a view to tidying the end in three passes. ie 1/3rd in, 2/3rds in and the last being the whole width of the work piece.

But the second pass is not as deep as the first pass even though the cutter height has not changed. The head is locked off and the work piece is secure…..

I did expect that cuttings to be bigger than splinters from most of the youtube videos I have seen… Just not confident to force the cutter in any faster.. I have tried slowing the cutter speed down by 150 rpm incase it is tougher grade steel than I expected and also increasing it 150 rpm on the original speed.Without any effect…

Can anyone offer any advice?

[Neil WyattModerator @neilwyatt]

You'd be better having the steel plate clamped horizontally, packed up from the table. Even a 25mm plate has some flex, and that's a lot of leverage that will exploit any flexibility in the vice..

Mainly though, you are climb milling and the action of the cutter is tending to lift it out of the work, it will also tend to pull the work along in a series of jerks

Try reversing the direction of cut. and see what happens.

Neil

[Jamie JonesParticipant @jamiejones42723]

Hi Neil

Thanks for the advice.. The item is larger then my machines bed.. It had two sides that was at the correct 90' so I used them as a basis to try and straighten up the other two sides.. I was concerned that due to the work piece's size that I might not get a secure enough clamping ….. That is why I used the vice as it would push against the base… Is this wrong?

I will try cutting from the other direction tomorrow…. Is my speed correct for this subject matter?

Any other advice?

[stan pearson 1Participant @stanpearson1]

Hi Jamie

Yes Neil is correct you should always feed into the cutter never with it, your lucky it hasn't dug in and broke the end mill.

Regards

Stan

[MattKParticipant @mattk47317]

Are those 'scars' on the plate signs of the dig in of the cutter? I have a bigger mill so don't have first hand experience of how rigid these machines are, but you have three factors stacked against you, climb milling as mentioned earlier, not a very rigid setup (even with a thick plate I reckon these will be a few thou deflection on that much overhang once some cutter load is applied) and maybe quite a large cutter relative to the machine size?

I can see your dilemma though with a plate bigger than the table. Maybe you could clamp to the table with some thin card underneath by clamping across the edge you are trying to mill. Maybe need to carefully move the clamping rather than doing it in single passes.

[Anonymous]

A few random thoughts:

1. There's nothing wrong with climb milling, but possibly not suitable for the combination of small mill and big cutter……….

2. I agree with Neil, having the work waving in the breeze and using the side of the cutter is very likely to result in vibration and chatter, as suggested bolt the work to the table on a support, or bolt it vertically to an angle plate.

3. 500rpm is about right for a HSS cutter in low carbon steel, possibly a tiny bit fast, but does your mill have enough power to achieve a decent chip load per tooth at that speed? What feedrate are you using?

4. The cutter just doesn't look quite right, what is its provenance, import may be?

5. I'm not sure what sort of chuck the cutter is in but it seems a bit odd, I would have expected to see a collet, or similar, by the nut rather than an annular space between the nut and collet?

6. There's a lot of overhang in the cutter chuck and the cutter, so the cutter is deflecting when the second and third cuts are taken. It's a fact of life on any machine, so you need to allow for it with finishing cuts.

Regards,

Andrew

[Jamie JonesParticipant @jamiejones42723]

Hi Andrew

Thanks for the reply.

3, Feeding by hand on a slow rotation……. What's your view on the Mills Power? It has an RPM range of 50-2250.

The Mill's Spec is set out below: Plus Link (But without autofeed)

4, Cutters See Link: http://toolco.co.uk/pages/bakery/20-piece-end-mill–slot-drill-set-397.php

5, The cutter is in a collet: This is the collet set I have

6, Not sure what you mean. by 'There's a lot of overhang in the cutter chuck and the cutter'

I am only taking thin cuts at this stage.

I was hoping to mill out slots in this bit of plate so that it could hold specific bits of work that I had planned to bolt down on to its surface. At this stage I am not confident that the mill and the cutters are up to the job.. It is £ 2,000 work of mill

Here is the mills Spec:

Specification:
Max drill capacity: 32mm ( 1.25" )
Table size: 840 x 210mm ( 33 x 8.25" )
Table width: 210mm ( 8" )
Vertical travel: 370mm ( 15" )
Longitudinal travel of table: 565mm ( 22.25" )
Cross travel: 220mm ( 8.5" )
Spindle taper: No.3 MT
Spindle stroke: 70mm ( 2.75" )
Head swivels 90 deg
T – slot size: 14mm
Gearbox range x 2: High / Low
Range of spindle speeds: 50 – 2250rpm in two speed bands
Motor: 1.1kw
Standard Electrics: 240 volts 1 phase
Approx net weight: 240 kgs

Edited By JasonB on 25/05/2014 07:48:49

[Ady1Participant @ady1]

You've got too much overhang, the cutting zone is far too far away from the vice and the milling cutter will create a levering effect

clamp the workpiece to the table, flat, with a support piece underneath to raise it from the table

Stiffness is priority one in a milling situation

 (as mentioned, you're also climb milling)

Edited By Ady1 on 25/05/2014 02:33:25

[John CParticipant @johnc47954]

Have you got the collet set up correctly? On my ER collets the front of the collet is flush with the front of the closing ring when tightened up. The collet has to be 'manipulated' into the closing ring, then the cutter inserted in the collet.

Rgds,

John

[JasonBModerator @jasonb]

Yes does look like the collet has not been snapped into the nut, have a look at this to see how they fit. Also makes them pop out of the body when the nut is undone.

If you clamp it to the table with half the work overhanging the edge of the table facing you there will be enough movement in the x-axis (side to side) to allow you to cut along one edge.

J

[Oompa LumpaParticipant @oompalumpa34302]

Take the setup apart;

1) Get the plate bolted down to the table as Jason suggests, flat and secure but packed up off the table with parallels or something solid at least.

2) get the head setup vertically.

3) set the collet fully into the collet nut and then put the cutter in.

4) don't climb mill until you have some more experience.

Your setup as illustrated is just so wrong I don't know where to begin but as everyone has said, there is room for error in every direction. Just with reference to your assumption that your setup "would press against the base of the vice" actually, you are "pressing" against fresh air, the cutter's action is edge to edge, not up and down.

I would suggest you get a bit of practice in with more forgiving materials before you take on something as challenging as this and this will give you a bit more experience of workholding.

graham.

Edited By Oompa Lumpa on 25/05/2014 08:32:46

[MadMikeParticipant @madmike]

Jamie, all first class advice above. Where are you located? There is probably somebody close by who could come and help you with this. HTH.

[Jamie JonesParticipant @jamiejones42723]

I will re set everything up again this morning and have another go. Thanks for all the advice so far.

I am brand new to this.. Had tried to get a three day course to be better informed. But work won't let me the time off …

i am based in Llandrindod Wells, Powys, Wales…. Which is a bit in the middle of nowhere. If someone was close by and could offer some advice to get me started I would most grateful. There is only so much that YouTube can show you. And I guess different machines have very different abilities.

[BazyleParticipant @bazyle]

Don't rule out trimming the end of a plate like this in the lathe clamped onto the cross slide.. Sometimes it can be better as the distance between plate edge and table (cross slide) can be reduced to mm keeping it ridgid.

[NobbyParticipant @nobby]

Hi
Climb milling on a conventional mill is fraught with danger as there is backlash in the screw and you could end up with damage or injury On CNC machines its fine
Nobby

[TomkParticipant @tomk39956]

Jamie

There is some pictures in my album showing both set ups on how I milled a 8" x 6" 0.5" piece of gauge plate.

You have to get a rigid setup to mill it in the vertical but it can be done, I used 2 cubes an 2 angle plates bolted together. I very rarley use a vice when I milling parts I always try and clamp to the table or to angle plates or cubes

**LINK**

In the picture of the plate being cut the fly tool is held in a morse taper collet with drawbar this give a more rigid set up also more clearance cutter to table.

[NJHParticipant @njh]

Hi Jamie

Lots of good advice above but, anxious as I'm sure you are to get going with your new machine, I would advise just pausing for a bit and doing a little reading on the subject. There are a couple of little books in the "Workshop Practice" series which will give you lots of useful information and hopefully avoid damage to your work, your machine or, worst of all, yourself!

They are:-

Workshop Practice Series No2 – Vertical Milling in the Home Workshop by Arnold Throp

and

Workshop Practice Series No 49 – The Milling Machine by Harold Hall

( Harold is an ex editor of MEW , a helpful & knowledgeable guy, who also has a website with lots of info. and pictures of set-ups)

regards

Norman

[Steve WithnellParticipant @stevewithnell34426]

I'd strongly support getting a copy of Harold Hall's book as per Norman's advice.

Personal opinion, but I think using a 20mm cutter to skim a 1 inch steel plate at one pass needs a big milling machine.

It's a bit like having a spade when you need a Caterpillar D8.

Steve

[John McNamaraParticipant @johnmcnamara74883]

Hi Jamie jones

Your setup is wrong…. Holding the plate vertically in a vice is just asking for the vibration gremlin to rear its head and spoil your work, the plate being so high off the table can lever the vice and the table bending it a few thou also taking up any looseness. If you have a dial indicator check how far you can move the top of the plate with this setup with hand pressure only. Also by rotating the head on your mill you are enhancing the vibration. The spiral teeth of the end mill will pull the work sideways until the resistance builds up in the system, at that point they will cut then the process starts again…. Vibration.

You need to clamp the plate to the table using packers as previously mentioned then cut it vertically.

Here is a photo

**LINK**

Today I was trimming the edges of some 6.35mm aluminium plates to size after sawing them from scrap. note the gap they are sitting on packers, you don't want to cut the table. You may notice there is another plate in front of the one being worked on… After clamping it in position I skimmed one edge with the mill providing a perfectly parallel edge stop to place my parts against. I got a good bright finish.

You should not just get dust chips when machining your part. Check your speeds and feed for the diameter of your cutter, For a light mill you will have to take it in steps down depending on the power you have available. start with a 3mm cut and work up from there.

Regards
John

Edited By John McNamara on 25/05/2014 14:15:18

[Russell EberhardtParticipant @russelleberhardt48058]

Another good book to get you started is Workshop Practice No.35, Milling a Complete Course. It takes you through the basics by a series of projects making useful accessories for the mill.

Russell.

[Anonymous]

Jamie: Here are some more thoughts:

3. It is difficult to say what power is available at the spindle without knowing more about the drive arrangements. However, I'll make an assumption that the mill uses a DC motor with PWM speed control? I note that the spec states two geared ranges; were you using the low range. We can do a simple calculation to get a feel for the power needed. A rule of thumb states that 1hp will remove 1 cubic inch per minute in low carbon steel. So if we assume that your depth of cut is 0.08" (2mm), width of cut is 1/4" (6.35mm) and feedrate is 6" per minute (~150mm/min) we get 0.12 cubic inches per minute, ie, about 90W. I would have thought the mill should have no problem achieving that. There is a caveat though; the setup may well not be rigid enough even though the power is adequate. The feedrate may seem a bit high, but it does take into account 'chip thinning' (Google it) as the depth of cut is shallow compared to the cutter diameter.

4. Personally I'd bin the cutters and buy a brand name one, say Dormer, Guhring etc. A HSS cutter should be fine, and no coating is needed. There are two rules for buying cutters. One, never buy cheap cutters; two, see rule one. Cheap unbranded cutters are often poorly ground with incorrect clearances, or even no clearance, and can lead to intense frustration.

5. The ER collet chuck definitely doesn't look right, you ought to be able to see the collet flush with the closing nut, between the nut and cutter. Follow the link provided by JasonB for details.

6. I meant that the distance from the point where the spindle exits the milling machine head to the end of the cutter is quite long, 5" or so? Cutting forces will cause the cutter to deflect and overhangs make it disproportionally worse. The rigidity follows a cubic law. In other words if you double the overhang the setup isn't half as rigid, but only 1/8 as rigid, so way more deflection.

I don't see why the mill shouldn't accomplish what you want, but I think the setup and cutter are the limiting factors at the moment.

Regards,

Andrew

[colin hawesParticipant @colinhawes85982]

In my opinion 500rpm on a 20mm dia cutter is too fast on any steel using a hobby machine I would settle for about 400rpm on mild steel and less for tougher steels. With a light machine it is often necessary to have the table locks lightly applied and the column lock tight to give more rigidity. Colin

[JasonBModerator @jasonb]

I've just done a couple of cuts using some of the figures andrew suggest, uploading the video youtube at the moment will post after lunch.

[Jamie JonesParticipant @jamiejones42723]

Thanks for the hepl

Sorted the collet out

I am only try to take out 1-2000th cut and it has been pullin the cuter out.

The work is very steady in the vice although I am going clamp it flat to the bed (on block) and try again

[Author]

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