Author Topic: Advice on buying a vertical mill.  (Read 7700 times)

Online steamer

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Re: Advice on buying a vertical mill.
« Reply #15 on: February 18, 2018, 06:08:03 PM »
Well if you're just snagging flame cut plates it's perfect!... Now if your trying to keep flat square to a  fly's but...well....not so much...
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Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #16 on: February 18, 2018, 10:06:29 PM »
Exactly!  I'll keep the old mill for rough jobs - a thou or two is neither here nor there when making centres for tractor front wheels - and use one with a bit more accuracy for fine work.

John.
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Offline john mills

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Re: Advice on buying a vertical mill.
« Reply #17 on: February 19, 2018, 10:01:38 AM »
the cracking sounds could be the spindle bearings have gone past the no preload to completely collapse soon on site recently (,i do labour hire work)  the turret mill made crunching noises as it lost drive to the spindle .several times.
when dismantled the cages had disappeared the balls were all around one side .the bearing were of very light ,the lightest section angular contacts .nothing like the bearings in the mills i am used to using .

Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #18 on: February 19, 2018, 11:42:18 AM »
John - I wouldn't be a bit surprised if that's exactly what has happened.  I've been having visions of collapsed cages!  Trouble is one of my (no doubt many!) failings is to keep using something until it packs up on me.  An unidentifiable engine noise becomes a tap, the tap becomes a knock, and the next thing you know you're in the middle of a field looking at an engine block with a connecting rod sticking out of it.  It happens, and not just to me!  It's not quite as daft as it sounds as the driver of a big old crawler probably can't hear the engine because the transmission is making so much noise.
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Offline Mcgyver

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Re: Advice on buying a vertical mill.
« Reply #19 on: February 19, 2018, 02:05:49 PM »
Here are my thoughts on it.

1) get out see them.  Dealers, locals classifieds etc- look in the eyes seller as well as the machine.  You learn when you've seen a bunch and will develope a sense of what is a nice one.

2) avoid ebay.  Buying a machine sight unseen is a mess waiting to happen imo.  This should be the last recourse reserved for those machine tool desert dwellers.

3) Operationally backlash does not matter.  If its an acme screw, there has to be some (clearance) or the thread wouldn't work.  If there is some, there is to much for climb milling....except extremely light climb milling using the table's inertia in which case again how much backslash there is doesn't matter. 

4) Where backlash does matter is an indication of overall wear.  A machine that was used heavily and not regularly lubricated with have more backlash.  Backlash is wear of the feedscrew and or nut and is usually localized so will affect long distant measurement.  That's where the value of a DRO comes in, that and general convenience.

5) I have reconditioned several machine tools, ground up scraping, and can describe exactly how to quantity wear through a complete survey.  Problem is the machine has to be in parts and it would take a day or two spread out all over the place.  In other words properly quantifying wear is not really possible at the vendors site.  Some basic tests, move things end to end, if cranking the wheel is consistent and they dovetail is not getting tighter, there is little wear....or the gibs have been loosened - check for that standing at the end of the table and see if you can move the table side to side a bit 

6) instead of quantifying wear, we look for it by proxy.  Does it look likes its had a long hard life, paint all chipped (or the worst of all, freshly painted at a dealer), when the saddle is moved to its extent, what do the ways look like?  are they dry?  And so forth.  This is where backlash does matter - as in indicator of wear.

7) What does it come with?  Wait until you get a really well accessorized one, ideally collets, end mill holders, power feed, drill chuck, RT, dividing head and vise.  maybe even a DRO, but imo that's the least important.  Loaded, they sell for more, but that increase is a tiny fraction of what it'll cost to acquire it all

8)  Warm the bearings up then take it up to speed, run the quill up and down.  everything quiet?  make some cuts if possible, load it a bit....still good?  Spindle bearing replacement isn't the end of the world, but putting in the good P4's is a significant add cost.  If its not under power, negotiate downward and assume you have to cover the cost of say bearings....hopefully not, but not being under power means the vendor should have lower expectations

Not that point 8 is particularly cool but in this smilie infested world, that's what you get with the numeral 8 residing next to the bracket

9)  There are lots and lots of vertical mills, a great of which are a little more robust than the bridgeport.  Don't limit the search to the one name

10) but a tenths indicator on the spindle.  Measure not just TIR, but apply some pressure to the spindle and make sure there is no movement.  This recently saved me from dog being sold by someone who is known as a really unsavory vendor.   Also inspect the taper, looking for obvious abuses.

11) if you haven't already, consider moving up to a 3P machine.  Lots of ways, now easy with VFD's, to get the 3P and it opens up the market substantially as to what is available

12) finally, patience.  The old cliche is so true for our stuff - you want it hi quality, low price and fast?  pick two
« Last Edit: February 19, 2018, 02:28:59 PM by Mcgyver »

Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #20 on: February 19, 2018, 02:49:41 PM »
Mcgyver - useful tips, thanks. 

The main reason I've looked at Bridgeports is because my friend has one.  I'd possibly prefer a slightly more rigid method of toolholding though?  My old girl is MT3, almost certainly with a worn socket, the Bridgeports are R8 I think, but Int. 40 would be even more rigid wouldn't it?  I've seen some of them at affordable prices.

For a novice like me DRO is important, but presumably can always be added, and a 2-axis one doesn't cost the earth.

Taking a DTI to test spindle movement is easy enough.  Good suggestion.

No I haven't considered 3P.  I might if I knew what it was though  :)  I had to look up VFD too.  One issue I have is that, being in the middle of nowhere I haven't got 3-phase so have to use a Transwave converter for the Bantam.  I know the output isn't quite like 3-phase but ordinary motors don't seem to mind.  Not sure about VFD though?   The mill I converted to 1-phase when the old 3-phase motor started blowing the trip!

John.
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Offline Mcgyver

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Re: Advice on buying a vertical mill.
« Reply #21 on: February 19, 2018, 03:12:28 PM »
3P =  3 phase power.   Is your transwave a static or rotary converter?  I used a static for years, it works, but does under perform other options.  Currently I have a 10hp rpc I built, some machines run on 240 3P for others I bump it up to 600V (my garage is a next of conduit!).  RPC (rotary) still the way to go if you have lots of machines because you really need i inverter (VFD) per machine, but if only one machine, go VFD

You can run 1ph into a VFD and get output to turn a 3P motor, this is extremely common now.  All the VFD does is rectify the incoming power onto a DC bus.....how it gets to that DC bus doesn't much matter.  You DO have to overate as you are only using two of the diodes for rectification and there is going to be more ripple.  Many vfd's are intended for this with 1P in specs.  The only downside is they get pricey as the HP goes up and you have to over rate them.  The plus side is silence, no drone of the RPC in the corner.

As for 40, yes, it is so much better.  I've an R8 XLO and that machine also came in 40.  As I see them come up i've been tempted a few times to upgrade but its a lot of machinery moving and I have a lot of R8 tooling....but given the choice between the two, 40 the clear winner.  I've an Elliot horizontal that is a 40, it will go through anything.

DRO's are a nice convenience to have, after holding out for 25 years, I added one 2 years ago and like it a lot.  But really, the only practical problem they solve is feed screw error over a distance (which you could overcome and I've done so with tool maker buttons and gauge blocks).  Other than that, long distance error thing, backlash doesn't matter much and everything can be done with the dials.  My point is they are a nice convenience but it would a lower priority for me in looking for a machine given 1) they are mostly a convenience not a necessity and 2) they can always be added.  If it had it great, but I'd be a lot more focused on the machine's condition and tooling.
« Last Edit: February 19, 2018, 03:35:37 PM by Mcgyver »

Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #22 on: February 19, 2018, 04:51:35 PM »
Of course I know what 3P is - typing finger was in gear but brain was in neutral  :)  Sorry.

My Transwave is static.  I think it runs up to 7.5hp.  It has about 10 (from memory) settings and I use #1 for my small 3P bench drill and #6 for the Colchester Bantam lathe.  I think the old mill used to like #3 before I converted it to 1P.  The only thing I have had that it wouldn't run was a 3P surface grinder I bought a while back.  For some reason the grinder seemed to have more wires going in than the Transwave had coming out!  I'm no electrician but have asked a couple of acquaintances that supposedly understand things like that, but they couldn't make it work either.  I know it was going before I moved it though.

I have a 3P supply from it running round the workshop in metal trunking, so it isn't too difficult to connect multiple machines.  I just need to alter the switch until the motor in question runs nicely - e.g. the lathe won't run at all on #1 but the drill motor is very noisy if I forget to switch back from #6.

John.
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Offline Mcgyver

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Re: Advice on buying a vertical mill.
« Reply #23 on: February 19, 2018, 05:46:05 PM »
The only thing I have had that it wouldn't run was a 3P surface grinder I bought a while back. 

your's sounds like perhaps a different issue (the omg there's left over wires issue), but I've been told static phase converters do a poor job on free wheeling things; i.e surface grinder, table saw etc.  It needs a bit of a load on it like a machine's gearbox provides, apparently.  One dodge is to get some other machines running first, their motors start to act like the idler in a RPC.  I haven't tried it, built an RPC instead.

Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #24 on: February 19, 2018, 08:26:58 PM »
Interesting.  I know the 'spare wires' issue isn't relevant, but in the case of the Bantam, the coolant pump won't run on its own.  You have to start the lathe motor first, then switch on the coolant pump.  That's because the converter can't cope with the small-power motor on its own though.

Incidentally I tried using the wires coming out of the surface grinder in various combinations, with some quite spectacular results.  Luckily the RCD and/or MCB in the main fusebox prevented major damage, apart from to my nerves!

John.
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Offline Manorfarmdenton

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Re: Advice on buying a vertical mill.
« Reply #25 on: March 10, 2018, 11:27:38 PM »
I'm considering this, subject to inspection.

http://www.gandmtools.co.uk/shop/hartford-5kv3-variable-speed-turret-mill-dro-3ph-80204721

It looks pretty substantial in the photo and the 40 INT tooling should be more rigid than R8 or my existing 3MT shouldn't it?  It also seems to be better value than a Bridgeport, probably because its not as popular a make?  I've tried to ring G and M but haven't spoken to them yet.  Any comments?  It probably won't fit in the space I had in mind but I can find a home for it!

John.
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Offline Jo

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Re: Advice on buying a vertical mill.
« Reply #26 on: March 11, 2018, 08:06:30 AM »
  I've tried to ring G and M but haven't spoken to them yet.  Any comments?  It probably won't fit in the space I had in mind but I can find a home for it!

That was the one Eric wanted to buy but I had to talk him out of it as he spends more time buying and selling machine tools that are "better than the one he already has" than making swarf  :ShakeHead: When you get into your 70's you need to get on and make all those models you waited all your life to build  :D

Jo
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Offline Jasonb

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Re: Advice on buying a vertical mill.
« Reply #27 on: March 11, 2018, 08:19:28 AM »
But he has also bought ones that he thought were better than he had only to find hidden problems once he got them home :-[

I would do a bit of research on that make as if you do need spares at least there are a few more options about for Bridgeports.

Offline john mills

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Re: Advice on buying a vertical mill.
« Reply #28 on: March 11, 2018, 08:47:06 AM »
int40 is a much more robust spindle taper and much more desirable have used them at work where R8 and number  3 morse would be of no use at all.
CNC machining centres often use similar BT 40 i have used BT45 which is even better. But machines  need  a
spindle and bearings bigenough for enough metal for the taper to fit. 

Offline Jo

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Re: Advice on buying a vertical mill.
« Reply #29 on: March 11, 2018, 09:01:10 AM »
But he has also bought ones that he thought were better than he had only to find hidden problems once he got them home :-[

I would do a bit of research on that make as if you do need spares at least there are a few more options about for Bridgeports.

If you mean the Karradi he knew that was a dog when he gave them the £500 for it delivered... But he thought a universal mill with 3 axis power feed and quill feed and shaping head was worth a punt if he could fix it ... Sometimes paying scrap money for a machine means they need a bit of work that one beat even him  ::)

All of those big machines at G&M came from Southampton University and have had little use.

Jo
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