Help recommend a milling machine?

[DiogenesParticipant @diogenes]

Such injustice 😁

I actually recommended MT because the opening post mentioned “a forging workshop” and a Bridgeport having been considered but being too big for the space – so the ability to use taper-shank drills and other tooling seemed to fit the bill, for the situation as I perceived it – all of the forges I have ever been into are distinctly ‘Archdale’ territory..

Nonetheless..

I’m sure we both recognise that the commonplace availability of R8 in the hobby-mill market is a relatively recent innovation and I certainly wouldn’t exclude a number of very good machines just because they employed a self-holding taper – I’ve certainly never felt any need to change just because of the taper.

[John MC]

On John MC Said:

On old mart Said:

I always recommend a mill with an R8 spindle size rather than any Morse taper if you have a choice when buying a machine. There are many more R8 tooling choices and it is a proper milling taper fit, wheras all Morse tapers were designed for drilling and so many people get the tooling stuck in the spindle.

I would not dismiss a Morse taper as just a method of holding drills in a drilling machine.

 

A good alternative is the Morse taper, again plenty of contact area and accurate location.   Plenty of low cost tooling is available.  The disadvantage that I am sure will be pointed out is that the taper is “self locking” and needs a tap on the drawbar to release its grip.  I’ve seen it suggested that striking the drawbar to release the taper will damage the spindle bearings or some other feature of the machine, it will not.  If it bothers the owner then fit a self ejecting arrangement.

The problem with the R8 is one of location.  A very short taper and an equally short parallel length.  These are known to wear in heavy use and lose accuracy.   Then there is the key, best described as the bain of the machinists life.  I’ve used Bridgeport type machines that have had the key fail and not replaced, just hope the short taper can transmit the drive to the cutter!

Going back to the previous comment I have quoted, if Morse tapers are for drills, what about the other tooling we use in the tailstocks of our lathes?

I’ve not experienced any issues with either of my MT3 mills, my first was an Elliott Omnill – an industrial machine. I have though made a small modification to my VMC to make it self ejecting. 

I too have heard lots of negative comments about R8, it’s not a proper taper according to some. Like the Morse Taper, for new machines it’s mainly found on hobby mills these days.

[PeteParticipant @pete41194]

Probably the largest 2 reasons for fewer manual machines using the R8 spindle taper today is the lack of repeatable Z axis tool positioning when pre setting tools, and a limit on just how hard you can drive the cutting tools since there’s no drive keys. Obviously the various 30,40 & 50 tapers are superior, but the R8 has been around for roughly 70 years now and is still used or offered as an an optional spindle taper by at least some industrial sized vertical mills today including Bridgeport. I’d suggest that’s not doing too bad for something that’s supposedly not a proper tool taper. My own Bridgeport clone has a 2 hp 3 ph motor and I’ve not found it’s R8 to be a problem yet. More limiting as far as how hard you can push most vertical mills is the head, knuckle and ram rigidity than the R8 spindle taper.

[richard1989Participant @richard1989]

There does seem to be a mixed consensus on what spindle taper is best here. Is buying the right machine for the size/power/weight, and accepting whatever spindle it has a reasonable outlook?

Also several of you have mentioned about changing the spindle taper, is this something I can outsource, if needed, perhaps a member on here would accept such a commission?

Currently, I wouldn’t use a vast array of end mills, drills, cutters, but I absolutely need to be able to change my cutting tools efficiently. The idea of them getting stuck in the taper is pretty disastrous, as my work does pay bills.

[JasonBModerator @jasonb]

If buying second hand then yes go by the overall machine and provided it is not some obscure taper you can’t get tooling for you will be OK.

Depending on the machine it may be possible to bore it out but that can depend on the OD and length available otherwise you may loose strength around the socket.

Mostly you are likely to leave a collet chuck in the machine and use that to hold the individual cuttres so you don’t have to release the taper every time. My most used mill is MT3 and in 18 years have never had a problem swapping collet chucks, drill chucks, Boring heads, etc all with their own MT3 arbours. I also have a couple of R8 machines and again no problems with them. If buying again I would go probably go R8 on a manual and INT on my CNC.

[richard1989]

On richard1989 Said:

…Currently, I wouldn’t use a vast array of end mills, drills, cutters, but I absolutely need to be able to change my cutting tools efficiently. The idea of them getting stuck in the taper is pretty disastrous, as my work does pay bills.

Morse Taper was the first attempt at a quick change tool system, and it remains popular today.   It’s relatively slow-change on a milling machine, because a drawbar has to be loosened and tapped with a mallet to release the grip.

Though MT works reasonably well, many attempts have been made to do better, most of them long forgotten!  R8 is a survivor,  originally only common in the US, but spread successfully.   R8 also has limitations and critics!  Larger machines go with INT, and similar.   MT and R8 are affordable, INT less so!

Speed changing commercially involves balancing labour cost relative to tool cost.  Time is money, but what’s the balance?  Therefore, necessary to put figures on statements like  ‘I absolutely need to be able to change my cutting tools efficiently.’   An MT tool-change takes two or three minutes.  Is that too inefficient?   What the mill is used for makes a big difference too – I mostly hold tools in an ER collet chuck, so R8 vs MT is mostly irrelevant!  R8 wins only if I had to rapidly swap tools in the spindle.   If time efficiency is a top-priority, plan the workflow carefully.  Aim to minimise tool changes.  An automatic tool-changer might be essential: fast tool-changing isn’t cheap, unless labour costs are even higher.

Some fear whacking drawbars with a mallet will damage bearings, but I’ve not found any evidence of this in normal operation.   It is possible to jamb an MT, either by brutally overtightening it, or by leaving it in place long enough for oil to gum or corrosion to set in.  Both avoided by sensible operation.  Over-tightening might result from forcing damaged tapers, so inspect ‘bargains’ carefully!   Male and female tapers should both be kept clean.   Posh machines avoid tapping with a release mechanism, and they can be home-made.   I’d rather fit an ejector than convert a machine from MT to R8.

The main reason I went MT is that tools can be used on my lathe and mill, a mild advantage that saved a few bob!  The lathe has MT tapers. At the time in the UK R8 tools were harder to find and more expensive than MT, but much less of a problem now.  And no complaints recently of machines converted too cheaply to R8 by simply boring the MT spindle out; that weakens it.

Dave

 

 

 

 

[richard1989Participant @richard1989]

Thank you! Both for the elaboration but also the point on efficiency. I am doing slow custom pieces, sometimes small productions of a few (which can be great for both efficiency and tuning in your processes to be even more efficient but also enjoyable, I have found). A couple of minutes to change is no big deal. I am just 1 guy scratching around in the dirt, not a sophisticated CNC, the only issue would something being genuinely jammed – but point taken about taper inspection before buying and general maintenance and care to negate this.

I love a metal lathe more than a mill but it’s not really essential or even that handy for my work. I did want to try and purchase a myford super 7 as well but I’m not sure I have the space, measuring up for a mill recently. But, who needs to stand on the floor anyway? Filling every inch of floor space and hanging from the ceiling sounds like a great way to spend an evening, chipping away.

[PeteParticipant @pete41194]

There were a lot of different spindle tapers tried over the years Richard. Some very difficult to now find tooling for them without a lot of searching. But that would only apply to some used, much older industrial sized machines. For the size of mill your thinking of, then today and for new, there’s usually going to be a choice of either a Morse Taper or R8. Possibly there’s some that may offer a 30 taper though. None that I know of in the more bench top sized mills though.

Because of there fine taper, Morse Tapers are considered as self holding such as in lathe tail stocks or drilling machines. For straight axial loading such as when drilling, they are self holding as long as both the spindle and tool taper are in good condition. Milling due to the radial loading and interrupted cut still requires the use of a draw bar. But it’s there self holding that makes them harder to loosen than an R8.

The R8 was invented as an “almost” but not quite self releasing taper because of it’s steeper taper angle. In general, a light tap on the end of the slightly loosened draw bar will release the tool shank.

I’ve owned mills with both MT 3 and R8. Without question the R8 is multiple times better for ease of tool release. But that MT 3 mill didn’t have a built in ejector. With one? The MT might be slightly more rigid, but in reality just about unnoticeable and of no real advantage in a more hobby sized mill. Either could work fine. But tooling costs for any mill quickly add up, choosing a machines spindle taper that has reasonably priced and easily available tooling should be a high priority. Probably in the UK there’s not much difference between a MT or R8 for that price and availability. A MT spindle might win out if you were doing a lot of large hole drilling and reaming with the capability of using integral MT tool shanks, by the sounds of it your not. But I’ve yet to find anything I’ve wanted, needed or had to do that isn’t made or couldn’t be done with R8.

The thing to remember and never ever forget is tool tapers both male and female are high precision surfaces. The allowable + – deviations for something like a Morse Taper are only a very few .0001″ end to end for the taper angle. Tool shanks and spindle tapers need to be protected as if there a fine mechanical watch or camera. And my own rule is if I wouldn’t use the tool shank to stir a pot of soup, then it’s not clean enough to be used in the spindle. Tool tapers hold and resist spinning inside the spindle by a combination of both friction and wedging action. To maintain that, both surfaces need to be kept spotlessly clean, undamaged and burr free.

If a tool taper can be changed or even restored back to new and undamaged, it’s not something for the non skilled to attempt. Ideally it requires specialized grinding equipment for the best results. Spindle tapers are one of the more difficult and expensive items to repair or change. Any damage is a direct result of the user. For any used machine, it would be the very first thing I’d check. And for any used but known brand name mill, this website is a great research tool. https://www.lathes.co.uk/page21.html

Direct fitting MT or R8 collets would be slightly better for rigidity and using up almost no Z axis height compared to a ER collet chuck. Most today including myself still use those ER collet chucks, so your changing collets most times instead of tool shanks.

But if efficiency is that important, I’d also suggest adding a dro as soon as possible. For the type of work your doing, I suspect work holding is going to be another issue because of part shapes. Shop made sub tables held in a milling vise would be a good start and there’s lots of videos on Youtube about them. But buying a larger mill than the minimum size will usually gain you more HP and rigidity. Those will help with surface finishes and efficiency. Given what I’ve learned about the additional tooling costs for any mill. The initial price for any of them is a lot less important than buying something that’s dependable and efficient. I’d also suggest buying this rather cheap book first, https://www.teepublishing.co.uk/books/workshop-practice-series/no-2-vertical-milling-in-the-home-workshop/ Read through it before making a decision about what mill you might buy.

 

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