4MT to R8 adapter – do they exist?

[ChrisBParticipant @chrisb35596]

I have ordered a set of R8 collets for my WM18 milling machine, and was wondering if I could use them on the lathe rather than get an other ER collet set and holder.

The lathe has a female 4MT taper inside the spindle so an adapter from 4MT to R8 would come handy – problem is I cant find any at all, is there any reason for that? True the R8 wont fit inside the 4MT as a reducer, but an extended adapter should be possible. I've searched the forum and the internet – nothing, no adapters nor collet chucks – is it something worth doing yourself?

[ChrisBParticipant @chrisb35596]

[KWILParticipant @kwil]

An extended adaptor will mean you are working much further out, why did you not go the other way and have an R8 ERxx collet set.?

[Ian ParkinParticipant @ianparkin39383]

You could get a r8 to mt3 female and then a mt3 to mt4 jump adapter but as kwil says it will stick out a long way

[ChrisBParticipant @chrisb35596]

Because the WM18 has an R8 spindle so the collets fit directly to it.

Posted by KWIL on 11/10/2017 11:37:36:

An extended adaptor will mean you are working much further out

By further out, you mean further out than the lathe spindle nose? Because as I see it, it should not protrude any further than a 3 or 4 jaw chuck, or a 5C type collet chuck would.

[David Standing 1Participant @davidstanding1]

A MT4 to R8 adaptor would look wrong, and frequently in engineering what looks wrong probably won't work best.

As KWIL says, there is much more frontal overhang with an adaptor, even if you could get one (and there's probably a reason for the fact you can't), whereas the golden rule is always keep overhang, be it in the spindle, tool holder or whatever, to a minimum.

I can also understand KWIL's comments re using ER collets in the WM18, so just an additional MT4 ER collet holder would be necessary for the lathe.

By coincidence I also have a WM18 with the R8 spindle, and a Myford 254S with spindle bored MT4.

Whilst ER collets do work, they are a compromise by design if you try and use universal ones covering a 1mm range for both metric and imperial, and in contrast the R8 spindle and collets are a great dedicated design.

For my WM18 I have a number of metric and imperial R8 collets in popular sizes, plus an ER40 collet set up to 26mm. I will always go to the R8 collets first, and only if I don't have one in the right size will I resort to the ER collets.

The R8 collets also give slightly less tool overhang, and more throat depth, in the WM18 than ER collets will.

HOWEVER, my biggest issue with using ER collets with a MT4 spindle collet holder in the lathe would be that ideally you would need to use the collet holder with a drawbar, for taper seating security.

[David Standing 1Participant @davidstanding1]

Posted by ChrisB on 11/10/2017 12:02:23:

Because the WM18 has an R8 spindle so the collets fit directly to it.

Posted by KWIL on 11/10/2017 11:37:36:

An extended adaptor will mean you are working much further out

By further out, you mean further out than the lathe spindle nose? Because as I see it, it should not protrude any further than a 3 or 4 jaw chuck, or a 5C type collet chuck would.

It wouldn't probably protrude any further than those, but you would almost certainly get flexibility and deflection (and thus accuracy) issues under side load from a cutter with the workpiece on the MT4 to R8 adaptor, that you wouldn't get with a chuck.

[MadMikeParticipant @madmike]

The real reason that an R8/MT4 adaptor is not available is probably because in the manufacturing world there is no demand for such a thing. They would simply pick collets to suit. If you want to use. R8 spindle is designed for milling machines. Your options then are (1) Buy a set of ERxx collets and collet chuck for your lathe. This has a cost but frankly it is not really that expensive.: (2) If you are determined to use the R8 collets in your lathe simply turn up the requisite adaptor to suit.

[Andrew TinsleyParticipant @andrewtinsley63637]

Interesting that someone says ER collets are a compromise. I was thinking of going the ER route for a milling chuck as everyone said that Posilock type cutters are on the way out.

I don't have a problem with throat depth, so I think I might go the route of threaded cutter. I am sure that you can get lots of blunt ones for not much money. I will then sharpen them and get in a supply of the dwindling threaded cutters, so I have enough to see me out!

Andrew.

[JasonBModerator @jasonb]

Posted by Andrew Tinsley on 11/10/2017 13:30:18:

Interesting that someone says ER collets are a compromise. I was thinking of going the ER route for a milling chuck as everyone said that Posilock type cutters are on the way out.

I don't have a problem with throat depth, so I think I might go the route of threaded cutter. I am sure that you can get lots of blunt ones for not much money. I will then sharpen them and get in a supply of the dwindling threaded cutters, so I have enough to see me out!

Andrew.

It depends how you read the comment about compromise, David said they at a compromise " if you try and use universal ones covering a 1mm range for both metric and imperial" But if you use them at the largest size in their range eg whole mm or frational imperial they are not really a compromise. They are however far more versatile as you can grip over a whole range of sizes that you can't even buy R8 or MT collets for.

I seem to remember a heated thread a while ago about the holding ability of ER collets when used slightly compressed and the loads they would hold when properly tightened were far more than our hobby machines could put them to.

If Chris did want to use ER on his lathe then better option would be to by a Er chuck to fit the spindle nose rather than one to fit the taper then through holding would be possible.

Only time I tend to use collets direct into the taper is if I'm short of head room or one one tool which has a larger shank than my ER collets will take, rest of the time I use ER.

Not sure about R8 collets giving you more throat capacity than ER as I can't see how that works Both types of tooling will be on the spindle ctr line and throat is measured from the column to spindle?

[jann westParticipant @jannwest71382]

mwhahahaha … Matthew 7:7

http://www.gizmowizard.com/deckeldapter/deckeldapter_main.htm

Apparently the global market was saturated at 20 units, but there is a plan on the site to DIY

But, like everyone else says, there's better ways to solve your problem.

Me, I'd send back your r8 collets, and buy a set of er40's (3-26) + the RDG extension box (27-30) and the R8 ER40 chuck and a suitable ER40 lathe spindle adapter

[David Standing 1Participant @davidstanding1]

Posted by JasonB on 11/10/2017 13:49:34

Not sure about R8 collets giving you more throat capacity than ER as I can't see how that works Both types of tooling will be on the spindle ctr line and throat is measured from the column to spindle?

Jason

Apologies, I had a brain fart. I of course meant table depth capacity, not throat!

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Jason,

Thanks for your very reasoned comments. I have checked my stash of MT2 tooling and I do have a posilock chuck and collets, much to my surprise! Amazing what you find when you take a look! I may as well get some threaded blunt cutters and sharpen them and use them. Probably a lot cheaper than buying new plain shank cutters!

If I ever run into headroom problems then an MT2 chuck and ER collets are not overly expensive. so I could get the best of both worlds! Anyone got any blunt cutters?!

Andrew.

[ChrisBParticipant @chrisb35596]

ER40 collet set is too expensive to justify for now. I was just trying to see if I could get more out of the R8 collets, might try a project making a chuck for them, would cost me nothing apart from material!

[not done it yetParticipant @notdoneityet]

Andrew,

Any chuck (whether posilock(?), Clarkson or ER) use up some of your head space.

The compromise may also be a drawbar, limiting feedstock length when used in the lathe. I was compromised when changing to mostly 2MT from 3MT – none of my morse taper collets fitted!

I think there is a law which says that whatever you get will be wrong for the job, sooner or later.

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