MT-3 or R8 for the X2

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Well-Known Member
Jul 8, 2007
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We have a couple threads running discussing the two tapers in the mini mill spindle.
I didn't want to highjack one with my personal opinions so I'll do that here. :D

I like Grizzly machines because their customer support exists if there is a problem.
I didn't buy a Grizzly mini mill because of the MT-3 spindle.
Instead I to the opposite extream and bought a Cummins mill from one of their
traveling truckload sales. If you have a problem with a Cummins machine you will
often find that YOU have a problem. I bought it there for the lower cost and
the fact that it had the R8 spindle taper.

The MT taper has been around for a long time. It was invented by Stephen Morse sometime
between the years 1864 and 1868. It's original intended use was to drive his new twist
drills. It still does that very well! In a drill application there is normally a slot in the spindle
that a drift is driven into to release the tool. In the mini mill the MT-3 tools are retained
with a drawbar. The tools are released by loosening the drawbar and rapping it with a brass
hammer. Given the long contact surface of the taper they often do not release easily.
Every rap is a lateral impact on the spindle bearing. Those are ball bearings that don't take
that kindly. You can find collet holders and collets for the MT-3, but very few tools.

The R8 isn't nearly that old. It was developed by Bridgeport Machines Inc. sometime after 1938.
It become an industry standard very quickly. The small X2 has a 17MM hex on the draw bar,
but the threaded end is the Bridgeport standard 7/16-20 imperial.
The steeper contact angle of the R8 allows for a much easier release when the draw bar is rapped
with a lighter hammer.
(OK I usually rap it with the side on the 17MM wrench I'd used to loosen it, but that's not good!)
Tool and collets are plentiful and inexpensive. I would much rather use a one piece R8 cutter
than a cutter held in a collet. They are easy to find.

Point taken Rick, but here in the Land of the Great White Wombat R8 stuff is not at all common and is roughly the same price, or a little more, than the MT3.

One solution to the pounding problem is to run MT2 tooling in the mill via a reducing sleeve with a screwed jacking collar. I first ran across this when I bought a boring head & went that way so I could use it in either the HM10 (X2) or the Myford.
I made the switch to R-8 from MT2 and MT3 with the purchase one arbor for my bring bar and a set of ER 40/ R-8 collets. I can even swap the boring head back and forth between the MT and R-8 arbors. I was totally surprised at how little the switch actually cost me. (total cost with shipping of less than $150.00) I've not needed to buy anything else since making those two purchases. If I'd known it was no more expensive than that, I'd have long ago converted my X2 to an R-8 setup. I simply have to chalk it up to my own newbie ignorance, that I didn't do so.

I'm am considering a set of dedicated R-8 tool holders after seeing how much more user friendly the system is. I don't "need" them, but they would be nice to have on hand.

Looking at the price of OS collets and tools compared to buying locally I can see me importing a lot of stuff for my mill when I get it.
I can see I'm going to need to go in and have a chat to the company I want to buy my mill from to see if they can supply it with R8 and if not sit down and do the maths and figure out is it cheaper for me to buy the mill with MT3 and then buy an R8 spindle for it and collets from OS or just buy MT3 gear locally. :-\

I love buying new machines but I hate agonising over whether my decision on which one to buy is the correct one for me.

I've got money itching to be spent and if I don't spend it soon the wife will on some other house renovation so I need to decide soon.
You are going to buy the X2 from Hare & Forbes in Perth, right?

Then they ONLY sell the M3 taper version.

Now to adding an R-8 spindle from overseas, then using R-8 to M3 adapters, yep, you sure can go this route, BUT, and remember the but, you WILL LOOSE HIEGHT under the spindle nose by doing this.
Have a good look at this lot and you'll see that the adaptor hangs down further, encroaches on the work envelope and cost more, why do this?

Now, as it's been said before, M3 is the most widely used and is readily available in Australia. The R-8 is the most used in the states and is cheap as chips over there, now where do you live?

All tooling for the X2 with M3 tapered spindle, is of a good price and readily available at the scary forbes shop, so why bother going down the R-8 route and making it hard on yourself when you want bits?

An old statement for you to ponder,------ horses for courses!

regards greenie
Agreed Greenie. Another thing to consider is this. I have always found H&F will bend over backwards for you in matters of backup and service BUT if you gut the machine and fit non-standard (from their point of view) parts that attitude could change.
Just a quick question to all you lads from down under.

How do you stop your machinery from falling to the ceiling?

We bolt it all down (up) matey. ;D The GOOD thing about it is that all the swarf drops clear.
One thing to consider is what tooling you already have.
When I bought my mill I already had alot of MT 3 tooling as that is the size of my lathe head stock and that effected my decision.
LMS sells a kit to replace the MT 3 spindle with R 8
Part #1625 $49.95
Bogstandard said:
Just a quick question to all you lads from down under.

How do you stop your machinery from falling to the ceiling?
tel said:
We bolt it all down (up) matey. ;D The GOOD thing about it is that all the swarf drops clear.

Tel ....... can you send me one of your "Aussie" bucket's ......... if I screw it to the ceiling all the swarf should end up in it .... ;D .... best send a couple of spares for John n' Ralph too ::)

CC ;)

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