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I am going to buy a mill….Decisions, Decisions !!

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jaCK Hobson27/06/2022 15:26:09
265 forum posts
93 photos

I slapped on a 2 axis glass scale DRO from 'Vevor' for £109.99 on my SX3.5. Bargain.

old mart27/06/2022 15:35:51
3912 forum posts
268 photos

I always say that if you are in the fortunate position to choose between R8 and MT3 spindle fitting, choose R8.

SillyOldDuffer27/06/2022 16:36:44
Moderator
8903 forum posts
1999 photos
Posted by old mart on 27/06/2022 15:35:51:

I always say that if you are in the fortunate position to choose between R8 and MT3 spindle fitting, choose R8.

Can you explain why please?

I decided to go MT3 rather than R8 because,at the time, there was more MT tooling about and it was a bit cheaper. This despite received opinion stating the opposite! Not done a price comparison since so maybe it was a temporary thing.

Not had any trouble with MT3 in practice, and it provides a level of compatibility with my lathe. Grips well enough and hasn't stopped me doing anything I wanted to do. Based on my experience, the difference between R8 and MT isn't massive.

Tapping the drawbar to release the MT tooling doesn't worry me because I couldn't find any solid evidence it actually damages the bearings. There are plenty of folk convinced it must, but opinion isn't evidence!

A positive objection to R8 on hobby machines is the possibility that the spindle of a small mill has been excessively bored out to take it. Unless the machine has suitably beefy spindle, my feeling is MT3 will be stiffer on hobby mills because less metal has to be removed to accommodate it. My mill is nowhere near as heavy as the Bridgeport for which R8 was designed. If you've got R8 on anything less than a Bridgeport, how thick is the spindle wall? Maybe it doesn't matter but...

Dave

Ketan Swali27/06/2022 20:02:59
1431 forum posts
134 photos

Dave - SOD,

A bit of history based on my observation over the years...

About 20 years ago, you could fill a room with the R8 and MT tooling crowd to find what is better for their machine, lock the room and tell them that they can only come out after making a unanimous decision. On the technical front, neither would agree that one was better than the other, arguing their corner as you have. On the question of price, MT won, as it was a lot cheaper back then in comparison to R8. Also there was justification to use MT in both their lathe and mill.

As newer people entered the hobby, various things happened...

1. Some such new people found it difficult to deal with the friction fit of the MT tapers, as engineering knowledge has been deteriorating over time. For example:

  • failing to clean the mating surfaces of transport oil.. making the friction fit useless
  • overtightening the MT tooling inside the spindle.
  • Combine the overtightening with expansion due to heat generation from use, so making it difficult to loosen the drawbar, because they fail to understand that they needed to allow the spindle area to cool down again... especially due to over tightening.
  • Using the wrong kind of hammer - ie using a claw type hammer (hitting the drawbar to kingdom come without getting a release) instead of using something like a rubber mallet, and failing to hit the drawbar sharp enough to release the taper fit

We fielded a high number of calls to address above issues when we offered options of MT3 and R8, As most of the machines we sell now are R8, such calls are very much in the minority with R8, as R8 don't generally have such an issue as it is not a tapered friction fit in the spindle. Above issues are user related based on poor knowledge.

2. Twenty years ago, MT was cheaper than R8. People were using end mills of a larger variety of shank diameters, threaded etc.. With exception of carbide end mills, sellers like ARC went down the standardisation route offering plain shanks in 6, 8, 10, 12mm with different cutting diameters on the end. So, the user could now consider R8 collets in four standard sizes, so one no longer needed to invest in a full range of collets.

3. R8 collets/tooling wasn't really ever more expensive than MT3. It was a marketing thing. Production of R8 has always been higher than MT3. When we first started in this business, we were advised to avoid selling R8 products at prices similar to MT3, as we would not be taken seriously. Those were the early mail order days. before internet became popular.

4. With the advent of Internet forums in early 2000s, the newer generation specially in the U.S., started talking about their negative experiences with MT3. A certain percentage of it was born out of fear and poor knowledge based on point 1 above, combined with the idea that the bearings would somehow get damaged by hitting the drawbar hard - which is not true, as you have explained.

5. Some of these new comers decided that they wanted to convert their machines to CNC. In the process, some wanted to adapt their cnc project to incorporate quick change tooling, especially R8 end mill holders and ER collet milling collet chucks. R8 provided easier ejection of R8 tool and better 'repeatability' in location than MT. A lot of these projects failed to get off the ground, but the seed was sown, and the ideas/concepts spread slowly across the world.

As a result of the points mentioned above, sales of MT3 machines reduced from 7 out of 10 back in 2004, to around 2 out of 10 by around 2015, in th case of ARC, and 8 out of 10 - predominantly a younger age demographic choosing R8 machines. If one wanted to re-sell their machine second hand, it was and is far more easier to re-sell a Metric R8 machine in the U.K., vs. an Imperial or MT3 machine.

ARC stopped selling MT3 machines when we had to hold one or two pieces of a specific MT3 models for nearly two years. Our sales are driven by market demand.

Hope the above adds to the reasoning for MT3 vs R8.

Ketan at ARC

Jon Lawes27/06/2022 20:06:10
avatar
995 forum posts

I chose R8 when I bought my mill and I'm glad I did; Primarily due to the extra headroom you get above the table.

Howard Lewis27/06/2022 20:21:02
6314 forum posts
15 photos

When I bought a Mill/Drill, a long time ago, I opted for 3MT, but buying now, I would opt for R8, since it is an easier taper to "break" when the time comes to remove the tools, or ER chucks.

Howard

old mart27/06/2022 20:45:34
3912 forum posts
268 photos

I did say "if you have a choice", and Ketan has given a pretty comprehensive explanation.

JasonB27/06/2022 20:51:39
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Moderator
23070 forum posts
2769 photos
1 articles

Dave, Ketan forgot to mention that certain red painted hobby mills have a beefier end to the spindle so the R8 hole does not weaken things.yes

15years ago when I bought the X3 and did not know any better I went for MT3 thinking it would be handy to swap tooling to the lathe but have done it so little it would now not be a deal breaker. Talking of breaking my balls bearings are still fine after 15yrs of hitting the drawbar with a copper hammer.

having now used R8 on the SX2.7 and KX3 with their self ejecting drawbars I would most likely go down that route even if it does mean a bit more head raising to swap tooling as you can't tilt R8 shanks like you can MT. Though I would not say no to a CNC equipped with INT20, 25 or 30

old mart27/06/2022 21:37:19
3912 forum posts
268 photos

_igp2428.jpgThe Tom Senior light vertical that the museum inherited had a MT2 spindle which I was not going to tolerate. The R8 spindle lower half was bought from ARC, a spare part for one of the Sieg mills that they sell. It was a relatively simple upgrade and the two part spindle runs very well indeed._igp2434.jpg

Kelvin Jouhar09/07/2022 18:25:30
6 forum posts
1 photos

Just to update this thread, I decided to order a WM16B mill from Warco and they are going to fit a 3-axis DRO for me. I already have a 3MT collet chuck and collets for my lathe, so I can make use of those, and buying a mill with the DRO already fitted means that I can get straight into learning how to use it - Thanks for all the input.

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