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