Retrofitting a 1986 Maho MH400E

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07 Jun 2019 06:38 #136175 by RotarySMP
Morning John,

Sorry, I only have those ones. You might need to turn up a special on a lathe.
Mark
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10 Jun 2019 16:24 #136486 by andypugh

RotarySMP wrote: Sorry, I only have those ones. You might need to turn up a special on a lathe.


My SK30[1] toolholders came with the wrong style of pull-stud. I just re-machined them.
This isn't always possible, of course.

[1] My machine was originally 30INT, then I converted to BT30, but when the job-lot of 20 SK30 holders @ £50 came up on eBay I was happy to shorten one drive dog to suit the SK30 standard.

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10 Jun 2019 16:30 #136488 by andypugh
Supplementary note: I think that you can find those pull-studs hiding inside 20mm shoulder bolts.
www.ebay.co.uk/itm/302707615863
A handily pre-threaded bit of high-tensile steel. Though looking at the price there, perhaps it is worth machining the thread yourself too.

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10 Jun 2019 19:22 #136505 by andypugh
Re speeders:

Here is a design for one that I keep meaning to build. It is based on a superchager that I once saw. It uses no gears, instead ball races drive an off-the-shelf eBay collet chuck using friction only.
The three bearings are free to float radially, and are clamped into contact with the centre shaft by the outer spring ring, which is also the static reaction part.

The design isn't 100% finished, I have not designed the outer case that would be needed to contain the oil. But I _think_ that can just ride on the drive pegs of the spring ring, with oil seals top and bottom.

I wanted the spring ring to be the outer case, but I don't think it is possible for that to have enough flex to do the job while still being oil-tight.

a360.co/2Iya5k3

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11 Jun 2019 07:22 #136558 by Glemigobles
Interesting design Andy. What would the output torque look like without gears?

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11 Jun 2019 07:30 #136560 by pl7i92
at 118Pages into projekt
Question is the machine running as expected with Linuxcxnc

is there a resume of all
what costs did you go for A cording to the new HAAS Mini mill reveal that puts Townsend of machines on sale

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11 Jun 2019 08:06 #136567 by Glemigobles
IDK what the new rebates are for Haas machines, but when I was considering my options before getting the MAHO in late 2017, a Mini Mill was 25% off from our local distributor (something like a 25% off for 25 years in business kind of deal).

That price put it at over 3x the cost of the MH600E, even accounting for the expenses associated with my crayon copy of Mark's retrofit. At this point I could probably send it off to a rebuilding company for way grinding, scraping, painting and general mechanical maintenance and it would still come out cheaper than a new Haas at a discount.

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11 Jun 2019 08:49 - 11 Jun 2019 08:56 #136573 by andypugh

Glemigobles wrote: Interesting design Andy. What would the output torque look like without gears?


I don't know :-)

But the Variator in my lathe was not dissimilar in theory of operation and could transmit 3hp continuous. The original supercharger application transmitted enough to do that job too. I think that rather specific oil might be needed for best performance.

Ooh, there is even a picture of the same arrangement on the bottle!
www.amazon.com/Rotrex-R50-S150-OIL-Super...-Fluid/dp/B00BV65EVC
Description of how it works here: www.dieselnet.com/tech/air_super_drive.php (now that I know it is a Rotrex drive)
Also interesting is that the slightly elaborate slottted axle arrangement I had is not necessary or helpful. Undersize shafts work better.
Last edit: 11 Jun 2019 08:56 by andypugh.

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11 Jun 2019 12:05 #136588 by andypugh
And here is the patent which explains how it all works.
patents.google.com/patent/US6960147B2/en
Maybe I do need to build one :-)
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11 Jun 2019 14:04 #136608 by Glemigobles
Maybe you can sell me one when you do :)

It's an interesting concept, and I'd love to have the machines necessary to build one and try it. From what a tool maker friend of mine said, mechanical speeders are really loud, this design might be a little quiter perhaps?

The other day I found an ebay auction listing a set of 3 electric spindles, all of which could be mounted on one's preferred toolholder size (40, 50), complete with an inverter. Two were 40000 rpm at 4kW, and one was 15000 at 12 kW. The price was around 5000€, but that's how much a single Air Turbine costs from Hoffman (and those require expensive air compressors to run reliably). There was also a gizmo for setting the speed. I just hope that I'll keep finding such interesting offers when I have more money again!

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