Chester 626 mill CNC Conversion

[Rob.Wilson]

You have bought a RH leadscrew, they should be LH on a 636 

John S.

BUGGER


Rob 

[Swarfing]

John you should no better   ....It's CNC so does not matter, just tell the motor to go the other way 

[Stilldrillin]

John you should no better   ....It's CNC so does not matter, just tell the motor to go the other way 

Fun, while it lasted though....... 

David D

[Swarfing]

Just hope Rob speaks Chinese so he can tell it to do so 

[Rob.Wilson]

Just hope Rob speaks Chinese so he can tell it to do so 

Looking at the pendant manual now Swarfing ,,,,,,,,,,,,,,,,, QUOTE  " The angle encoder of axle of photoelectricity belongs to the instument of high accuarcy, forbid beating and beating colliding at the time of installation, installation or unwise use of performance and life-span that will infuence the encoder "

not a problem sounds just like Geordie ,,,,,,,,, dont whack with hammer 


Rob 

[Swarfing]

LOL! 

[John Stevenson]

No if it was Geordie it would read WHACK with hammer..............

[Rob.Wilson]

No if it was Geordie it would read WHACK with hammer..............

  true  

[John Stevenson]

Rob,
Following you closely, got all the main castings of a new Myford VM-B from the Myford sale, missing motor, spindle, pulleys and all the respective drive gubbings but the main castings are complete, tatty but brand new.

Looks like it's been robbed for spares. Having a measure up at the moment for ballscrews. The rest is all on stock, power supply, drivers, motors etc.

Still got to decide what to do over a spindle. I want it for one job only, drilling division plates so max drill size will be 4mm max. Might use an outrunner motor driving an ER 16 extended collet chuck via belts but know sod all about these are what they need to run.

[Rob.Wilson]

Hi John

I would not follow too closely ,,,,, you may fall into  a hole with me     

You going to mass produce your division plates    ,,,,,,,, " outrunner motor "  ,,,, new one on me 

still thinking about the spindle in my mill ,,,,,,,, needs to be a bit more zippy ... somewhere up around the 5000 rpm range  .... 


Rob

[Miner]

Hi Rob,
Interesting build as usuall. How's things going?

How about a spindle speeder? Hemingway kits sell a kit for one.

Pete

[Rob.Wilson]

Hi Rob,
Interesting build as usuall. How's things going?

How about a spindle speeder? Hemingway kits sell a kit for one.

Pete

Hi Pete 

Things are going slowly at the moment  ,,,, cant get my brain cell to work    Cheers i will have a look at the Hemingway kit 


Hope your doing well 


Rob

[Miner]

  Things are..........ok, Somewhere I've got the Hemingway kit stashed away. It looks good, But going by memory it's set up with a single 6 mm hole in the spindle for tooling. After I'd scanned thru the plans I thought it would be far more versitile if the spindle working end was redesigned to use one of the smaller series of ER collets.

Pete

[DMIOM]

....How about a spindle speeder? Hemingway kits sell a kit for one.....

....After I'd scanned thru the plans I thought it would be far more versitile if the spindle working end was redesigned to use one of the smaller series of ER collets....

I had a look at that kit a couple of years ago and was a little concerned about the provision of bearings, even without adding anything extra like an ER collet, - I seem to recall that at least one of the shafts only had a bearing at the top or at the bottom.  Also, from memory, the output direction was reversed, so when in use under CNC you'll have to make sure that your CAM transposes M04 and M03 when the speeder is deployed ....

My impression was that it might be appropriate for light horological work, but not for long CNC runs.

In my case, I opted to add a Kress 1050 as a secondary high-speed spindle.

Dave

[Rob.Wilson]

Cheers Dave ,,,,,,for the heads up 


Well being under the weather today STILL ,, due to a self inflicted injury    ,, i thought i would have doodle with the ye olde CAD and see what i could come up with for mounting the ballscrew ends .





something like that

Rob

[John Stevenson]

It's not a good design, in fact it's very flawed.
One it reverses rotation, secondly no top support bearing and it only uses one planet wheel so it's trying to force the top of the spindle out of mesh and the missing bearing helps.

Using the same components and one extra planet redesigned it can be made to go the same way and have a 4:1 increase instead of the 3:1 of the original.

Original design.



Improved design using same parts but two planets



Four bearings for stability and can use an off the shelf collet chuck as the output shaft.

John S.

[Rob.Wilson]

Very interesting John    the redesign looks a big improvement on the original and making one would save the work of modifying the original head 

Rob   

[John Stevenson]

Rob,

Seriously look at using Oldham couplings, those jaw type couplings are often used but they cannot handle any misalignment in two planes.
In fact any misalignment is only handled by imposing sideways forces.



That square alloy block contains two angular contact bearings, the preload nut and the coupling, can't get much neater than that?

John S.

[Rob.Wilson]

Hi John

Now that is a very compacted design   

I was planning on boring the motor  joining piece to key snugly over the flange shown  in the drawing , the other end will be bored for the motor ,, if you get my drift .


Do have a question ,,, do you think i should key the coupling to the ballscrew ?


Rob

[Miner]

John,
Much thanks for the redesign, Now why didn't I ask about Hemingways design before I bought it?

Pete

[DaveH]

Rob,

Really very nice
 
DaveH

[John Stevenson]

Rob,
Do away with the bearing retaining nut.

Two bearings followed by the first half of the Oldham coupling, clamp type, which is threaded to suit the ball screw.
Drill and tap on the non split part for a grub screw and brass pad for a belt and braces approach.

Ball screw only need enough machined for the bearings to sit and the Oldham coupling to screw and clamp on. Nice compact job.

John S.

[Rob.Wilson]

Rob,
Do away with the bearing retaining nut.

Two bearings followed by the first half of the Oldham coupling, clamp type, which is threaded to suit the ball screw.
Drill and tap on the non split part for a grub screw and brass pad for a belt and braces approach.

Ball screw only need enough machined for the bearings to sit and the Oldham coupling to screw and clamp on. Nice compact job.

John S.

I have been wondering how you got it so compact ,,,,,,,,,,,,,, smart arse   

Already machined two screws 

Rob


Cheers Dave H 

[John Stevenson]

Already machined two screws 

Rob

No probs, just saw the parallel bit off that the crap lovejoy coupling was going to fit on, tap the Oldham same size as the thread on the screw.

[Brass_Machine]

Rob,
Do away with the bearing retaining nut.

Two bearings followed by the first half of the Oldham coupling, clamp type, which is threaded to suit the ball screw.
Drill and tap on the non split part for a grub screw and brass pad for a belt and braces approach.

Ball screw only need enough machined for the bearings to sit and the Oldham coupling to screw and clamp on. Nice compact job.

John S.

John... You have a picture of this? Having a hard time visualizing it... 

Eric