Slant-Bed CNC Lathe Build

[barnbwt]

I notice that nearly all linear guide blocks have threaded holes (including mine), but there are a few with bored through holes. Since my toolplate is about 3.5" thick, it seems like threading into it vs. drilling through is a lot more convenient. Thoughts? I'd rather not bore out the ones I have unless the pros outweigh the cons.

I also rejiggered how I am doing my turning-tool clamps (they are in pairs between tools, vs. staggered) and now have room for MT1 drill sockets (for short tools) if I really want them --only trick would be figuring out how to tap them back out from the rear of the taper, when it's a solid block of toolplate back there. So that's a total of 20 tool positions at this point. When the stock is only 1" max diameter it can fit between a lot of obstacles.

Another necessary change that may have a fortuitous, if unusual consequence was hanging the toolplate out 1.5" past the X-axis guide blocks nearest the spindle. This was done so I'd have access to the underside/backside of the tool plate where the ER25 collet holders plug in, so they could be secured with a pair of set screws (not super convenient, but better than all my other ideas). It's less than a 1:2 cantilever ratio so I'm not super worried about loss of rigidity, but it does mean the Z-axis guide rails can set back 1.5" from the spindle accordingly...leaving a very narrow gap-bed, that could accommodate a large diameter 5C face plate ('large' meaning <10"). Obviously I wouldn't spin the poor thing at 4000rpm, but it opens the door for respectable-sized sheet engraving using Y/C polar coordinates, and at the least improves user access at the tool change area. Maybe I could produce my own vinyl press-masters, lol.

 

[JimDawson]

I notice that nearly all linear guide blocks have threaded holes (including mine), but there are a few with bored through holes. Since my toolplate is about 3.5" thick, it seems like threading into it vs. drilling through is a lot more convenient. Thoughts? I'd rather not bore out the ones I have unless the pros outweigh the cons.

These are the ones I bought for my press project, I had the same problem, about 2 inches of steel to drill through, and I needed the wider hole spacing to accommodate the connecting rod. https://www.mcmaster.com/6709k13

I also rejiggered how I am doing my turning-tool clamps (they are in pairs between tools, vs. staggered) and now have room for MT1 drill sockets (for short tools) if I really want them --only trick would be figuring out how to tap them back out from the rear of the taper, when it's a solid block of toolplate back there. So that's a total of 20 tool positions at this point. When the stock is only 1" max diameter it can fit between a lot of obstacles.

Drill a small (3/8 ?) through hole to use a punch from the back?

Maybe I could produce my own vinyl press-masters, lol.

Great idea

 

[barnbwt]

These are the ones I bought for my press project, I had the same problem, about 2 inches of steel to drill through, and I needed the wider hole spacing to accommodate the connecting rod. https://www.mcmaster.com/6709k13




Drill a small (3/8 ?) through hole to use a punch from the back?



Great idea

Tool plate is about 8" square, MT1 is about 2" long...that's a 6" deep hole. Doable of course, but seems like it'll be a pain. Right now I have a couple large diameter holes drilled/milled from the top, so a stout 'pry bar' can be tapped to knock them loose. I don't know if that would do better than a long punch, though, and at least that way I could use the spindle to drill the holes in place. The impact from either on the taper wouldn't damage the guideway bearings, would it? Surely they're not that delicate.

 

[JimDawson]

The bearings are pretty tough. It normally does not take too much to knock out a MT, especially a #1. A wedge might be the best if you can get to the hole. That's what's normally used to remove a MT form a drill press spindle. Just butting up against the tailstock screw will knock them out of a lathe tailstock.

 

[barnbwt]

Ah, a wedge; I like that. Just remove a little plug, drop the wedge in the hole, and carefully tap it downward. Can even make the hole a simple drilled pocket about 1/2" or so diameter. You'd just have to make sure all your tapers are long enough to get at.

I figure they would only ever be used for center drills, but oddly enough those don't seem to exist in the MT1 size. Won't be too hard to make them, though.

 

[barnbwt]

Apparently there are MT1 tools with wee little drawbars (screws, really), so I think the through-hole is back in the lead. Not sure I think an MT1 fly cutter is a wise idea, but they're out there.

I have also perhaps a stupid question; I need a big honkin' step up transformer for my spindle servo (my drives can use up to 230VAC, servo is good to 300V IIRC) since my service will be 120VAC for the duration. Having received a *second* badly defective Chinese model (this last one has exposed wiring where the insulation was burned off all over the place before it even got here) I've decided to give up and explore alternate options.

-Do these big transformers work the same in both directions (step up/down) or is there some one-way impedance thing?
-Do dry, wound transformers go 'bad'? Should I be worried about buying a new/old-stock 2:1 industrial unit, besides the asbestos?
-Assuming the winding isn't burned from over-current, these things are pretty simple, right? Conductor pair in, pair out? Little to go wrong?
This one seems to fit the bill nicely (my spindle is 1kW max @ 300V, so 1.5kVA @ 240V should be plenty, plus this beast is 37lbs of copper)
https://www.ebay.com/itm/Dongan-1-5...Purpose-Transformer-80-1040-Used/173499024481

 

[JimDawson]

I would buy a used industrial transformer. They rarely go bad, normally only from extreme overload for extend periods, unlikely in normal operation.

Yes, they work both up & down.

I don't think I have ever seen asbestos in a transformer, that would have to be a really old one.

 

[Boswell]

Barnbwt and Jim, just want to let you both know this is a faninating thread and I have been following this build closely. Thanks for all of the great information.

 

[barnbwt]

I would buy a used industrial transformer. They rarely go bad, normally only from extreme overload for extend periods, unlikely in normal operation.

Yes, they work both up & down.

I don't think I have ever seen asbestos in a transformer, that would have to be a really old one.

I was thinking of an old slide projector me & my pa repaired a while back for an elderly family friend; took the housing off and the wire insulation was coming off as powder --"maybe we shouldn't do this inside the house..."

 

[barnbwt]

Barnbwt and Jim, just want to let you both know this is a faninating thread and I have been following this build closely. Thanks for all of the great information.

Thanks,
Hopefully I'll be able to dive into the spindle cartridge before too long

On that note; has anyone ever played with a 'jig grinder' on a lathe? Seems like it'd be the perfect way to get excellent bores & tapers, even more so than a toolpost grinder