[mrcodewiz]

My impatience is getting the better of me so I started converting my G0704. I would have liked to have bought one of Ellik's kits but I just can't swing the cost so I am just doing it cheaply for now - As cheaply as I can anyway. I am going to re-use all of the existing thrust bearings, screws,etc. Later on I will replace all of the bearings and then maybe switch to ballscrews.

So far, I have the X,Y, and Z stepper brackets made. Nothing real unique - because of my frugality, I am going with a front mounted stepper. I will just have to live with it and hopefully I don't drop a vise on it.

The Z axis is nothing more than a stepper mount. I am leaving the column cap and its thrust bearing just as it is.

Am I going to regret using the stock screws and bearings? I am just trying to spread out the cost a little - even once its CNC ready, you still need the electronics, the PC, and I will need to make some sort of enclosure and bench. I can scrounge up an old PC and I already have a couple spare 425 Oz Nema23s. I also already have licenses for Dolphin, Mach3, etc. I am guessing that not going to ballscrews and bearings would probably save me upwards of $300.

When I converted the X2 I went right to ballscrews. I would imagine the stock screws would be quite a bit slower.

[photomankc]

I think Hoss is doing it very similar in his thread. I'd imagine that the screws are going to wear out the nuts pretty quickly if adjusted to reduce backlash. On mine (a PM-25 not a G0704) I can't get my backlash down to less than 0.006" (originally about 0.011") and that's with the nuts really squeezed down. They used too small a screw in my opinion because my hex keys can't reach on the short side and the long side is now twisting instead of getting the screw tighter and it's getting noticeably harder to crank as I tighten down.

Anyway, I think it is a reasonable way to boot-strap and allow you to make more sophisticated parts for the better conversion later. Looks like no matter what, if this is the only mill you have that you may need some outside services to machine clearance under the table for the ball nuts.

I plan to go that route too and I'm waiting to see what Hoss puts together as phase 1 of his conversion. The quill-friendly belt drive he is making is at the top of the list too, mine sounds like a rattling beer can in low gear if there is any interruption to the cut. I think the gears have way to much free play back there.

[mrcodewiz]

Well, I have an X2 and an angle grinder - not sure if that will suffice. I plan on getting Hoss' belt drive plans here shortly as well.

[Fastest1]

You wont regret the screws you have til you know better. Great work on the stepper mounts. Keep your eyes open on ebay for some ballscrews for in the future.

[mrcodewiz]

OK, I decided to go with ballscrews. I ordered some from Chai - hopefully I will be able to mount them up OK. I am not too concerned about the X and Y screws - they are the RM1605 ones (screw is 16mm diameter and ballnut is 48mm diameter) but I opted for the RM2505 for the Z which is a screw of 25mm diameter and a ballnut of 62mm diameter - hopefully the ballnut will fit in the column OK. Won't know for a couple weeks I suppose - I am having him machine the ends for me as well.

[DogWood]

really interested inn how this turns out for you, I have a G0704 coming sometime in the next couple of months and I'm debating whether or not to go straight to ballscrews, may I ask what you ended up paying for them?
also what specs did you give Chai? or does he have some on hand for the g0704?

Thanks,
-Doug

[mrcodewiz]

really interested inn how this turns out for you, I have a G0704 coming sometime in the next couple of months and I'm debating whether or not to go straight to ballscrews, may I ask what you ended up paying for them?
also what specs did you give Chai? or does he have some on hand for the g0704?

Thanks,
-Doug

The ballscrews were cheap. Less than what I paid for Rotons when I did my X2 and I only got 3 nuts and a single bolt then - cut it and machined it myself. This time I got 3 individual ones, 3 ballnuts, custom machining, and 4 bearing locknuts.

I drew up the specs for him myself based off of the brackets I made. They will end up being off a little once I replace the factory bearings with AC bearings since the AC bearings are thinner than the factory ones but I will just make up for that with spacers - or possibly modify the brackets.

[DogWood]

I went with Nook XPRs when I did my X2, cut and machined them myself as well, still cleaning up the mess grinding them made.

[mrcodewiz]

Yesterday, I received the VXB bearings I ordered for my conversion. 2 AC bearings for both the X and Y axis, a thrust bearing for the Z (to complement the existing one), and some new AC bearings for the spindle.

Here are the AC bearings - I didn't have any luck finding shielded bearings for a decent price so I got unshielded. I am guessing that the side shown on the right is the side that faces the opposing bearing?



I made the bearing pockets to fit the factory thrust bearings so the AC bearings already sat recessed a little since they are thinner than the thrust bearings that came with the mill. I have decided to make some protective covers so I recessed the bearing pockets a little more.



They are recessed enough to fit these covers



The covers sit directly on top of the AC bearings and is made so that it only presses against the inner raceway. Here is one installed in the X bracket.



Here is a closeup of one of the covers installed on the bracket. They are just slightly smaller in diameter than the bearing pocket and sit flush with the outside of the bracket.



Here is the X bracket installed with the bearing and cover



Here is the Y bracket with the bearing and spacer installed



Now I just have to wait for the ballscrews....

[mrcodewiz]

I received my ballscrews from Chai yesterday. They look pretty decent. He did a good job on the end machining. I may have gone too big on the Z axis but I think everything will still fit. Looks like I will have to mill down the ballnut flange on the X axis a little - either that or create a groove in the table (that would be my last resort).

[Enraged]

are the flanges threaded on?

[mrcodewiz]

No, they are integral to the ballnut.

[mrcodewiz]

I started trying to figure out how to create the ballnut mounts for the X axis last night and I have a question for the group. These ballnuts are not the perfect type for adapting to the g0704 because of the space limitations under the table. The square rotons would be much better given the threaded shaft they have on them. Nonetheless, these are what I have. The problem is that the flange is not really large enough to fit down into the hole that the existing halfnut sits in so you need some sort of adapter. This was the best I have come up with so far.

Here is a crude drawing of an original RM1605 ballnut:



My plan is to mill out everything on the flange except for the area around the 2 opposing holes on the flange like this:



And then just use some 1/4-28 bolts through those holes into this bracket (shown with modified RM1605 ballnut)



My question is do you think 2 1/4-28 bolts through the assembly like that will be strong enough or will I have some issues with it flexing?

Another question - does anyone know if these ballnuts are hardened?

[amyers]

could you tell what the total was you paid for the screws and nuts from chai?
Did you have to give them the prints to turn the ends or do they already know that?
AM

[mrcodewiz]

I think it was about $215. that was for the 3 screws, 3 ballnuts, 4 bearing locknuts, and end machining on all three (plus both sides of the X). I came up with drawings and provided them to him for the machining.

[fatal-exception]

I'm pretty sure ball nuts are hardened all over. You could always grind off the parts of the flange that are in the way as long as you don't change the temper of the nut. Personally, I would modify the table and leave the nut alone. What if you ever have to replace it?

Two quarter inch bolts would be plenty strong enough though IMO.

Paul

[mwood3]

I'm pretty sure ball nuts are hardened all over. You could always grind off the parts of the flange that are in the way as long as you don't change the temper of the nut. Personally, I would modify the table and leave the nut alone. What if you ever have to replace it?

Two quarter inch bolts would be plenty strong enough though IMO.

Paul

I agree, modify the table...according to Hoss its a small amount to grind off if you use the rotor ballnuts. I think he mentioned 1"x1", 1/4" deep...

[mrcodewiz]

I agree, modify the table...according to Hoss its a small amount to grind off if you use the rotor ballnuts. I think he mentioned 1"x1", 1/4" deep...

roton ballnuts, probably - ebay ballnuts, definitely not.

[Enraged]

check EKs thread, he had to grind the ebay nuts to make them fit.

[mrcodewiz]

Yeah, milling didn't go so well so I ended up grinding it. It isn't pretty but at least it fits now.