[GarageCNC]

After reading the mammouth 200 page thread from Hoss (good work dude), I decided to get one of the BF20 clones. Here in the UK I bought a Chester Champion 20vs for around £850 delivered.
I got the thing out of the crate today and on to the bench.
First job was the three-bolt mod, which interestingly enough, needed no grinding down of the extra bolts, they were a perfect fit.
A couple of other things I have noticed so far is that I am hoping have a full 200mm of travel on the Y-axis if I remove the bellows, and also that the motor is 850watt. One more thing is the quill travel is 52mm rather than the quoted 42mm on the Chester website.
I will update this thread with more specs as I strip the machien down.

[GarageCNC]

I took the spindle out today, not too difficult, but it is a little diferent to the G0704. Surrounding the drawbar collar is a steel collar, which seems to be integral to the gear-drive. Once the spindle was removed I had a peek down into the hole, and looks as though this collar is joined to the splined section which is driven by the gears, and in turn, drives the spindle. This should make the belt-drive conversion easy, since I can just bolt the pulley straight onto this collar.
Anyhow, there are some photos of this detail below, and a piccy of the litle light which is up beneath the head too. Unfortunatley it only worked for a few seconds then blew the bulb.

The spindle bearings required for high-speed will be two of the 7005B variety, which I cannot find in the UK so will need to order from VXB.com These are the same size as thr G0704 upper bearing.

I have measured up for the ballscrews today, so once they are drawn up, I will order from linearmotionbearings2008 on ebay. He seems to be 70% cheaper than any UK store, unless anyone can tell me otherwise!

[Simon C]

Hi GarageCNC. i look forward to seeing your project unfold. Il be buying a BF20 type machine myself to convery to cnc. I have been looking at the one from Amadeal but they are out of stock atm. did you get the R8 spindal or the 3 morse? I have a Champion mill from chester but it isnt a very good candidate for a cnc conversion (it has a round colum) and the spindel quill is a sloppy fit even when locked, hows the fit of the 20VS quill?


regards
Simon

[fragger6662000]

If you are looking at steppers i would go for the g540 setup from keiling it is all that is required when using ballscrews. i have an spg version and get 1500mm/m on all axis and can plough through anything at a reasonable speed with good acceleration.

[GarageCNC]

Simon, I have an MT2 spindlem which is a shame really since I cannot use the Tormach quick change tooling system. Having said that, I already have quite a bit of tooling which will fit.
The spindlke has no noticable slop, although I have not done any test cuts yet.

Fragger, I read your article a couple of times already, did your mill have the steel collar covering the drawbar reatainer? I see you have already done the belt drive mod, I cant wait to reduce the noise from the grinding gears!
I am aware of the Keling setup, those digital drivers sound excellent. Unfortunately I have already got a set of 3.1Nm steppers with 4.2A drivers from Motion Control Products from an old mill. I will give them a whirl first, and see how I get on. Shame I gotta wait 3-4 weeks to get ball screws from China

[photomankc]

Does MT collets really prevent you from using TTS? I thought all you need is a 3/4" collet as long as there a spindle nose for the tool to index against? Does the MT collet system preclude that?


Sent from my iPod touch using Tapatalk

[hoss2006]

MT2 collets only go up to 5/8, MT3 will go up to 3/4 for TTS.
Hoss

[GarageCNC]

Just a quicky, I found a supplier of the 7005B bearings in the UK, although they only sell shielded ones. Easy enough to remove the seals though. Check out "Simply Bearings" Here

[GarageCNC]

Got the bearings this morning and had a go at a couple of spacers on the lathe. The pic below shows the completed spacers, the one with the step is for the top bearing, so when the lock-nut is tightened, it will put pressure on the inner race, and will pre-load the angular contact bearings.

Things did not go entirely to plan...I ended up removing the lower spacer and using it beneath the upper bearing with the upper bearing now in a sandwich between a flat spacer and the stepped one. Anyway, it is all back together and runs ok, just need to do the break-in now and keep on the tightness of the spindle. Just out of interest, how do you know how tight it should be? I assume the temperatures will be the giveaway if the pre-load is too tight?

[fragger6662000]

why are you changing the bearings?

i have been running the tapper rollers up to 4000rpm with no problems, are you planning on going much faster than that?

[GarageCNC]

Looking at 6000 rpm, (Sssh, sometimes I cut timber on the mill)

[fragger6662000]

the stated rating on the taper roller bearings are supposed to go up to 6000 with grease but that also dependent on preload. when i run my mill at 6000 there was alot of heat build up. so i think it is a worth while thing to do but i took the veiw that i can change them later.

[Mechan6]

Dear GarageCNC,
I Live in Scotland, and have recently bought the same Mill (Chester 20Vs.) am converting to CNC.Need help with sizes etc of the Ballscrews and the nuts.
i.e specification, lengths etc and how what support bearings you used.

Look forward to your kind reply.
Yours sincerely. Mechan6

[CL_MotoTech]

This thread hasn't been updated in 8 years so getting info from OP might be tough.

I want to say that most people use a 16mm by 5mm (5tpi) ball screw on their G0704's. As for lengths I do not know, maybe ArizonaVideo or another poster with experience will chime in.

[dazp1976]

Dear GarageCNC,
I Live in Scotland, and have recently bought the same Mill (Chester 20Vs.) am converting to CNC.Need help with sizes etc of the Ballscrews and the nuts.
i.e specification, lengths etc and how what support bearings you used.

Look forward to your kind reply.
Yours sincerely. Mechan6

If it's this one I would have avoided it and looked at Amadeal for a belt drive machine with R8 taper.
https://shop.chesterhobbystore.com/c...=7466463002671

As for ballscrews I don't know lengths but recommend using 1605DFU.
You'll have to measure it up and see what suits.
You could get them custom made at cost to fit the machine then just add your own motor/nut mounts.

If you go for the Chinese ones already end machined then you want to make your own bearing mounts too and fit 32x12x10mm AC bearings. Thrust bearings don't sit well on them at all.

[shooter123456]

On my PM-25 (very similar in size), I used 750mm 1605 double nut on X, 350mm 1605 double nut on Y, and 600mm 1605 single nut on Z.

[Stigoe]

On my PM-25 (very similar in size), I used 750mm 1605 double nut on X, 350mm 1605 double nut on Y, and 600mm 1605 single nut on Z.

I would suggest to use 2005 screw for Z instead of 1605. This is what Hoss recommended.

[Mechan6]

Dear dazp1976,
Many thanks for your kind reply and advice, much appreciated.

I will look for the 1605DFU ballscrews.

And at making the bearings mounts to suit the 32 x 12 x 10mm Angular Contact Bearings.

Yours sincerely.
Mechan6

[shooter123456]

You can do 2005, no harm there.

From all the spec sheets I have seen, the 1605 will have a dynamic load rating around 600 kgf. With a 75lb head (standard weight was around 55 lbs, then air cylinder and heavier motor added), when accelerating upwards at 150in/s^2, the load will be around 462 N * coefficient of friction from the ways. 462 N is 47 kgf, meaning the 1605 can handle 12 times what is being asked of it. Unless my math is very wrong or I am missing something, the 1605 is more than sufficient.

[109jb]

I use 5/8" diameter, 0.2" pitch Thompson rolled ballscrews on all axes of my G0704. These are pretty close to the 1605 metric and they have never given me any problem. I'm going to be using a 2005 screw for the head on my RF-45. The RF-45 is a lot bigger machine and I even think the 1605 would be sufficient here, but there was not much price difference and plenty of room. On the G0704, cramming a 2005 ballscrew, nut, and mount into the little column is going to be pretty tight. If I were going to do another G0704 size machine I'd still use 1605 ballscrews on all axes.