[hoss2006]

Here's the new G0704 MAD V2.
The first video is the construction and the 2nd is the operation.
The aluminum cross member does have a little bit of flex, maybe .010, but doesn't affect the operation.
I made mine using (2) 1/4-20 screws into the cross member but that seems a little too big
so I spec (2) 10-24 in the print to leave more meat in the side brackets.
One note about this mill since this was my first real use of it to make something, I LOVE IT.
It's the perfect size for sitting there running it, can get up close and personal.
The smoothness of the axis' and the rigid cutting make it a joy to use.
The noise of my gear change wasn't too bad at the lower rpm, could still hear my tunes.
One simple thing I would do if I was going to keep it manual would be to add some longer dial marks
for .005 and .010 so my old eyes could see better.
I like doing things manually, so going CNC will be hard, but I will.
One note about the bearings, even cheapo replacement TRs for the upper bearing that takes
the load from the tool change have static load ratings over 7000 lbf,
750 lbf from the tool changes is nothing to fret about, at least not to me.
The cutting in the first video shows it taking .200 DOC with .375 4 Fl HSS 1100 rpm
about 4-5 IPM, works out to a .001 chip load. Piece of cake.
First pic shows a poor mans dykem.
Hoss

video embedding seems on the fritz

[nomedia="http://www.youtube.com/watch?v=s8nbImWDnLg"]YouTube- G0704 MAD V2 Construction[/nomedia]


[nomedia="http://www.youtube.com/watch?v=86fWHkJiuSM"]YouTube- G0704 MAD V2 Operation[/nomedia]

[hoss2006]

AC bearings are in and the prognosis is good.
Have much more video, step by step, that I'll edit and post sometime but the gist is bellow.
After another breakin period, the AC's leveled off at 110 degrees vs 162 at 4500 rpm.
Seem good to go so I'll move on to the belt drive and see what happens at 5-6000.
Used the same high temp grease I used before so it's possible the good stuff
mentioned before could run cooler.
The bearings I used are from VBX.com
7007B Bearing 35x62x14 Angular Contact - lower bearing
7005B Bearing 25x47x12 Angular Contact - upper bearing
Hoss

[nomedia="http://www.youtube.com/watch?v=RntLo8nTC1k"]YouTube- G0704 New AC Spindle Bearings[/nomedia]

[jalessi]

Hoss,

Is there room to install a additional angular contact bearing in the bottom of the spindle verses using a spacer?

Jeff...

[machinechick]

Hey Hoss, thats cool the different type of bearings are running at a lower temp range at higher speed. I'm curious as to what kind of runout your getting with the VBX AC's?

[Starleper1]

Yeah, run out would be my biggest fear.

[ihavenofish]

Yeah, run out would be my biggest fear.

me too. i imagine its no worse than stock though. im not sure if he ever posted the stock runout.

[hoss2006]

Nope jeff, there's only about 5mm.

Runout is .0004.
typical for ABEC1 rated bearings and only $25 for the set.
If you are running tools small enough that this runout would be a problem
ABEC 7 or 9 are rated at .0001 and .00005, you're looking at $500-600+ a set.
Not a logical solution for a $1000 machine especially since the rpms needed
for tools that small aren't practical, an add on high speed spindle would be the way to go.
http://www.pacamor.com/technical/abectolerances.php
Hoss

[nomedia="http://www.youtube.com/watch?v=sRbV-uxhABQ"]YouTube- G0704 AC Bearing Runout[/nomedia]

[ihavenofish]

Nope jeff, there's only about 5mm.

Runout is .0004.
typical for ABEC1 rated bearings and only $25 for the set.
If you are running tools small enough that this runout would be a problem
ABEC 7 or 9 are rated at .0001 and .00005, you're looking at $500-600+ a set.
Not a logical solution for a $1000 machine especially since the rpms needed
for tools that small aren't practical, an add on high speed spindle would be the way to go.
http://www.pacamor.com/technical/abectolerances.php
Hoss

YouTube- G0704 AC Bearing Runout

4 tenths is fine by me!, thanks. i think ill see if i can use those bearings in my wmd16.

[BobWarfield]

YouTube- G0704 AC Bearing Runout

LOL, when I first saw that video it looked like the was a broach mounted upside down on the piece of rod. Thought you where up to something there, Hoss!

Nice job on the bearings. Looking at your spacer makes me wonder if there is enough meat that you could machine it to take 2 AC bearings at the bottom there and one regular deep groove at the top. That would considerable stiffen it up.

Cheers,

BW

[machinechick]

Even with just the pair (of AC's) I imagine it will be more than rigid enough for Al which is the whole point of the higher speed mods with this machine. It is a shame there's not more room to stack em, but the runout is minimal, and the bearings are inexpensive, after the belt drive is done these will be great mods for the Al crowd, pretty cool overall Hoss.

[ihavenofish]

Even with just the pair (of AC's) I imagine it will be more than rigid enough for Al which is the whole point of the higher speed mods with this machine. It is a shame there's not more room to stack em, but the runout is minimal, and the bearings are inexpensive, after the belt drive is done these will be great mods for the Al crowd, pretty cool overall Hoss.

for machining, yes, i think they are adequate for the power of this machine.

where id worry is the drawbar release, which hoss's simple auto quill release puts pressure on the bearings. that pressure is likely near or over the max static axial load on the top bearing.

[hoss2006]

The static load of an equivalently sized ABEC1 AC upper bearing is 1720 lbf, 1000 more than what
would be applied by the MAD V2 drawbar, no worries.
Hoss

[gd.marsh]

Just wondering which high temp grease you used on your spindle bearings. There seems to be some consensus on Kluber .. but I would like to find a less expensive alternative if possible.

gd.marsh

[hoss2006]

don't think you'll find cheaper than this but i'd go with kluber to be safe and sure.
http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=82984379
Hoss

[ihavenofish]

The static load of an equivalently sized ABEC1 AC upper bearing is 1720 lbf, 1000 more than what
would be applied by the MAD V2 drawbar, no worries.
Hoss

the listed load is usually radial. axial is alot less.

[hoss2006]

The equivalent static load P0 is a theoretical value (according to ISO 76). It is a radial load for radial bearings and an axial and centrical load for thrust bearings.

Angular contact bearings better support "combined loads" (loading in both the radial and axial directions) and the contact angle of the bearing should be matched to the relative proportions of each. The larger the contact angle (typically in the range 10 to 45 degrees), the higher the axial load supported, but the lower the radial load.

I wouldn't expect a radial bearing to have much axial load ability but an AC is designed to have both.
Seems to me they would rate an AC by it's axial load based on it's contact angle.
If they rated it by radial, the load would go down as the angle increased.
Seems they would want to hype the increased axial load achieved by the greater angle.
Hoss

[ihavenofish]

I wouldn't expect a radial bearing to have much axial load ability but an AC is designed to have both.
Seems to me they would rate an AC by it's axial load based on it's contact angle.
If they rated it by radial, the load would go down as the angle increased.
Seems they would want to hype the increased axial load achieved by the greater angle.
Hoss

yeah, the way they list loads confuses me. i know SKF's data lists raidial load by default. the static load of steel 7005 bearings with a 25 degree is only 5KN or about 1000lbs, some of which is already exerted by preload. thats radial as far as im aware, and axial will be much less (38% according to skf).

uuuunless ive read this backward, which i may have (i am an idiot of course) in which case the axial static load would be 13kn.

i think the second may be right actually, in which case.. uh.. "nevermind" :P

http://www.skf.com/portal/skf/home/p...ewlink=9_10_19

[SCzEngrgGroup]

yeah, the way they list loads confuses me. i know SKF's data lists raidial load by default. the static load of steel 7005 bearings with a 25 degree is only 5KN or about 1000lbs, some of which is already exerted by preload. thats radial as far as im aware, and axial will be much less (38% according to skf).

uuuunless ive read this backward, which i may have (i am an idiot of course) in which case the axial static load would be 13kn.

i think the second may be right actually, in which case.. uh.. "nevermind" :P

http://www.skf.com/portal/skf/home/p...ewlink=9_10_19

I would bet that if you took the radial load rating of a ball bearing, an angular contact bearing with the same size balls would support roughly that same load, but applied at the bearings angle. A little simple trigonometry will let you resolve that into radial and axial component forces. This would at least give you a very closer approximation.

Regards,
Ray L.

[Deviant]

How do you think using the quill for your tool change will effect the repeatability.

Can't view youtube at work....

So I'm assming that you..

1. Unlock quill.
2. Move the quill down.
3. Flip up your MAD bar...
4. Retract the quill which compressess the bevel washers and drops the tool.
5. Move quill down and flip MAD out of the way.
6. Retract quill and lock the quill in place.

If this is the order of events, do you think that the tool offset will change much or do you expect the quill to return to the same location everytime.

Keep up the good work.

[ihavenofish]

How do you think using the quill for your tool change will effect the repeatability.

Can't view youtube at work....

So I'm assming that you..

1. Unlock quill.
2. Move the quill down.
3. Flip up your MAD bar...
4. Retract the quill which compressess the bevel washers and drops the tool.
5. Move quill down and flip MAD out of the way.
6. Retract quill and lock the quill in place.

If this is the order of events, do you think that the tool offset will change much or do you expect the quill to return to the same location everytime.

Keep up the good work.

if you put a thin precision spacer between the quill and the head casting, you might be able to get more reliable repeat indexing.