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361  General CNC Chat / Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill on: March 17, 2012, 02:15:35 AM
Nice work, Mike.

50% axial load for a deep groove ball bearing... sounds too much to me too. Hope he knew what he was saying Wink

Dan
362  General CNC Chat / Show"N"Tell ( What you have made with your CNC machine.) / Re: Impact Engraving. on: March 16, 2012, 10:55:17 AM
Thanks for the video, Tweakie. Now I have a clue what 20Hz sounds like. It works fairly fast considering it stops at each dot location.

Nice smiley, by the way.

Dan
363  General CNC Chat / Show"N"Tell ( What you have made with your CNC machine.) / Re: Impact Engraving. on: March 16, 2012, 02:55:45 AM
Hi Tweakie,

Ah... so actual frequency is even higher. Will be interesting to hear the sound.

btw. Nice job you are doing on that milling machine very professional.

Well... I guess the only reason it would look like a mill is it being a Chinese lathe Wink Thanks anyway Smiley

Dan
364  General CNC Chat / Show"N"Tell ( What you have made with your CNC machine.) / Re: Impact Engraving. on: March 15, 2012, 02:13:40 PM
Brilliant Tweakie! And you always know how to best photograph and exhibit your work.

Are you saying it's around 21Hz? Then I think I was close with my experiments. Any chance you could record the sound? I would be interested to compare to mine, since I have no idea how better to estimate the frequency. How did you?

Dan
365  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 14, 2012, 12:55:28 PM
Here is the bearing housing for the X axis:


I went for a needle thrust bearings arrangement here. It is two needle thrust bearings closed from either side of a step inside the bore. They are combined with a deep groove ball bearing at the end to provide axial support for the belt tension. Here is the section of the arrangement:


The reason for this over angular contact ball bearings is that angular contacts at that size are pretty limited in the axial loads they can take. The needle thrust bearings on the other hand can handle axial loads several orders of magnitude higher than the angular contacts. Preloading is fairly easy too. And as a bonus they are only a fraction of the price of angular contacts Smiley

The bearing housing will be mounted on the back of the carriage (as the motor is going to sit on the back). There are M6 mounting holes on the back of the carriage seen on the carriage picture.

The two bosses on the bearing housing are for mounting the motor mounting plate.

By the way, it's not shiny in the picture as it got treated with a light solution of phosphatic acid to prevent corrosion. Works well.

Dan
366  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 14, 2012, 11:43:58 AM
Hi,

I am going to keep it flat. I have sheet metal guards designed to cover the screws so should be no problem there.

Thanks for the picture. I like your collet addition. Might consider it on my Emco C5 as I usually use bar stock there. Where did you get yours?

Dan
367  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 12, 2012, 08:28:22 AM
Thanks Russ.

For the Z axis I have a 14mm diameter, ground NSK ball screw I got from eBay. It's used but it looks in a very good shape. For the X, I got a Hiwin 12mm diameter C5 rolled ball screw from 1aballscrew.co.uk who tend to offer good pricing and also do the end machining.

Dan

368  General CNC Chat / Show"N"Tell ( Your Machines) / Re: 9x20 Chinese Lathe Conversion on: March 11, 2012, 01:19:58 PM
The front gib was more tricky in terms of mounting and size to prevent interference with the Z ball nut underneath. This is what I ended up with:


Again it's two pieces for the same reason, base being steel and the sliding bar cast iron. The two M6 holes at either end match up with the original holes on the carriage two bolts there will be used for adjustment. The 3 larger holes match with the 3 holes I bored in the carriage (bottom view photo in the previous post). These will have dowel pins.

It's hard to see on the picture, but there are M4 holes on the sides perpendicular to the M6 ones. They are for M4 locking set screws.

Dan
369  Tangent Corner / Tangent Corner / Re: MY NEW MAN CAVE! on: March 11, 2012, 01:05:06 PM
Love it!

Very impressive, 8 days from scratch to something like this!

Dan
370  G-Code, CAD, and CAM / G-Code, CAD, and CAM discussions / Re: Milling alloy on: March 09, 2012, 01:57:41 PM
Looks like 5052 or some other soft alloy. They don't machine well. Only way to successfully machine this stuff is using heavy flood coolant with fair oil concentration or Tapmatic cutting oil .

Aluminium alloys with excellent machinability are 6061, 2024, 7075. 6061 being the most common. Also, your feed is way too low. Assuming a 3-flute end mill you'd want to feed it around 350mm/min at that spindle speed.

Dan
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