[kong]

Eric, the bore got enlarged, only by a fraction, but enough to introduce extra runout or even wobble. Bear in mind most of my old cutters were less than 1/4" dia, so they press into the steel easier.
Stevie, thanks for the tips, perhaps one day eh!

[balsaman]

Eric

Punch the speed way up and it will finish nice with a 25-32 thou rad insert

Thanks Stevie. You may have been a tool and die maker for 37 years but you have the enthusiasm of a teenager! I like your projects.

Eric

[kong]

Eric, I have just through the thread again, looking for how you handled the y-axis ballscrew. On my mill, there is no rear support bearing, so I was wondering if you had one in there, or whether you left it floating? Thanks, Jason.

[balsaman]

floating

[Stevie]

I have a ball screw with LH and RH threads; I'll be cutting it in 2 soon; the problem is it's a 2" pitch with 2 starts and dubble ball nuts; with one nut usable travel would be about 14"; it could make a nice gantry setup; with a common drive centered and the opp threads working together one on each vertical
THe speed would be huge with a 2" pitch; so I'm thinking it will be of little use to me; but some router guy might just love it; it is a ground thread version; brand new; if the 2 nuts are used travel would be just over 10" I think
Anyway I'm rambling on here; these would be used as floating also; or if needed i could grind a bearing diameter on the cut end; I think it's a 1" diameter; not sure it's at work right now (for cutting)
If anyone could use such a pair of high speed ground ball screws let me know?

[Stevie]

Thanks Stevie. You may have been a tool and die maker for 37 years but you have the enthusiasm of a teenager! I like your projects.

Eric

One day if your passing through Sarnia; you'll have to drop in!!

Steve

[Rockabye74]

I just scanned through the entire forum, and I have to say I am impressed by all of you. I recently purchased an OLD Bridgeport mill for home use, and will be planning out a CNC Conversion. I can't help but thank all of you for your wonderful information, and I hope that it goes much smoother thanks to all of your good ideas.

[balsaman]

Glad we can help!

Eric

[MikeAber]

I just went thru the entire thread on this project and I am also very impressed with the knowledge I gained. You can bet I have saved a set of notes for my Harbor Freight gearhead (round column) mill conversion project. I am especially gratified at the openness exibited by all the contributors, it is nice to see that I am not the only one boring holes in the vise during the learning process.

I congratulate Eric on a job well done and I appreciate the extra effort to document this project for the rest of us. ------ THANK YOU! ------

I have the same motors, I will mount the encoders on the end of the ballscrews and use preloaded double nuts on the X and Y axis to help control backlash.

MikeAber

[mattinker]

There may be a solution to round shaft alighnement. The Urwhick metalmaster had a round column with a patent, triangular key and key way. This eliminates alighnement problems.

http://groups.yahoo.com/group/Urwick_MetalMaster

Let me know if this helps, Matthew

I have read all the horror stories about the round column mills and the PITA when you need to reposition the head on the column. My question is, if I can live with the 5" quill travel, does this mill do a good job machining with the quill extended?

What are the odds that I can build some sort of external keying (using THK rail and bearings) into the round column and move the whole head up and down on the column as a z axis? If not that, perhaps I can still use the quill for z but use the keying to keep the head in position on the column when manually moving the head?

What do you think of using the stock lead screws? I am considering the Mcmastercarr 5/8" rolled ballscrews but are they any better than the stock lead screws as far as acuracy is concerned? I know they would be more efficient. Also If I used two ball nuts for preloading will they bind because of the fact that the screw is rolled and thus not that acurate?

Anyone with experience out there I would apreciate your feedback!

Eric[/QUOTE]

[Robin Hewitt]

Ok, I am about to embark on a Enco style round column mill-drill conversion.

This one specifically:

Hi

Just joined the forum, thought you might be all posh with lasers and such, but the very first thread I read is about something that looks suspiciously like the one I'm doing

http://www.robinhewitt.net/cncmill.jpg

I'm a newby to this cnc lark, just discovered that after 25 years cutting uphill I'm suddenly supposed to switch direction, sounds horrendous

best regards

Robin

[timsshop]

Eric,
I also have a round column mill and have planned to secure the rack with
bolts & roll pins (split pin, spring pin).
This seems the shortest & easiest solution to round column movement.
The drilling of the hardened material will be the worst part of the project.
Good Luck.

Tim

[balsaman]

No need to secure anything with pins etc. just tighten it up and it won't move.

There is too much play between the rack and the slot to provide any accuracy for head movements.

I just set the head once before the job starts, and have managed to get stuff done despite the round column drawbacks. One solution is to buy a set of screw machine drills (short). Then turn the shanks down to standard collet sizes and forget the drill chuck.

The other thing I do is have the mill bore fussy holes to .020 under size with an endmill using a helical tool path then ream to size on a standard drill press.

Basically, if you can figure out how to drill the holes using short tools, you rarely need to move the head up and down during a job.

Deep holes is another story. Then I use the mill/drill to start or centerdrill the hole, and finish it on a drill press.

Eric

[Robin Hewitt]

I have back the raising handle off after using it or the rack rattles against the column

[mbschuette]

A Friend of mine just sent me article from Digital machinest that fixes the problem with the head on the round column drill mill. It uses a clamp on the top and bottom of the column, and a guide that follows the rack up and down. It is said to be accurate to within. .001". My son is a machinest and will be making one for me