Keeping the X on a round column bench mill

[tweinke]

That's what I'm saying use the laser, Mark the spot before cranking the head then realine to that spot and lock up the head. It should be close. It would be straight up + down in the same plane. Parallel.

Yes I definitely get that. Was just thinking if a guy had a nice flat and straight bar set up parallel with the column and an indicator mounted to the head as long as you do not swing the head it would be easier to get back to zero. Although if you swung the head to one side it could be limiting the swing. The laser would certainly eliminate that issue. The creativity here certainly makes this a good place to be combined with the fact no one flames you for adding your thoughts!

 

[Eddyde]

Here is some more discussion on the laser approach, relating to vise alignment:
http://www.hobby-machinist.com/threads/milling-vise-alignment-in-13-seconds.39171/
However, the concept is the same.

 

[This Old Lathe]

Why not set up a vertical reference point that is parallel to the column, make a bracket to hold a dial indicator and use that as the reference to reestablish zero?

That's what I do. Very straightforward and as-accurate or more so than the more-involved methods described in this thread. I do understand the desire to have some 'built-in' feature to accomplish it though ....

 

[Canuck75]

Hello Mark F, Tom and R.J. ,-

Sorry, I've away from the site for awhile and have just now read your comments.

First of all the rack on my mill was within .001 to .002" in width originally and with some buffing was close enough (10ths) that the guide blocks could be moved end to end by hand with some friction. The fit needs to be snug.

Secondly, I agree with the comment about the ratio of column centreline to the rack and the column centreline to the quill centreline, that is why nothing can be sloppy.

Third, and because my mill has a split casting and two bolts, experience showed that if the top bolt was tightened first, the head would retighten in the exact same manner each time, thus, in my case, would return to the same X reading within .001" each time. I posted a video showing this to be the case.

I am confident enough under normal circumstances, that I can move the head up or down without having to reset the X. If I'm doing work where there is a "pucker factor" involved, the only thing to do is recheck - that's life.

Thanks for the comments.

Canuck75

 

[Uguessedit]

Seems to me that a pair of bearings at the top and bottom snug to the rack would keep it well guided and friction free. I have a round column with hiwin rails on the base with extended axis and a 10000 rpm capable spindle. I haven’t had any issue with the rack myself since I don’t use that much z to cnc and was able to get a solid 5” out of the spindle though I only use about 3.5”. Really if you use a probe or edge finder it’s probably not that big an issue if you need to machine the same part at different heights. Typically for myself if I’m changing parts it don’t matter since I reset zero and home anyways so it’s been a moot point. Perhaps manual use that’s different. Neat seeing different ideas. I use mine as a backup mill and to do drill arrays where the z height isn’t something that’s critical for the application.

 

[Garryloy]

In about a month I plan to post a new solution to this problem - if my idea works. I have a RF-31 that I have modeled in 3D (SW) and I have completed all the design work on the new approach. It looks really good on paper. I have all the materials and I am in the process of making the parts now. It's hard to find time for it with 14 grandkids.

 

[minsk]

I have posted some information on this forum before about my machinery and have made many modifications to the mill, but this article is specifically about addressing the problem of keeping the X on a round column bench mill when changing the head position.

My particular "King" mill has a 19.2" X, 8" Y and 5 3/4" quill travel plus the head travel on the column. This capacity meets all my hobby machining needs. I dreamt of having a universal turret/ram/ knee mill but space and money dictated my choice. I saw this used bench mill on Kijiji and within driving distance. Mill looked a little scuzzy so did a full teardown, cleanup, repaint. Also started plans to make improvements.

During operations I find I often raise and lower the head to keep everything as short as possible for rigidity sake and to get room for the boring head, chuck and drill etc. Redialing or edge finding after each head change was required. The question of keeping an accurate X during these changes kept bugging me. Other owners of this style mill have posted opinions on this subject indicating we all want to make one of these basic mills do more than they were originally designed to do - in other words make a silk purse out of a sows ear - well why not! I went through a lot of "what ifs". I established several parameters relative to what I needed my mill to do. First: I don't do work big enough that I need to rotate the head to reach far corners of a work piece, or, even to get it out of the way; Second, if you do rotate the head you relatively loose some of your Y travel range not having a "ram" to compensate (even in a commercial machine shop I seldom had to rotate the head and when I did I always needed to use the "ram" to offset the change in Y reach): and, Third, I do have to raise and lower the head often during machining operations thus a desire to control the X accuracy setting if possible.

Having accepted this, it was just a matter of what way to do it. Others have made made very good stand off frames to control the X which also retain a head swing capability but I'm not sure what guarantee of accuracy you will have when you swing the head back and clamp everything up again. Based on my personal "parameters" I chose the non rotating head solution. I know others have thought of fixing the gear rack to the column and using guide blocks (I presume) on the head, so thought I would give it a try. It could always be undone with no harm done. Also the whole mod is basically invisible so the aesthetics of the machine are not altered which is a personal preference.

The attached series of photos shows the results of my effort. Subsequent up and down tests show an accuracy of .001". If on occasion I am really paranoid, I can always edge find or dial indicate for that particular operation.

First photo shows the purchased condition just for interest. Photo 2 - pinning the rack moving up the column with the assist of a dial indicator as in photos 3 and 4. Photos 5 and 6 show the top and bottom guide blocks bolted to the head - this was done with the head on the column, in position, and using the pre drilled holes in the guide blocks to drill the head and then tap. The last 3 photos show the test results. First with the head at the bottom and after a X and Y edge find setting the DRO to zero. The second to last photo is with the head raised 5.5",quill extended, and table brought back for X and Y edge find to see how it would compare to the DRO - .001", and last photo is with quill retracted and head back down and another edge find comparison to the DRO - .001".

I,ve added one photo of the top guide block showing the slightly modified middle pulley bracket to accommodate the movement of the bracket when loosening and tightening the belts.

View attachment 67718

I welcome any comments.

View attachment 67507View attachment 67506View attachment 67508View attachment 67509View attachment 67510View attachment 67511View attachment 67512View attachment 67513View attachment 67514



View attachment 67506 View attachment 67507 View attachment 67508 View attachment 67509 View attachment 67510 View attachment 67511 View attachment 67512 View attachment 67513 View attachment 67514 View attachment 67718

how are you doing dro on your computer?

 

[Canuck75]

how are you doing dro on your computer?

minsk,-
Thank you for your interest. Am still pleased with my DRO setup after nine years. New glass scale systems are now very cheap but won't change unless my system fails.

 

[minsk]

dro pros is really nice...but my mill is not nice enough to warrrant it

 

[Canuck75]

dro pros is really nice...but my mill is not nice enough to warrrant it

Yes, budget is always a concern, and at the time the system I have cost ~$500 Cdn, which was a very big expenditure for me. However, Using a DRO, even on these mills increases your capability many fold. I like to build model engines and cannot see doing it without one. Highly recommended.

Thanks