DRo on BP knee...

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lakeside53
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DRo on BP knee...

Post by lakeside53 » Wed Mar 04, 2009 8:07 pm

After the knee handle fell off twice on Monday, and I lost count both times... Time for a(nother) DRO. I already have an X-Y and spindle.

I dug out an old Anilam Wizard (early 80's?) and the scales. The front panel is worn though in many spots but it works fine. I thought I could use the shorter 16 inch Y axis scale but no joy - only about 12 inches of travel. Cutting the longer X axis scale (from a 42 inch table) looked like a disaster, so I just mounted it. I'll knock this out in a couple of hours... lol... a day later...

Mounting the knee scale is PITA. There is no frame of reference where you mount, and all mounting is on rough castings with 1/8 inch of putty covering a host of sins. The scale needs to me mounted such that it's parallel and square to the plane of the movement within about 0.003. The moving portion with the head has to track that within 0.005 max. My method was to make everything adjustable, and I needed it. I used the flat surface of the column way as the reference to mount the scale, and adjusted the knee portion to that. It's really obvious now, but I had to scratch my head a few times in the process.


The mount brackets rotate and have slotted mount holes. The head mounting plate is mounted on three 1/4-20 all-thread posts and is slotted about 50 thou. My original intent was to use this only to figure out the size of three mount spacers, but it's rigid enough as is.


BTW.. I deliberately mounted the scale so the "seals" faced away from the chip path.

Good use of stuff I'd had lying around forever... I was waiting for a broken Wizard DRO with a good from panel to surface, but nothing...
Attachments
DSC_8102 (Medium).JPG
Top mount bracket - bottom is identical. Made from sawn U channel
DSC_8101 (Medium).JPG
Lots of displays and lights!
DSC_8104 (Medium).JPG
knee and head mount.

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GlennW
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Post by GlennW » Wed Mar 04, 2009 9:28 pm

A 12" steel rule (engineers preferably) screwed to the column or with a wire pointer screwed to the knee works well to. Just bend the wire pointer to whatever indication on the rule you see fit and you are all set. Marks on the rule with a china marker or Sharpie will always get you to known spots without counting turns. Works well if installed on the X and Y axes too. Especially for repetitous work. The wire pointer needs to be about coat hangar diameter and a few inches long to have decent flexability.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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GlennW
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Post by GlennW » Thu Mar 05, 2009 9:31 am

I occasionally see evidence of others spending money on DRO's for their mills when in many instances, this will work just fine and is far less expensive.

This is what I was attempting to describe above.

This s a little more sophisticated with a sliding pointer, but a wire pointer will work just as well and is a lot simpler for installation purposes. This is not something I made, the machine originally had them installed.

The numbers on the scale are basically meaningless in this application, but most rules come with them!!

Image
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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thedieter
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Post by thedieter » Thu Mar 05, 2009 11:46 pm

Glenn:

That appeals to my frugal nature and has started the wheels turning for my new G3617 mill.

I wonder who makes those scales.

Best regards, Jack

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BadDog
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Post by BadDog » Fri Mar 06, 2009 3:15 am

I've got a DRO on my mill, and lathe for that matter, but I've still considered setting up hard stops for each. I used it all the time on my old lathe, pretty much no choice there when you have no DRO. But I really hate watching the DRO counting to some arbitrary number (including zero) and trying to stop at the same point every time. Problem is, the power feed safety limits occupy that position on my Bridgeport table, so there seems no easy solution.

I'm thinking it would be really nice to make some kind of quick mount to swap a hard stop and the micro-switch block. Then just leave the limit stops since they are well outboard, and make up some half-twist stop blocks to insert on the table side slots at a convenient location. That would be better than a DRO for quite a lot of the stuff I do, but the key is being able to quickly/easily swap the hard stop for the micro-switch housing.
Russ
Master Floor Sweeper

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GlennW
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Post by GlennW » Fri Mar 06, 2009 6:01 am

Hello Jack,

I believe you may be able to find one at a Drafting/Architects supply house. That is if they still exist sinc the world switched to CAD!

http://www.draftingsteals.com/20592.html

You might call them and see if they are available in 10'ths (engineers)rather than 8th's (architects)
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

schwabw
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Post by schwabw » Fri Mar 06, 2009 7:33 am

All,

Part question, part suggestion: is losing the knee handle that big of a deal? As I recall, that would throw off counting, but not the dial itself?? My thought would be to toss a scale or "gage block" in there to measure height to the tool to get back into synch with the dial. I rarely count in x,y; it's often easier to measure to the correct revolution and then use the dial to get the last couple of digits right. I _assume_ that I would find something analogous in z on a knee mill.

Bill

lakeside53
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Post by lakeside53 » Sat Mar 07, 2009 1:06 pm

Lose count? Only when it wacks you on the foot or you skin your knuckles, or when SWMBO want to talk in the middle of whatever, or the phone rings or... I had to make some large knee (10 inch) movements to change tooling and opertions, then get back to my reference...

Yes, a ruler, block or anything would certainly help, but in my case an old dro made life so much easier. I mill with the knee rather the the spindle. Anything less to remember in my old age helps :wink:

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Frank Ford
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Post by Frank Ford » Sat Mar 07, 2009 1:56 pm

Bad Dog -

I wanted a hard stop, too, and to avoid having to swap out the DRO limit switch, I made a pair of heavy stops that fit the edge T-slot on my mill table:


Image

Here's the full story:

http://www.frets.com/HomeShopTech/Tooli ... estop.html
Cheers,

Frank Ford

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BadDog
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Post by BadDog » Sat Mar 07, 2009 2:12 pm

Thanks Frank, I saw your article before (was just reading some new ones today, THANKS!). But my problem is kinda the reverse. I already have good outboard stops on the table side slots. But they currently bump the power feed limit switch. That limit switch is what I would like to figure some way to quickly convert to a hard stop. If it were not heavy plastic, I would have more options. So I'm thinking perhaps a sort of "U" shaped bracket that surrounds (hides) the limit stops plungers (providing the hard stop), and then some twist-in t-bolt mounted stops similar to yours (but with the twist ins) so I can insert them inboard of the safety limits without having to remove them. Rigging some that could stay in all the time and bypass each other when not needed would be an added plus, and I've pondered some options on that too...
Russ
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Frank Ford
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Post by Frank Ford » Sat Mar 07, 2009 2:47 pm

Ah, so. My stops hit the Y-axis casting, below the table, and my power feed limit switch is in the middle , out of the way of the hard outboard stops - under the vise in this photo:

Image
Cheers,

Frank Ford

lakeside53
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Post by lakeside53 » Sun Mar 08, 2009 1:59 am

That sure is a purty table :D

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