42 replies to this topic

[Rob Voska]

Stuff like this & if it breaks you only have to replace one.

 

https://www.ebay.com...8oAAOxyvSVRENI9

[havlicek]

The read-out is not the issue - plenty of those around.  It's the scales and appropriate mounting brackets that will take some planning.

 

EM

 

 

Your statement  that "no off the shelf DRO is available" is false, at least as stated.  Your subsequent statement makes no sense...per this:

https://sherline.com...direction-mill/

 

[Phil Hackett]

And a correction - a CNC system can function as a "DRO" but it is not the same - the DRO directly measures movement (like a pair of digital calipers) while the CNC system infers displacement by counting turns of the lead screw and is therefore subject to leadscrew and backlash errors.

 

This leads me to speculate on the possibility of a hybrid system: steppers to drive the motion and control acceleration, deceleration etc but absolute position controlled by scales  (and if this is like most of my Eureka! moments, it has already been done.

 

EM

 

On most CNC machines there's an option for glass scales for feedback to the control to detect dimensional changes due the temperature variation.  Most "professional" machines use ballscrews where there is no backlash. Absolute encoders attached to the screw(s) are incredibly accurate. The CNC control then makes adjustments based on the scale feedback.

[Ecurie Martini]

 

 

Your statement  that "no off the shelf DRO is available" is false, at least as stated.  Your subsequent statement makes no sense...per this:

https://sherline.com...direction-mill/

 

 

Thank you.  I stand corrected.  I overlooked this option because I have looked primarily at options for the Taig mill since, as I mentioned earlier, it would be my choice vs. the Sherline.  The Taig leadscrews are 2X the size of the Sherline ( 1/2" vs 1/4") and the basic structure is more rigid.  These differences would come into play in consideration of cutting capacity - tool size, depth of cut, cutting rate & material so, with appropriate limits there should be little difference in performance between the two.

 

EM

 

EM

[havlicek]

 

Thank you.  I stand corrected.  I overlooked this option because I have looked primarily at options for the Taig mill since, as I mentioned earlier, it would be my choice vs. the Sherline.  The Taig leadscrews are 2X the size of the Sherline ( 1/2" vs 1/4") and the basic structure is more rigid.  These differences would come into play in consideration of cutting capacity - tool size, depth of cut, cutting rate & material so, with appropriate limits there should be little difference in performance between the two.

 

EM

 

EM

 

No problem

[Dennis David]

The leadscrews on my mill fall somewhere in the middle at 10mm but the German Kress 1050 Spindle is rated at 5000 - 25,000 rpm. The rails are 30x60 T-Slot extrusions and i am looking to use a low profile T-Slot Cast Aluminum plate and custom made low profile fixtures. The vast majority of my material will be 1-3 mm thick carbon fibre, 7075 aluminum and C380 brass so I should be good to go. As Alan warned me I've already spent $600 on German solid carbide cutting tools.

On a recent visit to Datron's US location in Livermore, CA they showed me Datron's new "mini" mill ... $80k LOL

[Phil Smith]

I believe the Sherline DRO works off of the lead screw rotation. They must be  really good with very little backlash for that to work. But I guess it does work. Other than diameter, what kind of lead screws and nuts does it have?

 

I saw on https://www.hobby-machinist.com/ a comment, "You can do small work on a big mill but it's hard big work on a small mill. Get the biggest mill you have room for and can afford." I really don't want for slot car work. I want one for general hobby machinest work. So I really think bigger is better for what I want to do. On the hobby machinist forum, it seems most members have small, American made knee mills. And that would probably be best for what I want to do.

 

That said, I have come back down to earth a little. I should get something affordable to begin with. I think I'm going to get an Sieg X2 like Bill has, except I'm going for the https://littlemachin...?ProductID=4962 version. It has a solid column as opposed to a tilting column which is supposed to be more rigid. And I think going get a lathe while I'm at it, since they'll ship both for the same price as one. https://littlemachineshop.com/products/product_view.php?ProductID=4959&category=1271799306

 

I have them in the shopping cart on the website and almost ordered it today, but I can't seem to make myself hit that buy button. I don't know why. I can afford it. I should just do it.

 

PS: You can get a complete Chinese 3 axis DRO with scales for about 300 on ebay, plus or minus. Here's one. There are many listed: https://www.ebay.com/itm/112213435660

 

 

[Ecurie Martini]

 

That said, I have come back down to earth a little. I should get something affordable to begin with. I think I'm going to get an Sieg X2 like Bill has, except I'm going for the https://littlemachin...?ProductID=4962 version. It has a solid column as opposed to a tilting column which is supposed to be more rigid. And I think going get a lathe while I'm at it, since they'll ship both for the same price as one. https://littlemachineshop.com/products/product_view.php?ProductID=4959&category=1271799306

 

I have them in the shopping cart on the website and almost ordered it today, but I can't seem to make myself hit that buy button. I don't know why. I can afford it. I should just do it.

 

PS: You can get a complete Chinese 3 axis DRO with scales for about 300 on ebay, plus or minus. Here's one. There are many listed: https://www.ebay.com/itm/112213435660

 

 

 

You might want to consider their "High Torque" version.  It is $300 more but you will almost certainly be spending $150 on a gear-to-belt conversion when the (plastic) gears in the X2 break and break they will.

 

EM

[Phil Smith]

Alan, like I mentioned, I've been researching and debating this for weeks. I've watch several hours of youtube videos as well as read a lot on the web. Frank Hoose has several good videos on home mills. It seems he may be paid to promote little machine shop products, but he doesn't seem to be too biased. He had me sold on the LMS X2 because of the column, and later on the 3990 because it's quieter and more powerful. And then I decide that I need something bigger than that and decide on the Precision Mathews that I linked to in my first post. Then during this thread I decide I need even more power and rigidity and start looking at knee mills. So the price kept going up and up.

 

I may not like this as much as I think I will. I've decided I need to go cheap as possible to start with. If I stick with it I can move up later. If I don't I can sell these in my pawn shop for little to no loss.

[Phil Smith]

I haven't been able to sell my HO track yet, but I got to digging in boxes and found a ton of HO cars. I knew I had a lot but I had way more than I realized. Ebay sales of those and some microphones has gone well, so I've upped my budget.

 

I want a knee mill. This is the cheapest one I can find. https://www.harborfr...hine-40939.html It gets pretty good revues, all things considered. Any thoughts or advice?

 

Way heavier than I wanted, but everyone says you need to take them apart and clean the casting sand out of it. So I can take it apart at work, clean it up and reassemble it at home. 

 

 

 

[Phil Hackett]

I will again warn about the Z axis capability.  Anything you put on the table is going to use that distance up. Then don't forget what sticks out of the spindle also uses that distance up. One of the comments about the machine says a mod increases the Z distance to 13" (NOW you're talkin'!)...

 

The good thing is that it uses an R8 taper. There's a ton of Bridgeport tooling that will fit this machine and you're not forced to buy a bunch of special tools made just for this machine. If you decide you want something bigger you can take that tooling to the bigger machine. No need to start over.

 

The 1/2 t-nuts slots are another nice touch. They are cheap... McMaster has them...

 

Just some impressions....

[Phil Smith]

I will again warn about the Z axis capability.  Anything you put on the table is going to use that distance up. Then don't forget what sticks out of the spindle also uses that distance up. One of the comments about the machine says a mod increases the Z distance to 13" (NOW you're talkin'!)...

 

 

I missed your post. Thanks. I found the comment about incrasing the Z on my own after you posted this. So that was good news! The other day I also found that some people make a spacer to insert in the column, so there's potential for even more Z travel.   I ordered an ER32 collet set. They burn about 2" of travel, so I'm not sure that was a good decision.

 

The mill arrived yesterday. The vertical mill was in the horizontal position, and severely damaged. I refused the shipment. So maybe the next one will show up in one piece, instead of three like this one. I would order from someone else, but the cheapest comparable mill is a Grizzly that cost over $1K more.

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[Rob Voska]

If your getting another offer them $100 for it so you have spare parts!

[Half Fast]

What a bummer!

 

Good luck next time.

 

Cheers

[Phil Smith]

If your getting another offer them $100 for it so you have spare parts!

 

Good idea, so I gave it some thought. The only parts I'd really like to have for spares are all the spindle parts. They have to see it before they'll send me another, so I'd have to pay $200 shipping plus whatever they want for it. Not really worth it.

 

What a bummer!

 

Good luck next time.

 

Cheers

 

Thanks! I have my fingers crossed.

[Rob Voska]

Wonder why they would even bother delivering it in that condition.

[Phil Smith]

That's a good question. I guess it doesn't hurt to see if the recipient will accept the shipment. It's hard to imagine anyone would, though.

[Phil Smith]

The 2nd mill arrived last Thursday on a truck without a gait lift, even though I had paid extra for that service. I wasn't here, but the truck driver told my employee that the pallet was crushed and he couldn't unload (please do not hyphenate) it anyway. So it arrived today on a proper truck and it's in the back of my shop. A little damage, but nothing like the last time. Can't uncrate (please do not hyphenate) it until later today. Fingers crossed!

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