Using just the handwheels (vs a DRO)

[Alcap]

mmcmdl would you be able to start a thread on uses , maybe pictures on how you use them ? Dos and don’t s , I’m sure there are many of us that would appreciate your knowledge on using them .

 

[mmcmdl]

Jig bore rods or trav-a-dials ?

 

[BiggerNoise]

I took delivery of a Sherline mill a few weeks ago. My CNC-ready model came with the zero-able handwheels. I adapted the mill to install the wheels without steppers for the moment so I could get a feel for using it manually first.

But what DRO system could fit this teeny-tiny mill?

Edit: Oh, you mean Sherline's DRO system? I would not recommend that. It measures the wheel's motion only, not the true position of the x-y stage. That means it knows nothing about the backlash of the system, and hence small errors will creep in at random, at least unless you maintain backlash discipline yourself. That's harder to do on a mill than on a lathe, and doing away with that need is a main point of a DRO on a mill. Hence, I don't think Sherline's solution is good enough.

I'll just say that I have never heard anyone that actually uses the Sherline DRO complain about its system for backlash compensation. It certainly works extremely well on my lathe. I'll admit that I'm new to this and basing this judgement more upon indicator readings vs a lot of experience with making parts.

 

[Aaron_W]

Doing the rough layout on the part is a good practice and helps in other cases than just losing count of revolutions. I have a DRO now, but I do recall having one part with lots of revolutions between features that I couldn't (or just didn't think to) do the layout on and I resorted to a cup with the right number of washers in it. At every revolution I took one out of the cup and put it in my pocket.

I've thought of using one of those little hand clickers they use to count people in line. The main reason I haven't got around to it is I'm afraid it would just distract me and just create a new issue.

I took delivery of a Sherline mill a few weeks ago. My CNC-ready model came with the zero-able handwheels. I adapted the mill to install the wheels without steppers for the moment so I could get a feel for using it manually first.

But what DRO system could fit this teeny-tiny mill?

Edit: Oh, you mean Sherline's DRO system? I would not recommend that. It measures the wheel's motion only, not the true position of the x-y stage. That means it knows nothing about the backlash of the system, and hence small errors will creep in at random, at least unless you maintain backlash discipline yourself. That's harder to do on a mill than on a lathe, and doing away with that need is a main point of a DRO on a mill. Hence, I don't think Sherline's solution is good enough.

Sherline's DRO needs to be treated more like a digital trav-a-dial. As long as it is reset at each use backlash shouldn't be an issue. Personally I don't think it is worth the cost for what you get, but it seems to be functional if you accept its limitations. Not really a DRO though as most people think of it.

 

[Cisco541]

A fair number of folks don't use a DRO, preferring to count revolutions of the hand wheels.

I've tried counting each turn out loud, but it seems more often than not I end up off by one count.

What's a good way to keep count of the turns?
If you lose count, how do you re-establish your location?

I always set dial to zero first......if your machine has lots of backlash you need to carefully elimat without moving the table..then set dial to 0. Easy to count the times zero comes by and then any addition dial reading needed. If you go past just backup past the last zero to remove backlash .....the back to zero. Works for me!

 

[BiggerNoise]

I've thought of using one of those little hand clickers they use to count people in line. The main reason I haven't got around to it is I'm afraid it would just distract me and just create a new issue.



Sherline's DRO needs to be treated more like a digital trav-a-dial. As long as it is reset at each use backlash shouldn't be an issue. Personally I don't think it is worth the cost for what you get, but it seems to be functional if you accept its limitations. Not really a DRO though as most people think of it.

Definitely agree that the Sherline DRO is very pricey for what you actually get.

 

[RJSakowski]

For more than twenty years, I operated my mill/drill by the dial, counting turns and dealing with backlash. I had more than my share of operator errors in that time. The turning point was a series of jobs for our startup company that required some precision machining. The part was mounted on a rotary table oriented vertically which permitted machining on five faces without changing the setup. More than twenty tool changes were involved, requiring setting tool offsets for most of them. Machining by the dials would have been a nightmare. (For those interested, the operations file is below.) The DRO made the work possible and saved my sanity.

Aside from the issues of counting turns and recording positions when using the dials, there is the obvious issue of dealing with backlash. My old mill/drill is tired and there is a considerable amount of backlash. This backlash is caused by three factors; play in the thrust bearing, wear in the lead screw nut, and wear of the lead screw.. The first two can be compensated for but the last one is problematic.

The x axis on my RF30 clone has .018" of backlash at the extreme left table position.. It has .033" of backlash at the center of travel. In the y direction, it has .037" of backlash at extreme outboard position but .048" of backlash at the center of travel. The extreme positions will have the least amount of lead screw wear so backlash will be attributed to lead screw nut wear and thrust bearing free play. That leaves .015" of backlash attributed to lead screw wear on the x axis and .011" on the y axis. Assuming equal wear on both flanks of the screw, ir would mean that if I position by the dial, I will come up short the the actual distance traveled by .0075" and .0055", respectively.

However, it is actually worse than that as the flanks didn't see equal wear. Moving the table to the far outboard position and removing backlash, I zeroed the dial and the DRO and moved the table in 3.500" by the dial. The DRO showed the table only moved 3.4888" or .0112" short. Reversing the direction I showed the table moving .0004" less than the dial indicated movement of 3.500". This indicated that almost all the wear occurs on the rear facing flanks of the lead screw.

Checking the x axis lead screw, Moving the table 10.000" to the left by the dial showed the travel coming up .0062" short and moving to the right, .0088" short. Lead screw wear will be uneven depending upon what regions saw the most use in history.

It would be possible to map out the entire travel of the lead screws and use correction values but the tedious nature of that activity would make me want to take up ballroom dancing as a hobby instead. The addition of the DRO to the mill eliminates all of that uncertainty and returns the functionality to better than new.