I've got a question but don't know if I can explain it.

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terryw123

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I'm not very good at explaining or describing what I want to do but I will try. I have a lathe and I have a special devise I want to make for it. It is a big/long job that will last maybe a year or more (off and on), for a customer, and if I can make this work it will be a lot faster. It is a combo cutter and tool post grinder. I will cut from one side and grind from the back side (not at the same time). For talking we will say I have a 3 inch diameter shaft about 2 ft long. It is furnished by the customer and I think some special alloy. I've tried turning it and there is no problem turning it. I don't have to grind the full 24 inches, but 3-4 spots at different diameters.

Anyways, I have to have it ground to about 2 1/2 inches in diameter when done. What I want to do is cut the bulk of it off with a regular cutter down to about 2.510+- or there about and then grind the last few thousandths off with the tool post grinder on another pass.

My problem, and I don't know how/if I can do it with the Chinese DRO. I am only using the x axis (cross feed) and I want the dro to read the rough cutting dimension, then just push a button or 2 and switch the dro readout to the tool post grinder position. Then switch back on the next shaft. Can this be done with the DRO?
 
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So you will advance the cross slide in one direction to make the rough cut, then go the other direction to grind? Interesting.

Here's a thought - (haven't tried this myself, obviously):

Find a cheap DRO where the scales can be cut to length.
Cut the X and Y scales to the same length, and mount them both to the cross-slide, but mount one in the usual way and one backwards, so that as one "axis" counts up the other counts down.
Touch off with your cutter, set the forward axis and rough cut to your 2.510" dimension.
Switch to the tool post grinder, make a light pass, mic the part and set your backwards axis, grind to finished dimension.
 
I assume that you will be doing a number of these parts in a run. I wouldn't even worry about the roughing dimension relative to the DRO, just use your dial to get close. Do the first part, get it on size, set the dial to 0, then just come back to 0 each time. Your dial may not be super accurate over a distance, but I'll bet it's repeatable. Then use the DRO to do the final grind. I would also cut to about +0.001 then finish grind. Taking off 0.010 with a tool post grinder is going to take quite a while.
 
I love the concept for the sake of efficiency, but I don't see how you could do it exactly (assuming I'm understanding it correctly) because the grinding wheel is a consumable item. That makes it very hard for a DRO to know where it is in relation to the workpiece over multiple cycles. Personally I'm not sure how reliant I would be on a DRO for grinding. Good for keeping track of carriage and cross slide movement, but not part size so much because it wears out during use.
 
Thanks MrDan. I understand exactually what your saying. First of all that might work but those cheap dro's don't read radius (which I could recalculate 1/2) but since I have a $500 new dro, I'd like to get it to work with out buying more stuff. Also your idea would work, cut in one direction and grind in the other, but I was gonna start over and grind the same direction as cutting. No big deal though.
 
Most DRO's have a tool library, each tool has a tool position, tool 1 turning, tool 2 grinding for example.

Set each one and it will remember the positions until changed by you or you have physically moved the tools, quite simple really.

Many contain math functions such as bolt circles on a mill and tapers on a lathe, Accu-Rite makes excellent controls that will do what you are looking for, not cheap however.

Good Luck
 
Wreck......Ok that sounds like what I need. (tool position) Big problem I have and I'm sure you've already heard it many times, the darn chinese operator manual sucks. This is the DRO I have. Would be perfect if someone here had this model and could guide me step by step.
 
Jon made a good point though, even if you can set a tool offset for the wheel, the actual offset gradually changes with every pass as the wheel erodes, and changes even more every time you dress it. Seems like you would end up chasing your tail trying to keep it updated....
 
Mr Dan.....I agree about wheel eroding . I didn't get in to details about this job, but I won't have to grind the whole 24 inches. The customer even offered to supply the wheel, which money is no object so I assume it is a good one and will hold up. Anyways if I can get this cutter / grinder thing to work on the DRO readout, I have other jobs I can make use of it.
 
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