Fitting a DRO to a BCA

[Jo]

I have had a couple of queries as to how I fitted a DRO to my BCA. So I thought it would be best to add it here:

Initially I questioned a 2 or 3 axis setup and in the end opted for a 3 axis, it was only an extra £80 and it was well worth it. I brought my kit from Colin at CBR Electronics for £370, all three axis are slim sino scales, the standard ones  will not fit. There was an option for a graphical display that would have allowed the rotary movement of the table to also be taken into account but I decided that that capability was beyond my machining knowledge/skills and more expensive.

So the fitting the X axis is the easy one:



The ruler at the front of the table has been taken off and the read head mounted using the original pointer mounting plate with simple straight piece of metal screwed into the bed at either end . Watch that bolt under the Y axis: that is the bed lock and there is also a lubrication point you need to keep clear of.

The Y axis was more of a challenge:



I ended up hanging it off the left hand end of the bed because you need access to the rotary table lock on either side of the rotary table. I purchased a longer scale than necessary for this axis so that it was easier to mount. The glass scale is mounted on the two dowels on either end they are both 1/2" diameter: I keep questioning if it is safe there but so far it is doing ok. The read head is shimmed/screwed on to the end of the bed.

Now the challenge the Z axis, this was a real headache as the head needs to be able to tilt and the scale needs to miss the belt:







In the end I found it was just possible if I dropped of the bed stops and used its Tee slot and a bit of angled aluminium channel to mount the read head on the side of the BCA head. The glass scale is mounted top and bottom on two bits of thick aluminium angle. I normally try to make any DRO mounts such that the read head doesn't move so that the cable doesn't either but I couldn't see an alternative on this one. The result is the cable runs over the top of the top bracket and I have put a plastic P clip to enable the protected cable to have a smooth run.

I would advise anyone to go with a 3 axis setup... And my only complaint? The BCA is more accurate than the scales. The scales only go to 0.005mm, with more accurate/expensive scales you could easily do 0.0005mm.

Jo

[Firebird]

Hi Jo

Nice stuff. I have the cheapo scales on my X1 and X3 mills and would love to fit the better quality ones. I have seen mention of the BCA machine any chance of a few pics of the machine.

Cheers

Rich

[Jo]

Rich, you will see lots of photos of her in use in my threads. So let me just add the overall picture of her:



Jo

[steamer]

Nice write up Jo!....thanks!...

I eventually want to put one on my SB.....so I'll be sure to pay attention!

Dave

[Firebird]

Hi

Thanks Jo, now I want one 

Cheers

Rich

[Jo]

Rich, no you need one,  trust me.

Jo

[pgp001]

Everyone should have one. Just go for it.

Phil

[steamer]

I have a very basic one on my Clausing mill.......Trust me .....If it didn't have it I'd get it!

YOU NEED ONE!


Dave

[mklotz]

I think that sending the message that a DRO is essential to the novices and lurkers who may be reading this thread is a bit irresponsible.

Let's face it, they're nice to have but generations of model engineers have built wonderful things without them.

[Mosey]

Inexpensive import DRO's mounted on an old, not-so-tight machine by a novice sounds like a good use of resources. Learn how to make a simple mount, get very accurate movements on your machine is worth a lot to some like me. I don't think he said that you must do it.

Mosey

[steamer]

Yup   They have.

I still want one.....My lathe doesn't have one....and with a lathe...you don't need it as bad.

But on a mill...with a worn lead-screw, with more backlash in the middle than the ends, and small dials that are very hard to read....it's tough...and as my eye sight gets worse...it's tougher.

My Van Norman never had a DRO on it...and I had the backlash in the middle down to .004"...and zero at the ends...it wasn't so bad...other than counting the many turns and then loosing your count....very irritating...so you rely on your layout lines....you did put those in right?

Yes Whitworth didn't have linear scales....but if they were available....he would!
Now is it the first thing you should buy? ....NO...I think plenty can be accomplished without...no doubt.

But as funds are available...and other things squared away...go for it

Dave

[Tennessee Whiskey]

Ok, education time. I've heard and read numerous times over; With a DRO You don't have to worry about backlash. Now, I catch myself bumping the dials to get .ooo with no regard of cutter rotation. A bump this way and then maybe a harder bump that way. I swear I'm going against everything I was taught sometimes. Once I take that big "bump" out do I still need to take that little "bump" out in the opposite direction. I hope that made sense. If not I'll  try and re-ask

Whiskey

[steamer]

Hey Eric,

Not sure what you mean....but I'll try if you do!

 

Dave

[Don1966]

I think what Eric is talking about is when you bump forward or reverse to zero the dial or set the dial, does it take out the Backlash. As lone as you move it it direction of the cutting force. What I usual do is move it back and advance the dial slowly towards the cutter to set my scale. That way there is no backlash in the dail to move the axis. Also lock the axis that is not moving. I believe this is what you wanted Eric.

Don

[steamer]

Yes!

Dave