Author Topic: Grizzly G9249 Lathe Improvements and DRO install  (Read 10316 times)

Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #15 on: February 20, 2022, 02:30:24 PM »
Craig,

You're absolutely right - it is vital to get the scales properly level, and the read heads mounted parallel to the scale in order to get accurate results. Although I understand that these magnetic scales and readers are amazingly forgiving. I have seen some photos of installations that looked decidedly questionable, but the users claim good results. Of course, what you need for accuracy, resolution and repeatability in the home shop vary user to user, therefore what gets reported as "good" has to be taken a bit with a pinch of salt sometimes. I like to at least give it my very best shot in the installtion to get everything properly level to get the best out of it. I think this set up should work.

That's great that you have that history on your Bridgeport, very satisfying to know when / where / how it was set up and used. I have had a chance at a couple of Bridgeports but the history was so questionable I let them pass. They looked kind of beaten up - but that could easily have been all cosmetic. I just couldn't take the chance.

Dave - yes indeed the scales have a groove feature along both edges, and these little toe clamps are made to fit in that groove. DRO PRO's supply one pair of clamps with the 40" scale. I had another pair left over from my mill install, so decided to use the extra clamping.

The directions supplied with the scales have a suggested 3 point mounting scheme for uneven surfaces, where you put a mounting plate behind the scale at the ends and in the middle, leaving the spans unsupported. The advantage being that you can machine the mounting pads individually to get the scale mounting surfaces co planar. That should work, but I am not certain about the unsupported spans staying flat. Another way might be to take the same approach, but also then mount the scale on a very stout and flat bar which in turn mounts to the 3 blocks.

Those are back up plans that I have in mind - I think my shimming approach should work. If for some reason I cannot get the scale flat enough then I can always start again with one of the other approaches. The cross slide scale is mounted on a ground surface, so that one is easy.

Also, I didn't make much mention of it but as I machine the read head mounting brackets, I am machining them at angles to account for any draft on the lathe castings, and present the read heads properly to the scale. I think the more care taken to get this right, the more accurate and repeatable the readings will be.

Stuart

Forging ahead regardless.

Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #16 on: February 20, 2022, 08:54:05 PM »
Hey Stuart,

I plan on making 5  3"plinths.   The end 2 will be for bolting on, while the center 1 will have a jack screw, and I think I'm going to grout the scale in with thickened epoxy  (JB  weld )


I think I'm going to do it like the guy who mounted them on his SB with a dedicated drill sled and get them all the same depth from the inner V way
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #17 on: February 20, 2022, 10:56:35 PM »
Oh man - that's a brilliant idea. At first I was thinking "if only I could mount the lathe bed on the mill and machine some flat surfaces", but could not make the leap to a similar, but differently implemented idea.

That might now be my preferred back up plan if my shimming approach doesn't work out. Your way will likely be more solid - I do worry about shims shaking loose over time in some locations. Guess I'll see what happens.  :zap:
Stuart

Forging ahead regardless.

Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #18 on: February 20, 2022, 11:07:34 PM »
I'll sketch up what I have in mind....and share it....be patient....

Dave
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #19 on: February 20, 2022, 11:14:16 PM »
I'd appreciate that very much. And no rush, I'll keep going with what I have, but removing it and reinstalling it is really not that big of a job.   :ThumbsUp: :ThumbsUp: :ThumbsUp: :ThumbsUp:
Stuart

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Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #20 on: February 20, 2022, 11:31:45 PM »
Heres kinda what I had in mind    Im considering it as 2 pieces .   A U shaped nest that you put the jB weld in and a stand off busing with a screw in it.

I would probably put a strip of packing tape down the middle to cover the head of the screw,    I don't suspect the mag strip is going to go bad and need changing out, but if it did, you could easily cut either side of the bracket and spin it off.

Dave
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #21 on: February 21, 2022, 12:15:54 AM »
I like that a lot. I really like that a lot. That will make for a very solid install. Going to give this some serious  :thinking:
Stuart

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Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #22 on: February 21, 2022, 12:23:37 AM »
I am reluctant to give a design to someone for something that I haven't already proved out.   That said.   Think very hard about it, and test what ever you can before you do it.

Dave
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Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #23 on: February 21, 2022, 12:57:15 AM »
To work correctly, the scale has to be grouted up and down as well as in and out.   That way it's in a zero stress state when the epoxy kicks

Dave
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #24 on: February 21, 2022, 01:28:10 PM »
So the epoxy is to secure the scale in position once it's levelled? Do you see any particular advantage to that over just using levelling screws or mechanical fastenings?

I'm now quite disappointed in my scale mounting. As I look back at it on this thread it just looks very half baked. I think I would like to take the 3 plinth approach, but I'm interested in mounting the scale to a stout, flat bar, which is in turn mounted to the 3 plinths. I have to do a bit of measuring and see how flat an aluminum bar can be held when clamped on 3 points. I think extruded aluminum bar is pretty straight.

I should have thought this through more carefully before demounting the lathe. I think I will need to replace the lathe to make some parts to mount the scales. However, removing the lathe is actually not all that difficult.

EDIT: In reviewing the DRO PRO's customer gallery again, it is very common to have these long scales just mounted on 3 points, with no supporting bar behind. I'm now doing what I always do and second guessing myself, and getting in a confuzzle.  :headscratch:

It's a good time to have to leave the project for a bit and return to the real world. But I'm pretty sure I'm going to start over on the long scale. This little bit of wheel spinning usually obtains a result I'm happy with though.
« Last Edit: February 21, 2022, 01:45:24 PM by propforward »
Stuart

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Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #25 on: February 21, 2022, 02:32:48 PM »
The center support is to prevent flexing.   To do that I'd use a grout in my concept.    You've built may wonderful projects Stuart.   Don't second guess yourself.   It'll be fine!

Dave
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #26 on: February 21, 2022, 02:49:51 PM »
Oh I understand now. You jack the center into place in setup then grout secure - got it. Makes sense.

Thanks for the encouragement and following along! I appreciate it a lot.
Stuart

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Offline steamer

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #27 on: February 21, 2022, 02:55:56 PM »
Oh I understand now. You jack the center into place in setup then grout secure - got it. Makes sense.

Thanks for the encouragement and following along! I appreciate it a lot.

Yup  with screws top an bottom .   Then once set put some epoxy in there and set it back down one last time..    Set it up dry a couple of times to make sure it will repeat, and take your time.   The epoxy won't be drama if you do the set up well.

But lots of ways to skin the cat.....   Just get after it.      8)
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Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #28 on: February 26, 2022, 11:04:02 PM »
Right so, welcome back to Stuart ties himself up in knots.

I didn't get to work on this during the week, so first order of business was to finish up the chip tray, so the paint can dry while I work on scale mounting.

I have to turn the gaping hole in the lower right corner into a 5/8" barbed hose fitting.



Which I did by drilling and milling a suitable size hole in a piece of 1/8" stainless I had lying about.



I have to admit - reasonably happy with the welding on this.









Got it a little too hot at this point.



Then cleaned it up with acetone and rattlecanned it with some hammer finish paint.





I think my welding and paintwork is at least as good, and probably better than the original Chinese finish.

This is a much neater solution than my original bolt on brass fitting.



Anyway, while the paint dries, back to the long scale install.

The magnetic scales have jack screws each end, so I spent a little bit of time tweaking those to see if I could get the scale straight - and I expect I could have got it there, but it was taking a lot of time to make minor improvements, and that side of the lathe is just so non flat that I didn't feel it was a robust solution, so I decided to move on to a 3 point mounting block solution.

First off, I thought I'd do a measure of the straightness of the scale itself, just to reassure myself.

 

So what I have there is the scale sat on two 2-4-6 blocks. The scale is not clamped down. I rest it up against a 1-2-3 block in the vise, and position a DTI on the scale. Then I gently fed the scale back and forth, lightly holding it on the 3 blocks. I did it this way because I wanted a feel of straightness in an unrestrained fashion. It is flat within .004" over the full length using this method - which I accept is not perfect. But the scale does not have significant bow in it. If I can make 3 mounting positions that are co planar then this scale can be mounted flat.

Stuart

Forging ahead regardless.

Offline propforward

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Re: Grizzly G9249 Lathe Improvements and DRO install
« Reply #29 on: February 26, 2022, 11:09:15 PM »
The kit comes with a variety of brackets, and included in the kit are a couple of these black mounting blocks. They have jacking screws in the corners and are made to hold the scale at the ends.



I set up the first block and got it level relative to the carriage travel. I did then mount up the scale - and already it is more straight than I got with the prior method. However, jacking the blocks around with the scale on is a bit difficult. I have there fore removed the scale again, and I'm simply levelling each block in turn, referencing them back to the first one. After that it should be very simple to get the scale mounted and straight.

That's where I'm at anyway, and I feel much better about this as an installation method.

I'm about done for the day, and my wife just texted me saying that it's time for stiff rum drinks, so I'll round off the days activities with a look at my lovely new Aloris toolpost.



I've been trying to lay my hands on a used one, but at auction they seem to sell for barely any less than a brand new one. So I went that route.
Stuart

Forging ahead regardless.

 

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