Help with making a rotary table more rigid

[RSG]

Pete,

Thanks for the detailed reply, it's always appreciated. I googled set-tru chucks after reading your post last night and found quite a bit of info. It looks promising. The new chuck I just bought is a plain back chuck from Shars which is cast steel so I can drill it. I'm going to research it a bit more before making anything for it.

After reading Harold's comment regarding working to a half thou on a mill being challenging it has me wondering if maybe it's impossible and I shouldn't try to pursue it. Currently I strive to achieve about .002" - .003" accuracy on the mill but the reason I push for more is that the product I make (Center pin fishing reels) must be as concentric as possible so they don't run out of balance.

[NP317]

I'd be happy keeping things around .00005"

[snip]

LOL ooops! Sorry it was late I came in from the shop and was tired Yes I meant .0005"

That's OOOOOOK.
~RN

[Harold_V]

After reading Harold's comment regarding working to a half thou on a mill being challenging it has me wondering if maybe it's impossible and I shouldn't try to pursue it. Currently I strive to achieve about .002" - .003" accuracy on the mill but the reason I push for more is that the product I make (Center pin fishing reels) must be as concentric as possible so they don't run out of balance.

Don't let my comments discourage you. Sure, it's hard to do, but it can be done, and you should be able to accomplish the task. You simply have to pay attention to everything, including how you lock the slides. Mills are not high precision machines, so pretty much everything you do makes a difference. Use good work practice, tighten things consistently, don't lean on the table or saddle, and keep the gibs snug, although make sure the slides have full travel. If you work with a DRO, you'll likely have a lot less to worry about, too. Screws demand high skills for tight tolerance work.

Rule of thumb (mine, I have not read it anywhere) is that working to a thou, on a mill, is a difficult task.

H

[RSG]

Thanks for the vote of confidence Harold. I've always tried to work to the tightest tolerance I could (+/- .0005"), whether or not I actually am....

Your advice about not leaning on the table and locking slides is well taken for I have witnessed exactly that. Simply leaning on the table will influence the pressure on the cutter. It's easy to see when you put a TDI in the mill and sweep something, touching the table and even the fixture can move even a couple of thou or more while static. I imagine it is even more when the mill is running with vibration. I have a good DRO so that helps. Getting an 8" Rotab and new fixture should help immensely as I estimate taking about 6" off the height of the fixture.

I'll post my success and finished fixture when I have it ready...in the mean time I appreciate all the positive support from the board members.

[GlennW]

The larger the diameter of the RT, the more support you will have, which will aid in rigidity.

I'd go with a 10" if you could. Depending on the design,the graduations can be a bit larger as well, which pays off with older eyes and also equals better accuracy.

I have always used a 12", but I find that it somehow keeps gaining weight each year.

[tornitore45]

Rule of thumb (mine, I have not read it anywhere) is that working to a thou, on a mill, is a difficult task.

That makes me feel a lot better regarding the way many of my parts are coming out.
Is 0.002 over and now, all of a sudden is 0.002 under.

[Harold_V]

I have always used a 12", but I find that it somehow keeps gaining weight each year.

Yep! That's what I use, too, and it's now extremely difficult for me to handle it. Still, it's a better choice than one that doesn't perform well.

H

[RSG]

I'd go with a 10" if you could.

I would if I could but my Mill won't handle it, the table is 8 x 29".

The larger the diameter of the RT, the more support you will have, which will aid in rigidity.

I wish I knew then what I've know now! Back when I first started this venture I figured I didn't need "big" but now I understand what "big" can do for accuracy...

[GlennW]

I'd go with a 10" if you could.

I would if I could but my Mill won't handle it, the table is 8 x 29".

My Bridgepot has a 9" wide table and I use the 12" RT.

[RSG]

I'd go with a 10" if you could.

I would if I could but my Mill won't handle it, the table is 8 x 29".

My Bridgepot has a 9" wide table and I use the 12" RT.

I suppose I could have as the RT could hang over both sides but the work is still only 5" dia. I have an 8" on order but don't necessarily have to take it. I'll look into it a bit more perhaps.

[RSG]

I thought I would look at some 10" RT table and I stumbled on this. http://www.shars.com/products/workholdi ... ry-table-8

It's an 8" tilting table. It's intriguing because a lot of my operations require Milling horizontal then immediately on to the vertical. So my question to those that may have used one, are they rigid enough or should this be avoided?

Thanks

[GlennW]

Thay may be a good option, as when standing up a 10" or 12" table up, spindle clearance keeping you from reaching down to the part can be a real issue!