CNC Noob Fixture Plate Question

My theory on the fixture plate is why drill ALL the holes ahead of time? Drilling and tapping hundreds of holes is a lot of unnecessary labor up front when most will go unused. I simply put a zero locating dowel in the center x,y so to add more holes I just need to drop it on the table, the dowels on the feet fit snug in t slots so just indicate center pin in table and drill new holes as req.
I don't tap the holes. Instead I use F drill .257 and c-bore for standard press fit type bushings. 1/2"od x 1/4"id x 1/2"h. Bushings are a slip fit to the c-bores and serve to elevate the stock off the plate. Very inexpensive and I have about 8-10 but usually 4 is plenty to hold the work. Reason being is I make pattern cores from HDPE and modeling board and all the sides get tapered and machined down to the bottom. Rather than screw down to a wood or other spoil board I just elevate on the spacers.
If 1/4-20 is too large a thread to tap in the part I have used 10-24/32 screws with washers. The spacers still work the same located in the c-bores.
Now I know there are lots if ya but's about this way of doing it.
Its not good for every situation. Not the most rigid/super accurate if re-locating the part becomes necessary.
I cut stuff all in one and done.
For hogging steel its not the way
True, tapped holes in the bottom of the part may not always be acceptable.
Being raised up off the table allows me to take it on and off without messing with my vise.
If need be I can make taller standoff feet or space them farther or closer together.
It sacrifices about 5" of Z height.
If I need to clamp from the top, the .257 holes are conveniently the tap drill for 5/16-18.
The only real purpose for the c-bores is to keep the spacers aligned with the tapped holes in the part. Lot less fiddling with my 6" scale fishing underneath moving them around to get them in line.
Raised up and thru holes I never need to mess with clearing packed chips out of holes or using a jillion setscrews which still get chip packed in the hexes.
I don't wear out/gall/strip threads in aluminum plate.
Much less labor than threading all them holes.
My table stays mint, no rust between plate etc since the table comes off when finished.
Thats my story and I'm sticking with it....
 
Cheeseking, I like the idea of the spacers you can mount your fixture plate without having to remove the vice.
 
Cheeseking,
I like what you did for projects that don't require a lot of rigidity.
If you don't want to remove the vice, and the fixture plate is small enough
have you considered making a plate that clamps into the vise?
 
Jonathans said:
Cheeseking,
I like what you did for projects that don't require a lot of rigidity.
If you don't want to remove the vice, and the fixture plate is small enough
have you considered making a plate that clamps into the vise?
Click to expand...

Yes I do that occasionally. Have even screwed material down to a S4S pine board clamped in the vise. For one off light work it does the job.
For ready made fixture plates check these out - http://www.baselabtools.com/Tables--Breadboards_c_11.html
I stumbled on them awhile back. Looks like its for optics prototyping but pretty cool
 
Cheeseking said:
Yes I do that occasionally. Have even screwed material down to a S4S pine board clamped in the vise. For one off light work it does the job.
For ready made fixture plates check these out - http://www.baselabtools.com/Tables--Breadboards_c_11.html
I stumbled on them awhile back. Looks like its for optics prototyping but pretty cool
Click to expand...

Thanks for posting that, any ideas of the flatness specs on those plates?

Thanks,
Dave
 
I don't but there may be specs listed somewhere on their website. We have a laser marking machine at work and another engineer bought one to fixture parts. I thought it was cool and made note of their site. Prices arent bad a 3/4" 12 x 18 was about $200 iir.
I think the way these are used (or at least how I do) the flatness really isn't relevant. My twist on the fixture plate is sort of a offshoot of the OP's original question. If folks are looking to laminate their tables with something larger, semi permanent where vises get mounted on top then I guess the super flat, million threaded hole plates are better.
I added mine to the sprutcam fixture library...
f181b83c116bb4081e17a7fb0227e4fb.jpg
 
thanks for the info, I actually checked the sight closely and I don't see anything so I will shoot them an email.
 
Just an update, those plates are only guaranteed to be within .015" which is not good at all for what I need.

Just wanted to share in case anyone was serious about buying one.
 
I once got a 2x3' X 1-1/4" aluminum plate called MIC 6 that was flat , it's made for cnc fixturing plates
Got it cheep , it has turned into smaller plates now
 
Cheeseking said:
Yes I do that occasionally. Have even screwed material down to a S4S pine board clamped in the vise. For one off light work it does the job.
For ready made fixture plates check these out - http://www.baselabtools.com/Tables--Breadboards_c_11.html
I stumbled on them awhile back. Looks like its for optics prototyping but pretty cool
Click to expand...

I really have to thank you for this link. I've been back and forth between making and buying a tooling plate since I posted on this back in April. They have a 6x18 plate, which is probably a good fit for my G0704 at a very reasonable price, and not that much more than plates half the size for Sherlines I see on eBay. To top it all, those eBay plates aren't anodized.

Seems like a good compromise. Most of the time, the flatness is probably acceptable.


Bob
 
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