[photomankc]

I was working on something tonight where I needed to square a part that had no good place to start with gnarly edges all the way around so I figured the easiest route was to go after it side-milling and clamp it to something so I could make a decent reference side to start with. Quickest way that came to mind was to use the 123 blocks as a half-assed tooling plate and that worked nicely. I was able to square it all up very well.

That got me wondering though. Maybe it would be nice to make a little table to clamp that odd shaped item to that I can clamp in the vice and go. I'm not ready to look at a full-on full table plate yet but I was thinking maybe an 8.5"X4" table supported on a 7.5" x 3" x 1.25" block for the vice to clamp onto.

I know there are some places I can grab a bit of MIC-6 plate from and I would plan to just lightly skim the clamping block to avoid it warping. Is this a total waste of time? Anyone tried it and thought it was useless? Seems like I can think of a few projects that I could use it on coming up.

[mattbesquare]

I love it, get one of those table attaching vise grips, and maybe a threaded hole under where the pad grips so you can use replacible/disposible blocks to hold your work. Square three sides of your pice, unlatch and clamp in your vice for the 4th, or 4th and 5th if your squaring...

Surplis center has a huge sekection of workholding clamps. Some have truly good holding power.

[rowbare]

I think it is a great idea. It isn't uncommon for shops to have vise clamped fixtures for recurring short run jobs and this is similar.

If you define your work coordinates to your vise jaws, you could put a stop block on the bottom of the fixture plate. This would give you a repeatable means of clamping it. Once you have the plate built, you can drill and ream a few locating holes. Once you have that you can just clamp it in and go.

I think it would be very useful.

bob

[photomankc]

Finally after 2 years I circled back around to this. Made this up from some scrap MIC-6 plate that I got a hold of. The odd length is me just trying to avoid some of the dinged up areas and some holes that had been drilled into it. I wish I had made it a bit wider in the Y direction. Wasn't thinking of just the extra clamping space. I do have another plate so I can refine again if I find anything too lacking in this plate. It's 44 3/8-16 holes on 1" centers. The top sits on a 9" x 3.75" x 1.425" block of 6161 to hopefully keep the rigidity up and let me use a plate larger than I could clamp in the jaws. Surfaced the plate with my 2.5" facemill. Wish I had the 4" or 5" for this job but it worked alright. The surface measured out to 0.0005 front to back and dead flat over the X travel. They Y tram never is perfect so there are a few tenths of rise over each pass but I doubt that will be the limiting factor in my work.

I like this pretty well I think and looking a few past parts I have been working on I think I woould have liked to have it when I was doing them.

Next step will be to create some holes for dowel pins. My plan is to create it in CAM but edit it to always approach the holes from left to right in each row working top to bottom. That should allow it too take up any backlash to keep the positions. Spot drill, pilot dril, drill to 0.007 to 0.010 under size then ream to a close fit for the pins. I don't plan to use the pins for absolute positioning but instead just to align the parts to repeat to the work peice zero each time on multiple parts. I'm planning to use 3/16" pins for that, maybe 1/4" havent decided.

I have set screws coming to plug the holes to keep them from packing up with chips.

[hoss2006]

Have a look at 2lincs pallet vise for some ideas.
Pallet Workholding and Fixturing System for cnc machines
If I was going to make a bunch of small parts I'd go with this type of pallet system.
Hoss

[photomankc]

Wow! That's super cool. Thanks for the link to that. I see several items there that I could make up to use with this.

[Rikk]

I made one over xmas out of delrin to see how the idea would work, purely for thin ali and delrin. I had a part to make for a friend that needed holding down to cut so seemed an ideal opportunity to try the idea out.
The intention was to remake it in ali but it works so well for the small parts I make I may well leave it.

It's threaded for M6 with the idea being I can use larger M6 or smaller M5 fixings.

[kawazuki]

Am I missing something here? In the first photo a lot of effort has gone into a clamping system that could have been achieved with parallels and the vice alone, not to mention the considerable loss in the Z axis capacity that could have been an issue? And in the latter pictures why not just mount the fixture plate to the table - why involve the vice at all? In fact if rapid, repeatable work fixture is required what's wrong with using the table / 123 blocks / stop pins and clamps? Not dissing anyone - just can't see the point!

[Rikk]

For me it's simplicity, I can mill a part in the vice, pop the fixture plate on then do another bit. I don't need to keep indicating the vice in.
I can even get the stock mounted onto the fixture plate while another part is cutting in the vice. All the things I do are small <200mm and quick to cut 10-30 mins so constant messing around vice on/vice off, indicate etc is a pain.

Also if I mess something up on the fixture plate, ie going a little deep the cutter/drill goes through that rather than the bed of the mill.

edit. admittedly the stock in that first pic unless the sides where being machined I'd of squared two sides up, popped some parallels under it and clamped it between the vice jaws.

[photomankc]

The point to me was always that any time I needed to run a plate part larger than 3 inches I had to pull the vise. Yes I can mount the part out on the edges and leave the vice but I know that the overhanging weight and wedging action makes the edges of the table less accurate than the center so I either pull the vice or live with +/-0.006 out there. My table aint perfect either so I have shimed the vice to be a better reference surface than the table. All that adds up to a PITA every time I pull it to set it back up just so. I prefer not to if I can avoid it. It also will help me run parts where I can't use holding tabs without making up a new fixture each time. Again, I know I can do without it but since it cost me about $40 in scrap to put it together it really isn't costly to make it and it's practice for when I need to make a full-blown plate for the mill table which is definately on my list.

My work is going to be in robotics and electronics. Drilling circuit boards and making fairly small parts. Seems like this may be usefull for that. We'll see.

[wizard]

That is on top in the sense of the jaws moved to the back sides or their respective mounting surfaces. This to give me the ability to grip a larger plate. This comes in handy for repetitve but not mass production jobs.

Wood (decent quality plywood) works nice if you are doing machining on sheet metal panels. That is if you are machining through holes for push buttons, switches and component mounts. A couple of dowel pins for locating the work and a couple of long bars for clamping and you are all set.

As long as you are safe for the process involved I don't see any reason for concern. One thing you might want to look into is transfer blocks. There is a guy in PA who sells castings to the hobby industry that sells a casting just for this sort of use. Sorry forgot the name of the business. In any event it is the type of thing one could DIY with a block of steel or cast iron.

In any event the possibilities are endless.

[pete from TN]

I have been using all sorts of fixtures to make parts since I have gotten the CNC. It is just simply part of the process and there are no end to the different types of fixtures. Some of the more interesting are the vacuum chuck ones that I see and the one Hoss posted the video for is one of the better ones I had seen awhile back. It is a great way to get the best of both worlds. The vise can even be mounted to a fixture plate and can be quickly and accurately replaced and removed using the vacuum system. I have not made one yet but it is high on the to do list for CNC. There are just too many cool things to do with it to ignore. For instance these parts I am currently deburring are a prime example. If I had a vacuum plate I could have machined them a lot more quickly and maintained a more flat substrate. Not having that technology yet I did what the last poster recommended. I used a plywood substrate. I used some high grade furniture plywood I had here and it is very nice actually for this. You can put a screw down ANYWHERE and it will hold pretty well if you are cutting relatively conservatively. I was using an 1/8 inch cutter at around 15 IPM full slot at stepped depths and there is very little force acting on the part in 6061. I would say you could cut anything up to around 3/4 inch plate this way if necessary as long as you put down enough screws. I just hit it with my fly cutter before I placed my workpieces on it.

I think another interesting aspect of a vice mounted fixture is to use your vise setup with the jaws on the outside of the moving jaw allowing clamping of a much larger fixture plate. You can make a quite large plate like this, remain flat, and be able to keep your vise located. It is even more capable if you have dual vises that are matched together. The possibilities are quite endless in fixture design. a quick youtube search will yield all sorts of cool ideas. Peace

Pete

[photomankc]

I added the locating pins a couple of days ago. Worked out really well I think. I consider this a test run for a bigger plate later on and wanted to find out how well I could do those locating pin positions. I was pleasantly surprised. My first go at running the reamer for them worked great. They are on the nose in 1" increments to the best of my ability to measure it.

I did a spot drill down deep enough to chamfer the hole for the final diameter, then followed with an undersized drill of about 0.008" then followed with a 3/16 reamer. The holes came out right on size it seems. About 35% of the dowel pins that are on the upper end of the tolerance will not fit, the rest are a tight sliding fit.

I altered the program so that it did not rely on backlash comp, it returned to X -0.100 after each row was finished and then proceeded to drill the next row. Worked it bit like a manual machine would to keep backlash out of the equation so its down to screw accuracy and the positional accuracy of the drilled holes. I don't have a mill boring bar that can deal with 1/4" or less holes or I would have bored to eliminate the drill wandering errors but it seems to have really done quite well anyway.