This test piece is set up for inserts rather than 6mm threaded holes but the basic design applies to both.
The center section, the actual fixture plate, is 26” X 20” (slightly smaller than actual cut area). This provides wiggle room for machining/facing. It sits proud of the side and back plates a few millimeters. Also, if need be, the sides and back can be removed and shaved down to enable deeper re-facing of the fp, an important feature for me as I make a lot of mistakes!
I’ll stick with the mdf sides and back, at least to begin with and machine the fp from 7/8” ATP5.
How are you progressing?
What I found on my non-surfaced MDF fp:
About .0015” in X and about 0.004” in Y. Kind of surprising I think.
The main centerplate’s and detachable sides are a really smart idea, wish I would have though of that before putting in an order for the stock. I think with a aluminum main center plate you could also use HDPE or phenolic for the side plates for moisture resistance if misting.
I got my two plates from Midwest in the mail yesterday along with a small piece to run test feeds and speeds on. Next step for me is to prototype and run through the whole operation in MDF before. Getting the whole thing to be consistently flat across two plates might be a bit of a challenge though as I have to surface them individually, but I think shims should solve this issue if it were to come up.
I think at this point I could either stick with my original idea of two ~26x16 fixture plates, or alternatively, I could have one smaller 26x16 plate to cover the majority of the cutting area and sub-plates made from the rest of the stock. I’m not sure if I have enough stock to get full coverage with 3 sub plates, but I could always just go HDPE and use the remaining stock for other projects.
Lined the plates up, probably better to stick to the 2 plate design. Hard to tell from the photo but the join line is pretty much at the center of the bed.
Griff
(Well crap, my hypometric precursor device is blown…)
57
BTW, practice threading in wood first.
Also, I’ve changed my strategy for hole boring. I’m using the Drill/chip breaking option in F360.
Using an end mill that is very close to the diameter of the hole being bored is much different than using, for example, a 1/8” bit for a 6mm hole. Something obvious to machinists I’m sure, not so much to me.
One thing to check and possibly be aware of is when using the jogging quick points at least on my HDM the center point doesn’t line up with the center T track for some reason its a few MM off. I don’t know why and it almost cost me but luckily I noticed it before I drilled my older plate.
Where center falls for the Rapid Position points is determined by:
physical position of the homing switch (there is some adjustment possible)
Travel Dimensions
It should be possible to adjust those two so as to get things perfect centered (for values of perfect w/in the precision of the switches and the distance of a micro-step on your machine).
Griff
(Well crap, my hypometric precursor device is blown…)
60
Curious to hear your strategy for drilling/boring?
I’ve been working on learning peck drilling myself.
Griff
(Well crap, my hypometric precursor device is blown…)
61
Hopefully some others will share too. Not much about peck drilling with hobby machines on the web.
At present I am peck drilling 5.05 mm holes with a 5mm single flute uncoated Datron mill.
So far, I’ve learned air blast is not needed, chips are large and clear nicely. Lubrication is definitely needed, especially as you get deeper.
I rigged a WD40 reservoir and connected it to my cheap Chinese mister. Low airflow + 50-75% open mist valve results in a nice drip. The higher viscosity of the WD40 helps to reduce flow.
Looks good! What did you finish the MDF with? Maybe the stuff I got from home depot was a bad batch or something but a single drop of water will cause a 1-2m fuzzy raised spot after just a few seconds, dosent seem to happen with the stuff I got before ore the slats that the HDM came with. Maybe wd-40 wont disturb it as much but I’m planning on using an alcohol mister.
Does drilling with the endmill work well? I got a 4mm carbide drill but it may be of questionable quality and might be a bit small. I was going to just bore the hole out with a 5mm endmill hole afterwards anyways so it might not matter much.
Griff
(Well crap, my hypometric precursor device is blown…)
63
Spray shellac, 4 coats or so, dries fast.
Curious to see how your approach works out. I’ve got so many holes on 20mm spacing I’d hate to cut ‘em twice! Also, I think you’ll find alcohol is not much of a lube.
The end mill peck drilling is working well. Not ready to commit to a full plate yet though.
I think at this point I’m just going to skip boring and go straight to peck drill with an endmill like you did and go straight to threadmilling. I figured that the threadmilling is what decides the screw fitment, not so much the hole itself.
As for the jig, I want to use MDF because it’s cheap. I’m going to cut the aluminum plate to size and then drop it in to a recessed rectangle cut in to the mdf so I can easily repeat it for the second plate. I’m just worried about it warping from the mist and messing with the tolerances. The shellac shouldn’t affect the tolerances right? I’m 90% sure that it dosent matter but I tend to worry a bit too much.
As of now I’m just waiting for some endmills to arrive from 2L so I can start a model.
If you cut a bunch of material from one side of mdf it will warp. It will warp even more when you put finish on it. The mist will also cause it to warp unless your finish is completely waterproof which is very difficult to do. You can compensate for all that by having a lot of clamping to your hybrid table all the way around the edge and minimizing how much material you remove from the mdf. A bunch holes in the middle that line up with the t-slots for additional hold down would not hurt either. Also, depending on how accurate you are trying to be with this, the hole size before threadmilling will absolutely affect accuracy and thread fit.
The hole size matters due to the percentage of thread engagement. If your hole is too small, it will not fit obviously. However, if your hole is too large you’ll lose a lot of thread engagement which will weaken the holding power of your threads.
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Griff
(Well crap, my hypometric precursor device is blown…)
67
Okay, my 26x20 ATP5 plate arrives tomorrow.
My plan, as soon as I finish the 4 cabriolet legs I’m cutting now, is to align and clamp the plate to my MDF mock-up.
Then machine the anchor holes and countersinks.
Remove the plate, remove the MDF mock-up, align and bolt the plate down.
Check the plate for flatness, face if necessary.
Bore and thread the “million” holes.
Thanks for the info, learn more everyday. After looking it up a 5mm would be the appropriate size for a M6 thread right? I don’t think a .05mm different should affect it that much.
As for the MDF I may end up buying a thick sheet of plastic like HDPE and use that as a temporary jig. It’ll be more expensive but at least I won’t have to worry about warping as much.
Will you be boring with a 4.5mm endmill to get to a 5mm hole?
I plan on just drilling and threadmilling because a 4.5mm wouldn’t reach the full 1 inch. I could surface off 1/16 on each side to get the stock to 7/8 and use a 4.5mm 22.5mm reach endmill.
