EZ-Loc / MDF Failure (again)

[Brett Whitman]

I have no idea what I'm doing so please laugh in private.

My spoil board on my Desktop is MDF and I use two locating pins and two 8-32 machine screws to secure my work piece. The screws go into EZ-Loc threaded inserts which work great - for awhile.

I can't find a threaded insert with enough bite in the external threads to survive multiple iterations in the MDF; they all 'pull out' eventually and never at a good time.

Before I switch to a phenolic spoil board, can anybody point me towards a more substantial threaded insert?

Thanks,
Brett

[scottp55]

Brett,
Big box store MDF? Inner layer is more like sawdust, and density is all over the place...I had to use 3 different clutch settings when I did my 300.
Had WAY better luck on second spoilboard with the same MDF by Linseeding it thinned 50/50 after drilling holes for inserts.
One trick I've used on 3 "spinners" on my spoilboard was to use thin CA into the MDF around the insert, and it works well.
Furniture grade MDF/Plum Creek/Extira have had good things said about them.
I like the inserts because I've accidentally drilled right through one at MDF speeds and the bit survived:)
If already using a high quality MDF, then I can't help.
My next spoilboard will be like Bob Dodd's HDO one with the EZ's.
I was going to go BBPLy,but HDO should be more stable with the edges and holes sealed.
What diameter hole are you drilling?
For 1/4-20's I used .32" on 2 spoilboards when I had 2 Desktops, and had problems with only 6 inserts out of 660.
scott

[Brett Whitman]

Scott, thanks for the quick reply as I need a solution today. Actually, I needed a solution yesterday but did not know that until I made scrap today. I was able to learn that BBPly and HDO are types of plywood but what is CA?

My MDF came from my hardwood store but I wouldn't know good MDF from bad. I don't know what Linseeding is. I'm drilling the insert hole at 15/64" but am guessing EZ-Loc would specify 1/4".

I'll grab some hardwood plywood when I go to get replacement stock for all the parts I've scrapped over the last ten days (been a rough run). Thanks again for the sage and speedy advice.

Brett

[Kyle Stapleton]

CA is super glue
We use t tracks on our desktop works very well.

[scottp55]

Brett,
Try to get Baltic Birch Ply if you can...pretty much no voids, and all birch layers, but MDF from a hardwood supplier is usually a good step up from big box stores....I'd ask if they have a step up from what you bought just for reference.
IF the inserts are always at a certain location, then I think doing a pocket inlay of hardwood would be a quick and good fix at those locations.
Whatever the material, I think end milling a few test holes of different diameters in scrap is called for.
Sorry about confusion on Linseed Oil (Boiled Linseed Oil), I used Interlux Teak Oil on the second one I did to make the **** MDF(Lowes) I had to make it denser and less susceptible to humidity changes.....Read the contents after it sucked up a full quart, and it was BLO and Naptha(guessing at 50/50). Naptha was probably for penetration, and I've used both citrus thinner and paint thinner since depending on where it will be drying. I use Polymerized Linseed from Earthpaint for finishing because it dries faster and doesn't have heavy metal driers like BLO usually does.
I know from Bob Dodd's HDO spoilboard that he machined the holes to .31" (.01" smaller than my holes) and it worked great he said for the 1/4-20's.
Yep, Rockler thin CA in my case, but that's like regular super glue consistency. Soaks into MDF so fast it doesn't get into the interior threads.
I think Brady said one of the most stable spoilboards (MDF) he used was Extira( but they say the dust is horrendous for you), and no matter what you use, try to seal it against moisture on both sides/edges/holes.
Overkill probably, but once I had to countersink buttonholes that were drilled the day before, and lost 10 buttons before I noticed the countersink was .01" off cutting into design:(
Sorry if I'm confusing you more:)
Try "drilling" with an end mill 50-80% of the hole diameter, as a "Profile inside line" and add a spiral ramp to it. Fast and using the "allowance offset" you can fine tune hole diameter while leaving the holes in the drawing nominal.
Kyle,
Are you adding on 1/4" MDF when you've surfaced down close to the tracks?
s

[Kyle Stapleton]

Have not got there yet, but planing to put on 1/2".

[scottp55]

Better than me trying to use up this 3/4" junk MDF and cutting it down to .3" :)

Oh, Brett....Maybe go an oversized spoilboard(24X30" works well) so that you can add fence and clamps outside the cutting area...then you just glue on 1/4-1/2" MDF for the cutting area itself and trim the added MDF to exactly 24X18" with a true 0,0 cut by machine(just like rabbeting the spoilboard the very first time you got machine).
When you surface down close...just glue a new piece on, and you never touch the the oversize substrate(except for AW S*** operator errors:)
Like these pics when I rescued the second spoilboard(top) I made by index doweling/bolting directly to my original after pocketing out the mess(dowel holes/inserts 50/50).
scott

[Michaelodunk]

I use T nuts which you insert for the back. Find them on the internet or Amazon has them.

beware of plywood it is not flat and and real ugly when you try to surface it.

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[tlempicke]

Try a search on this forum for Raptor Nails and Omer Nail guns. They are plastic nails and strong as all get out in tension and not very strong at all in shear You simply plop down your piece and nail it to the spoil board in places where you will not be cutting, or in places where you will cut if you don't mind a freckle later on. If you cut into one the tool never knows it and just keeps merrily on it's way.

when you finish cutting just give the piece a good whack sideways ton remove. Am couple of swipes to the spoil board with sandpaper and you are ready to go again.

[scottp55]

On this vid from TJ it shows how Shopbot itself uses an Extira oversized spoilboard with a raised cutting area at the mothership(starts about 6:40 in tutorial)
Same idea for the Desktop so we have the full cutting area available.
https://www.youtube.com/watch?v=_Nr89_jZacs

[Brett Whitman]

So far, so good. Can't thank everybody enough. Will incorporate more of the excellent suggestions on the next spoil board.

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