I know there is a ton of variety in what people do for work-holding, but I was hoping to get some advice from those who like to bolt things down. I started with just a grid of holes, but it was very inconvenient to try and hold the nut underneath the spoilboard while bolting it down.
Then I thought I would be clever and replaced them with threaded inserts so that I could bolt from just the top. The problem is that if I get a bit of dust in there, there is enough friction that trying to tighten the bolt from the top just unscrews the threaded insert from the bottom.
I was curious what others do here. Some of the options I’ve considered:
Putting a dab of superglue or epoxy on the insert. In theory this sounds good, but I’ve been trying to avoid taking the spoilboard off the table to keep the holes at perfectly known positions. So I’d have to do it upside down.
Used a thread cutter to directly cut threads into the spoilboard, but I am using MDF and I can’t imagine the thread lasting very long.
Milling small pockets for nuts on one sheet of MDF then gluing another one on top of it. I was worried it would be hard to have perfect alignment between the top layer and the bottom layer. But perhaps I can leave a little space for clearance and allow the nut to move slightly.
Since I imagine I’m not the only one dealing with this I’m curious what others do.
Did you have any trouble with the t-nuts coming undone?
I do a decent amount of two sided machining, and I find the grid makes it super easy to locate my index holes. (Although I do need to replace a couple of bolts with dowel pins to get rid of the slop.)
Then again I have them on a 1 inch spacing, which is just way too may places to put insert nuts on all of them.
PS, I really like both the content you are putting on youtube, the the code on your github.
I don’t have trouble with them coming loose… but it was placed on top of my metal table, so that would support them in some spots, but also cause a problem of bottoming out screws, which was annoying. The ones not supported didn’t get pushed out, and the t-nuts really embed well in the MDF — they are hard to push out. I got a pack or two on Amazon (1/4-20 ones).
1” spacing sounds like it will give you lots of flexibility with layout; I think I did mine a lot further apart (I’m away from the shop and can’t check right now).
Over the years I have built and owned four CNCs. I ve tried spoilboards where you just screw stuff down, T-Track, threaded inserts, dog holes, and various combinations of all those. Currently Im using T-Track and Dog holes.Im about to redo my spoilboard and switch to Microjig dovetail slots and dog holes. In reality you will be resurfacing and/or replacing your spoilboard at some intertval. This allows for change. The trick is to find what works for your applications, there is no right or wrong way. I find that I use the T-Track, dog holes and screwing stuff down all the time. The Microjig slots will be new system for me but I see it as being like T-Track but not having the expense of having to buy a bunch if I want the tracks closer together. The fun of this is being able to experiment. FYI my current setup is based on the Jay Bates spoilboard. I didnt use the same fancy T-Track he did, its expensive. Hence the idea of going to the Microjig dovetail slots.
I have a t-nut based system which has worked well for me. Allows for easy bolting of holddowns, vise etc. I have 4” spacing which has not been granular enough on occasion so I will go 3” next time. Board is open underneath and I have never has a t-nut drop out
I have tried using a thread mill to cut 1/4-20 holes with 1" spacing. I used Baltic Birch for the spoilboard and treated the threads with very thin super glue. It has held up very well and I like it just as well as tracks. With 1" spacing I have not found any issues. A little care needs to be taken when tightening things down but they provide a very strong hold and I think will last as long as the spoilboard does. If I strip out one I think I could just fill it with epoxy and re-mill the threads but I have not tried it yet.
Thanks for sharing, it is interesting to hear directly threadmilling can be strong enough to be useful.
I appreciate hearing what others have done.
For the curious this is what my setup looks like. In the upper portion of the photo are 3d printed jigs to help me use every bit of the wood for one of my common projects.
The dogholes and clamp are used to drill initial holes before bolting them down.
The non threaded holes are use for either locating with dowels or just holding a nut to the underside of the spoilboard.
I do recommend the nylon bolts for the first time running a program. I have definitely accidentally cut them, and it is much better to take a chunk out of the bolt rather than ruin a bit.
I use threaded inserts, inserted from below. The inserts have a small flange around them. Mine must have the external thread threaded the other way because there is no tendency to unscrew when tightening. I guess I could have trouble unscrewing.
A vacuum does a wonderful job of cleaning any of them out. The only ones that I get clogs in are the ones that are over the braces from below.
E-Z LOK - 901420-13 E-Z Lok Threaded Insert, Zinc, Hex-Flanged, 1/4"-20 Internal Threads, 13mm Length
