Material hold down techniques

I have never used hot glue before. How hard is the glue once it has set? When I am milling an edge that I cannot get to without sticking it down, I use 3M painter’s tape and a heavy duty CA glue. I have some video clips of squaring edges using a couple of methods (ignore the MDF). I calculate the depth and add a fraction for the tape so that the cutter is not blunted by the paper tape. I have also used a method where the tape is not applied right to the edge of the workpiece to leave a space for the cutter flutes.

Chip load, chip thinning, cooling and heat transfer is one way to get consistent results. You can amass
decent amounts of date but I have found that many different types of wood create a different situation and the whole testing setup has to be run through again. For example, when I cut walnut, I know that I am going to get a lot of chips, all similar size, and finding a good traversal speed can be a nightmare, because I am not getting a consistent chip size of 0.001 ~ 0.003".

This mandates a return to seat of pants milling. How does the cutter sound, what is the finished surface looking like, what is the cutter heat? I also use a mechanical sympathy method in conjunction. When the cutter engages with the workpiece, If I note (or feel) a slight rise in the X rail at the point of engagement, I reduce the speed of cut and or the percentage of cutter engagement.

@jepho in your second video for squaring, after you get your MDF secured, I would put a 3/4" long fillet, 2 places each side on the Y (north and south, up and down) of that and it will not move. The glue sets up in a couple of minutes, cool to the touch. I use an arrow GT11 mini gun from the blue box, also available on Amazon and mini glue sticks. I use whatever is handy to cut a slice through the glue to remove the part and the Stanley Scraper model 0-28-590 to remove the glue from the spoil board. Works with anything wood but have not tried it with aluminum yet…
I also use indexing pins to locate everything, similar to your main base but no where near as fancy. Drill pin holes in base, locate jig, and drill pin holes in jig, tighten board to pins in jig and glue down. REMOVE PINS! Surface if required or just run the file. And yes, always seat of the pants until you get things dialed in.
@Fredymac I use a 1"-3 wing surfacing bit on #3 at around 80" / min and use the ++ button in gsender as required for the type of wood. #3 and 80" is a good starting point for that size bit with 3 cutters. Glad your new bit is happy!

@jepho @RickW I created a new topic for your hold down discussion. I figured that it could get lost in the Makita feeds and speeds discussion.


Thanks Grant. Much appreciated.

Thanks Grant, I did get off topic…

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Hi @RickW. Thanks for explanation of the hot glue.

Once I have fixed the workpieces into the modular vices, it matters not whether I am using glue or just holding the workpieces as they are, they do not move at all. The heavy duty CA glue was my preferred choice because it has a relatively long open time of around 30 seconds.

I make use of that open time to move the workpieces on the stationary support. I am almost treating the glue as if it had thixotropic qualities. I was a real skeptic before I started using glue and tape but I have to confess and say that I have never had a workpiece let go under pressure from a cutter.

This is the reason I do not use any fillets. I used to before I had a baseboard that was a sea of holes (840) with M6 threads. I had limited clamping options and used two 30 degree angled strips with reversed angled to hold against the workpieces and keep my clamps out of the way of the cutter.

I would probably not want to secure metal with glue or tape. The main reason that I went with the American company (SMW) indexed fixture tooling plate was that I had wanted to mill aluminium and brass and I could not apply sufficient holding power. Once I had obtained and set up the fixture tooling plate, I have not regretted it.

My first aluminium job was 20mm (0.79") deep and I milled it with a 6.35mm (.25"). My working tolerance was ±0.001" and it was maintained throughout. Solid work-holding is key to working with metal and although one works to larger tolerances with wood, it does not take away form the work to hold the workpieces really securely.

Link and shoutout to Saunders Machine Works who provided my Shapeoko SO3 fixture tooling plate, stiffener rails, the modular vices plus Mitee Bite jaw inserts and index pins. It was not especially cheap to import their products into the UK but the company were very helpful. I was delighted to deal with that company. Highly recommended by me.

Hi @jepho
Exactly, hot glue or CA glue or surface clamps. The trick is dowel indexing pins. I use indexing pins ( aluminum dowel) to locate everything. The pin holes in the spoil board were created with the Longmill only on the Y axis at 4" on center, straight edge (plywood) across the pins to locate the jig, and created pin holes in the jig after gluing it to the spoil board. Slide the part tight against the aluminum pins, hot glue it down to the jig, set up gsender, remove pins and set zero. By the time I load a file to cut, the glue is solid. That sea of holes is really cool though, may have to get one of those. Thanks for the link. I agree not trying hot glue with metal.

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Yup, SMW were on their A game when I ordered my stuff. I don’t have any work-holding issues now because the two sets of vices can be set to any distance within the work envelope. I have moved away from index pins too because although they do work much of the time, if you need say… 4 index pins in a 12" square workpiece, I have found that only the slightest bit out is usually enough to prevent proper workpiece location when two sided milling. Now I just rely on the well fixed vices.

I will continue to use CA glue and painter’s tape, where I have no other prospect for work-holding and I wish to avoid issues with clamps. Generally speaking, my planning skills have improved when I tell myself no glue. It makes me think about machining operation order and various practical work-holding solutions.

@jepho seems like you have a machinist brain too :wink:
I only use wood dowels as indexing pins for two sided jobs in my jigs and only two, one at each end of the X centerline axis. If I cut partially through a wood pin, not a big deal. Yep, did that.
Two sided bowl coming soon to the freebies…

If only that were true. :thinking: It seems odd to consider that initially, I had no clue about machining operation order. Now, it makes some sense to cut smaller pieces which have the best support, first. I think the general rule from real machinists is to work from the inside outwards. :upside_down_face:

I usually make jigs for many jobs where I need to do more than one off. My worry with two pins along the X axis is that a large work piece could potentially shift. I will be most interested to see the bowl. It sounds like an interesting project.

Bowl project posted in the freebies. File size limit so you can send an email to get the full zip file.

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I will await the completed project. I do not know how to use .crv files. I suspect they are the proprietary Vectric format.

@jepho project is completed and finished with 3 coats of clear poly. The little black land shark Rubie Rottie ate the first one but have made several others. Yes, crv files are vectric specific, sometimes it’s fun just to run gcode files and see what happens. Speeds and feeds are conservative for the Longmill
crv3d files are huge so couldn’t post it even zipped.

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Understood. A picture of the completed item would be great. I don’t trust myself to enough GCode to run any manner of code without first seeing what my be damaged on my machine if I get it wrong.