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View Full Version : Low profile, compact work-holding solutions. Advice sought.



Wal
14-07-2014, 07:54 PM
Hello all,

I've recently completed a test project in mother of pearl - it was an intricate inlay to be used on a guitar fretboard. Here are some pics:

12778 12779

I stuck the blank to a piece of perspex using double sided. As my XY 0,0 was in the middle, I'd milled out a very shallow pocket so that I knew where to stick the blank.

It went reasonably well, but after 16 hours of cutting (that's what you get for pocketing with a 0.2mm end-mill) the double-sided let go on the final cut-out pass. Managed to stop the machine before the cutter had a chance to ruin the work completely, but it meant having to re-align the stock manually to get myself an outer profile cut that was deep enough to manually grind back to (and under a bit) and maintain the illusion of a nice clean line. I did this with some level of success, but it's lop-sided and not good enough to pass as a usable piece.

Anyway, if I do this again, I'll essentially employ the same method (double sided) but this time I'll make that initial shallow pocket in the perspex deep enough to accommodate the majority of the depth of the blank, which will be a nice snug press-fit into the hole. I may also mill a smaller through hole in the perspex so that I can 'poke' the finished work out from behind, should it need poking.

Any other suggestions..?

Wal.

Robin Hewitt
14-07-2014, 08:02 PM
I like Celtic. The old fodies way to stick something down for machining was shellac. You melt it using heat for the fixing, either melt or dissolve with methylated spirit for the removing.

JAZZCNC
14-07-2014, 08:27 PM
Pocket the perspex and use vacuum. Even a standard vacuum will hold this down provided you don't cut thru the vacuum seal.

gorbo
14-07-2014, 08:37 PM
Nice work, I have used Silicone sealer to stick down with some degree of success

Wal
14-07-2014, 08:44 PM
Pocket the perspex and use vacuum. Even a standard vacuum will hold this down provided you don't cut thru the vacuum seal.

Hmm, dunno if I'd get my hose under that...

Did have a quick look around for vacuum solutions, though. Found this:


https://www.youtube.com/watch?v=xr3lfAvQuJs

Rather impressive.

Thanks all for suggestions so far.

Wal.

JAZZCNC
14-07-2014, 10:49 PM
Not hard or expensive to make small vacuum system if you use a Pod system and don't cut thru. I've got one here that use's a fridge compressor and I've held and engraved brass with it.
So long as your not cutting thru then it holds full vacuum no problem and it won't let go if the material isn't pourus. Attach compressor to a Tank and pull tank down to vacuum and it will hold part without pump running provided you have a good seal that doesn't leak.

You only need lots of vacuum volume if you don't have a good seal or material pourus or your cutting thru. Normal vacuum machine into larger chamber with a small output pipe to a pod would work provided chamber didn't leak and had enough volume to pull part down to full vac and hold before vacuum drops to low. Try it I think you'll be surprised just how well a normal vac pulls down.!

EddyCurrent
15-07-2014, 10:46 AM
I like Celtic. The old fodies way to stick something down for machining was shellac. You melt it using heat for the fixing, either melt or dissolve with methylated spirit for the removing.

In that case animal glue should work too, but these days maybe hot melt glue would work.
With double sided tape, I've discovered the strength seems to be a function of how hard you press it all down, in fact 3M I think call it 'pressure sensitive' tape.
With a job this small you would think the tape might have some sideways movememt that could be significant in proportion to the job size so a physical restraint such as a pocket would be best.
Maybe you could machine a shallow pocket in wood or perspex then fit the workpiece inside it, held down with double sided tape in the bottom.
Nice job by the way.

Wal
15-07-2014, 11:56 AM
Maybe you could machine a shallow pocket in wood or perspex then fit the workpiece inside it, held down with double sided tape in the bottom.
Nice job by the way.

Cheers Eddy - yeah, I was leaning that way - although a micro DIY vacuum chuck might make a nice project... Will look into it a bit further to see if it's something that I could manage...

Clive S made a very good point earlier - I'm losing 20% of holding strength by using only the 1 strip of tape and leaving part of the blank 'unstuck'... Never really stopped to consider it, but when written down in numbers it becomes a lot more obvious!

Wal.

Boyan Silyavski
15-07-2014, 04:10 PM
Hole in plastic. Detail in the hole. Hot glue gun.Glue it. Wait 1 min. Do the job. Spray can filled with alcohol/rubbing or whatever/. Spray on the hard hot glue. Unglues like miracle. No traces on job or board .Thats it.

I use mostly hot glue to hold almost anything. Double sided tape is pain in the a**s to clean. Even when i used very very thin one/ used for photo prints to fix on a support and lexan top/ it makes a mess. Especially if you have a cut through or hole, the last mm should be very slow or bit breaks in the goo.

Wal
15-07-2014, 07:02 PM
Do you mean like this, silyavski?

12802

How easy is it to ensure that the stock stays 'flat' (perpendicular to the cutter) when seating it on the glue..? The mother of pearl show-face is usually ground flat (already pretty thin) and bonded to a rough stone substrate which gets surfaced parallel to the show-face before starting the job. If there's too much of a rise in the stock once it's glued then it might be problematic... Hey, but good suggestion and worth a try for sure.

Thanks!

Wal.

Boyan Silyavski
15-07-2014, 07:34 PM
Hi,

No glue below. Fit it in, then glue around. Once you know the hot glue, you can stick anything with barely just enough glue to hold firmly and at the same time to remove it very easily.

In case like yours, where fine elements can be damaged by pulling by hand or lifting with screwdriver/that's what i do/, so use alcohol.

I can't imagine a life without hot glue :-)

See some example, just right now what i have on my machine. The wood is bend, that's the weights are for. See how little glue i use. you do the same, just your element will be a little inside the fixture hole :

12803 12804

Wal
15-07-2014, 07:40 PM
Aha, okay.

Will give it a go sometime. Cheers!

Wal.

Boyan Silyavski
15-07-2014, 07:49 PM
I start repeating my self about Chinese thing, but have to say it- don't use Chinese glue sticks. You will know them that they are softer and yellowish. You need transparent white or whitish. The Chinese ones don't harden enough and stick in an awful manner + clog the gun.

Try it, you will like it. Its the fastest way to hold something, especially various things at home .

Wal
15-07-2014, 07:58 PM
Any manufacturer in particular..?

Boyan Silyavski
16-07-2014, 08:46 AM
Any glue sticks that sell in local shops in packets of at least 1kg.

The glue gun does not need to be very expensive, not necessary but better is to have automatic-off function. Most importantly it should be slim so later can reach in difficult places without a problem. 12mm glue sticks.

A Stanley gun will work, 3m, Locktite, Dremel guns are good, these are very nice - https://www.powerbond.co.uk/categories/shaped_hot_melt_adhesive_glue_guns.php

As for the glue the best glue stick i used are Tecbond, a bit overkill for the purpose. You should look for rebranded general purpose sticks in some big local shop. I buy them normally for 15 eur the kg but from time to time in very big shops they sell them 7eur per kg.
http://www.gluesticks.uk.com/multi-purpose-clear-12mm-glue-sticks-5kg-p-13.html

StevenT
16-07-2014, 12:22 PM
I have used super glue which work fine, as the glue has a low viscosity the work piece will sit flat in the pocket and can be removed with heat or and acetone.

Wal
01-10-2014, 01:13 PM
I recently made a couple of custom logos in MoP. Based on earlier recommendations, here's how the (this time very successful) work-holding went:



Machined a pocket in a flooring off-cut to hold the stock (very snug press-fit). Also used a bit of double sided tape and a couple of dabs of hot glue to help prevent the work lifting. Note the access points at the corners to aid in lifting out the work.
Once cut, I shaved off the glue and then dabbed a few drops of meths through the shell and onto the double sided tape which let go straight away.


http://www.mycncuk.com/attachment.php?attachmentid=13516&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13515&stc=1http://www.mycncuk.com/attachment.php?attachmentid=13514&stc=1

I guess it's basic stuff, but if it helps someone out on a first job, then so much the better.

Wal.

GEOFFREY
01-10-2014, 09:53 PM
Looks good Wal - well done and thanks for showing. G.

YulianY
06-01-2016, 11:14 AM
We develop a thin film for hard works may be it can do the job better then your double sided tape, by the way what king of double sided tape do you use? please take a look at the movie. https://www.youtube.com/watch?v=PbCqkUomf5M

Wal
06-01-2016, 01:58 PM
That is a strong piece of tape..! What's it like removing the work..?

I use a generic double-sided tape, not a bargain-bin brand but not engineering grade either. It's pretty strong but to be honest, for the smaller pearls stuff I'm mostly just using hot glue around the edges of the stock nowadays.

Less fiddly scraping off the tape..!

17134 17133

Clive S
06-01-2016, 02:04 PM
We develop a thin film for hard works may be it can do the job better then your double sided tape, by the way what king of double sided tape do you use? please take a look at the movie. https://www.youtube.com/watch?v=PbCqkUomf5MVery nice, but its a shame that the camera man is on LSD

Wal
06-01-2016, 02:11 PM
Heh. Clive, try this one:

https://www.youtube.com/watch?v=axS-CjLoIPA

Looks like the LSD scoffing camera-man has swapped places with the machinist and forgotten to turn the air on...

But no, seriously. The tape looks excellent, provided that it comes off. Any samples going..? :pig:

JAZZCNC
06-01-2016, 02:40 PM
Best bit of Video for me is seeing a Gas cylinder hanging mid air inside VMC cabinet. . . That's what you call useful Health and safety.. :hysterical:

Billythefish
26-08-2016, 10:45 PM
Very easy. Superglue. Clean surface, glue to metal plate, clamp plate. 16 hours later put plate in acetone. Wait, enjoy finished part. Wont work if part dont like acetone...

cheers,
billy.