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  1. #1
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 4-5 years. Has a total post count of 276. Received thanks 21 times, giving thanks to others 6 times.
    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:

    Click image for larger version. 

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    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.

  2. #2
    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.

  3. #3
    Pocket the perspex and use vacuum. Even a standard vacuum will hold this down provided you don't cut thru the vacuum seal.

  4. #4
    Nice work, I have used Silicone sealer to stick down with some degree of success

  5. #5
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 4-5 years. Has a total post count of 276. Received thanks 21 times, giving thanks to others 6 times.
    Quote Originally Posted by JAZZCNC View Post
    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:



    Rather impressive.

    Thanks all for suggestions so far.

    Wal.

  6. #6
    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.!
    Last edited by JAZZCNC; 14-07-2014 at 10:54 PM.

  7. #7
    Quote Originally Posted by Robin Hewitt View Post
    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.
    Last edited by EddyCurrent; 15-07-2014 at 10:51 AM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  8. #8
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 4-5 years. Has a total post count of 276. Received thanks 21 times, giving thanks to others 6 times.
    Quote Originally Posted by EddyCurrent View Post
    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.

  9. #9
    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.

  10. #10
    Wal's Avatar
    Lives in Stockport, United Kingdom. Current Activity: Viewing Has been a member for 4-5 years. Has a total post count of 276. Received thanks 21 times, giving thanks to others 6 times.
    Do you mean like this, silyavski?

    Click image for larger version. 

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    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.

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