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Author Topic: Home made composite laps  (Read 683 times)

FlashGP

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Home made composite laps
« on: October 12, 2020, 09:05:07 AM »
Has enyone tried to make their own laps using epoxy and grit?

I am thinking of using a worn out plated lap as a base, 1000 grit carborundum and liquid glass (the type used to finish table tops) as the bonding agent.

Bunnings no longer sell Wattle 7008 2 pack floor finish which would be runnier and may better wear characteristics as it should be a little more flexible.

I chose carborundum because I have some on hand and it should be easier to dress the lap using a diamond dressing tool.

I think usung teflon tape wrapped twice atound a half inch dowell stuck in the hole of the plated lap should create the spindle hole, All I need to do is work out how to create a 6 inch mould.

I am aiming for a 2 to 3mm layer of grit 2 pack mix.

Any ideas?
Yours Sincerely
Flash (Gordon)

Robol

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Re: Home made composite laps
« Reply #1 on: October 12, 2020, 11:22:42 AM »
How about a block of modelling clay which you should be able to buy from an art supplies store.
They should at least be able to point you in the right direction.

Good Luck 

RoughCreations

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Re: Home made composite laps
« Reply #2 on: October 12, 2020, 06:14:39 PM »
Hi Flash,
There's some good info from a German forum in the attached pdf file (poorly translated into English). Whilst the disk maker is using diamond, the principle is probably still applicable, ie: add copper powder.
Hope this helps,
RC
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steveo

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Re: Home made composite laps
« Reply #3 on: October 13, 2020, 05:11:38 AM »
Have heard of using two part epoxy with mixed in diamond on a worn out diamond belt. Have to keep running slowly till its dry.
Steve

FlashGP

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Re: Home made composite laps
« Reply #4 on: October 13, 2020, 08:52:48 AM »
Thanks all.

RC, I think the copper powder used in the pdf was really a filler to prevent the diamond settling before the epoxy set as the diamond would be held in solution rather than have a chance to embed in the copper.

But it may be that diamond breaking dree if the epoxy during use may embed in the copper particles on the surface of the lap during use.

It may be an interesting combination to combine a slightly flexible epoxy with annealed metal particles and a grit, you may end up with a more forgiving sintered lap alternative.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

RoughCreations

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Re: Home made composite laps
« Reply #5 on: October 13, 2020, 06:02:14 PM »
Thanks all.

RC, I think the copper powder used in the pdf was really a filler to prevent the diamond settling before the epoxy set as the diamond would be held in solution rather than have a chance to embed in the copper.

But it may be that diamond breaking dree if the epoxy during use may embed in the copper particles on the surface of the lap during use.

It may be an interesting combination to combine a slightly flexible epoxy with annealed metal particles and a grit, you may end up with a more forgiving sintered lap alternative.

Regards
Gordon

Yes, that is my way of thinking. A 'composite' in the truest sense of the word.
from Wikipedia:
Quote
A composite material is a material made from two or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure, differentiating composites from mixtures and solid solutions.
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Dihusky

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Re: Home made composite laps
« Reply #6 on: October 17, 2020, 08:46:02 AM »
May be try Clear casting resin and add fumed silica powder as a bulking agent so you get more of a paste consistency?

FlashGP

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Re: Home made composite laps
« Reply #7 on: October 21, 2020, 08:52:07 AM »
Hi Di, not sure what fumed silica powder is.
Yours Sincerely
Flash (Gordon)

Dihusky

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Re: Home made composite laps
« Reply #8 on: October 21, 2020, 04:17:35 PM »
Fumed Silica is a bulking or suspension agent, very fine with a surface area of 200 m2 per gram. It thickens the epoxy to help hold suspended particles in suspension and preventing them from dropping out of suspension. You'd need to experiment a bit to see what quantities will help hold diamond powder in suspension, a lot will also depend on the grade of diamond

Faceting Frank

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Re: Home made composite laps
« Reply #9 on: October 21, 2020, 04:50:49 PM »
What exactly do you intend to cut with it Gordon. To me it sounds very soft and will quickly dish.

FlashGP

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Re: Home made composite laps
« Reply #10 on: October 22, 2020, 08:54:06 AM »
Hi Frank

I was thinking of making a silicon carbide 1000 grit lap to preform my stones.  The 8” plated 1200 lap I use at present is tearing tiny points out of the surface of the facet resulting in me having to spend too long in the 3k lap to cut away the surface damage.

If successful I plan on a cerium oxide lap,I have 150 gems of the stuff bought for polishing, but it was a bit course and scratched. May make the equivalent of a 14k ore polishing lap.

I can resurface it with a diamond tool sharpener, but have plans on making a cnc style lap surface grinder to resurface laps while they spin on the platern. 
« Last Edit: October 22, 2020, 08:58:01 AM by FlashGP »
Yours Sincerely
Flash (Gordon)

Dihusky

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Re: Home made composite laps
« Reply #11 on: October 22, 2020, 04:42:05 PM »
A surface grinder for skimming laps on the platern sounds really interesting, something I have also been thinking about only I don't have a machine shop to play in

Rusted

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Re: Home made composite laps
« Reply #12 on: October 22, 2020, 05:10:29 PM »
For fairly cheap laps have a look at printed circuit board material, it usually comes in 6" by 8" pieces for about $10. Copper on one side so can be used like a normal copper lap or fibre on the other, handy for polishing, and cheap enough to be disposable with no heartache once it wears out. Use like a normal topper lap as they are fairly thin.  Usually easily found at electronic shops like Altronics or similar, Online from various places as well.

FlashGP

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Re: Home made composite laps
« Reply #13 on: October 22, 2020, 06:51:00 PM »
Hi Rusted, great idea.  I may try that.

Hi Di, I wish I had a machine shop.  I made my concave Facetors in a Plywood base as a stiffener with all the bearings mounted on 3mm aluminium angle and was planning on doing the same for the surface grinder. 

Recently bought aluminium brazing rod, which should make the job easier as I can weld pieces together rather than drilling, taping and bolting them in place.  I just need the time to try it out.

My thought is to mount a diamond cup burr or large diamond core drill in the end of the spindle as the grinder.

The whole assembly will need to be adjustable so the grinder can travel at exactly the same height across the face of the lap, ie the direction of travel must be parallel to the platten  or the lap will dish or dome.

Using a grinder should overcome the problem of the job ringing as the cutting bit runs across the lap and should make the cutter last a lot longer than carbide based tooling.

The plywood is great for prototyping.  I use T nuts designed for timber to bolt the aluminium angle in place.
Yours Sincerely
Flash (Gordon)

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