Any tips on shaping Eva foam grips? I’ve done cork grips no problem on my little homemade lathe with a hand drill but I was playing with some Eva before I shape some grips and have trouble not getting striations or tiny cracks horizontally in the foam. I started with 80 grit and then went to 150 and then 400 then 800 grit sandpaper. FYI it’s 3/8 in inner diameter foam that I have on a 1/4 in mandrel that I arbiter with tape as my lathe won’t accept the 3/8 in rod. Is there anything I’m doing wrong to get those tiny cracks? Starting with too coarse of sandpaper?

I think 80 grit is too aggressive. I would start with 120 to see how the EVA responds. Granted starting with a finer grit will take longer but the results will be better.
Also while shaping try to keep the pressure light to avoid over heating the EVA.

Have fun

John

EVA will soften a bit when you turn it, and is prone to heat damage so I don't stay in one place long. Don't think I've ever used lighter than 200 on it either, that's my best guess, the cracks may be some kind of glazed EVA maybe.



Edited 1 time(s). Last edit at 02/20/2019 04:01PM by Spencer Phipps.

You don't want to generate top much heat as this will permanently soften the EVA. I start with 60 or even 80 grit. This allows me to get the size down and shape in without having to sand for very long, so there is less heat generated. From there I go to 100, 150 and 250 and that's about it.

I doubt your sandpaper is causing lengthwise cracks. Something else is going on.

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Hmmm...I was staying in one place for a while. Maybe the heat did it. I’ll experiment some more tonight and see how it goes.

It’s also not a solid color foam. It’s that kind that has vertical stripes in it. Could it be a foam problem? I guess I could try some of my solid color Eva and see if that does it too.

I cant' disagree with everyone stronger - heat from turning doesnt' do anything to EVA. I have turned several thousands of EVA grips, both plain and with inlays. THere is video of me starting with a solid block, boring it, knocking the corners off and then sanding it to size in under 2 minutes. I turn at 4000RPM, and I use 40 grit to start with as much pressure as I can put on it. I can feel hot hot the EVA is as it it spinning and the dust is hitting my fingers, and the EVA itself is hot. NEver has teh EVA gotten soft from overheating. EVA is used for orthodic shoes, and it has a molding temperature of around 275-300 depending on the type of EVA. This allows them to ress the EVA into a mold and get it to fit the shape of your foot. When it cools, teh EVA comes back to the same hardness as it had before. THe overheating causing softening is a myth.

YOur problem is simple, you went too far with teh 80 grit, and didnt' remove the sanding "lines" when you switched to 120 and the finer grits after.

Not all EVA is the same density, or hardness. I like the harder, higher durometer, stuff.
I stand corrected Billy, you've shaped far more foam than me.



Edited 1 time(s). Last edit at 02/20/2019 04:28PM by Spencer Phipps.

good to know..Thanks Billy!

Ok, cool. Good info. So basically hit it with the finer grit stuff until all sanding lines are gone. Sounds like a plan. I’ll experiment some more tonight when I get home.

You have to go through each grit. You can't use 80 and then skip to 320 and think you're going to get rid of the earlier sanding scratches in a half minute.

In your original post, you said the cracks were "horizontal." I assume you meant lengthwise. If this is the case, then sanding scratches are not the problem.

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Just don't go too far with the 80, just use that grit to reduce teh size to 1/8" over the size you want). TEh 120 use to shape and slihghtly oversize (less than 1/8" over whatever ID you want) and 150 to get it down to final size and shape. 220 to finish is all you need, beyond that is a waste of time.

Don't be in a rush, take your time. THe way I turn the grips is after a ton of time and experimenting with everything so I could work the most efficiently without sacrificing quality. I don't recommend people try to turn a grip in 30 seconds,

My experience with EVA is that the warmer it gets the more resistant to abrasion it becomes and you have to bear down harder to remove material. I find high speed and light touch and progressively finer grit will produces the best results.

Its no different than sanding wood, metal or composites start coarse and end up fine.

Have fun

You guys were right. I just wasn’t being patient enough and went too heavy on the 80 grit. I was able to smooth it out with some 220 followed by 400. Went and shaped by fighting butt for the casting rod and it came out perfect! Thanks for the help! Going to do the rest of the grip soon so I can get the handle all glued up.

Without knowing what kind of EVA your are using, I have found that a certain amount of heat generated by friction is actually your friend.
Similar to Billy, I've turned a fair amount of EVA over the years, including some that were glued up from strips to make designs.
Always went faster once they got warmed up from friction.
That being said, the designs had to be well glued and set.
I usually start with drywall screen, which tends not to leave sanding marks, yet takes material off rather quickly.
Then stepped down at least twice in grit.
And have left some fairly rough on fore grips to aid in handling while wet.
And the same goes for cutting to size, heat makes a nice clean cut.

Hope this helps,

Best wishes,
Ron Schneider
Schneider's Rod Shop
Mountain Home, Arkansas
[www.schneidersrods.com]
mtnron40@yahoo.com
870-424-3381

It was just Eva from mud hole. I think the lines were me being impatient and going heavy on the 80 grit. Tried again with shaping last night and it came out great with no marks.






Ron Schneider Wrote:
-------------------------------------------------------
> Without knowing what kind of EVA your are using, I
> have found that a certain amount of heat generated
> by friction is actually your friend.
> Similar to Billy, I've turned a fair amount of EVA
> over the years, including some that were glued up
> from strips to make designs.
> Always went faster once they got warmed up from
> friction.
> That being said, the designs had to be well glued
> and set.
> I usually start with drywall screen, which tends
> not to leave sanding marks, yet takes material off
> rather quickly.
> Then stepped down at least twice in grit.
> And have left some fairly rough on fore grips to
> aid in handling while wet.
> And the same goes for cutting to size, heat makes
> a nice clean cut.
>
> Hope this helps,