A challenge for engineers?

May 7, 2010 4:50 PM

Can anyone identify this screw/bolt head and tell me what type of tool I need to remove it? The screw head has 5 radiating flanges/splines, with a raised central hub. It does not appear to be a (security) Torx head. Photos: bolt closup and bolt in situ. The bolt/screw in question is located in a Braun coffee grinder (model KMM30, 3045). The grinder was made in Mexico and sold in the USA.
posted by Susurration to home & garden (15 answers total)

It looks to me like a polydrive screw, which is a weird choice for a coffee grinder, so I'm probably wrong.
posted by BitterOldPunk at 4:59 PM on May 7, 2010

Here's a pretty good guide to security screw types and here is someone explaining how to get around these screws in a Braun coffee maker.

Maybe a Bristol?

My trick with screws that don't want to come out, either because they're stripped or because I don't have the right driver, is to use an old pair of diagonal cutters to grab the screw. either that or cut your own slot with a Dremel if you have one.
posted by bondcliff at 6:05 PM on May 7, 2010 [1 favorite]

The problem with both of these are that they have an even number of sides. My bolt/screw has 5 sides/splines. So I'm still looking for suggestions ... :-)
posted by Susurration at 6:17 PM on May 7, 2010

You might try the second suggestion here. It involves sacrificing a plastic ball point pen and melting it to custom fit your screw head. Might not work if the screws are tightly installed, but cheap to try, as all you need is a pen and a lighter.

BTW, I spent some minutes looking for those bits didn't come up w/anything. They are apparently highly proprietary.
posted by mosk at 6:21 PM on May 7, 2010

This looks like a 5-slot version of a "TAMPRUF" or tri-groove or 4-notched screw (scroll down for descriptions of each fastener).

Do you have a Dremel with a cut-off wheel? You could use it to cut a single slot across the face and then turn it with a regular flat blade screwdriver. If it's recessed, then gripping with pliers won't work, but you could just cut through that too if it's in the way.
posted by buzzv at 6:24 PM on May 7, 2010

If the Dremel isn't handy, then perhaps you could drill two small holes to match up with a spanner screw driver bit.
posted by buzzv at 6:27 PM on May 7, 2010

Are you just trying to get at the inside to clean it? Removing those screws may not be necessary. Here's another set of instructions.
posted by jedicus at 6:28 PM on May 7, 2010

Many thanks for all the great suggestions here. I got as far as removing the gears, but as I burned out the grinder by overloading the motor, I need to go deeper to check if I just blew a fuse or if I can find a replacement motor ... :-(
posted by Susurration at 6:36 PM on May 7, 2010

I take it you've tried needle nose vice grips.
Cutting a slot is often a great way to go. I don't see how you can do it in this case.
I would drill a hole and use a screw extractor. They cost about $3 and are super handy.
posted by mearls at 6:38 PM on May 7, 2010

Cut a slot in a regular flat head screwdriver so you have two points to reach two of the indentations in the screw.
posted by gally99 at 6:40 PM on May 7, 2010

If that were some critical not-easily-replaceable equipment at work, I'd take a flat chisel with a width the same-ish as the screw diameter and pound that sucker into it, then turn that like a screwdriver. It'll make its own slot, unless it's a ridiculous titanium screw or something. Or just drill it out and replace the screws with slightly fatter ones, but it looks like that central hub is strategically designed to make it hard to center your drill. Devious a-holes.

What I'd do in your case is buy a new grinder and make sure it was not a Braun.
posted by ctmf at 7:18 PM on May 7, 2010

I'm with gally99 - take a regular flathead and notch it in such a way that the remaining two points will fit in two of the slots on the screwhead.
posted by davey_darling at 8:09 PM on May 7, 2010

Vise Grips?

If that doesn't work, can you drill a hole in the center and take it out with an easy out?
posted by Kid Charlemagne at 9:10 PM on May 7, 2010

You know, I don't think they're bolts at all--I think that pattern is peening, that is, they're essentially metal rods with no threading, and the top has been struck/deformed to lock the top part down. The star pattern is the mark left by the tool that struck them. If this is the case, everyone who says cut it off is right.
posted by pullayup at 4:13 AM on May 8, 2010

Many thanks to all who suggested strategies for removing the screws. bondcliff's link helped me think of the solution, so that gets best answer (although they were all excellent suggestions - thanks!). Eventually, I succeeded by applying torque to one of the slots in the screw-head via a small screwdriver. Only to find that the motor is a sealed unit, soldered together. But at least I think I can see what I blew - now, I just have to identify it. Another day, another challenge ...
Oh - and _dario, I sustained myself during the effort by imagining that I was applying torque to the head of the design engineer ... :-)
posted by Susurration at 11:54 AM on May 8, 2010