5mm mandrels getting very hot?

Fluffstar · August 30, 2015, 02:44:26 PM

Hi Everyone,

I did a search but couldn't find anything...

I made myself some 5mm mandrels from cold rolled steel rod because I'm a cheapass. I'm finding that the 5mm ones are getting really really hot, to the point where even if I hold it at it's end (8 inches or so) it's almost too hot to hold. I don't work each bead for very long really, 10mins or so is probably the longest as I'm still a beginner. I have my flame candles at about 4mm long, I'm on a bobcat (I always get a mental image of a person riding an actual bobcat through a forest whenever I read that!)

I am asking if anyone else has found that 5mm mandrels heat up much more than the 2.4mm ones? I am thinking it might be something to do with the fact that mine a different alloy, or the larger width allowing more heat to transfer.

Thanks!!
Kathy.

Moira HFG · August 30, 2015, 03:28:23 PM

Off the top of my head, I wouldn't think the alloy makes a lot of difference to heat conduction.
Usually the flame is directed onto the bead - glass doesn't conduct heat well, and the bead release will act as an insulator too. So I'm wondering if you are playing the flame onto the mandrel as well as the glass? Maybe try working in a smaller flame so the heat is concentrated onto the bead.

I'll be interested to hear if any of the metallurgists on the forum have other views!

Pauline · August 30, 2015, 05:08:07 PM

yup I did the same with steel rod from B&Q and they also got too hot to handle. have given up and bought proper 316 ss ones and they don't get nearly as hot. Mandas ones with athinner handle are even better

Fluffstar · August 30, 2015, 05:17:15 PM

Thanks all! I'm going down to mangobeads for my 30th birthday in October so I might be able to convince my mum to get me some posh proper ones! =)

ajda · August 30, 2015, 09:52:24 PM

Solid stainless steel 5mm rod is what you want. I think my 310 grade ones are best, but really any grade will do OK. I have made hollow ones for people who want a lighter mandrel and I might have some of that left if you are interested...

Fluffstar · August 31, 2015, 10:09:29 AM

Quote from: ajda on August 30, 2015, 09:52:24 PM
Solid stainless steel 5mm rod is what you want. I think my 310 grade ones are best, but really any grade will do OK. I have made hollow ones for people who want a lighter mandrel and I might have some of that left if you are interested...

Ooh! I've been using hollow stainless chopsticks from ebay to make my vessels but because they have a rounded end I was ending up with vessel necks that narrowed towards the vessel, if that makes any sense! I was hoping that by using 5mm mandrels I'd have even vessel neck widths the whole way down. I'd be very interested, shall I send you a PM?

ajda · August 31, 2015, 12:56:01 PM

Yes, pm me - I'll just go and check whether I've still got any 5mm tubing left...

oliver90owner · August 31, 2015, 11:18:04 PM

Typical thermal coductivity values on this link:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Copper is shown as around 400! Steel around 40 -50 and stainless approx 17. It will depend on the type of steel. Different included metals/elements will have an effect.

Fluffstar · September 01, 2015, 08:49:00 AM

Quote from: oliver90owner on August 31, 2015, 11:18:04 PM
Typical thermal coductivity values on this link:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Copper is shown as around 400! Steel around 40 -50 and stainless approx 17. It will depend on the type of steel. Different included metals/elements will have an effect.

Wow excellent resource! Thank you! So yes, stainless all the way :-)