Hard Time's build diary

**Laser** · 14th September 2010, 19:42

Hi guys bought some drills today, took them apart and they luckily still work! Soon ordering some 15mm HDPE and trying to get my robot up and running ASAP.

**Laser** · 18th September 2010, 15:18

Bougth some plastic yesterday, getting it early next week.Getting a bench drill from grandad soon and going to get my robots chassis resdy in the next few weeks. Can you put a nut to make 125mm blue wheels with plane bore into 125mm blue wheels with nut insert?

**beast** · 18th September 2010, 15:40

you should beable to i would put 2 in each heat them up and press in

remember they are 3/8 UNF thread

**rallikas** · 18th September 2010, 19:39

Another way is to weld a washer to the nut and bolt it on the wheel!

**Laser** · 18th September 2010, 20:47

Thanks for the advice, if I was to melt the nut into the wheel how would I do it?

**Metal Demons** · 18th September 2010, 20:59

Drill the wheel out to a mm or so under the distance between opposite flats on the nut, then heat the nut up with a torch and shove it in (ensuring it goes in straight) with an arbor press/bearing press or whatever (bodge a jig using a vise I guess).

You can use two at once by threading them onto a bolt (making sure the flats on both nuts line up) and shoving the whole lot into place, this will help you make sure it goes in straight.

**Laser** · 21st September 2010, 14:38

Got the plastic yesterday(15mm 500x500 and 6mm 1000x500 HDPE) cutting it tonight. Is a jigsaw the best way to cut HDPE if not what is?

**Metal Demons** · 21st September 2010, 15:17

Abrasive waterjet.

Somehow I doubt that was the answer you wanted... so of the less expensive options a bandsaw is your best bet by far, but if you don't have access to one a jigsaw/scrollsaw will work. You want to use lots of coolant (though lubrication isn't an issue, you can even get away with water) and go pretty slow, in addition to using a coarse wood cutting blade.

Problem with HDPE is the same as a lot of thermoplastics, it will soften and melt very easily from cutting heat resulting in a messy cut, bound up blade, or the material reforming itself behind the blade. Those are the best ways to avoid it.

**calumco** · 21st September 2010, 15:42

i've found, that using a jigsaw is fine and aslong as you take your time you can get good cuts, other day i made 2 hdpe rings to hold a co2 bottle in place in my feather weight and they turned out great.-- but i use a metal cutting blade which has much bigger teeth, i found on the small toothed blades for cutting wood it takes ages and the teeth used to clog up.

never bothered with any lubricant or anything for HDPE, as any roughness which as nick said you would get from the material reforming/melting back together beind the blade can just be filed off to leave it looking smooth and you dnt have to bother getting all the lubricant off afterwards either.

but when cutting ali and other metals you do have to use lubricant otherwise you'll go through blades like nothing else.