El Beast - Initial design phase, comments and critique welcomed!

[Chaz]

I just got a piece of SRBP to try. It's incredible that it's made out of resin and paper, it looks really tough and quite heavy. I only got a 400x300 piece, in 15mm, as it's quite expensive, I think you use larger sheets?. I am guessing that Tufnol is a brand name, but the same thing?

I just wanted to ask roughly how thin does it get before you discard it, with regards to having enough thread left in the holes with sufficient strength to clamp the piece, 8mm or so? If you use M5 bolts, I suppose you need a good 5mm of thread? Secondly, I assume that you don't skim it every time you cut a new piece, provided you have enough of a flat, clean area left for the next piece to sit flat, is that right? Also, what's your favourite tool for skimming the SRBP? Does it machine similarly to Delrin? (the only plastic I have machined).
Keep on posting about your progress, the more the merrier:)

Edward

Its pricy alright, £60 for my size machine. That said, if its makes machining a lot easier, its worth it. Also keen to understand if there are variations of this material that might be worth looking at.

[Edward]

I paid £44.32 including the £15 for UPS, for the 400x300 piece. I guess if you ordered a few pieces it would just be the one-off transport fee. At least they provided an invoice, so I can discount it off my tax as a legit expense.

They also call it Phenolic Sheet.

Edward

[Desertboy]

At prices of Tufnol I'd glue it to a 12mm sheet of mdf then you can mill through the whole lot screw wasting any.

If you have issues with losing 12mm of travel on the Z then you really have issues lol

[Chaz]

At prices of Tufnol I'd glue it to a 12mm sheet of mdf then you can mill through the whole lot screw wasting any.

If you have issues with losing 12mm of travel on the Z then you really have issues lol

Problem is that MDF absorbs fluid and 'pulls' apart.

[Davek0974]

Yep, MDF is pretty duff for metalwork, great for woodwork.

At these prices, has anyone priced up a slab of aluminium?
Its pretty reasonable in 12-15mm thicknesses.

[Chaz]

Yep, MDF is pretty duff for metalwork, great for woodwork.

At these prices, has anyone priced up a slab of aluminium?
Its pretty reasonable in 12-15mm thicknesses.

Oddly, was thinking the same. £86 + VAT + Del for 12mm tooling plate at 650 x 450. Normal plate is still £75.

[Edward]

Yes, similar prices. So what's the attraction? Is Tufnol easy to skim, I bet it skims like butter and really fast, probably quite messy, though not as messy as MDF and harder?

[Zeeflyboy]

Tufnol is a brand name, Kite is their equivalent product. Tends to be a bit more pricey than the generic SRBP... I've been buying attwater brand from ebay.

As for why it's better than alu, it's probably not really! It does skim very quickly and easily with minimal mess (I skim 0.3mm at 6000mm/s using a single flute 10mm cutter)... I like to cut past the work piece in general so I set a cut through of around 0.2mm which then gets completely cleared out at the next 0.3mm skim.

The main advantage to my mind is that it's softer than alu so more forgiving of plunging down into it quickly so for drilling/tapping it's quicker. Also if cutting CF/FR4/G10/whatever then the fishtail burrs I use for that wouldn't like cutting into alu below the piece but they don't care about cutting into SRBP.

Alu can also leave a bit of an upward edge/burr where it's been cut which might mess with your perfect level bed until the next skim. SRBP doesn't leave any burr that I can see.

Both would be perfectly valid, I just tend to use SRBP for the above mentioned reasons. It is also cheaper than tooling plate... eg a board of 600x400x15mm is £50.46 vs £99.36 for the same size of tooling plate from Alu warehouse (both including VAT). That's half the price... adds up when you consider it's a sacrificial board that your machine will consume over time.

I used a 12mm board which is a bit cheaper than the 15mm... I think it will be too full of holes before I skim it down to a height that's unusable, so there's probably a balance to be found between over-paying for a thicker board that won't be used to it's potential before becoming too full of holes. Will depend on how big your bed is and how hole intensive your work is!

It is also worth considering that you don't necessarily need a piece to cover your whole bed, only big enough for the largest piece of work you need to hold down.