Folding devices

[Andy B]

In my thread on developing an etched kit, Ian T said "I'll be interested to see your thoughts on folding tools".

Well, I've been giving it quite a bit of thought over the past few days.
For anyone building a lot of etched kits or who can simply afford one anyway, the 8" or 14" 'Hold and Fold' tools look like a great tool for G3 modellers. I've never actually tried using one though - anyone on here have one and can comment?

But for anyone who doesn't relish paying out £60-100 for a lump of CNC machined alloy, or doesn't have the facilities to make a machined masterpiece, what are the options?
I concluded that the most difficult part of a folding device is the 'pad' that has the edge over which the bend is made - it must be flat on its face, it needs to have a straight edge and that edge needs a bevel of at least 15 degrees to enable over-bending that allows for the material being bent to spring back slightly. It either needs stiffness of its own to resist buckling, or it needs to be easily backed up with another piece of bar, and it ideally  has holes through it for locating pins and/or clamping screws.
Is there anything available 'off the shelf that meets all those criteria?
I have considered and discounted the following:
Gauge plate - easily available from engineering suppliers in a variety of widths and thicknesses, is flat, has a straight (but not bevelled) edge. Can be easily drilled for holes. Someone skilled with a file could probably put a bevel on one edge to within, say, 0.5mm of the back face or go a bit further and finish it off with a piece of plate glass and a few sheets of wet'n'dry (working up the grades)
Bevel edge rulers - steel ones are just pressings and not straight enough, alloy ones (that I have seen) are either too thin, have too bigger radius on the bevel edge or the bevel edge is raised from the base by 1-2mm
Alloy extrusions for other purposes (e.g. door thresholds) - similar problems to the rulers above.

The most promising solution yet is based on using a planer blade knife. Usually made from High Speed Steel (HSS) they are ground all over (i.e. flat), have a straight bevel edge ground on and sometimes include holes.
Scroungers and skip-divers may be able to find one (or a pair) that have reached the limit of re-grinding for minimal cost. But if we look at something like these Electra Beckum blades, they work out a just over £10 each (buy a pair a get a friend to make a folder too!).
Or there are 130 x 30 x 3mm blades for just £9.36 per pair - no holes but they say they can supply all lengths of those blades. So with a small selection of smaller widths, one could effectively have a set of 'fingers' as in a box & pan folder.
A piece of flexible magnetic strip could be bonded to a piece of angle (ally or steel), which would hold the 'fingers' in place whilst being clamped up against the part to be bent -see picture
The blades would obviously need blunting off before use (240 grit wet'n'dry on a flat surface)

I've wibbled on for long enough, I think - any thoughts on whether this idea has merit or not?
Or any other ideas for cheap and effective bending bars?

Andy

[Traininvain]

This guy on ebay makes excellent bending bars:

http://www.ebay.co.uk/itm/Bending-Bars-Model-Making-and-Kit-Building-/200637609293?pt=UK_Trains_Railway_Models&hash=item2eb6eef54d#ht_745wt_1141

He made me a larger set some time ago and they're extremely useful and easy to use in a vice

Ian

[Andy B]

Ian,

Do they have a bevelled top edge?
Can you post a close-up picture or 2?

Andy

[Traininvain]

Square edge - sorry no time to post pix at moment

[IanT]

Hi Andy,

I was moving some photos around this afternoon and came across this in my library from 2008 - I cannot remember its source now but I think this is the general idea of what might be required... your planer blade would work well with this set-up. The hinges have to have their centre line along the fold....

Regards,

IanT

[MikeWilliams]

Working on Trainvain's experience, if anyone wanted to ask the vendor for a longer set, I'd be happy to order one too, if a small batch would help the cost.

Mike

[keith Bristol]

Mike Good suggestion, i need one too..

[MikeWilliams]

Trainvain - how long were those you ordered?  Would you be prepared to co-ordinate a small order please?

Anyone else need a set?

Mike

[Traininvain]

Bit tied up to co-ordinate anything at moment, but he has a larger set at

http://www.ebay.co.uk/itm/BENDING-BARS-MODEL-MAKING-KIT-BUILDING-HEAVY-DUTY-/200639306329?pt=UK_Trains_Railway_Models&hash=item2eb708da59#ht_763wt_1141

All I think you need do is get in touch with him and order a set

[hornbeam]

After reading this I prdered a set. The length between bolts is 250mm. Hesa really decent guy toeal with, kept me updated regarding shiping for example.
ive never done full etch brass lits before and been meaning to, so will give it a go  with a 16mm Roundhouse live steam body I needto build. The bars are nicley made. not sure how best to use them mind!