Wednesday, 15 February 2012

Homemade shear scraper ... ...

I've had my lathe for a while now and although I have enough tools to keep me busy I'm always looking for new ones (can't help it, I'm a bloke) the trouble is that some of the more interesting tools can cost a bit, and as I try to save cash where I can, I can't really justify buying a £20 chisel, and that's actually cheap, some of the more expensive turning systems can cost over £100 !

But all is not lost, like a lot of wood turners I have made my own tools from scratch, adapted old tools into new tools, this saves money and gives you a better understanding of how things work.

So bearing that in mind I thought I'd make a shear scraper, now if you're wondering what one is have a look here - Robert Sorby Shear Scraper (opens in new window) this one is a small one, but even so it's £20 that could be better spent elsewhere.

This however cost less than £8 and I can make 2 handles and probably about 10 extra cutting bits, and I can make them to suit me, so in the long run I'll save quite a lot.

My newly built shear scraper -

Surprisingly easy to make, with the right tools.
This works well, but the cutting bit needs tweaking, I've only ground an edge on it to see how it feels to use it.

Close up of the cutting bit - 

Needs tweaking.

The handle is made by wrapping some natural fibre string round the metal and sealing it with glue  (I used Mod Podge on the last ones, this time I used pva) like I did for my Oland tools, I quite like the feel of the string, and I seem to be able to get a better grip on the handle compared to wooden handles.

To make this type of tool does require a little more work, and you'll need a tap and a tap wrench for threading the hole for securing the cutter, the shaft is a piece of steel bar, which you can buy from places like B&Q (my bit cost £5 and will make 2 tools)

Obviously you'll need something to make the cutter from, Ebay is your friend as it's about the only place I've found tool steel at (what I consider to be) a cheap price.

I got this piece for 99p (plus £2 postage) it's 1inch diameter, a good size for making cutting bits for the scraper.

Tool steel - 

It's best to use an angle grinder to cut this.

I already had the tap and die set, and I've always got nuts and bolts lying about, as it turns out cutting the steel was easy with an angle grinder, I wouldn't even bother trying to cut it with a hacksaw, you'll be there for hours.
Basically you need a slice a few millimetres thick (3 or 4mm should do) and you'll also need to drill a hole in it, which in theory sounds easy right ? I found it is not so, none of my drill bits would even make a dent in it, which resulted in much swearing.

The slice of steel for the cutting bit - 

Not as even as should have been, but it'll do.

And look I managed to drill a hole in it - 

It's meant to be off centre.

In the end it was my multi-tool and a small grinding bit that prevailed over the steel, I suspect it was heat related, by that I mean the drill bits weren't producing enough heat to soften the metal and cut into it, this stuff is very hard.

You will need to flatten a section of the steel rod, you can use square rod, but I wanted round, I used my bench grinder to make a flat section on one end, this makes a nice seat for the cutter to sit on.

Ready for the cutter - 

This flat section will house the cutter.

Once you have the end prepared you need to drill a hole in it and then use the tap to thread the hole, this will give you a good secure way of fixing the cutter.
Now when you need to drill a hole in any type of steel before you start drilling, mark where you want the hole and use a centre punch to make a small pit in the steel, this will make sure the drill bit goes where you want it to and not all over the place, and if possible use a post drill as this will make sure the hole is straight.

Centre punch (one of many I seem to have) - 

This one is quite new.

Basically you put the pointed end of the punch onto the mark you've made and give the other end a good thump with a hammer, easy peasy, then you can go ahead and drill the hole, try to get it in the middle of the piece of steel you're using as a shaft for the tool, another thing to remember is that when using a thin drill bit you need a quite high drill speed setting, and for larger drill bits you use a slower speed.

Hole ready to be threaded - 

I used an m5 tap for this.

The tap and tap wrench - 

Try and get a good quality tap for this.

Using the tap - 

All done.

There's a trick to using a tap and die set, you don't want to try and make the thread in one hit, you will most likely snap the tap in the hole, and they don't come out easy once that's happened. Take it slow, start turning the tap until it bites, you'll know when this has happened as it will get harder to turn, then turn it slowly, when it gets really tight, turn it about quarter to half a turn backwards, then start turning it the right way again (turn it the same way you would if you were doing up a bolt) and keep doing this until you've got the thread you want.

By turning the tap a little bit in the opposite way every few turns will clear any metal in the hole, it also helps keep the part of the tap that cuts the metal clear, just remember the tortoise and the hare story, slow and steady wins the race, and you'll get a better thread.

Then take your bolt, and a spring washer (this help keep things from undoing) and fix the cutter to the end, and that's about it,all you need to do now is grind the cutter in a way that suits the jobs you want to do, and if you get enough steel you can always make a variety of cutting bits.

The cutter fixed in place - 

Not the neatest of jobs, but it works.

I plan to make some different shaped bits for the scraper, and with the other section of steel rod I'll make another tool, which I'm going to put a bend in so that I can hollow out ball shapes, that way I'll have 2 tools that I can use, with out having to mess about changing cutters all the time, so really I've made more than 2 tools, for less than £10, saving a few quid, can't be bad.




If you're interested in the other tools I've made for wood turning here a link to the post, to save you searching - Oland tools (opens in new window)

Thanks for reading.

1 comment:

  1. I recently came across your blog and have been reading along. I thought I would leave my first comment. I don't know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.


    Susan


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