Thread: 30 thousandth of an inch slot

Originally Posted by STAR

Rather then clog up the other brass back thread while ray is doing the high finance I have the following question.

It appears that ray is going to have it sloted to 20 thousandth of an inch to suit the saw steel we are going to get.

My question is about the Bunnings scrapers which are 30 thousandth of an inch. Is it an easy job to do at home to increase the slot by an other ten thousand to take the scraper steel.

I think it might be but do not know for sure and I do not want Ray to cater for different slots so it is at my end i am interested in.

I see where IanW is making a Bunnings scraper saw. I wonder if he will call it a Bunnings, or upmarket it to match the new saw nuts. Loooks like it will be a bastard for sure with mixed parentage.

I cannot wait to start on mine and my first one will be with the bunnings scraper as the steel from Ray will be put in cotton wool for a while until I get on top of this.

Peter

Hi Peter,

I was wondering about that as well, the brass should be soft enough to spread the slot to take the 30 thou scraper blades. A slight chamfer on the edge of the blade to get it started in the slot might be needed.

Later today I have to go to Bunnies so I'll pick up a scraper blade (if they have them) and give it a try.

Regards
Ray

Hi Peter,
Being only 0.25mm difference between 0.02" and 0.03", you might be able to ease the slot open with the blade in question.
Other options might be to cut it with a hacksaw blade (I don't know what thickness they are though) or maybe a metal cutting disk on a Dremel.

If you open the slot up more than the 0.75mm you could always clamp the blade in the slot by squishing the brass (sorry for using such technical terms ) in a vice.

Originally Posted by Vernonv

Hi Peter,
Being only 0.25mm difference between 0.02" and 0.03", you might be able to ease the slot open with the blade in question.
Other options might be to cut it with a hacksaw blade (I don't know what thickness they are though) or maybe a metal cutting disk on a Dremel.

If you open the slot up more than the 0.75mm you could always clamp the blade in the slot by squishing the brass (sorry for using such technical terms ) in a vice.

Squishing won't work as well as crimping the unfilled gap to almost nothing and then inserting the blade into the closed gap. This way the blade is held in the back under some pre-tension.

When I made my saw back from 3 mm brass angle I folded the angle over till both sides of the angle were touching. Then I made a slotted piece of wood and placed it over one of the long edges of the saw blade and placed the other long edge of the sawblade on the closed gap between the brass sides and just hammered the slotted piece of wood which forced the blade into the brass slit. Like Ray it would not surprise me if a 0.03" blade could not be just hammered into an 0.02" slot since I had zero slot in my case. It probably wont quite go in as far but as Ray says you could aways file a chamfer onto the inserted edge of the blade

BTW A 100 mm x 0.03" slitting saw blade costs $25 from Mcjing. A 60 x 0.02 blade is $10.
You will need a suitable arbor etc to hold these in - ie best left to a competent metal worker.

PS: There is more to folding the brass angle than it seems - if you wish to pursue this method it must be annealed first otherwise you will just crack the brass - the folding process also knocks & bends and hardens the brass in a major way so it needs lot of smoothing and sanding afterwards - once again it's best to anneal it before this is done as this helps the blade go in as well. Annealing means using a furnace - ie something not available to everyone.

Bob's right, a bit of interference fit is a good thing.

I filed a chamfer on the top of the scraper blade and started it in the slit
with a wooden mallet.



Moving to a bigger mallet, (if it doesn't fit, don't force it get a bigger hammer)
and hammered it down.



So the answer is, it goes on ok, a bit tighter than I would like, and you need a decent mallet,
and the blade must be fully supported. (I wouldn't go hitting the blade btw)

Regards
Ray

The scraper blade shape reminds me a bit of the Disston D9, style, might have a go at one when the weather cools down...

seem to recall a hacksaw blade is .025" Might be worth checking , if so grind the set off a new blade without blunting the teeth tips and you can open the slot up a bit.