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bobbybeef
06-24-2005, 02:57 AM
The fine finish on some engineering exhibits is I understand called draw filing.
How is it done? Is there an easy way to get this silky smooth finish?
Grateful for any comment.
bobbybeef.

Ted Coffey
06-24-2005, 05:44 AM
Draw filing is simply pulling or drawing a file toward you at a right angle (more or less) to the work as you would use a draw knife on wood.
Finish is controlled by selecting the various coarseness of files.

[This message has been edited by Ted Coffey (edited 06-24-2005).]

Al Messer
06-24-2005, 08:55 AM
And keep your Chalk stick and File Card handy and keep those file teeth CLEAN!!

Swarf&Sparks
06-24-2005, 10:41 AM
Amen Al!
Perhaps you should enlarge on your comments though.
Rule 1: clean the file
Rule 2: clean the file
rule 3, 4, 5 (OK, you get the message)
Rule (what are we up to now?)
then rub ordinary blackboard chalk into the file teeth, take a deep breath and....
holding the file flat to the work, at right angles to the stroke, in both hands....
you will feel the file cut, if it's in good condition. If not, clean it AGAIN!. You really don't need to see a 25 thou pin mark in a surface you've just spent 30 mins filing. Catch my drift?
The chalk helps avoid filings (swarf) sticking to the file teeth. But, please, don't think I'm joking when I say, clean the file with a card or wire brush every 3 - 4 strokes.
Rgds, Lin

Evan
06-24-2005, 10:41 AM
This is an example of draw filing on the edge of aluminum angle. This is the file finish, no polishing. You must clean the file every stroke so it doesn't pin.

http://vts.bc.ca/pics/file1.jpg

Your Old Dog
06-24-2005, 10:46 AM
The chalk board chalk is optional but it does help save the file from hanging onto the swarf so hard.

And, you don't pull the file, you push it. Lay the file flat on the edge of the work that is secured in a vice and take one deliberater push across the work. Then, move the file a tad and do the same being careful not to use the portion of the file you just used. After several pushes, each using fresh clean teeth, you have to card off the swarf with a file card. Fail to clean the file, or use dirty section of the file and you score the work you are trying to dress up. Much easier to do than it is to describe!! I like using a 10 - 12 inch millbastard file the best.

It's a super quick way to get a good lean looking edge on many projects. Good luck....

[This message has been edited by Your Old Dog (edited 06-24-2005).]

Swarf&Sparks
06-24-2005, 11:00 AM
OK YOD, some truth there. But a mill bastard?
10" mill fine works here.
I shoulda mentioned too, if you expect any kinda flat, do not put pressure on the ends of the file. You will bow it and curve the surface. Rather, put your thumbs in the middle of the file and try to even out the pressure across the surface of the work.

Paul Alciatore
06-24-2005, 11:47 AM
I have both pushed and pulled but it should be mentioned that when draw filing, the crests of the teeth are set at a shallow angle to the direction of motion and they must be going "forward" in the sense that the stock enters the cutting edge from the same side of the tooth as in normal filing. So, for most files, the handle will be on the left when pulling and on the right when pushing.

Files with teeth set at an angle across the blade are held perpendicular to the work for draw filing to produce this shallow angle. A file with teeth cut straight across could also be used for draw filing but it would be held at perhaps a 70 or 80 degree angle to the work, instead of perpendicular. Again, the teeth must be oriented to cut in the forward direction.

I believe that the reason it produces such a nice finish is because each tooth is in contact over a much longer section of it's edge and this helps prevent any oscillation of the file in an up/down direction as can happen in normal filing. I have frequently seen a file produce a washboard surface with a spacing approximately equal to the file's tooth spacing. I normally correct this by changing the angle of the file and draw filing is just an extreme angle change.

Paul A.

Your Old Dog
06-24-2005, 01:30 PM
Push - Pull? I stand corrected I guess. I've never picked up a file with the tang anywhere but in my right hand. You're right, if the tang is in left hand you would pull http://bbs.homeshopmachinist.net//biggrin.gif Where was that post about how many forum members does it take to screw in a light bulb LOL...

Swarf&Sparks
06-24-2005, 02:48 PM
They just hold the light bulb and pontificate. The world revolves around them http://bbs.homeshopmachinist.net//biggrin.gif

bobbybeef
06-25-2005, 09:14 PM
Thank you guys,
Your instructions were followed to a tee. Stuffed up a few times and really learnt how to clean a file,after every stroke.
tried it on steel and brass with good results. not as good as Evans'on the aluminium. I need to get a few files just for brass. Had some difficulty with one piece of steel on a brass attempt. sure can ruin your day.
Thank you everyone,
Bobby.

chief
06-26-2005, 08:30 AM
In addition, when you get your new files, break them in on a piece of scrapn ssometimes new files have burrs and will gouge the work.
People underestimate a file's value. They can be very useful and save time.
Years ago I was handed a set of files, a block of aluminun and a can of dye and told
Once you make the block flat and square then maybe we will teach you how to use a hacksaw.

BillJ
06-27-2005, 02:32 AM
When I did forestry work in my youth our brushhooks were kind of like a short machete blade on a 3/4 axe handle and we sharpened them by drawfiling with a mill bastard file.

They would easily shave your arm and would fell a 2 1/2" stem with one good swing if you hit it on the correct angle. I could never have got that kind of edge with a normal filing stroke.

Darn near took my own head off on a deflection one day, but it was the back side of the blade that hit my neck.

Evan
06-27-2005, 11:12 AM
Bobby,

Keep a separate set of files strictly for non-ferrous metals like brass and aluminum. Never use them on iron. My aluminum files are nearly 30 years old and are just starting to get nicely broken in.