looking for cutter for manually cutting parallel grooves

[surplusjohn]

this is for a fine art printmaking application. ie engraving/ drypoint. i am looking for a cutter that would scrape fine lines into plexiglass. around 50 lines per inch, and an inch or so wide. EC Lyons makes an engraving tool called a half tone cutter that is the right idea, but only about 1/4 inch wide. I have one of these but need a wider tool. I don't know what it would be for but there might be a standard cutter for some other purpose that would fit the bill. could be tool steel or carbine, but this would only be used in acrylic or PETG or polycarbonate, never metal. and only used in a handheld tool holder. What i am doing is making clear plastic printing plates by scratching into the surface vs etching a metal plate. these plates are printed by forcing ink into the scratches and then wiping off the top surface so that only the scratches print. To print, heavy damp rag paper is placed on the plate with 3 layers of wool felt on top of the paper and then put through a roller press that forces the paper into the scratched grooves which picks up the ink. I imagen EC Lyons would make me a special tool but i wanted to ask here first, THanks

 

[sfriedberg]

1) Use a straightedge or similar tool to guide your narrow tool in parallel paths. Set uniform spacing by planting a tooth or two of the tool in the previously cut set of grooves.
2) Serration cutter for milling machine. These are generally cylindrical in shape, with multiple cutting gashes in the perimeter, each gash being shaped to cut multiple grooves. Mount it in a handle and/or grind away all but one flute of the cutter. 50 LPI is going to be hard to find, though, as most serration cutters have a larger pitch. Also there may be more of a radius at the bottom of the cut grooves than you desire.
3) Gunsmith's checkering cutter. Hand or power tools for cutting parallel decorative grooves in gun stocks. Available in several sizes, but probably not as fine as 50 LPI.
4) Use a coarser pitch tool, but overlap strokes with a fine pitch offset. I.e., cut 50 LPI with two strokes of a 25 LPI cutter. And the range of 25 LPI is probably readily available.
5) Do it old-school and cut each individual line by hand with a burin.

 

[Mtndew]

Know anyone with a wire edm? This could be made relatively quick. They could just wire out a 50 tpi style cutting edge on a 1" wide piece of steel.

 

[michiganbuck]

Might stacking sharpened .020 full hard shims make a suitable 50 lines per inch

 

[Booze Daily]

Might try to rig up something to hold a 1/4-20 tap sideways.

 

[Booze Daily]

Might try to rig up something to hold a 1/4-20 tap sideways.

Edit: That’s not 50 grooves, that’s .05 spacing.
Nevermind.

 

[L Vanice]

Thread pitch gages include lots of different standard screw thread pitch thin hard steel leaves, usually with sharp points. It is easy to find one with a 48 TPI leaf, but 50 would be harder to find. Metric pitches will include some sizes close to 50 TPI, like .5 mm.

This set has both 48 and 50 on the USA 60 degree gage. Note that Whitworth gages will probably not have sharp points, but maybe you would prefer their rounded points.

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There is a tool called a radius gage holder that would work to hold one of the pitch gage leaves while dragging it across the plastic.

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Larry

 

[sfriedberg]

Know anyone with a wire edm? This could be made relatively quick. They could just wire out a 50 tpi style cutting edge on a 1" wide piece of steel.

If we are talking about shop-making, a chunk of woodworker's cabinet scraper (non-burred), a triangular file, and (finish with) a sharp triangular Arkansas stone.

 

[Limy Sami]

Wht about a 50 TPI tap, .can't remember the name of the co that des the cheapies - someting exchange? ...out New York way ?????

 

[memphisjed]

Use hand or hammer graver and naw out 50 lines on a 1 inch wide price of w1. Harden and grind nose/front relief like a small line graver.

 

[sfriedberg]

can't remember the name of the co that des the cheapies - someting exchange? ...out New York way ?????

Victor Machinery Exchange yes, that's a decent source for special thread taps and dies.

 

[Limy Sami]

Victor Machinery Exchange yes, that's a decent source for special thread taps and dies.

Thankyou, had a quick look but couldn't find a 50tpi - I was thinking there's your ''all but ready made tool''

 

[johnmontrose]

A 0.5mm pitch thread chaser (Coventry die head) used like a planer tool and skew it so that the 50.8tpi is the hypoteneuse and the longer side of the triangle is 50tpi.

You might have to draw it at enhanced scale to see if the width increase of the grooves due to the skew is acceptable.

 

[henrya]

I’d love to see one of your prints.

 

[michiganbuck]

QT Op: (but this would only be used in acrylic or PETG or polycarbonate, never metal. and only used in a handheld tool holder.)
(around 50 lines per inch, and an inch or so wide. )
So the grooves would be .020 apart. How deep and wide would they need to be?

That is why I thought hard shim stock might work as the cutter bits, perhaps surface ground to .010" if .010 wide grooves would be the desired width, They might be set on a box holder and run like a shaper or planer operation.
With no shaper or planer machine one might vise the part and travel the shim tooled box cutter on a surface grinder or a mill using only long travel.
The shims perhaps .o20 x 1/2 x 6" " would be ground to be thin cutter tool bits on the surface grinder by grinding each shim end to .010 thin x 1/16 or 1/8th" length of tooth, with having clearance of 10*, and having a tooth face with no side clearance...but having a tooth face being a section of a 1/4" radius that would be perhaps .03 deep.

I would clamp the box holder on the wheel head of my B&S surface grinder and long-travel the part (with no crossfeed) for ten .001 passes / or twenty .0005 down feed passes.

Sharpening the box cutter for the first use, and resharpening when dull would be standing the box @ 10* and surface grinding .oo5 off the nose.
The cutter box might be 1"x 2" x 6" or what...with a 1.010 opening for the blade tool bits.

Hard shims are tough to grind because of heat, so would use my most open-wheel (46-I) , Wet with a full chuck load and very small down feeds, a slow long-travel, and a cooling pause at right and left long travel...might try one first to see how best to grind them... might need to hand notch the wheel OD with a parting wheel.

 

[surplusjohn]

Thank you for your suggestions. I actually did try a 4-40 tap but it doesnt dig in. Perhaps if I had a more rigid way of holding it. A fine hack saw blade cut off and held in a handle starts to work but not great. Thinking about this gives me some ideas on how to improve the saw blade idea. In the meantime I asked everyone lyons if they can custom make one for me.

 

[Ries]

They actually used to make machines to do this, a couple of hundred years ago. They used them to make engraving plats to print things like money. 30 years ago I knew a printm in Seattle who had one, but I can’t eve remember which one it was. But they do exist.

 

[atex57]

Check the tooth count on the edge of a file. Drag it along the edge.

Ed.

 

[michiganbuck]

Seems like a 4-48 tap would work if you could improvise about 50 pounds of pressure on it, and an incremental down travel...a clunker surface grinder could do that

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[surplusjohn]