Hand Tools Archive

Product Dev. & Some User Data *LINK* *PIC*

E Phillip Smith
There's been good discussion recently around plane blade product development by Lee Valley via accelerated testing. I spent much of my career in R&D developing new products and we ALWAYS did accelerated testing. I just is not commercially viable to development new products otherwise. I've looked at the Lee Valley data set and it is impressive. See link below for their summary data. I liked the data so much that I've a set of the chisels and plane irons. The chisels hold and edge well, better at chopping than my CPM 3V chisels. Don't have data on plane irons yet.

Reason for this post is that I have many of the plane irons that they list in the summary data and in particular CPM high carbon M4. Other than Derick I'm likely the only forum user to have experience with M4. Bruce Norton and I made 4 M4 plane irons years ago when we working with Wiley and co. to make 3V plane irons. One of the irons lives in my Clifton no. 5 and the other lives in my LN 4.5.

From Crucibles web site M4's composition is 1.4% carbon; 4% Cr; 5.5% Tungsten; 5.25% Mo; 4% V for a total of 18.65% of Hard carbides. It's also hardens up to RC 64.

From Lee Valley's web site relative wear and ease of sharpening are:

Ease of sharpening O1 - 10; A2 - 6; V11 - 6.5; M4 - 1 From experience these all look good and if anything the 1 rating for M4 is a little generous. Even with diamond it is slow compared to the above steels and the CPM 3V that I've used. When Bruce and I made the M4 irons machining in the annealed state was no problem but once hardened this steel very wear resistant. If memory serves correctly the bill for surface grinding 4 irons after heat treating was $100.00, lots more that the bill for the 3V irons. Polishing the back even with diamond was much slower than any other steel I have used. Once the back is polished the plane iron takes and keeps a very good edge. As much as I like this iron I can't imagine anyone making a commercial iron. Manufacturing cost would be too high and customer relations would be terrible. Without experience with diamond honing this steel is impossible to sharpen.

Wear Rating O1 - 1; A2 - 1.5; V11 - 9; M4 - 9. From experience the O1, & A2 are where I would expect. Haven't gotten around to using the V11 and my CPM 3V is somewhat better than the A2. The M4 is in a different class than the other irons.

Now for some user data. Last year I finally got around to finishing a table top for my son. Top is walnut with lot of curl/figure. Top is: 34" wide and 64" long approximately 1" thick with 3/8" X 1.5" bevel on bottom of table. The table was larger than I was willing to try running bevel on table saw or shaper so I cut the bevel with a LN 4.5 hand plane with M4 plane iron. Iron was sharpened with 1 micron diamond on cast iron plate. It's the only effective way to sharpen these irons. Plane was set to take shaving of 0.002 to 0.003 inches so I assume average shaving of about 0.0025". At the center of the bevel the thickness of bevel is 5/16" and at edge it is 3/8" so with a shaving thickness of 0.0025 that works out to 125 to 150 passes per edge assuming you have perfect registry with is not likely. That works out to aroung 2000 to 2500 lineal feet of shaving by time I was finished. Plane was still cutting cleanly at finish. Pictures of table follow.

First is picture of planning end grain of table to clean up saw marks.

Next is picture of line for edge of bevel marked with gel ball point pen.

Edges were planed end grain, edge, end grain, edge.

End grain bevel.

Edge bevel.

Some pin knots at finish.

Table top was sanded to 220 grit sandpaper, stained with gel walnut stain, and finished with 2 coats of conversion varnish.

First is picture of table bottom to show some of the figure.

Next is picture of finished table.

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