Advice needed on LN #4-1/2 fault finding

Re: Lapping *LINK*

paul womack

>I think that successful (flat!) lapping depends on low loading of the abrasive, and uniform wear of the abrasive.

In conventional "engineer's" lapping, these is achieved by the lapping surface being a good deal larger than the worked item (which are normally smaller than planes!). The abrasive is ultra open coat (in effect).

A final problem (IMHO) with using lapping on large areas is that as the item (hopefully) approaches flatness, the area in contact with the abrasive increases, and the cutting pressure reduces.

I suspect these factors, in combination, render flattening some like a #6 or bigger increasingly difficult by the usual technique.

You know my solution!

BugBear


Flattening with Reference to a Surface Plate

Re: Advice needed on LN #4-1/2 fault finding

Derek Cohen (in Perth Australia)

>Do you flatten plane bottoms on a stationary belt sander? If so, do you add a piece of verified flat steel (or something similar) under the belt?

Hi Tony

No, I would not use my belt sander for this - I do noyt think that I could control the grind to do the precision work necessary. So I use a 1 metre long piece of 12mm thick float glass which is attached to about 50mm (2") of MDF. This then rests on a flat section of floor or a low bench. I glue to this lengths of belt saw belts.

My belt sander is only used for grinding the primary bevel of blades. I do add a piece of flat steel to the cast iron table to ensure a flat grind.

Regards from Perth

Derek

Re: Questions of uniform heat treatment?

Derek Cohen (in Perth Australia)

>Hi Dave

The reason I concluded that the blade hardness was not uniform (harder at the sides and softer at the centre) was this:

(1) After honing the blade I checked that the edge was flat.

(2) The blade started out cutting evenly but stopped after about a dozen shavings.

(3) If the blade was skewed so that the side edges projected a tad, then these were still sharp enough to cut fine shavings.

(4) A straight edge over the blade now revealed a slight hollow in the centre section.

What do you think?

Regards from Perth

Derek

Re: Lapping

Fred Krow

>"I think that successful (flat!) lapping depends on low loading of the abrasive, and uniform wear of the abrasive."

I agree, in my experience the most efficient material removal on a DMT Extra Coarse plate is by using mineral oil, when the oil becomes dark,,,,I will stop and remove the oil/swarf with a paper towel,,,apply some more mineral oil and countiue. I tried water but prefer the slightly thicker film of mineral oil.

Incidentely with cast iron, I can use considerable downward force and get good material removal,,,with a hardened tool steel blade one must be very careful to use rather light force or the diamond particles with pull away from the nickel bond,,,,this quickly destroys a DMT hone.

I must attempt to experiment again with abrasive paper glued to a glass or granite surface,,,,,it may be poor technique that causes convex (side to side) and rocker shape on all of my used Stanley planes. I have an old No. 5 Corsair that was ground flat in a machine shop for reference, good benchmark for testing on SiC paper.

Thanks for replys,

Fred Krow

Re: Questions of uniform heat treatment?

Fred Krow

>It is highly unlikely poor heat treatment (harden & temper), the A2 tool steel is Air Hardened in batches and is very thin cross section. If the LN blade is the early 1095 steel, the heat treat cycle is similar with quenching in oil most likely.

I believe the manuf/owner must have ground the blade on a powered wheel and exceeded the tempering temperature thereby making the center softer than the edges. The thin edge of a blade will easily overheat and very quickly soften on a wheel. The tempering temperature for 1095 at Rc62 is only 400 degrees F, exceed that and the Rc is dropped lower. I would speculate approx. 0.060" back from the edge, the hardness will be fine.

Regards,

Fred Krow

Re: Questions of uniform heat treatment?

Derek Cohen (in Perth Australia)

>Thanks for that info Fred. I'll grind the blade back a bit more on my (coolish) belt sander and see if the state of the steel alters.

Just for the record, the owner bought this LN in 2000 (so it would be pre-A2 steel), and I understand that it was never used! He recently upgraded the cap iron. In other words, to the best of my knowledge, the steel was as supplied by LN.

Regards from Perth

Derek

Re: Lapping

paul womack

>I must attempt to experiment again with abrasive paper glued to a glass or granite surface

You may find (at least some of ;-) this thread helpful:

UK Workshop thread

There are some details of Steve Knight's experience and practice.

BugBear

Why

Bill Houghton, sunny today yahoo in Sebastopol, CA

>would someone buy a new cap iron for a plane he hadn't used in six years?

LOVE . . .

Steve Mackay

>Or finaly found the "right" one. Or finaly uncovered the plane from "the pile".