Thread: Grinding and Honing A2 Blades Using Tormek T7

Originally Posted by Dovetail

Hi All,

I recently purchased a LAJ plane from LV together with three blades. I wanted a 25, 38 and 50 degree but ordered three 25s in error. LV were happy to exchange the blades but, of course postage would be my responsibility. I decided to grind the 38 and 50 on my Tormek T7. The grinding took some time, I can tell you! Unfortunately, reshaping a blade does. I roughly shape on a bench grinder and do the final bit on the Tormek.
I had set the Tormek bevel angle jig to 37 degrees anticipating that a microbevel of 1 - 2 degrees when honing would give me the result I was looking for.

Problem 1: The bevel angle when finished grinding was more like 41 degrees rather than the 37 I had anticipated! I don't know why. The edge of the bevel was on the wheel at the set up. Could it be that because I was grinding down the edge, the angle changed, becoming steeper as more material from the edge was removed? Yes. The wheel diameter is decreasing a little and the blade is getting shorter thus altering the projection from the jig. When removing a lot of metal it pays to check the angle frequently.

I suspect this is the reason and that the other alternative of the blade having moved in the Tormek jig is most unlikely. And if my reasoning is correct, how do I avert the error when I have a go at the next blade - grinding to 50 degrees? See above.

Should I set the grind up at say, 45 degrees and make adjustments to the jig along the way, or what?

Problem 2: Eventually, having achieved a clean hollow grind to 37 degrees, when setting up for honing with the Mark 2 Veritas jig set at 37.5 (or close to) degrees, the initial honing occurred at the back of the hollow grind at not at all at the edge until I had honed the hollow grind away in its entirety and ended up with a flat primary bevel! I would use a Texta to mark the blade and see where it bears on the stone and alter the jig.

The secondary bevel looks perfect.

Haven't got round to the acid test yet - actually using the blade.

Cheers
Brian

I hope this helps.

Thanks . Very helpful and essentially confirms my suspicions.

I'll grind the next one on the grinder - white stone - first. I don't have any sort of jig for this. It probably doesn't matter much because I don't think this grind has to be terribly accurate and I'll fix this on the Tormek.

Do I have to worry much about heat build up in the A2 steel? If so, is quenching the way to go or will micro cracks be an issue. I'm not sure how A2 rates against HSS which, I believe, can be heated to virtually cherry red without problems.

Cheers
Brian

Brian, don't know how much of this sort of thing you do, but I can recommend the Tormek BGM-100 for your bench grinder. I have one setup and the combination of bench grinder with white Alox wheel and a wet grinder is great.

http://www.tormek.com/en/accessories/bgm100/index.php

Being able to set up the Tormek jigs on both the wet grinder and the bench grinder saves a lot of time, and a lot of wear on the (expensive) Tormek wheel.

Another thing to say re the speed of the business, and I quite agree with that doing most of it with a bench grinder is the way to go, that once you transfer to the Tormek then use lots of pressure and deglaze the wheel every couple of minutes.

Quenching is not a good idea cos of microfractures in the steel; HSS you can go to dull red under natural light but like you I'm not sure whether A2 is closer to HSS or HCS.

You can by taking your time do the whole bevel on the spark grinder and then just use a benchstone to create and refine a micro bevel; easy to freehand it with that thickness of blade with a hollow ground bevel. Just takes a few strokes on each grit.

The point of greatest risk doing the whole process on the spark grinder is when the whole bevel is being ground and when you come to the corners - cos they dissipate heat more slowly than the centre. This is where you might get down to only one or two full passes before placing the blade onto another like it as a heat sink to cool it quicker.

I agree with Fred and Ern. Don't quench. I sit a hot blade on the lathe bed. 40 feet of heat sink.

STOP WITH THE GRINDING!!!!!!

Did I make that clear enough?

You are trying to use a BD plane sharpening technique for BU plane blades. With the high angles on BU plane blades you need to use microbevels.

Further more - this is very important - if you plan to camber the blades, then you ONLY want to use the blades with a 25 degree primary bevel. Why? Because it is easier to add a camber to a low profile where there is less steel to remove, than a high profile (where there is much more steel to remove).

For details of this, read my article at The secret to cambering Bevel Up plane blades

While this appears at first to be about creating the camber for a jack plane (on a LA Jack), it is about the ease of cambering for all blades on BU planes.

Note: if you do not plan to use a camber on your blades, then go ahead and regrind your blades to the angle you wish. Once you start you will wish you had not!

Regards from Perth

Derek

One more point ...

I only use 25- and 50 degree bevel angles on BU plane blades. This equates to a 37- and 62 degree cutting angle, respectively.

I have two 37s, one straight for the shooting board and one cambered for planing across grain when leveling a board. The 62 is cambered and for smoothing.

Actually I also have a 35 degree bevel (47 degree cutting angle) with a 8" radius for use as a jack for rapid removal of waste, but that is probably not what you are after.

I do not see the point in a 38 degree bevel (50 degree cutting angle) for most of the hardwoods I work as anything less that 60 degrees leads to tearout. The strength of the BU planes lies in their ability to work at extreme angles (low and high), which BD planes cannot get to. For moderate grain I use BD planes. Why? Mainly because I prefer to freehand hone blades, which is fine for BD plane blades, but high angle BU blades need to be honed with a guide.

Regards from Perth

Derek

Derek must have much more patience than I do.

These blades are 3/16" thick, and certainly cope with bevel reshaping on a Tormek and also with care on a spark grinder.

But with that kind of grinder use a light touch, dress the wheel often and use a cheap jig like this one to keep the blade square to the wheel.

As it happens I'm facing the same task, have acquired an assortment of irons with new and 2nd hand V. planes and started in on rationalising the bevel angles.

Hi Ern

I doubt that I have more patience than you .... but I have been using BU planes for several years and am voicing my experience.

I hollow grind all my blades on a Tormek, chisels and both BU and BD plane blades. The high angle BU blades are given a micro secondary bevel on a 25 degree primary bevel/hollow using a honing guide. The low angle BU blades are freehanded on the same 25 degree hollow - no secondary bevel needed. I learned that this saves a great deal of time and effort when honing these blades.

Regards from Perth

Derek

once you transfer to the Tormek then use lots of pressure and deglaze the wheel every couple of minutes.

hi Ern, how do you deglaze a Tormek wheel please?

That noise you're hearing is the penny dropping!

I was indeed planning to camber the blades but, I must say, not to the extent that you have Derek. In fact after spending ages wet grinding then honing yesterday, using the camber wheel with the Veritas honing guide, I thought I would achieve a camber for the microbevel. Well, I did, but it is a micro, micro camber and I foresee many more hours on the Shaptons before a visible (or functional) camber is achieved.

I'm now left with two 25 degree blades one of which will end up with a 50 degree microbevel only as I think grinding - whether or not one intends to camber it - requires not only a lot of time and effort but there is a considerable wear and tear on the equipment. I've attached a couple of images showing just how much steel has been ground off trying to achieve a 38 degree bevel compared to an as yet untouched blade.

Derek, am I correct in noting that the microbevel on the blade shown in your posting on "How to camber .........." doesn't actually extend to the edges of the camber. Or is it a trick of the light?

Thanks to everybody for your contributions. I'll never stop learning....

Cheers
Brian

Derek, am I correct in noting that the microbevel on the blade shown in your posting on "How to camber .........." doesn't actually extend to the edges of the camber. Or is it a trick of the light?

Hi Brian

That is a trick of the light, although I think that I did not put as much pressure as I could have on the guide for the corners and the microbevel at that point is smaller.

I pleased the article made sense and could help.

Regards from Perth

Derek

I don't do a lot of grinding but whenever I do, I always wish I had a decent jig. I've been looking around for ages in an interested, but not fanatical way, for a jig like you have identified in your post, Ern. Thanks for the heads up. The Tormek BGM-100 looks great but at nearly 3x the cost...Hmmmm. Think long term and always get the best you can afford is my usual maxim.

Well, I've gone so far with the 38 degree blade, I'll try it in the plane now and see what results I get. At this stage, I might be happy to simply get a shaving that doesn't result in tram tracks on the stock.

In the meantime, I'll need to consider my plans for the third blade. I'll leave the standard primary 25 degree as is but I wonder whether or not there is any chance of achieving an accurate 50 degree bevel using the Veritas honing guide with the cambered roller on a really coarse wet & dry al la Scary Sharp?

The Tormek booklet describes how to achieve a camber using the wet wheel. I previously tried this with a Stanley blade and discovered that not only am I heavily right handed (even when trying not to be) but at best, the results were unacceptable with both sides having more ground off but still square to the stone; three steps - if you know what I mean?

Cheers
Brian

Brian, I'd wonder about the effect of coarse W&D on the guide roller. Dunno; just thinking out loud.

Another thing I do that may be of use to you is when starting with a small secondary bevel on a blade I write the angle on the primary bevel with Texta. Saves a bit of peering and wondering, cos the 2ndary bevel is too small to start with to fit my bevel gauge.

Jill you deglaze the wheel with the supplied (re)grading stone.

Brian, if you're on a mission with steel removal with the Tormek, you can use the truing tool to take a generous bite and pass it across the wheel quickly (as mentioned in the manual). This will leave grooves and effectively increases the pressure of the bevel on the wheel.

As for angles, while the V honing guide is wonderfully accurate piece of kit, on the Tormek side of things minor variations in setup (beyond my ability to control anyway) will lead to minor variations in angles and sometimes squareness. And this is something I've had to learn to live with.