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setting up the tool rest on a bench grinder

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Forum topic by thedude50 posted 552 days ago 3549 views 2 times favorited 39 replies Add to Favorites Watch
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thedude50

3437 posts in 979 days


552 days ago

I just got a new bench grinder A Porter Cable 8 inch with a lamp and variable speed it is a slow grinder and works very well. Of coarse I removed all the guards as i wanted to use my One Way Wolverine Jig on it. The grinders base was so high I didn’t have to use the 1/2 inch riser block for the grinder like i did for my old 6 inch grinder. I mounted the tool locks centered under the wheels and was very happy with how straight they are. I then went to set up the tool rest for the regular tools. it is the flat square tool rest it is nice and wide and very stable. This is when it hit me How do I set this up for 25 degrees. I simply took a chisel I have that is new and has a known 25 degree bevel on it and aligned it to the wheel. that got me to thinking and I dont have an answer for this one on the top of my head but how do you set up a tool rest for bevels you dont have a reference for to get say an accurate 27 or 35 degree bevel on. Say I want to regrind some chisels to this new bevel for pounding out mortises or some other reason. I figured a set up block would work but what is the best way to get an accurate bevel to use as a reference for setting up the grinder. ALL HELP IS APPRECIATED. thanks Lance

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech


39 replies so far

View Jim Jakosh's profile

Jim Jakosh

10248 posts in 1607 days


#1 posted 552 days ago

Use a Wixie box to set the table angle!!

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!!

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thedude50

3437 posts in 979 days


#2 posted 552 days ago

I tried that it does not work because the wheel is an angle while I thought it would be fine it was off by miles

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech

View waho6o9's profile

waho6o9

4448 posts in 1078 days


#3 posted 552 days ago

Basically the left indicator is the diameter of the wheel and the
right indicator is the angle you want.

Except you need the indicators reversed if I understand the
situation correctly.

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thedude50

3437 posts in 979 days


#4 posted 552 days ago

Yes as you are trying to adjust the grinder to the tool rest so you can not simply place the table at 25 degrees the bevel wont be the same because of the wheel Geometry. I discussed this with my wife she is a geometry teacher and said she can figure this out but that some poor woodworking math wiz most likely has already figured this out so I went back to the search engines thank god for Google There I found this link after many hours of searching different phrases. Here is the best answer I have found I will be making these jigs on Monday as I am Off to Pasadena in the morning for the wood show So Many tools so little time the trip should be great but I am on a tight budget as the state is screwing me again.

So if you like me and you want to get good results off your bench grinder so you can go from bench grinder to tormek to Whetstones or how ever you get a razor edge this is the key to setting up your grinder the right way. Click Here for the PDF to cure this Problem

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech

View Wildwood's profile

Wildwood

859 posts in 636 days


#5 posted 552 days ago

http://www.harborfreight.com/dial-gauge-angle-finder-34214.html

These angle finders with magnetic base will get you close. Can pay a little or lot guess they all about the same.
This will tell you angle of the table in relation to wheel most of the time. I leave the table at 90 degree if free hand sharpening a gouge or skew. I was disappointed with angle finder for set up to do scrappers. So just lay scrapper on table rest and adjust to wheel.

-- Bill

View lwllms's profile

lwllms

528 posts in 1783 days


#6 posted 551 days ago

Because you’re grinding on the tangent of the wheel, the tool rest needs to be set differently for the thickness of each tool. I make grinding templates the same thickness of each of the tools I grind. These are about 3/4” wide and 6” long. I cut a 25º bevel on one end and a 30º bevel on the other. The tool rest is set by eye so that the wheel contacts the bevel of the template, using the desired angle, in the center.

If you set the tool rest for a 3/16” thick tool and grind a 1/8” thick tool your bevel will be more obtuse than desired. If the rest is set for that same 3/16” tool and you grind a 1/4” tool the bevel will be more acute than desired. The grinding templates I make are the easiest way I’ve found to deal with grinding on the tangent of a wheel. Angle finders just don’t work on grinders.

View rance's profile

rance

4106 posts in 1662 days


#7 posted 551 days ago

Lance, The pdf you provided seems to be a decent method, however, it may not work equally well for all users. It seems that some of the newer grinders have less and less of the actual wheel exposed thus not allowing a longer stick to be effectively used. The pdf does mention this though. In addition, the grinder table that comes with your Wolverine jig sits even higher, further limiting the use of this kind of jig.

They also do not address the issue of wheel wear affecting its use. That should be considered.

After thinking about this a little more, realize that the thickness of the blade being sharpened will have an effect on the Bevel Angle as defined in Figure 1 in the pdf. In other words, to get a 25 degree angle on a thin blade will require a different grinder-table angle than when sharpening a thick blade of the same angle.

SketchUp, SketchUp, SketchUp…

From my calculations(which could easily be wrong), using a new 8” wheel, the table setting for an 1/8” thick blade is 2.3 degrees different than for grinding a 1/4” thick blade. From this, I would say that the method in the pdf is in error. Actually this error would be inherent with many other gauges commonly sold. Do any of the gauges take the thickness of the blade being sharpened into consideration? Hmmmmmmm. But in all reality, unless you switch from grinder to grinder, 2.3 degrees may be a moot point. The biggest effect I could see is possibly grinding off more material than necessary, thus slightly shortening the life of the tool.

Edit: I see that while typing, lwllms has pointed out the same issue with the thickness.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View thedude50's profile

thedude50

3437 posts in 979 days


#8 posted 551 days ago

Ok guys I will send that information to the math guy that came ofp with the grinding templates so he can rebut this or confirm it . On the size of the wheel I think he did address it at the beginning or on the web page I got that linked to the Pdf I posted. I will check on this. My desire is to get an accurate grind on my planer blades that when I take them to the Tormek I am not regrinding a new bevel rather I want to be smoothing the bevel I already ground and I want it to be the same as the accurate bevel I got from the Tormek. Also I want to build an accurate set up block to hone my bevels with a honing guide. On most of my work I do this freehand but there are times when free hand is not the best way like when doing the Iron for my Shoulder planes trying to hold those little suckers straight is a bear I would give in and use the honing guide if I knew my set up was dead on accurate to my Tormek.

I want to thank you all for your help solving these issues once we do. I think A blog is in order to teach everyone the methods we figure out together so others don’t have to struggle with Geometry and can get accurate repeatable results on their grinders.

Have any of you guys used the Tormek Grinder jig and if so does it address these issues? I am not married to the ONE Way jig and I can afford the Tormek Jig and if it does address these issues. I could be sold very easily.

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech

View rance's profile

rance

4106 posts in 1662 days


#9 posted 551 days ago

Lance, I stand corrected. I went back and read more of the pdf(rather than just looking at the pictures). He in fact admits to the thickness affecting the accuracy. He also mentions referring to graphs which are included in Hollow Ground Geometry to determine the necessary angle corrections.

I think it is kind of odd that having seen many of these type of angle jigs, this is the first time I’ve ever heard of the need for corrections due to blade thickness. Interesting. I’m glad you posted this.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1616 days


#10 posted 551 days ago

Dude
I have looked into the tormek for a cupple of years
and as I remmember it they only thought of the wheel diameter and the bevel angle
with that anglefinder Jiig
nothing about thickness on the blades

thanks for bringing this up another new for me :-)

Dennis

View Joe Lyddon's profile

Joe Lyddon

7447 posts in 2553 days


#11 posted 551 days ago

Lance, I’m not much into this… BUT… will this work?

Take, say a piece of 1×2 at a good length…

At one end, using a protractor, draw and cut the desired angle at an Endpoint.
This is the sharpening angle you want to grind on your wheel…

Lay the board on your adjustable grinding table & move your table around at the various angles until you can get your Wooden Angle against your grinding wheel flush & tighten it.
This should be the angle required.

Place your tool onto your table (like the wood was) and grind your angle.

Does that make sense?
... or am I way off the mark?

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: http://www.ncwoodworker.net/pp/showgallery.php?ppuser=1389&cat=500"

View CessnaPilotBarry's profile

CessnaPilotBarry

864 posts in 611 days


#12 posted 551 days ago

I cut 1/2” – 3’4” thick scrap sticks to the various angles I want to grind. Next, I make a mark on the end of the stick, distanced from the bottom edge equal to approximately half of the thickness of the tool I want to grind.

The mark is KEY, the angle is not enough.

These sticks are slid up to the wheel with the mark touching the wheel and I adjust the rest to match the stick.

Lee Valley sells a setup block that work exactly the same way, included with the Veritas rest but apparently not available alone. Scroll down to VERITAS ANGLE SETTING GAUGE

My sticks have one angle at each end. Five degree increments from 20-55 degrees, and a 27, took about 10 minutes to make. They work GREAT, account for wheel wear, and angles are easily repeatable.

-- It's all good, if it's wood...

View Dusty56's profile

Dusty56

11605 posts in 2189 days


#13 posted 551 days ago

Very interesting post , dude. Thank you : )

-- When you arrive at my front door, please knock softly but firmly. I like soft , firm, knockers : )

View Bill White's profile

Bill White

3188 posts in 2462 days


#14 posted 551 days ago

This makes my head hurt.
I just adjust the rest to the blade, grind, hone, I’m done.
The obsession with accuracy to the nearest .000005” in woodworking has become absurd. Just know that I’m an old fa@t, and learned most of my skills (such as they are) from folks who did not have microscopic measuring devices unless they were working in a machine shop. I do use precision devices when metal working.
Know that I’m not beatin’ up on those who wish to use the after market devices which promise extreme measuring. I just don’t want to deal with changing batteries every 10 minutes.
Makes ya wonder how the old masters ever made anything using a ruler, a story stick, and a compass.
I’ll put my planes and chisels up against any of those sharpened with a zillion bucks worth of “stuff”.
There! I feel better now.
Bill
Bill

-- bill@magraphics.us

View rance's profile

rance

4106 posts in 1662 days


#15 posted 551 days ago

+1 to Bill.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

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