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Grinding wheels
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=37912		 Page 1 of 1
Author:  WendyW [ Thu Oct 04, 2012 2:19 pm ]
Post subject:  Grinding wheels
I would like to order a Carruth scraper, after reading what everyone has been saying in another post. The problem is I don't have a grinder for sharpening it. So now I'm trying to justify buying a grinder, so I can order the scraper gaah So my questions for all of you are;
1)What do you use your grinder for?
2)What INEXPENSIVE grinder would you recommend?
Thanks, Wendy
Author:  Michael.N. [ Thu Oct 04, 2012 2:41 pm ]
Post subject:  Re: Grinding wheels
Never liked the idea of a powered grinder. Scare me although I'm sure they are very safe if you observe all the rules.
I use a hand crank Grinder. Takes a bit of getting used to.
I use it mainly to sharpen blades, that and a 8,000G waterstone. It also works well on my 'Carruth copy'.
Author:  Markus Schmid [ Thu Oct 04, 2012 3:17 pm ]
Post subject:  Re: Grinding wheels
Hi Wendy,

Two months ago I was stuck at about the same point. I had (still have) a cheap, small bad grinder with a coarse wheel and a crappy small belt sander attached (shakes like hell) and I didn't really want to buy the nice scraper just to ruin it on that thing or upgrade with a 700$ grinder. So I first made my own scraper out of an industrial 3mm thick hack saw blade scrap, and it worked just fine. Due to the coarse wheel did not produce the ultimate surface quality like my "normal" scrapers do, and it doesn't hold the edge as I would like it would (I didn't even attempt to re-harden it after shaping (= overheating) it on the grinder, but it works!

Then, for the price of about the cost of the Stradivarius-Hutchins-Carruth scraper I found a used grinder (ca. 30 years old) with a nicely adjustable and stable tool rest (this is crucial if you don't want to build your own tool rest) and a fine grinding wheel (white aluminum oxide, these run a bit cooler than the gray or green silicium carbide grinding wheels). Now I get a really nice scraped surface with my shop made thick scraper. I then also (finally!) bought the stewmac scraper which simply saves me taking it to the bench grinder every two or three days!

If you are on a budget I recommend you to get a used high quality grinder, if possible with a fine aluminum oxide wheel and a stable, angle adjustable tool rest. When new, those quality grinders were in a price range starting at about 500 to 600$ (at least here in Europe, possibly in the US quite a bit less). If you only want to use the grinder for sharpening your scraper it doesn't matter if the wheel is not square anymore, but must likely a used wheel will be better balanced (centered) than a new one, which is what counts.

Theoretically, it is possible to sharpen the scraper decently with a bad grinder equipped with a 80-grit wheel, but it would not be much fun (noise and vibration), and an additional or at least tweaked tool rest would be a must. You can sharpen it not-so-decently with just any grinder and a coarse 36-grit wheel.

Hope that helps! ;)
Author:  Tom West [ Thu Oct 04, 2012 4:36 pm ]
Post subject:  Re: Grinding wheels
A powered grinder is one of the safest of the power tools. Not like the more visious finger removing table and band saws, meat grinder jointers,and do it all shapers. Use a good wheel,set the tool rest right and wear goggles and generally grinders are your friend to sharpen drill bits, chisles, and plane blades etc.
Tom
Author:  Chris Pile [ Thu Oct 04, 2012 6:48 pm ]
Post subject:  Re: Grinding wheels
Quote:
A powered grinder is one of the safest of the power tools. Not like the more visious finger removing table and band saws, meat grinder jointers,and do it all shapers. Use a good wheel,set the tool rest right and wear goggles and generally grinders are your friend to sharpen drill bits, chisles, and plane blades etc.


Absolutely right, Tom! You want to talk about dangerous tools? Let's talk drill presses!
Author:  Tom West [ Thu Oct 04, 2012 7:50 pm ]
Post subject:  Re: Grinding wheels
Sorry to upset you Filippo.
Tom
Author:  Beth Mayer [ Thu Oct 04, 2012 8:17 pm ]
Post subject:  Re: Grinding wheels
Hi Wendy. Nice to see another AZ gal on the OLF!

I was surprised by the responses here. I bought an inexpensive Duracraft pro slow speed grinder, which seems to be more thn adequate for the job. It does not have precision tool rests but does come equipped with ones that stay in place where you tighten them and really, that seems Tom be the only requirement. Al tells you how to set up the grinder to do the job. I think I paid 40 $ or so for this grinder.

Enjoy the "cool" temps ( we only got to about 99 degrees here in Tucson today)!

Beth
Author:  Trevor Gore [ Thu Oct 04, 2012 8:26 pm ]
Post subject:  Re: Grinding wheels
I use a Ryobi bench top grinder like this. I've had it for ~10 years, works fine and it's had zero mechanical/electrical maintenance. Best to use it with an aftermarket tool rest, but easy enough to make your own. It still has its original wheels installed. The wheels, of course, have to be maintained, but a tool for this came with the grinder. Truing the wheels has to be performed periodically, but you should be able to get an industrial diamond to do this for ~$15 or less.

I would find it hard to do without a decent grinder for machining primary bevels on edge tools and even truing up pieces of shell. Have to be careful not to over-heat steel tools, though, but it is easy enough to rig a water drip to keep the tool cool.
Author:  nyazzip [ Thu Oct 04, 2012 9:20 pm ]
Post subject:  Re: Grinding wheels
i don't see the need for a grinder to put a nice edge on a scraper. i use a surfacing stone and various grits of sandpaper for scrapers and most other blades. for the scraper i use a level as a support to keep the scraper perpendicular on the surfacing block/sandpaper.
i bought my surfacing stone some years back at Woodcraft i believe; it is just a slab of marble that has been machined perfectly flat. a piece of granite counter top would work quite well, and plate glass, or even just regular window glass if you are careful
Author:  nyazzip [ Thu Oct 04, 2012 9:33 pm ]
Post subject:  Re: Grinding wheels
i actually got a Tormek T-7 awhile ago, it is a sweet machine, but i didn't get it for scrapers; i got it mostly to grind new edges on eBay tools that have been abused. maybe i'll give the hollow ground scraper a whirl
so to directly answer a part of Wendy's question: i wouldn't recommend a "cheap" grinder; you need low RPM, and ideally water cooling, to preserve the temper in the metal.
Author:  Michael.N. [ Fri Oct 05, 2012 2:35 am ]
Post subject:  Re: Grinding wheels
I don't know much about powered Grinders but I think that Al is creating the burr on a fast, dry grinder. The metal is barely touched on the stone, using a fine wheel.
Author:  Trevor Gore [ Fri Oct 05, 2012 3:04 am ]
Post subject:  Re: Grinding wheels
Michael.N. wrote:
I don't know much about powered Grinders but I think that Al is creating the burr on a fast, dry grinder. The metal is barely touched on the stone, using a fine wheel.

Al uses a fast grinder on his thick scraper and barely touches the wheel, because barely any material needs to be removed to create the hollow ground edge and consequently any temperature rise in the tool is negligible. The scraper can then be used in this condition or have the edges and faces honed to produce a very sharp, hard, dead square edge which scrapes quite well. I actually prefer card scrapers, but I've been using them for a lot longer and I don't do much by way of arch tops and recurves.
Author:  Arnt Rian [ Fri Oct 05, 2012 3:05 am ]
Post subject:  Re: Grinding wheels
I use a grinder, but several people have commented that you can use an ice skate sharpener for this. Skates have steel of similar thickness, and are sharpened with the same hollow grind as Al's scraper.
Author:  klooker [ Fri Oct 05, 2012 6:39 am ]
Post subject:  Re: Grinding wheels
I'm a fan of older grinders. Check Craigslist or you may have a surplus machinery dealer in your area? School auctions are also good but I think most have sold off all of their shop equipment.

The old grinders have heavier cast iron construction - extra mass is good in a grinder.

Friable wheels are a good idea but cost more and are not entirely necessary if you use a light touch. If you like to build instruments, having a light touch shouldn't be an issue.

My grinder is usually used for reshaping damaged cutting tools or making custom new tools, sharpening lawn mower blades, splitting wedges, axes etc. From a guitar building standpoint, I think Filippo has a great idea of putting a buff on one side for polishing metal parts.

If you don't mind doing a little metal working, here's how I made my rests
Cut off a piece of angle. drill & tap.
Image
Get out the hack saw or put a metal blade in a jig saw. I was lucky to have access to another grinder to help with the job.
Image

I don't have any pictures but the other pieces were made from flat stock using a metal cutting blade in a jig saw, drill and grinder.
Image

Kevin Looker
Author:  Tom West [ Fri Oct 05, 2012 7:42 am ]
Post subject:  Re: Grinding wheels
Arnt:What a super idea about using a skate sharpener!!! The ideal radius I'm sure.
Tom
Author:  Mark Fogleman [ Fri Oct 05, 2012 8:34 am ]
Post subject:  Re: Grinding wheels
I use an inexpensive high speed grinder with a Norton 3X blue stone http://www.nortonconsumer.com/Wheels-3XBenchPedestal.aspx for any grinding that would take forever on the Tormek and other sharpening stones. Before I started using this I was petrified that I would burn the steel. The key to not burning your tool is the friable nature of the stone which constantly exposes fresh grit and rounding over the stone surface into a semi circle. This limits the amount of steel touching the stone at any time. If you can find the Fine Woodworking May/June '08 issue there is an excellent article by Joel Moscowitz (from Tools for Working Wood). He has a good price on the stones a diamond stone dresser here: http://www.toolsforworkingwood.com/store/item/NO-WHEEL3X.XX/Norton_3X_Super-Cool_Grinding_Wheels and here: http://www.toolsforworkingwood.com/store/item/MS-MPDRESS/Search/wheel%20dresser/Multi-Point_Diamond_Wheel_Dresser A good tool rest is also important. I use one from Lee Valley.
Author:  WendyW [ Sat Oct 06, 2012 2:28 pm ]
Post subject:  Re: Grinding wheels
Busy week, so I finally have time to get back on here. Thanks for all the good information and options. I'm checking them all out now, trying to make up my mind which way to go.

Hey Beth...went to walk my dog this morning and I had to go back in to get a sweatshirt! Only 70, what happened to our nice warm temps?
Author:  Beth Mayer [ Sat Oct 06, 2012 4:26 pm ]
Post subject:  Re: Grinding wheels
callyrox wrote:
Busy week, so I finally have time to get back on here. Thanks for all the good information and options. I'm checking them all out now, trying to make up my mind which way to go.

Hey Beth...went to walk my dog this morning and I had to go back in to get a sweatshirt! Only 70, what happened to our nice warm temps?


I got my Carruth scraper today and it's awesome! Feels good in the hand, and I like the weight of it. Now that temps are cooling down, it's time to start building the new workshop next to the house!!! bliss Had absolutely no interest in doing it during the triple-digit temps. Give a shout if you're ever in Tucson, and have time to visit the east side.
Beth
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