Surface Grinder

If you get a good finish on the folder blade flats with a surface grinder, you don't need to hand sand the flats, cause you're done.

I can see where a surface grinder with a belt would be fine for taking the scale off steel billets where no water cooled blanchard type grinder was available. A surface grinder isn't the machine for that.

I still think a machine with wheels is the way to go for making folders. Belt type surface grinders are pretty much unknown in the tool making indistry and there are reasons for that - many of which a poster above has already stated.

The problem with most surface grinders for knifemakers is the size and weight of the machines. Most of these machines weigh in starting at 1.5 metric tons and go on up from there. I looked for a smaller machine for years as my freight elevator won't carry one of the big 'uns. I ended up with a manual ABBA from 1942. Sure wish it had a hydralic feed but I don't know what I'd do without it.

Surface grinding is about the most difficult operation I've tried to master in knifemaking. It looks easy, but it ain't!

A fellow has a Boyer machine for sale over on the USN knifemaking supply forum. Looks like a real nice machine if he hasnt sold it yet, you might have a look there.
 
Darren, pricing depends on location and timing. I see small hydraulic machines come up pretty often int the $2K - $2500.00 range, but I live in So Cal where we once had a great manufacturing base that is now collapsing. That's twice what the HF machine would cost, but would also be a more rigid machine and if you're talking about adding CNC, the price gap would be even closer. Shipping one sucks though, so local proximity is a big plus.
 
Kevin, do you have a picture of a blade with an as ground finish?

Don showed me pieces he had ground, and while the finish was really nice and clean, it still looked like a machine finish.

I suppose at the end of the day there are always going to be advocates for both schools here. I certainly don't want to start any arguments over it!!!



Another thing about a belt (for me) is that Don told me you can easily spend 10 years of full time work on a surface grinder before you get the process mastered. I won't speak for anyone else, but I don't want to spend that kind of time to figure it out.

As hardcore as he is about precision, when he saw what I could do with my grinder and how I use it, he said it was a good decision to add the conversion.

Also, all I have to do is take the wheel off, and I can throw a stone back on it (but I never do).

Just spouting off some random thoughts :)
 
Hey Fox, can you send me those pics please? Thanks!

I've got a few years working SGs. They can be tough to master, but easy to learn to flatten blade blanks and the like. As Nick was saying, the tolerances aren't that critical in knifemaking. Many folder makers I know don't even use an SG and their knives are pretty smooth as well.

Ideally I would like to have a cheapo HF grinder, set up with a 2x72 for flattening damascus billets and handle materials. Then a more-precise SG with good grinding wheel for precision flattening of folder parts. :thumbup:
 
Wow! This thread took off since I posted my reply yesterday. A couple of things to add concerning how my machine is set up and works.
1. I chose the belt conversion for two reasons......I can use the same size/type abrasives that my other grinders use. This means less supplies to purchase. And, I don't have to worry about wasting time dressing wheels all the time. I personally found dressing wheels to be a real time consuming, pain in the rump.

Next: If your going to convert a surface grinder to use belts, the contact wheel you choose is the most important consideration. That being said, you CANNOT purchase a contact wheel that is appropriate for a surface grinder application in North America. The hardest commercially availble wheel your going to find is a 90 durometer, which will cup on anything but the very lightest pass. The ONLY contact wheels that I have found to be acceptable for use in converting a surface grinder to belts comes from Bertie Rietveld in South Africa. (Here's a link to his site) These wheels are 100 durometer urethane..... the amount of down force required to cup these wheels will stop most surace grinders. The prices for the conversions kit (contact and idler wheels) WITH postage is often times is less than you will spend on a single 90 durometer rubber wheel. He also has drawing on his site for building the idler stand, and I believe he will also sell a kit for that same idler stand.
Since setting up my machine to accept belts, I've worked on several other surface grinders that still use the wheel, it's just my opinion, but I found them to be slow and tedious compared to the belt setup. With the urethane wheel, properly trued to the chuck, your time on the machine is decreased dramatically, with no loss of accuracy. The additional fact of being able to easily go from course to fine finish by simply changing the belts makes it even nicer.
If you have in mind that you want to purchase a surface grinder, and use it straight out of the crate, then I would recommend purchasing one of the higher end models, or something of that nature. However, if your willing to do some minor work/modification (which I seem to do with any machine I purchase anyway) then the HF surface grinder will save you some bucks, and will make a fine addition to your shop.
One additional note: The type of belts you use make a big difference. Butt spliced is the only way to go. Even some of those such as the Klingspoor LS-309s will cause difficulties with the belt joint slapping. I have great success using the Norax belts for finer finishing on the surface grinder.

Darren: I've never thought about putting a power feed on the small surface grinders...... with the setup that I have I don't spend enough time on it to make it worth the cost. Although I'm sure it could be done.
 
Jeff, pics & Bertie's plans have been sent.

I would like to add a few thoughts for those considering this conversion.

This was all about cost/benefit for me; meaning the time factor. For precision work in a precision environment there is nothing like a stone. I know folder makers who use this conversion for their folder parts and their knives are as smooth and finely made as any in the business. My contention is that for a knife maker, time is money and the precision available from a stone is not required, even for folders. A stone will do the work, but a belt will do it much faster and still give you the tolerances you need. I spent a lot of hours with my little HF machine and the stone and eventually became pretty good with it. Unfortunately, it takes a lot of time using a 1/2" stone when trying to flatten a 13" x 1.5" x 5/16" billet. I can take that same billet and use a 36 grit belt and have it flat within 5 minutes. With Norax belts I can have it precision ground to exact tolerances in the finish I want in another 15 - 20 minutes. I could not come close to that with a stone.

As Ed points out, this is all about the right contact wheel and right belt type. Norax are superb for this. I have tried others (notably Trizact, Hermes and Klingspor), but the butt slap from the splice leaves a poor finish. Not so with the thick Norax belts.

Nick also makes a good point about "walking" the wheel across the piece. Do not center the part on the wheel, but run overlapping passes. What I have found is that belts, to some degree, are "self truing", meaning that by using the whole wheel the grit will wear evenly and give you an excellent finish.

Since I have no micrometer, I used my Starrett dial calipers to check a billet I recently did. It finished out with a 220 grit belt at 1.75" x 13" x .230. It took me 25 minutes from start to finish, including changing belts. I started from a fully scaled billet with small divots in the steel, left over from the press and forging process. According to my calipers, the thickness is exactly the same on both sides of the billet along its entire length. That is plenty accurate enough for me.
 
@Nick
I don't have a pic of the surface that I can find, but the finish does look like it was machine done, it doesnt't look like a hand done satin finish. I thik it works very well on tactical knives or blades of CPM S90V which takes a crap satin finish anyway.

I haven't ever used a belt machine but I hope to get a chance to see one in action some day! I have no doubt they are the way to go for doing forged billets.

And it does take a while to get any good at all with a stone wheel. I've had my machine more than 2 years and I am still learning every day.

@Fox
Don't get mad, but if you don't have a good quality micrometer, you can't acurately check your work. A caliper is not the right tool for checking thickness.
 
Kevin Wilkins said:
. . .snip @Fox
Don't get mad, but if you don't have a good quality micrometer, you can't acurately check your work. A caliper is not the right tool for checking thickness. . .snip
Click to expand...

Kevin, you are 100% correct and we are cool. Having worked in a machine shop I understand the need for a good micrometer when tolerances must be held. My post was intended as a quick example of how well the belt method works. I recall one folder maker telling me that the belt conversion allowed him to hold variances to less than .001 over the small surface areas used for folders. He uses a micrometer for his folder parts. Perhaps some of the folder makers can comment; but how much more accuracy is needed? The learning curve for using a belt conversion is miniscule compared to learning surface grinding with a stone. The speed of production is dramatically higher in every instance that I am aware of.

One person noted that industry does not use belt conversions, and there are a number of reasons for that, but that does not mean it is not viable for other applications. A belt conversion requires regular intervention, which in itself is reason enough not to be used by industry, which is all about automation, production and consistency.

Someone also mentioned that there was no way to true the polyurethane wheels. Nonsense. I use a small, sharp triangular file and it works great. I have heard of some makers that use the same diamond nib they use on stone.

Guys, I am not trying to change anyone's mind here, and maybe we just need to disagree. Using a belt conversion calls for a paradigm shift in one's thinking, especially for those with machining backgrounds. IMHO, for new and experienced makers who are thinking of getting a surface grinder and learning to use it, a belt conversion is the ticket.
 
Kevin, next time you're by my shop, we'll fire up my belted SG and listen to a little Newbury! Bring something you want to surface.
 
Fascinating discussion. I had no idea there was so much to know about SG...
 
rhrocker said:
Kevin, next time you're by my shop, we'll fire up my belted SG and listen to a little Newbury! Bring something you want to surface.
Click to expand...

Man, next time I'm in Waxahachie to visit the folks, I'll take a spin by Uvalde! Love to do that!

I'm not disputing anyone's claims for the belt machines. I just ain't had a chance to see one in operation. Anything that reduces the learning curve on a stone machine would be good by me. I was surprised by just how difficult that is. Milling is much easier to get a handle on than surface grinding.

BTW, if you get up to Dallas, stop by Commerce Street Grinding and check out the machines they have. One machine you can drive a car onto the magnet and they'll grind you a convertable!
 
Kevin, there was one like that for sale at Boeing awhile back. I think it was only something like $370,000.

I should have bought two!!! :D
 
Having a big automated SG would definitely be a plus, but the cost on them is outrageous. I'm in the Fox camp on this one. I have yet to see any knifemaking processes that require the use of a stone vs the belted setup. Also we should keep in mind that while an SG can be a timesaver, its is not a necessity. Go to Kelly Carlson's website and check out his knives. They are all as nice as any I have ever seen. Precise and smooth actions like butter. He doesn't even own an SG.
 
You must log in or register to reply here.
Back
Top