someone convince me to not build a double wheel grinder

C

crank78

Joined
Dec 21, 2013
Messages
336
is there a reason i shouldn't build one. it seems like it would be easier to use and speed the process up quite a bit, but maybe there is something i am missing. also thought about using cbn wheels and grinding them hard.
 
The idea about double wheel grinder has been around for long time. The reason why it isnt use by 99% of quality maker because it not good. Better dont waste your money.
 
Double wheel grinders to grind hollow grinds are used in industry, but are a bit too complex for most hobbyist. You would be far better to build an uber-grinder with water cooled belts.

Hard grinding wheels are also used in industry, but require different types of grinders and total flood coolant. Again, a good grinder with a water cooled belt setup would do as good or better for most knifemaking. CBN wheels are for grinding hard and small things like carbide tooling. It would be a poor choice for knifemaking.
 
The simplest way to do it would be two identical 10" 1hp bench grinders and 4 matching cbn wheels. 2 60 grit, and 2 120 grit. You could go with smaller wheels and weaker motors, but I think that would be a future regret in the making. I toyed around with the idea of a two wheeler for a while. Even thought about two platens facing each other because I dont like hollow ground blades. There was video of a 8 or 10 year old kid using a double wheel belt grinder that only had one motor, and doing a decent job iirc. I cant find that footage, and have looked for it several times.
 
When I was first learning to grind, I put a lot of thought into a 2 side belt grinder. There are a few issues, mostly related to setupability, but with independent frames linked together on sliding and rotating axis, it can be done. Independent frames, motors and drives, linked together by a heavy mainframe, running in reverse, with angular and linear adjustment (I was going to do flat platens). The platens or C plates would ideally have set screws to adjust rotation so they could be tweaked flat relative to each other.

It would take up a lot of space, and require a fair amount of setup time each time it was changed from one grind to the next, and precludes the ability to grind variable angle geometry. Your limited to a scandi type grind, carrying the same angle from choil to tip, and can only vary it in the height/angle you take it to.

I never pursued it because as I got better at grinding on a single grinder and lost interest in doing runs of multiples of the same knife, it's investment:return ratio doesn't pan out for me. The fraction of time I spend grinding bevels on a particular knife is now 15-20% of the total time invested. Speeding that process up is not worth the cost, time or space to build, house, and set up a double grinder for me any more.
 
One of the custom razor makers used to use a home made version of one of those IIRC. I seem to remember that he switched to just doing freehand on a wheel.
 
Stacy E. Apelt - Bladesmith said:
Double wheel grinders to grind hollow grinds are used in industry, but are a bit too complex for most hobbyist. You would be far better to build an uber-grinder with water cooled belts.

Hard grinding wheels are also used in industry, but require different types of grinders and total flood coolant. Again, a good grinder with a water cooled belt setup would do as good or better for most knifemaking. CBN wheels are for grinding hard and small things like carbide tooling. It would be a poor choice for knifemaking.
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man those ubers are quiet. i like that. i wonder how much the motor and vfd are. those run off air correct?

edited nm i was wondering how they made a pneumatic grinder lol. it would have been a airhog. i just seen another video its just the tension arm thats pneumatic.

my thoughts was to make a knife grinding station down the middle of my shop. double wheel grinder on one side for roughing. ill scratch that idea now ty... 2x72 on the other side, and one for handles and wood with the other one. was planning on using 2 double shaft motors running on a pully system so i could disconnect the sides not being used atm.
i guess i could just do 4 separate grinders, using 2 motors. 1 with a big wheel, one with small wheel attachments, 1 with flat platen and one for handles. lol. i like an assembly line. i hate changing belts, setups, tooling arms and such lol.

i wonder how it would be grinding with a flood set up. i can grind decent but im slow. i have to watch what im doing or i screw up. im not sure i could handle the limited visibility with the flood system.

i really wanna be able to make 100 knives a month. not that ill sell that many but if there is a knife show coming up in a month i want to be able to make enough stock to go, and make it worth while. i highly value your opinion and appreciate all you do for the community. if you got any ideas you wanna share feel free to help me out again please.
 
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jdm61 said:
One of the custom razor makers used to use a home made version of one of those IIRC. I seem to remember that he switched to just doing freehand on a wheel.
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that was lewis. he caused me to make a straight razor a couple weeks ago. if you never shaved with one i suggest trying it. no more razor burn at all, and its pretty cool shaving with something you made yourself. i done went crazy and got a 60$ shave brush, a stand, 2 soap cups, and about 5 different soaps. lol im hooked.
 
Hard grinding or CBN wheel grinding with flood coolant is usually a CNC based process, where visibility is not a concern. If you're just hand grinding, you'd be better off with a water cooled platen or a mist coolant system. As for the double wheel machines, I think they're more of a gimmick than anything. I don't know of any well known/established makers that use a double wheel set up, and there are probably many other well spent ways to gain efficiency. Have your blanks waterjet, hire a person or two (or three), etc....

Just my $.02.
 
jdm61 said:
One of the custom razor makers used to use a home made version of one of those IIRC. I seem to remember that he switched to just doing freehand on a wheel.
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Yeah he did. There Is a video out on YouTube about his grinder. He says I built this awhile ago and actually don’t use it any more. Was not what he thought it would be.
 
go to youtube and look at Alabama Damascus Steel. They have one segment showing a worker grinding on a double wheel grinder.
 
i found a couple of theirs using the double wheel. it looks like a extremely rigid grinder. unlike the rest that i have seen made.
 
knife to a gunfight said:
Hard grinding or CBN wheel grinding with flood coolant is usually a CNC based process, where visibility is not a concern. If you're just hand grinding, you'd be better off with a water cooled platen or a mist coolant system. As for the double wheel machines, I think they're more of a gimmick than anything. I don't know of any well known/established makers that use a double wheel set up, and there are probably many other well spent ways to gain efficiency. Have your blanks waterjet, hire a person or two (or three), etc....

Just my $.02.
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Yea im going the water jet route for about 4 different models in going to make. I was going to buy a plasma cutter but a local shop is going to cut them from 1-2$ a blank. Cant beat that. Min 20 per pattern. And said if i need to throw a one off in there every now and then that's ok to as long as provide the cad file.
 
Added a lathe to the shop today. Now i can make my own drive, and idler wheels. Should have a mill sometime next week then a small cnc mill comes next. And looking for a surface grinder. Anyone got any ideas that will help speed the process up?
 
Do you have experience on a lathe of the size/type you have? Do you have the tooling needed to bore bearing pockets and/or ream the drive wheel? Do you have a grinder planned for the wheels or are you working with an existent frame?
 
yea i got plenty experience with a lathe. custom pool cue maker for 10 years before i quit. i just got a small 7x10 and ordered a extension for it. later ill cnc it... no im ordering tooling now. im going to build 3 more grinders. i got one 2x72 and 2 almost complete 1x42s that i was gonna build a double wheel grinder with lol. and i still think i might put them together. i think i have a way to make them work but set up time would only be worth it if i was grinding several of the same blade, or just to let my 5year old use it. he made a good looking knife with the flat grind machine i made, but its way way way to slow. yes it has guards in place there is no way he could get injured.
 
How will the motors mount on your grinders? This will dictate how you should make the drive wheels. They should be 2 1/4 -2 1/2" wide. With a face mount to 1/4" plate, and another 1/4" gap behind the wheel this will put a centered set screw right at the end of the shaft. This can be avoided by drilling the hole from the face at an angle. Watch northridge tools video on YouTube with the drive wheel being machined. They leave an extra nub on the backside of the wheel to get more contact on the shaft. Ream/bore and do all the facework on the outside of the drives. Broach the key ways. Drill/tap for the set screws. Machine an accurate STEEL dummy shaft. Use the set screw to secure the wheels on the dummy shaft to turn the backside and diameter using light cuts. This will result in a better balanced wheel. The tracking wheels need to be the same width as the drives. This will make setup easier. The easiest way to make the tracking is to drill/bore a precision hole about 3/16 smaller than the o.d. of your bearings. Make a dummy shaft slightly shorter than the width of the wheel minus the width of one bearing. You can then either drill/tap for a set screw down the center of the wheels or use super glue to hold the wheels while you bore bearing pockets and heat to remove. This is much easier, and more acurate than flipping the wheels and realigning. Especially if you only have a three jaw. The same technique can be used on platen wheels, but platen wheels should only be 2" wide.
 
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I was talking to Travis Wuertz, after BladeShow last year. I mentioned that it would be great to fabricate a two-grinder work station in such a way that the grinders could pivot toward each other, with one on a track for fine adjustment to get the gap right. His eyebrow raised with a sinister grin... but we were pretty full of imagination fluid at the time. It would be cool to sit and think on that, sober.
 
Crank, if you want to make more knives per month, just get better at grinding... the guy I am learning from can rough grind out a hunter/skinner in less than 5 minutes.
Not saying everyone can get to this level, but lots of guys can. (I know I can’t... yet.
 
Rick Marchand said:
I was talking to Travis Wuertz, after BladeShow last year. I mentioned that it would be great to fabricate a two-grinder work station in such a way that the grinders could pivot toward each other, with one on a track for fine adjustment to get the gap right. His eyebrow raised with a sinister grin... but we were pretty full of imagination fluid at the time. It would be cool to sit and think on that, sober.
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it would have to be super heavy, but it could be done pretty easy. stafferieo "that's probably not spelled correctly" but they have a decent looking build of the double grinder. theirs doesn't turn tho. basically build it on a couple x, y, tables with one or both on a turntable.
 
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