How to overcome foreshortening of the bevel towards the tip, grinding using 2x72 and an angle jig?

F

FloWolF

Joined
Sep 15, 2017
Messages
70
After nearly posting this in 'around the grinder', I woke up and made it here!

I've made maybe 50 knives previously, all bevelling work done on a home made filing jig. Worked really well, fabulous results, but time and labour intensive for this battered body so last year I got a basic 2x72 grinder and built a couple of hinged aluminium bevel jigs, and set to.

With the filing jig I could see where the front bevel was trying to cut short and make adjustments to my filing angle, but I can't quite see with these jigs how to make it work? - I draw the blade across the belt, approaching the tip I pull the handle end of the blade away gently leaving the tip in contact until last, aiming the contact to cut towards my marked centre lines evenly.

I get my bevels towards meeting evenly, but the angle of the grind changes and I get a higher angled, shorter bevel running around the curve to the tip.

With kitchen knives like I'm working on at the moment, if anything I' actually want the bevel angle and height to go the other way towards the tip - smaller angle, longer bevel, but since this is a jig I'd just settle for getting it even!

Is there a way for me to do this without swapping to freehand?.. The one thing I have not the time/money/general resources for is tons of trial and error practice to work it out, which is how I used to do everything, but now any time spent and work done has to actually pay by selling.

Thanks in advance for any tips - I've managed to work out most other stuff by reading and videos but this bit has remained elusive.

Cheers!

Shaun/FloWolF
 
Jigs are rigid. You need to turn/twist the knife as you go over the tip. Either do it all by hand or after making the straight bevel on the jig, finish the tip by hand.
Personally, I feel a fixed bevel jig is a hinderance in grinding.
 
Appreciate the reply Stacy.

I get that the jig is limiting, and just slows down development of freehand skills.

On the other hand, other jig users, are managing better results than I am getting. There may be some slight foreshortening towards the tip visible on some of their work, but not quite to the degree I am seeing.

I'll get to doing more by freehand down the line, but for now I really need to use the jig to the best of its capabilities, and I know they are capable of doing this better than I have been managing.

Thanks again!

Shaun/FloWolF
 
If you use a rigid jig (hinged plate), you will get a straight line. You will have to make some adaptation or manipulation to allow turning the blade as you go over the tip.
Nathan's hanging parallelogram is the perfect way to do that, as it only holds the blade in one plane and allows rotation in the other two. It is super simple and costs almost nothing.
 
Nathan comes up with some of the coolest stuff. If he isn't the original designer of some of these tools, he's just the 1sr I've seen with them. The water-cooled platen and some of the other platen related tools are really neat as well.
 
Stacy E. Apelt - Bladesmith said:
If you use a rigid jig (hinged plate), you will get a straight line. You will have to make some adaptation or manipulation to allow turning the blade as you go over the tip.
Nathan's hanging parallelogram is the perfect way to do that, as it only holds the blade in one plane and allows rotation in the other two. It is super simple and costs almost nothing.
Click to expand...

Thanks heaps for that - I'd watched that about a month or two ago and then forgotten all about it, which is strange for me.

Does this setup need to be used blade-edge-down as per the video? Any reason the angles can be adjusted to cut blade edge first, or reasons I shouldn't try?..

I just grabbed a section of rectangular tubing I should be able to fasten a nut to the end of, I'll see if I can grab some chain and hooks from somewhere soon and see.

I just set up the grinder for wet work - old little aquarium pump, tubing and tap, bits of plastic sheeting, a tub or two and a paintbrush to deliver the water and have switched to grinding post HT with the water. It's so darned smooth going this way, I love the feeling back through my hands of the abrasives and water doing their thing to the steel, especially using the Trizact belt. Kinda like a steady, soft 'SSshhshhshhsh' heheheh. Ahem.

Thanks very much once again!

Shaun/FloWolF
 
If your grinder platen will tilt forward, I don't see any reason you can't grind edge up.
Another option is to make an adjustable angle fixture to hold the blade on the parallelogram. I plan on making one that way and testing it out sometime. This would deal with flex, which might be a problem with thin or long blades
 
Stacy E. Apelt - Bladesmith said:
If your grinder platen will tilt forward, I don't see any reason you can't grind edge up.
Another option is to make an adjustable angle fixture to hold the blade on the parallelogram. I plan on making one that way and testing it out sometime. This would deal with flex, which might be a problem with thin or long blades
Click to expand...

I made a quick lash-up of the parallelogram idea, can even make it so it cuts edge up if I want, but I'm leaving it for now as there's a definite new knack to learn and also, even though I grind edge up, I'm really wanting to have the belt go the other way over that edge especially as it comes to the finish - I already managed to trash 3 virtually new Trizact belts working edge up into the motion - I know this could have been mitigated by improved technique, and that in the end that was at fault, however it just wouldn't have happened were the belt direction reversed. I'll wait to try it until I have some 'spare' steel for the bin to chew on heheheh...

I've been trying to make mine go in reverse, but as-per it wouldn't track. Checking things out the motor mounts were holding the motor skewed compared the how the wheels were aligned. Fixing that and I noticed they are also welded so they hold the motor over 1/4 inch too far inboard, so all the time the tracking wheel is working its bearings off just to keep the belt aligned going forwards. It should have been a great little budget machine, but comparing it to the others I've seen he's made mine looks like it was put together in sleep during a nightmare. I'm now trying to find a way to get the welds cut and re-positioned, but to be honest I'm scared that I'll then find out the rest of it isn't aligned right either...

At this rate I'll be back to pushing files across my metal and taking heaps of painkillers again heheheh!
Cheers!
 
FloWolF said:
I made a quick lash-up of the parallelogram idea, can even make it so it cuts edge up if I want, but I'm leaving it for now as there's a definite new knack to learn and also, even though I grind edge up, I'm really wanting to have the belt go the other way over that edge especially as it comes to the finish - I already managed to trash 3 virtually new Trizact belts working edge up into the motion - I know this could have been mitigated by improved technique, and that in the end that was at fault, however it just wouldn't have happened were the belt direction reversed. I'll wait to try it until I have some 'spare' steel for the bin to chew on heheheh...

I've been trying to make mine go in reverse, but as-per it wouldn't track. Checking things out the motor mounts were holding the motor skewed compared the how the wheels were aligned. Fixing that and I noticed they are also welded so they hold the motor over 1/4 inch too far inboard, so all the time the tracking wheel is working its bearings off just to keep the belt aligned going forwards. It should have been a great little budget machine, but comparing it to the others I've seen he's made mine looks like it was put together in sleep during a nightmare. I'm now trying to find a way to get the welds cut and re-positioned, but to be honest I'm scared that I'll then find out the rest of it isn't aligned right either...

At this rate I'll be back to pushing files across my metal and taking heaps of painkillers again heheheh!
Cheers!
Click to expand...
If your Trizact belts wear quickly, could it be that you are using the 337 belts wet? I've tried that once and the belt dissolved into a green slurry pretty quickly. The 347 Trizact belts are the ones that work for wet grinding.

What type of grinder do you have? Maybe you can move the drive wheel a bit further out on the shaft. There is typically a set screw that secures the key that transfers power from the motor shaft to the wheel.

Getting a grinder to track in reverse can be tricky. Having the drive and tracking wheels aligned is a good start. The tracking wheel can be adjusted in one axis to change tracking via a knob. The other direction should be aligned as well. Whether that can be adjusted depends on the particular grinder model. Lastly, the contact wheel or platen wheels also need to be aligned. I have one contact wheel that tracks perfectly forward and reverse. Another one is mounted not quite at ninety degrees and barely tracks in reverse. I keep meaning to fix that but I hardly ever run the grinder backwards. Before you take an angle grinder to the motor mounts, maybe post some pictures of what you've got, somebody here might have an idea how to fix it that does not involve cutting up the grinder and welding it back together.
 
Hubert S. said:
If your Trizact belts wear quickly, could it be that you are using the 337 belts wet? I've tried that once and the belt dissolved into a green slurry pretty quickly. The 347 Trizact belts are the ones that work for wet grinding.

What type of grinder do you have? Maybe you can move the drive wheel a bit further out on the shaft. There is typically a set screw that secures the key that transfers power from the motor shaft to the wheel.

Getting a grinder to track in reverse can be tricky. Having the drive and tracking wheels aligned is a good start. The tracking wheel can be adjusted in one axis to change tracking via a knob. The other direction should be aligned as well. Whether that can be adjusted depends on the particular grinder model. Lastly, the contact wheel or platen wheels also need to be aligned. I have one contact wheel that tracks perfectly forward and reverse. Another one is mounted not quite at ninety degrees and barely tracks in reverse. I keep meaning to fix that but I hardly ever run the grinder backwards. Before you take an angle grinder to the motor mounts, maybe post some pictures of what you've got, somebody here might have an idea how to fix it that does not involve cutting up the grinder and welding it back together.
Click to expand...

The belts are wearing normally running wet, so I presume I have the right ones. The problem is with rubbing and nicking of the belts on the edges causing them to slice and tear. The wear rate itself is brilliant and I love how they machine fine shavings of metal rather than create just metal grains/powder - it comes of the knife and forms into little wire-wool-like bundles.

As for the grinder - put together in a guy's workshop over here in England, I am guessing from laser cut kit parts and bits of sheet and tubular steel and wheel kits. The motor mounts consist of strips of steel with a headless bolt stud welded through, ground flush then welded to the base plate with a single bead on one end of each strip. They are not properly aligned, and now it seems they are also set too far to one side. I can't alter this by the drive wheel, it will not go further onto the shaft - it's fasted with a bolt through the end of the wheel into the end of the drive shaft, and then the grub screw secures it into the spindle keyway. There's not enough metal on the wheel to make the shaft hole deeper, as it is further in-board it needs to go and not further out.

It's a very basic machine, put together poorly - I'd not be risking anything cutting the weld beads off with an angle grinder and placing the mounts correctly, and I'd do it all myself if I had welding experience as I have a MIG in the workshop, but I've not got the experience yet and have struggled just trying to set the MIG up so I'll try and get someone else to do it.

I read a fair bit about trying to run these things backwards and am aware of what I'm up against, and that I may not get it to work, but that motor cannot stay mounted like that anyway as it's stretching the belts unevenly and they are riding hanging off the edge of the tracking wheel.

I'd love to post some photos but at the moment I am struggling to get my media and machines to all work together outside of 'social media', so I've not been able to post pics in forums for a while.

I'm new to doing the work on a 2x72 but I'm 53 y/o and have messed with lots of different things over the years and am generally pretty competent, but my head has taken a beating and sometimes things aren't as clear as they should be!

Thanks again, and cheers!
 
Just had a possibly useless thought - does the drive wheel need to be a subtly crowned type, or could it essentially be a straight sided cylinder allowing the belt to track along that cylinder just where the tracking wheel guides it?..
 
FloWolF said:
The belts are wearing normally running wet, so I presume I have the right ones. The problem is with rubbing and nicking of the belts on the edges causing them to slice and tear. The wear rate itself is brilliant and I love how they machine fine shavings of metal rather than create just metal grains/powder - it comes of the knife and forms into little wire-wool-like bundles.

As for the grinder - put together in a guy's workshop over here in England, I am guessing from laser cut kit parts and bits of sheet and tubular steel and wheel kits. The motor mounts consist of strips of steel with a headless bolt stud welded through, ground flush then welded to the base plate with a single bead on one end of each strip. They are not properly aligned, and now it seems they are also set too far to one side. I can't alter this by the drive wheel, it will not go further onto the shaft - it's fasted with a bolt through the end of the wheel into the end of the drive shaft, and then the grub screw secures it into the spindle keyway. There's not enough metal on the wheel to make the shaft hole deeper, as it is further in-board it needs to go and not further out.

It's a very basic machine, put together poorly - I'd not be risking anything cutting the weld beads off with an angle grinder and placing the mounts correctly, and I'd do it all myself if I had welding experience as I have a MIG in the workshop, but I've not got the experience yet and have struggled just trying to set the MIG up so I'll try and get someone else to do it.

I read a fair bit about trying to run these things backwards and am aware of what I'm up against, and that I may not get it to work, but that motor cannot stay mounted like that anyway as it's stretching the belts unevenly and they are riding hanging off the edge of the tracking wheel.

I'd love to post some photos but at the moment I am struggling to get my media and machines to all work together outside of 'social media', so I've not been able to post pics in forums for a while.

I'm new to doing the work on a 2x72 but I'm 53 y/o and have messed with lots of different things over the years and am generally pretty competent, but my head has taken a beating and sometimes things aren't as clear as they should be!

Thanks again, and cheers!
Click to expand...
I guess I misunderstood your previous post, I thought the motor was sitting a 1/4" inboard from where it needs to be.

Could you just drill the correct bolt hole pattern in the base plate directly (after removing the current motor mount)? You might have to put some feet under the base plate to create clearance for the bolt heads if the base plate is not thick enough for flat head bolts, but it would not require welding. Just a thought.

You can upload your pictures to imgur, you don't even need an account. Once they are uploaded, you can insert them into your posts by clicking on the image icon in the editor tool bar. There is a thread with more details in one of the sticky threads.
 
No worries, I'm not sure I had it all fully clear in my head when I wrote it and maybe that rubbed off!

Anyways yes, I'd been considering this solution yesterday, but to be honest the motor mount holes are difficult to access with a marking tool directly, and with this machine I don't want to do it by measuring the hole footprint and then trying to find something properly square to reference the positions from.

I'll have to cut the 4 mount plates/bolt assy pieces off anyway, and I figure if I can bolt the cleaned up plates to the motor in the correct alignment, I can place the motor and check it runs in line with all the wheels, and because the edge of each plate protrudes out from under the shadow of the motor and mounts, they can be tacked in place right there before removing the motor again and finishing the job of properly. I fear once I've drilled holes, well, for better or for worse they're gonna stay drilled, and there are several bits of this machine I cannot trust the squareness of enough, not for my ability and track record, heh.

Can I UL to imgur directly from my android phone? My photo posting problems started when my favourite camera got smashed, and then I started using the smart phone camera, but my PC is on linux mint now and won't read my phone for the pictures, so they are essentially hijacked and bound between phone and social media and/or the bloody google photos cloud wherte I can't seem to pluck them from anyway, in such a way that I haven't the first beginnings of a clue how to unravel and to be honest, even trying is likely to make my had pop altogether. I am not very current with these things, I fell way behind when I decided I didn't care anymore and went off hunting mushrooms, obsessing in the workshop and having a family instead.

When I remember I'm gonna order a compatible bluetooth dongle and fire the photos straight to the PC from the phone that way - the one I bought and tried already doesn't support LM it seems.

Thanks again Hubert appreciate your time.

Good night now! ',;~}~

Shaun
 
FloWolF said:
No worries, I'm not sure I had it all fully clear in my head when I wrote it and maybe that rubbed off!

Anyways yes, I'd been considering this solution yesterday, but to be honest the motor mount holes are difficult to access with a marking tool directly, and with this machine I don't want to do it by measuring the hole footprint and then trying to find something properly square to reference the positions from.

I'll have to cut the 4 mount plates/bolt assy pieces off anyway, and I figure if I can bolt the cleaned up plates to the motor in the correct alignment, I can place the motor and check it runs in line with all the wheels, and because the edge of each plate protrudes out from under the shadow of the motor and mounts, they can be tacked in place right there before removing the motor again and finishing the job of properly. I fear once I've drilled holes, well, for better or for worse they're gonna stay drilled, and there are several bits of this machine I cannot trust the squareness of enough, not for my ability and track record, heh.

Can I UL to imgur directly from my android phone? My photo posting problems started when my favourite camera got smashed, and then I started using the smart phone camera, but my PC is on linux mint now and won't read my phone for the pictures, so they are essentially hijacked and bound between phone and social media and/or the bloody google photos cloud wherte I can't seem to pluck them from anyway, in such a way that I haven't the first beginnings of a clue how to unravel and to be honest, even trying is likely to make my had pop altogether. I am not very current with these things, I fell way behind when I decided I didn't care anymore and went off hunting mushrooms, obsessing in the workshop and having a family instead.

When I remember I'm gonna order a compatible bluetooth dongle and fire the photos straight to the PC from the phone that way - the one I bought and tried already doesn't support LM it seems.

Thanks again Hubert appreciate your time.

Good night now! ',;~}~

Shaun
Click to expand...
I'm running linux as well and I just send pictures from my phone to myself as an email attachment, then I can open them on the linux computer and upload them to imgur, often after some light editing in gimp (mostly cropping).
 
Hubert S. said:
I'm running linux as well and I just send pictures from my phone to myself as an email attachment, then I can open them on the linux computer and upload them to imgur, often after some light editing in gimp (mostly cropping).
Click to expand...
Thanks for that, soon as I've managed to clear enough memory on my phone to put the email app onto it, I'll give it a try.

Cheers!
 
Coming back around to the original point, looking more closely at what I've been doing, and comparing the kitchen knife which was worst with the bevel shortening, with the mini-bushcfraft knives which are less effected, I think I've maybe been been pulling the back of the knives out a little too much sometimes making the natural issue worse. I'll pay closer attention next time I start a grind and see if there's much improvement.

As for the tearing up of these lovely new pyramid grain Trizact belts I've immediately become smitten by, it seems I've been digging the sharpening choil end of the blade into the edges of the belt a little, and of course that bit suddenly becomes a proper 'edge' as the bevels start to meet and the inboard 'edge' of that 'U' is grabbing and slicing into the belt(s).

I'm workin' on it!

Cheers folks,

Shaun/FloWolF
 
You must log in or register to reply here.
Back
Top