Jump to content

Recommended Posts

It's been a week with no further replies from the supplier of my grinders, so I guess I'm on my own.

My plan is to have about 70/80mm wheels cut from aluminium and nice, big bearings, and a considerably longer platen than I have now.

The frame of the grinder and the platen intrudes on the left edge of the current platen which also needs to be eliminated in ver. 2.0

Apart from that, I've rejected every idea I've had for the frame, can't think of a way to achieve clean access to both sides using the bar of mild steel I have.

Any plans, ideas, critiques welcome.

Share this post


Link to post
Share on other sites
On 8/9/2019 at 11:15 PM, Bob Ouellette said:

Do you have any pictures?

I'll post some, light in my shop is not great (problem) so the photos usually suck.

Spent some time brainstorming with a friend, because I want a longer platen the whole assembly will need to move backwards, meaning I'll need to trim the tool arm shorter most likely.

I hope to visit an engineering shop this week, get some rough pricing and find out how they feel about steel vs Aluminium for the wheels.

Post-brainstorming the 2 big issues are unobstructed access from both sides as well as being able to swivel/tilt the platen to adjust the angle relevant to the work rest.

Share this post


Link to post
Share on other sites

Got a reply from somebody higher up at the manufacturer with a 3rd version of what went wrong.

Lies break trust, I don't have money to gamble.

Their only suggestion is I send the wheel back to have the bearings replaced.  This is unfortunately not an option because it's a cross-border return to another country with duties and taxes on top of courier fees.

Cheapest option would be to buy a replacement wheel, but the 1st and 2nd excuse I got from the salesperson basically sent that possibility out the window.....

Share this post


Link to post
Share on other sites

The grinder with the platen fitted, and the platen loose seen from both sides

IMG_20190812_125943[1].jpg

IMG_20190812_130022[1].jpg

IMG_20190812_130031[1].jpg

Share this post


Link to post
Share on other sites

I'm holding the checker plate roughly where I plan on trimming the frame, the two knobs are what holds the work rest.

2nd photo is the "tool arm" without the platen

IMG_20190812_130116[1].jpg

IMG_20190812_130130[1].jpg

Share this post


Link to post
Share on other sites

Update:

I've been to a machinist to commission the wheels, retiree that couldn't stop working, solid old mills and lathes and he obviously knows what he's doing.  Long conversations are part of the price.

Basically I asked for two wheel similar to the larger one on my existing platen, and the old man is very insistent about the bearings to use....

Just need to make clear that I do not intend to use these wheels as contact wheels, the whole effort is to get a longer....and working platen.

I asked for steel or aluminium, he also mentioned the possibility of a certain plastic.

In the case of plastic I'm a bit worried about heat, but I would appreciate any recommendations about the 3 possible materials.

 

Still waiting for a quote, but I plan on disconnecting and taking the grinder for him to see and get a better idea of what I plan to do.

I also intend to have him mill me a perfect platen surface from some 10mm 5160 which I will heat treat.

Share this post


Link to post
Share on other sites

If those are not contact wheels, they should remain cool. I guess it's up to what you are willing to pay, idler wheels don't need to be very sturdy imo...mines are made of FRN(fiber reinforced nylon). 

  • Thanks 1

Share this post


Link to post
Share on other sites

Not sure about the plastic he intends using, but I suspect I've seen where it's sold and I know machinists often use it.

Thanks, I feel better about the plastic option now.

Share this post


Link to post
Share on other sites

I have an acceptable quote for the wheels made from PTFE, and a reference to a company that could laser cut the back plate of the platen.

Should sell two knives next week, some money for the platen build kitty

Share this post


Link to post
Share on other sites

PTFE (Teflon) seems to be a strange material choice for the wheels.

It's very low in friction, but I'm assuming you'll still have bearings, so that doesn't matter here.  (Don't try to run PTFE wheels without bearings.  They won't last long with high surface speeds)

PTFE is not terribly dimensionally stable.  It's know to cold flow (move) under high speed or high pressure conditions.  It's also very expensive.

I'm not a plastic expert, but I think I would be machining them from UHMW, or Acetal.

 

 

 

Share this post


Link to post
Share on other sites

Thanks for the input Brian. If you have to guess, how could it fail?

I'm a bit worried about the plastic as well, the machinist who is in his 60's........and German, thinks otherwise. 

When visiting you need to bargain on a 2 hour chat....on completely unrelated subjects :lol:, but he's convinced it will work.

He was adamant about the bearings we should use and his logic seems sound.

PTFE is the cheapest option he can provide, and I figured if it doesn't work we can salvage the rest and replace the rollers with aluminium or steel.

 

I was at a company yesterday that can plasma cut the back plate for me, just need to do an autocad drawing

Share this post


Link to post
Share on other sites

I'd say if he can get the material cheaply and intends to put bearings in, then PTFE would be OK.  In my part of the world, PTFE is several times the price of UHMW, and not as robust, so I wouldn't have considered it for this application.  However, if it was available cheaply, I would be less concerned about the difference in toughness.  In other words, I wouldn't want to pay a premium for something that isn't quite as good, but wouldn't worry about the difference if the price was the other way around.

  • Thanks 1

Share this post


Link to post
Share on other sites

Just got a message the wheels are done, I annealed the piece of 10mm leafspring for the platen yesterday, dropping that off to be milled to shape......I'm a bit apprehensive  because the machinist likes talking more than listening, so I hope it's not $1000 (local monopoly money) in the water.....

Breaking my head about heat treating that massive piece of steel in my vertical kiln......

Share this post


Link to post
Share on other sites

Good news bad news.....

The wheels were a bit more than the initial quote, and no shafts.....no way to mount it.

Also, despite my protests, the old fart went and used circlips to hold the bearings in.  I suspect I basically paid through the ears for four good bearings, and I'll pay him, or somebody else.....to do it again, and right this time.

Good news is the guy making the back plate can easily duplicate the mount & adjustment holes and slots as on the original, just need to do the Autocad drawing.

Also found out (again) my measurements by eye is not very good, the leafspring is 15mm thick not 10mm, so I should end up with a contact surface of 300mmx50mm and 12-13mm thick.

Should hopefully stay straight in the quench.

Share this post


Link to post
Share on other sites
14 hours ago, Dave Brownson Jr. said:

What's wrong with snap rings holding the bearings in place?  If they are seated right they should hold quite well. 

The only thing I've got to go on is the fact I've not seen a single grinder or photos of a grinder with circlips in the wheels, no engineering experience.

1.5kW motor with VFD and a slightly oversize drive makes me fear where those can fly if something fails.

Share this post


Link to post
Share on other sites

I can't see how well made the parts are, but I don't think I would be too worried about snap rings in that situation.  I suspect they will be quite serviceable.

Share this post


Link to post
Share on other sites
On 9/27/2019 at 2:39 PM, Brian Dougherty said:

I can't see how well made the parts are, but I don't think I would be too worried about snap rings in that situation.  I suspect they will be quite serviceable.

 

I hope you're right, I've been informed they are balanced....so fingers crossed.

My dad finished the autocad drawing of the back plate, sent that on so it should be done this week.

 

While doing some research I had a horrible realization......

There's another manufacturer in South Africa that I know produced my contact/drive/idler wheels on my machine, and browsing his site I saw it.....

He also sells a "three wheel grinder", first sight it looked familiar, as it should because it's built from the same kit......

 

I don't know who stole from who if that is the case, or just a bit of crooked business......

 

Fact is, if I flipped over the base plate and assembled with the tool arm on the left instead of the right side, my platen would've been right side up and the work rest would actually function with both mounting screws in place

:angry::angry::angry: 

Share this post


Link to post
Share on other sites

I'm 1900 of my monopoly moneys into the build.....but I'm very happy with my beefy 5160 platen B)

 

Slightly nervous about heat treating it, but if it warps i'll be on the lookout for somebody with a surface grinder :ph34r:

Still waiting for the quote on the backplate.

 

 

IMG_20191016_165602[1].jpg

IMG_20191016_165621[1].jpg

  • Like 3

Share this post


Link to post
Share on other sites

Got the quote for the back plate, so reasonable I ordered 2....just in case.

  • Like 1

Share this post


Link to post
Share on other sites

The chassis is with the machinist to get the center hole tapped and the shafts for the wheels made.

 

Platen was heat treated and tempered, and as far as I can tell it stayed straight. Still plan on sanding down the face a bit using a quench plate as backing.

 

Soon........ :ph34r:

  • Like 1

Share this post


Link to post
Share on other sites

.......and 3pm yesterday I got a call, shafts were done and the wheel mounted.

 

Still can't upload photos...TIA....but it turns out my belts are too short :P 

I was a bit exuberant with my platen, I expected some belt clearance issues with the foot piece, might be able to fix that by flipping the chassis 180, but there's no way the belt will fit all the way around.

That means I will have to chop & change between my two grinders and use the smaller drive wheel of the two for the platen, longer tensioner  spring and an extra hole in the arm to move idler wheel a bit lower.

I anticipated some of this....but not quite to this extent :ph34r:

 

Kind of sucks because I realised I will have to finish 5 knives before I can rip the lot apart a lego together.

Low speed test run with the belt over just one of the new wheels went okay.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...