Thread: Tool Post Grinders - Can A good one be made?

Originally Posted by Anorak Bob

Might have applied in the case of the mic. I'm not sure if with the 0 - 25 rod in place, the collar is zeroed relative to the rod end's position. It may only be out a whisker but you are taking whiskerish measurements.

I do like your set up Simon, worth replicating if I get around to checking my preload spring.

I will check my pulley widths for you.

Bob.

Hi Bob,

It matters not if the rod is zeroed or not, in fact I didn't even look. I'm merely using the mic as a comparator, measuring the zero position and then the compression. The actual initial depth is purely arbitrary.

Simon

From my flat belt research, pulley width should be around belt width +10%

Michael

Originally Posted by simonl

Attachment 350944

Incidentally, we may have to report you Simon - that looks suspiciously like a large expanse of uncluttered floor there.

Michael

Originally Posted by Michael G

From my flat belt research, pulley width should be around belt width +10%

Michael

That's kinda what I allowed for…. for a 3/4" belt. Mind you I didn't research it and I didn't formally make the 10% width calculation, I just thought 3/4"+ a little extra to allow for tracking when first powering on.

If I have to redo them, it won't take me long this time. I'll also reduce the cresting amount too.

Simon

Originally Posted by Michael G

Incidentally, we may have to report you Simon - that looks suspiciously like a large expanse of uncluttered floor there.

Michael

Yea sure. Don't look at the mess on the floor. I'm yet to sweep up after I had a clean up. Mind you, I'm still struggling with shuffling of stuff after making room for the sg. The drill press was only just put there a day before but I'm not sure if I like it there. I'm also scared that this recent exposure to (basic) cylindrical grinding by means of TP grinders will leave me wanting more………. Cylindrical grinders….. hmmmm.

You will also find it mildly amusing Michael that I actually have the next part of my sheet metal folder sitting next to the mill waiting to be done, but I got side tracked yet again with something new to me so it's more interesting. You watch, it won't be long and I'll need to fold up a box or something again and then I'll be cursing myself.. again!

Edit: If I was to run my own business, I don't think it would survive very long!

Simon

Not much happening on this ATM. School holidays have slowed me down as usual. Those that have been following would know that I took a chance and bought a single 7200 precision bearing. This turned out to be a bargain but has left me looking for another! Numerous searches have unearthed this offering on ebay
http://www.ebay.com.au/itm/261948095...%3AMEBIDX%3AIT

It seems like a good deal but if I was going to buy a matched pair then I'd be mad not to take up Phils offer of $103 for a pair. The ebay seller does not offer postage to Aus so it would need to go via Shipto. Anyway, I asked the seller if they could sell a single bearing, they advised it would not be a good idea as they are matched pairs and using unmatched pairs would result in the spindle not being "perfectly concentric" and that the bearings would prematurely wear because they were unmatched.

Relutantly, the seller has agreed to source a single bearing and list it for me. My question to the masses are what are your thoughts on the above theory?

I feel that the small amount of eccentricity created by "unmatched" pairs would be so low as to be negligable since each wheel needs to be dressed anyway. I do have a concern about the premature wear theory.

Yes, I know I should just buy a matched pair and be done with it but $50 on ebay goes under the radar, $150 does not, especially in school holidays when we seem to spend so much more money!

Any thoughts?

Simon

Originally Posted by simonl

they advised it would not be a good idea as they are matched pairs and using unmatched pairs would result in the spindle not being "perfectly concentric" and that the bearings would prematurely wear because they were unmatched

Is that the same seller that confused the rust proof oil as "Pre-lubricated". That's old RHP stock, they are swimming in rust oil inside the plastic packet. Its not lube.

It makes no difference what the preload is or if they are matched, if they are not going to be rigidly contained on the spindle or in the housing. Your spring applies the pre-load.

I'll have a price for you on a one off single within the hour.

Regards. Phil.

Simon.

How does a 7200 CTP4SUL in German FAG sound. $51.00

I can have it here in 10 minutes.

Phil.

Originally Posted by Machtool

Simon.

How does a 7200 CTP4SUL in German FAG sound. $51.00

I can have it here in 10 minutes.

Phil.

Hi Phil.

That sounds great!

I'll see if I can find your banking details. Can you post it?

Cheers & thanks!

Simon

Originally Posted by simonl

they advised it would not be a good idea as they are matched pairs and using unmatched pairs would result in the spindle not being "perfectly concentric" and that the bearings would prematurely wear because they were unmatched.
I feel that the small amount of eccentricity created by "unmatched" pairs would be so low as to be negligable since each wheel needs to be dressed anyway. I do have a concern about the premature wear theory.
Simon

I've only had a bit to do with bearings, but it's the first time I've heard of that. My way of thinking is that out of the thousands of bearings made are they going to pair them up. Perhaps someone with more knowledge can let us know, as I'd sure like to know if its true or not.
Kryn

Hi Kryn, I am by no means an expert either but yes you can buy bearing sets that are super precision matched pair. Have a read of this SKF bearing catalogue, page 11 makes mention of bearing configurations. I get the impression that these matched sets are for very specific applications. http://www.google.com.au/url?sa=t&rc...mmLfKS4JfdXHdQ Cheers, Simon

Thanks for that Simon. Some interesting reading there. I've saved it to print off should I ever need it.
Kryn

Well the bearing arrived today thanks to Phil (Machtool).

I'm looking forward to re-assembling the spindle. I have a question regarding these bearings; They have various marking on one side (as most bearings do) one of these markings include an arrow on the inner race. Is this of any significance? Does it just indicate which side to preload?

Simon

Hi Simon, I think in the SKF book there was something about it, I vaguely remember seeing something with arrows, but no Indians though.
Kryn