The Shop > Tools

Recommend prismatic type universal indicator stand

<< < (3/5) > >>

PekkaNF:
Funny part is that I complained about the orginal missing fine adjustment on the dial holder. They said they would send a new holder. They could not find a adjustement parts and finaly sent me a completely new stand.

I checked it and it looked fine, but because packing was only cardboard it had been dropped somewhere on the way to floor and pagaging had a hole in it.....

Because it is cast iron I used diamond file to file of the raised edge. Then I got a little enthusiastic and took a laping plate, abrassive and parafin oil. 15 mins of good fun and some cleaning/checking showed the base to be straight and level to better than 0,01 mm trougout the whole lenght of the base. Sorted.

Butthe old one is another matter. It is usable, but it's corners are a bit high, it has slight twist and step on paralelism of top to bottom surface. Gave it a bit more workout and it became better, but it is hard to correct with hand lapping.

Pekka

Pete.:
If you handled it with bare hands then those readings after lapping could be just bending from heat.

What did you lap it with? Something coarse like fine valve grinding paste will remove scraping marks in minutes. Another thing is the pattern you use when lapping, if you don't describe large enough circles you might not keep an even thickness of slurry under the part and lap a hollow in the base. That said, for the use you're going to put it to, a slightly hollow base is far better than a crowned one.

PekkaNF:
Thank you. All very true and good points. Let me explain a bit more what I was trying acieve by lapping wrong way.

That lapping plate is 350*250 two sided model it is prooven to be pretty straight.

I used coarse valve grinding paste, but first used other piece to break it down. I know it is not ideal, but this piece is not ideal either and it this bases were ground, not scraped. No precision instruments were harmed.

I'm normaly using large figure of eight in multiple direction on the plate and on the part. As you say you wear part and plate too unevenly if you use only repeated pattern. Random is king here.

I did lapped very little the better one, just to remove the burrs and it the first specimen is straight enough. measured it and left it alone for time being. I'll be watching it.

it was the second one (with marked 0,01 mm markings on it.) I was goofing around. I was trying to make top and bottom planes parallel. I know that hand lapping is not normal way of doing it. Manual lapping is generally used only to even out irregularites on one surface. And it is actually hard to keep top and bottom surface parallel if you don't randomize.

What about if you do want to use this weaknes of the method for your benefit?

You know that if you hold the part high it wears more the side on the forward stoke leading edge. I used that with the figure of eight - on forward stoke I used high grip on corner I wanted to wear down a bit more.

That heating phenomenon is a real consern. Specially when I was handling the part with bare hands (well nitrille gloves) and washed it well with soap and warm water, but I allowed some time to settle.

I'll repeat the measurement and see if changes today.

You are right on thet one too that all bases should err on hollw side to avoid rocking. I though of getting it firs almost straight and then just a tad more from the middle.

Pekka

Pete.:
Flat is all you need for an indicator stand. If you were going to use it as a comparator then parallel too.

Also, given the method you're using to check it, make sure that the other face has no raised edges or dings. Blue it up on your surface plate to check both sides.

PekkaNF:
Pete, now you got me on the run....with this little accuracy I assume that lapping plate is staright and check the pattern, but this is "new" plate and now my asumptions wer shaken.

Phuh. It's all good. I checked with dykem hi spot. Anyone who has used it probably understand why I did not take any pictures middle of it :lol:

Pekka

Navigation

[0] Message Index

[#] Next page

[*] Previous page