Edge Finding

[kcstott]

A couple thousandths is exactly what I am observing with my edge finding. A 0.005" hysteresis means there is a registration error of 0.0025 in both directions.

I will also look into deburring the parallels. I had not thought that this could be the problem. If the parallel has a burr in it ... this can easily account for the 0.005" offset. 0.005" is not much. However, for the work I am about to do, it is alot!

Exactly. That is the key to doing precision work. Taking into consideration every little detail that can influence your set up. Burrs on parallels dirt, dust, debris, and keep in mind parallels are parallel but they are seldom flat so depending on how you are taking your reading you may be reading how out out of flatness your parallel is or how out of square your vice jaw is. all those little bits add up. And I trust nothing to be true and square until i test it, then it's either good or i grind it in until it is.

Now if you think thats bad try getting something to repeat on a surface grinder within .0001" over two inches. that will make you sweat.

[johnjohn301]

Very new to milling - really enjoyed following along with you through this thread.

[krwada]

Exactly. That is the key to doing precision work. Taking into consideration every little detail that can influence your set up. Burrs on parallels dirt, dust, debris, and keep in mind parallels are parallel but they are seldom flat so depending on how you are taking your reading you may be reading how out out of flatness your parallel is or how out of square your vice jaw is. all those little bits add up. And I trust nothing to be true and square until i test it, then it's either good or i grind it in until it is.

Now if you think thats bad try getting something to repeat on a surface grinder within .0001" over two inches. that will make you sweat.

That reminds me of a story from many years ago. As I have mentioned earlier; I was a graduate student over at UC Berkeley. I learned how to DIY machining from the shop-master at the Lawrence Labs. He was the sort of fellow who would ONLY show you once, then let you struggle to figure out how to put into practice what he told you.

One day, I was doing some work on the student mill, (there were two sets of equipment in the shop ... the regular stuff, which was hands off, and the student stuff, which we were allowed to use). Anyhow, I was working on the mill, and not being careful, I dropped the collet on the table. I can tell you this, the shop-master had a fit! He came on over and said ... now you need to re-surface the table! I asked ... what? Then he said, you just dinged the table, it needs to be reground! Then I asked ... How do you do that? Then he said ... I will not do that ... You will do that! Then I asked ... HOW? Do I get a stone or lapping compound and finish it by hand ... Then he said ... Are you DAFT? NO ... You will ruin the table! You need to run the entire thing through the surface grinder. We only have one surface grinder here that can do the job. I will get one of my apprentices to help you take the table off and mount it on the surface grinder, and he will show you how to operate it.

I asked ... WHAT? I know nothing about surface grinding. To which he said ... It is time for you to learn. I then said ... Now, wait a minute, I am just a student here and ... He interrupted: "You messed it up ... You fix it!"

!@@@#!!!! Man ... I struggled with that thing for over a week! The first time, I did the surface grinder thing ... I managed to get it under 0.001" over 3". The shop-master ran the test indicator over the thing and grimaced ... You made it worse! I need this thing to be less than 0.002" over the entire length of the table! Plus... you have the lube adjusted all wrong. You are getting the thing way too hot. I asked... "Too hot?" He said yes ... If you do not properly adjust the lube, the feed and RPM, you will get the thing too hot, and you will never get the table right.

Sheesh!

I had not realized this at the time ... but he was asking me ... a total noob to resurface that table to 0.0001" per inch.

It took forever to get that table to within his spec. There was a lot of cursing and sweating on my part. It was fortunate that they did not need that surface grinder for the week I worked on this. At these dimensions ... EVERYTHING MOVES.

I find out later, from one of the apprentices, that the shop-master wanted to get the student mill, (it was a bridgeport), to get re-surfaced ... I just happened to be "in the right place at the right time".

[krwada]

Parallels are NOT flat

Exactly. That is the key to doing precision work. Taking into consideration every little detail that can influence your set up. Burrs on parallels dirt, dust, debris, and keep in mind parallels are parallel but they are seldom flat so depending on how you are taking your reading you may be reading how out out of flatness your parallel is or how out of square your vice jaw is. all those little bits add up. And I trust nothing to be true and square until i test it, then it's either good or i grind it in until it is.

Now if you think thats bad try getting something to repeat on a surface grinder within .0001" over two inches. that will make you sweat.

I found this out ... Yes, parallels are not flat. The ones I purchased, (cheap knockoffs), are actually bowed. Do you grind these things flat? Actually, I believe the stationary part of the jaw is pretty good. I managed to get it 0.0005" over 4" with respect to the head.

[kcstott]

Good you did learn something. That comment that everything moves. A lot of people don't get that.

As for the parallels nope I don't grind them at all. I use 123 blocks for set ups parallels are just to support work and not much else.

Now what I meant about your vise is not the straight ness to the table but how square it is to the tab. You table is horizontal your vise jaw is vertical. Are they 90 degrees within .0005" from top to bottom of the jaw?? If not that can be you issue with the edge finder too.
Everything has to be square.

[krwada]

Good you did learn something. That comment that everything moves. A lot of people don't get that.

As for the parallels nope I don't grind them at all. I use 123 blocks for set ups parallels are just to support work and not much else.

Now what I meant about your vise is not the straight ness to the table but how square it is to the tab. You table is horizontal your vise jaw is vertical. Are they 90 degrees within .0005" from top to bottom of the jaw?? If not that can be you issue with the edge finder too.
Everything has to be square.

Hello KC;
Yes ... I had not thought of that! I will also do this measurement too. Also; I had not thought of using the 123 block. I will use the 123 block for the edge finding tests

[ROOS_HAPPENS]

Demanding a mill table be reground for dropping a collet on it is BS. That's a minor stoning job. It wasn't holding a 10 pound boring head, was it? If a magnetic chuck was used to hold it while being surface ground & the bottom of the table wasn't shimmed where necessary, and if the surface wasn't checked for flatness & parallelism while in a relaxed state, then it is probably warped, and the original mfgr. is dismayed. Surface grinders are notorious for that.

Re: your edge finder problems: If your DRO repeats in Y (without moving X) on a ground stationary vise jaw with either a short piece of ground drill rod or your edge finder, then you've cleared both.
I'm assuming you have the barrel type of edge finder. If it's single or double sided, there's a spring inside, into which the .200" dia. contact screws. As others have advised, clean your EF well, and try adjusting that .200" contact until it skates freely.

Thin, high parallels should be parallel in height, but I've seen them with bad side-to-side warpage due to the above described pull-down problem with magnetic chucks while being surface ground.

[krwada]

I think you are right

Demanding a mill table be reground for dropping a collet on it is BS. That's a minor stoning job. It wasn't holding a 10 pound boring head, was it? If a magnetic chuck was used to hold it while being surface ground & the bottom of the table wasn't shimmed where necessary, and if the surface wasn't checked for flatness & parallelism while in a relaxed state, then it is probably warped, and the original mfgr. is dismayed. Surface grinders are notorious for that.

Re: your edge finder problems: If your DRO repeats in Y (without moving X) on a ground stationary vise jaw with either a short piece of ground drill rod or your edge finder, then you've cleared both.
I'm assuming you have the barrel type of edge finder. If it's single or double sided, there's a spring inside, into which the .200" dia. contact screws. As others have advised, clean your EF well, and try adjusting that .200" contact until it skates freely.

Thin, high parallels should be parallel in height, but I've seen them with bad side-to-side warpage due to the above described pull-down problem with magnetic chucks while being surface ground.

That story of re-surfacing the table happened over 30 years ago. I was pretty gullible back then. Looking back, i think the master machinist needed the table re-surfaced ... and I was cheap ... basically slave labor!

I do have the barrel type of edge finder. It is single sided. I did verify that the DRO and a dial indicator agreed to within 0.001" on the Y axis. The problem is with the Y axis by the way.

Until this thread started, I did not know that the edge finder needed to be really clean ... including clean from that packing goo. And yes ... my edge finder is NOT skating freely. It does catch a little bit. I can feel it when I move the probe around a little bit.

[71MUSTY]

God, I wish I understood 10% of this thread.

[krwada]

Machining

God, I wish I understood 10% of this thread.

Awhile ago, I asked the community here whether or not it was OK for me to post general questions and threads about precision machining in general. What I got back was that doing so here at Calguns is OK.

There are a lot of very highly skilled and knowledgeable folks here.

From what I can understand ... one has to have machining skills 1st ... then it is on to firearms.

I am currently doing a 80% 1022 build right now ... thinking ... Hey ... it is a .22 right? It has to be easier than doing an 80% AR right???

Hoo boy ... was I ever wrong!

[Mr Wizard]

God, I wish I understood 10% of this thread.

+1 this^^^^

Is there a secret handshake too?

[geedavell]

These are the most accurate way to set to an edge or corner

[12voltguy]

what do people think about the laser edge finders????????

[71MUSTY]

+1 this^^^^

Is there a secret handshake too?

When I saw the thread title I thought it was going to be about sword edges. Another subject I know little about but one I could at least follow.

Actually I do understand 10% His equipment isn't trued and he can't figure out why. That's about as far as I can go except

USE A BIGGER HAMMER

[geedavell]

what do people think about the laser edge finders????????

if you have any runout you won't get an accurate reading.
Reneshaw probes have to indicated in to within .0001-.0002 for that very reason