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New 10" X 54" mill ordered.
- Thread starter John Conroy
- Start date
I did a copy/paste embedded code and had to do some cleanup.....
You have one of those stupid metric DTIs as well Eh. Was glad when mine crapped out and had to be replaced.
I want Johns DTI mine only measures to 0.0005"
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I bought this one on sale a few years ago from KBC. I think it was $90
https://www.kbctools.ca/itemdetail/1-808-513403
https://www.kbctools.ca/itemdetail/1-808-513403
When it comes to cheap accessories I have been disappointed by a few that didn't live up to the sellers accuracy claims. PM sells this ER40-R8 collet chuck and claims -runnout of +-.0002" which is another way of saying .0004" or less total runout. Again I was skeptical but for $30 USD I thought I'd take a chance. I checked it yesterday when I was do a bunch of other accuracy checks on the machine. It passes but just barely.
https://www.precisionmatthews.com/shop/er-40-collet-chuck-r-8-mount/
https://www.precisionmatthews.com/shop/er-40-collet-chuck-r-8-mount/
I did a series of checks with a tenths indicator held in a collet in the spindle and a 2-4-6 block. The block was pre tested on my surface plate to be square to within .0001" and the head was trammed beforehand to within .0005" deviation in a 10" circle
I moved the table in all 3 axes with the power feeds and the gib locks lightly snugged. For the X and Y tests the block was lightly snugged in the vise. I am frankly quite amazed at the results as the indicator did not move more than .0002" on any of the 3 tests over 6" of travel on X and Z or 4" of travel on Y.
I moved the table in all 3 axes with the power feeds and the gib locks lightly snugged. For the X and Y tests the block was lightly snugged in the vise. I am frankly quite amazed at the results as the indicator did not move more than .0002" on any of the 3 tests over 6" of travel on X and Z or 4" of travel on Y.
Thanks guys I'm very happy it turned out be be so straight. While watching Clough42's videos he suddenly went from using a new PM940 square column mill to a new PM935 knee mill. The only explanation he gave is that the X and Y axis were not perpendicular to each other on the 940 and PM did a trade/upgrade for him. No details but it made me want to verify mine
I noticed that too. I guess Monday machines can happen with any re-seller, but I bet Matt made it right. I've heard of some of the early RF-45 style Chinese machines where the (bolted) pillar column was out of whack relative to the base so had to be disassembled, shimmed & re-grouted. Do-able but not fun. And others where the Y dovetails had some issue. I can see spending time on a used machine but when it comes new out of box one wants to start making parts & not rebuilding the machine & rectifying factory problems.
I learned something about this style of variable speed head over the last few days. When you crank the variable speed handle toward the slow speed setting you will notice that it's much harder to turn than cranking it toward high speed. This is because the belt is being forced toward the center of the motor pulley/sheave. In order for the belt to go to the centre of the sheave it must compress a very strong spring which makes it harder to crank the handle. When you crank the handle to go faster the spring assists in pushing the belt outward on the sheave so it cranks easier. I already knew this and anyone who has this style of variable speed head probably already figured this out as well. What I learned is that you should not leave the belt cranked to the low speed position for any length of time when the mill is not being used. When you do that the belt is being crushed between the 2 sheave faces by the force of the spring and it will develop a flattened out area in that crush zone. Similar to the flat spots that develop on vehicle tires when they sit in one spot for long periods of time. I learned this when I left the machine sitting in the low speed setting for 2 days without using it. When I went back to use it there was a significant vibration and sound from the flat spot on the belt as it went around the sheaves each time. I removed the belt access cover and could see the belt vibrating. After about 20 minutes of use the vibration and sound completely went away as the belt warmed up and resumed it's original shape just like tires do after driving the vehicle until the tires warm up. Since then I have been cranking the head to the high speed position before shutting down for the night and had no more vibration or noise. The only reason this came to my attention is because this new mill has been so smooth and quiet that the sudden appearance of the vibration was concerning.The spring is number 44 in this picture.
I did 3 short videos on the the tram checks I did and posted them on YouTube in case anyone would like to see the process I used.
I'm seriously wondering if my in & out hum around a certain rpm level might have to do with this belt 'set'. What is a bit frustrating is I tend to operate around this rpm level a lot so of course in the noisy zone - either slower or faster & noise is not there. It could still be harmonics related to belt or spring or motor for that matter, but now you have me thinking. Do you think if I left it for a period in this 1000-1200 rpm then this is also where one would expect the noise? When you say crank it up to high for storage mode, do you mean like up near the red range? I'll have to record my sound again & compare notes with you if it sounds familiar to what you've discovered.
Pretty darn good. I'd say you're at the limit your blocks.. Unless those happen to be a brand like Suburban (spelled $uburban).
If your X is zero and Y is 0.0002" I still wouldn't discount the machine. It could be the block grind is a parallelogram. You'll need a squareness checker when you get that surface grinder LOL
I've been cranking it up to about 3000 rpm but I think just keeping in the 2000 range would probably be enough. With the vfd I can crank the speed up with the handle but turn the frequency down so the belt moves to the unloaded position but the actual spindle speed can be kept reasonable.
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I turned the block 180 degrees and got the same numbers. I checked the block on my surface plate and really couldn't see any more than about half of a tenth out of square in either direction. I have 2 blocks and one is very square and the second is about two tenths narrower at one end than the other.
It would be nice to have one of Suburban Tools squares but I'm not willing to spend that much considering how little it would get used. And I'd probably drop it! Lol
Somehow or another I stopped getting notifications about updates to this thread and I missed a lot. It's amazing what you have all done since you got the machine.
That belt compression thing was an eye opener but I think you are spot on! I like your ideas of how to deal with it but I didn't know you got a VFD for that machine. Or did it come with it? (sorry if you already mentioned this somewhere).