Question on mill/drill traming.

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SonofHarold - Metal Carver

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I'll try and keep this short but a little back ground. I have one of the older HF round column mill/drills. ( model 24976)I know it has it's limitations but I am trying to get it to be as good as it can be. Finally got the spindle/quill re worked, and a simple DRO to have something for measruing the Z ( it had nothing) so it's time to dial it in and get everything square.
The other night I cut some shims and was just going to get started and see just how hard or fussy it was going to be and to my surprise it was much closer than I expected.
So I started trying to make it better. Ended up chasing the indicator around for more than two hours and a couple dozen different shim combinations. Made it a lot worse at times but the best I could get was within about .003-.004. I was using an indicator and a new disc brake rotor placed on the table and sweeping about a 10.5 inch circle. Question is; should I expect it to get much better with this machine? I was working alternately on both the side to side and the front to back and was kind of chasing it in and out a lot.... Right now fairly well snugged up it's off about 3 and half thousands on the Y and about 2 thousands on the X. It that as good as it gets or do I need to drink a big cup or patients and go back at it?
Thanks-
 
Yep, I agree 100% with Norseman... just run the indicator on the table top. If it was my machine, I would like to see it within 0.001" A lot depends on what kind of work you will be doing and what kind of tooling you will be using.

Ted
 
That has a pretty small table and sweeping across the slots seem difficult, I think I found the idea of using the brake rotor on line someplace - maybe here(?)
I did try tuning the brake rotor 90 deg thinking there was some error in it because sometime it seem pretty consistant and others not so much but the readings on the indicater were the same +- a thou. or less.
But.... I did try going directly to the table and seems about the same as best I can tell, about .002 or a little less on the x, but sweeping acrross the slots make me question my accuracy too. Any ideas on that? guess I should take some pics of my set up.
So you would think that machine can be dialed in closer than I have it. Seems just reaching up to turn the spindle and touching the maching can move the idicator a thou or more if I am not gentle.
 
I have an RF-31 so it should be very similar to yours, John. I agree with the other guys that you should use the table surface as a reference PROVIDED it is clean and free from defects. The reason for this is that it is what we mount our vise or work to and that is what we want to tram to.

As for acceptable tolerances, there is no standard for this sort of thing that I am aware of. Most of us want zero deviation in all axes, most of us can get 0.001" or less.

My column is trammed with precision shim stock and onion skin (precision paper shim stock). It is 0.0005" high in the front of the table and zero in all other directions. It took two days, two days, to get it there. I used a torque wrench set to 35 lb/ft on each column bolt to be sure that didn't mess things up and when I got the final shimming done, I loosened and re-torqued the bolts to be sure nothing changed. I admit that I haven't looked at it since so it may have changed. I'll have to go re-check it soon.
 
So... I don't need a cup of fresh patience but maybe I should buy a case before heading out there? I did look around on the site a little more and found someone using 1-2-3 blocks and moving it from side to side when swining the indicator around. (?) When it warms up again some here I'll go try again, I shut down the heat a while a go out in the shop and we are going down to the teens overnite tonight so it might be the weekend before I warm up the shop again... unless I get bored ( I am sure you have no idea what I am talking about... just looking for sympathy... jk)
 
Yup, patience helps. Look at it this way. The accuracy of every single face or edge you cut on the mill is influenced by how accurate your tram is, and tolerances stack up quickly. If you cut a side and use it as a reference for the next side then it will be off a bit, then a bit more, and so on. I figure its worth the effort it takes to get it right and then do what it takes to keep it right.

I used a Starrett back plunger indicator to get tram really close. The tip slides over the slots so its easy. Once I got really close, under a thou, I switched to a Compact 215GA tenths indicator and moved carefully over the slots to avoid damaging the indicator. Two days of that taxed my patience but I did it because it matters.

What is really frustrating is when I move the head, all that careful work goes out the window. We don't actually lose tram when we move the head; we lost that centered position from which tram was set. If we can return to that exact position the mill will be in tram again so the trick is to get it repositioned again. Bruce Witham of Australia came up with the True Line 88 to do exactly that. Others have used linear shafting to do the same thing, or laser pointers. I bought a True Line 88 to see if it does the job and when I have the time, I'll install it and review it for you guys here.

Unlike you, time is my issue. It is currently 76 degrees with a cool 17 mph Northeast trade wind so I'm comfy but don't have the time to tear into my mill right now. Is there such a thing as a gonad-warmer?
 
That tru line looks interesting.
I'm wondering if the UHMW will hold tolerance over time, I've made lots of
industrial roller shaft bearings with it but they do wear quicker than bronze the trade off being
cheaper to replace, maybe over thinkin here.......................:rolleyes:
 
SonofHarold - Metal Carver said:
So... I don't need a cup of fresh patience but maybe I should buy a case before heading out there? I did look around on the site a little more and found someone using 1-2-3 blocks and moving it from side to side when swining the indicator around. (?) When it warms up again some here I'll go try again, I shut down the heat a while a go out in the shop and we are going down to the teens overnite tonight so it might be the weekend before I warm up the shop again... unless I get bored ( I am sure you have no idea what I am talking about... just looking for sympathy... jk)
Click to expand...
I do not like to use intermediate blocks of any kind when indicating something. Everything has a tolerance, is not flat or parallel, and using them as intermediates only confounds the readings. Use an indicator right on the table, and have it set up so the plunger can only go into slots or dings a few thou. Yes, it will bounce around some, but it will be measuring reality.
 
Norseman C.B. said:
That tru line looks interesting.
I'm wondering if the UHMW will hold tolerance over time, I've made lots of
industrial roller shaft bearings with it but they do wear quicker than bronze the trade off being
cheaper to replace, maybe over thinkin here.......................:rolleyes:
Click to expand...

To be honest, I don't move the head much thanks to the 5" of quill travel but it does move from time to time. What I want from the TL88 is for it to return me to my centered position, nothing more. Since it will see limited travel and limited use, I suspect the use of Delrin or UHMW material is a good choice. The vertical bar that travels through it is an accurately squared aluminum rectangular bar that is bolted to a bracket fastened to the side of the head and the Delrin block is anchored with a machined steel collar at the bottom. There is a hole in the Delrin that allows you to use a tensioning bolt to draw the sides of the channel tighter if needed.

All this thing needs to do is guide the head reasonably straight up and down and then allow the head to center accurately once the head bolts are tightened. My criteria for acceptable performance is for it to restore the head to centered position within a thou or less. If it does that then it is worth it.

I won't lie. I can easily make one of these contraptions but Bruce spent the time, effort and money to come up with this thing. I spent the money on it because it was the right way to do this and also because I wanted to review it for the HM membership. Since I bought it, I feel free to do an honest review, which I will do.
 
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