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View Full Version : Mill Table Regrinding In B.C.



uncle pete
05-02-2009, 10:28 PM
This is a follow up from what I posted last month, I took my mill table in for regrinding as when traming the table I had a .0015 deviation down the center of the table. I used Evan's recomendation to go to "William's and White" in Burnaby B.C.

Anbody that lives in B.C. then I highly recommend this company, Very professional and top quality work, (allthough they didn't fix my original problem but will explain latter) Really can't say enough on how well they worked with me. Unusual for a large company I was allowed into their shop. Very impressive to see how the pro's do things. They mounted my mill table into the largest surface grinder in operation in B.C. I'd estimate a 20 ft. stroke, Yeah I know, I screwed up cause I forgot the wife's camera so no pictures.

They showed me a 5 axis mill under operation, (lust, drooll, lust), They have (I think whats called a Blanchard grinder) with about a 5-6 ft. circumferance on the rotary table. Multiple lathes,mills ect. This place is set up for just about anything that comes thru the door. It functions like a old school type shop where the attitude is, We can do anything, Plus add CNC on top of that and other than really specialized,esoteric work then I'm sure they can do it.

So back to my mill table, Turns out under working condions I do have a low spot in the center of the table of about .0015 but when it was mounted on their surface grinder on 4 precision ground blocks set under the main flat bottom bearing way's the table is flat within .00025 over 35 in. in length and 9 in. in width. (No noticable deviation across the table only in the length of the table.
Now comes the problem, I have a twist in the table of just barely .001 over 35 in. ( The table rocks this much when it's sitting on the blocks on the surface grinder table) Williams and White can/could regrind the bottom bearing surface and dovetails, then regrind the top of the table true to the bottom plus a regrind on the saddle the table slides on, But they recommend having both parts hand scraped in to a proper fit. Estimated cost $2000 canadian. I paid $5000 for this mill brand new so unless the lottery gods smile at me it's not likely to happen.

I probably could live with the table twist but what concerns me is the hollow in the center of the table when it's mounted in the saddle. I haven't had time to remount the table back on the mill and when I do I'll be rechecking for table flatness. So anybody have any ideas why I had/have this problem?

Dial test indicators used for checking were two different Mitutoyo .0001 reading indicators and they both agree with each other exactly. Mill spindle was trammed to the table within .0002 over 24 in. left to right and within .0002 front to back over 8 1/2 in. The tapered gib was not overly tight as I had approximatly .004 clearance when tightening the x axis locks. So why would the table show a low spot down the center? As I said I'll recheck when the table is remounted, But I don't understand the readings I was getting. With the mill vice bolted down to the table I can run a indicator across the table beside the vice and I get .0000 So was my mill table built by Linda Blair while she was filming the Exorcist movie?

I forgot to add the contact info for Williams and White phone no. 1-604-293-2268
Toll free 1-888-293-2268
E-mail www.williamsandwhite.com
Ask for Matt Williams - General Manager

Pete

Forrest Addy
05-03-2009, 12:56 AM
Jell I woulda scraped ot in place for 0.0015 error. Probably take 8 or 10 cuts. That said you gotta do what works for you. Buiding skill for one job doesn't make much sense if an affrodable alternavie is handy like your grinding shop.

It's good to give people who dome you good a heart felt plug. Word of mouth is the most effective advertizing there is.

Machtool
05-03-2009, 02:45 AM
So anybody have any ideas why I had/have this problem?
Pete.

Sorry I didnít see your original post. This 0,0015 error your seeing. Thatís in the X axis or table moving left to right? My best guess is the amount of overhang you get out of those tables when it is at the extremes of travel. Thereís so much table hanging off the sides of the knee, cantilevered, back where youíre measuring the table is lifting. As you move the table back towards the centre. The table settles / balances evenly onto the knee saddle ways and that looks like a low spot. As you travel out to the far side, the table lifts again.

You mentioned 0.004Ē clearance on the gib. That would be a pretty fair running clearance. When you re-assemble it, Iíd be trying that snugger until you can feel the drag. Being a dovetail way, that will also stop it lifting when the table is hanging out in mid air.

Regards Phil.

oldtiffie
05-03-2009, 02:49 AM
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So back to my mill table, Turns out under working condions I do have a low spot in the center of the table of about .0015 but when it was mounted on their surface grinder on 4 precision ground blocks set under the main flat bottom bearing way's the table is flat within .00025 over 35 in. in length and 9 in. in width. (No noticable deviation across the table only in the length of the table.
Now comes the problem, I have a twist in the table of just barely .001 over 35 in. ( The table rocks this much when it's sitting on the blocks on the surface grinder table) Williams and White can/could regrind the bottom bearing surface and dovetails, then regrind the top of the table true to the bottom plus a regrind on the saddle the table slides on, But they recommend having both parts hand scraped in to a proper fit. Estimated cost $2000 canadian. I paid $5000 for this mill brand new so unless the lottery gods smile at me it's not likely to happen.

I probably could live with the table twist but what concerns me is the hollow in the center of the table when it's mounted in the saddle. I haven't had time to remount the table back on the mill and when I do I'll be rechecking for table flatness. So anybody have any ideas why I had/have this problem?

Dial test indicators used for checking were two different Mitutoyo .0001 reading indicators and they both agree with each other exactly. Mill spindle was trammed to the table within .0002 over 24 in. left to right and within .0002 front to back over 8 1/2 in. The tapered gib was not overly tight as I had approximatly .004 clearance when tightening the x axis locks. So why would the table show a low spot down the center? As I said I'll recheck when the table is remounted, But I don't understand the readings I was getting. With the mill vice bolted down to the table I can run a indicator across the table beside the vice and I get .0000 So was my mill table built by Linda Blair while she was filming the Exorcist movie?

I forgot to add the contact info for Williams and White phone no. 1-604-293-2268
Toll free 1-888-293-2268
E-mail www.williamsandwhite.com
Ask for Matt Williams - General Manager

Pete

Pete.

I'd have to say that the measurements on the grinder were right in that you have a 0.001" twist that you can live with and that everything else is OK.

I notice that you have/had "about 0.004 clearance when tightening the x axis locks" which rather suggests that the gib is much looser than it should be.

I would guess that your table top is OK (as said) but that when your "X" locking screws are unlocked, that you take your first reading in the "Z" plane with the table centred within its travel. At that point the table is balanced over the saddle. If the gib is too loose and the table is moved to one end, and if the point of balance moves past the saddle, the "heavy end" of the table will tilt/tip downward and the "light/er end" (possibly where you indicator is) will tip up. This will be compounded by taking the reading with the table at the other end of its travel. This can also be caused to a lesser extent if the "Y" gib is too loose and the "Y" clamps are loose.

I suggest you repeat the procedure and put an indicator on the under-side wearing/bearing face of the table (the flat face that sits on the saddle dove-tail) with the magnetic base on the saddle and see if the table lifts.

If it does, then tighten the "X" clamps at each end of travel and see what happens.

It is possible that your dove-tail is worn (usually in the centre of travel) and you may have to make a compromise as to how tight you have the gib/s.

This sort of thing can also be caused by machining with the table unbalanced which can either be due to poor set-up or as seems to be a habit with some here, of leaving a heavy rotary table or vice permanently mounted on the end of the table.

I balance all of my table-work and re-adjust my gibs to suit if required. My table has a bit of wear or less than perfect machined surfaces (very little - but I can feel a tight gib - same applies to lead-screw/nut adjustment).

I'd suggest giving it as try and see how you go. If it improves things it will be well worth the effort. Same applies if it doesn't improve it as you will at least have isolated some problems and perhaps have either eliminated others or at least know what they are and where they are and to take account and/or adjust accordingly.

JCHannum
05-03-2009, 08:21 AM
My advice would be to lose the 0.0001" indicators and use 0.001". A vertical milling table can sag from end to end due to it's own weight. Clamping forces, the weight of the fixturing device, such as a heavy vise or rotary table, the location on the table and movement from end to end can all cause that much deflection in a milling machine table.

Tenth accuracy is getting into the range of surface grinding and at the high end of a vertical mill's capability. If and/or when that level of accuracy is required, shim or otherwise true the setup to produce it.

uncle pete
05-03-2009, 09:15 AM
Sorry I wasn't clear enough in my explaination, The low spot is in the Y axis, X axis gib was backed off a bit as I was trying to find out why I had this low spot. Normally the gibs are adjusted to give me .001-.002 clearance. Mill is brand new but I've had it for 4 yrs. As I said I haven't had time to reinstall the table but when that's done I'll rerun the checks. Thanks for everyone's input, I appreciate it.

Pete

DFMiller
05-03-2009, 10:51 AM
I second the recommendations on Willams and White. They touch up a mill table for me in the past. They do what they say for the price quoted and they seem to be very happy to help out the non professionals.

uncle pete
05-03-2009, 12:05 PM
DFMiller, Yeah exactly my experience too, An unusual attitude for a professional shop today. Most employees I met there were 40+ yrs. old and a lot seemed to be from Europe. With my machineing skills I'd be impressed if they let me sweep the floors. I will be taking further work to them.

Pete

DR
05-03-2009, 12:50 PM
Pete,

I'm curious how much they charged to setup your table and determine the problem.

If they didn't charge, my guess is they wouldn't want any more "non professional" type work.

Time is money for shops like that, hoefully they charged you.

I've done favors for individuals in the past without charging. There's no quicker way to learn no good deed goes unpunished than when they tell their friends. Soon, everyone expects freebies.

uncle pete
05-03-2009, 08:28 PM
DR, No charge as the general foreman said they didn't fix my problem, I gave him $100 anyway. I don't work for free and I don't expect anybody to work for free. There will be no problem with me getting further work done at this shop and they have no problems working with non pro's. Foreman was supprised at what I gave him but I know they will remember me, And will work with me in the future. Sometimes it's not what you got today but what you recieve in the future. If I never get anymore work done there then it was still money well spent.

Pete

Robin R
05-03-2009, 09:57 PM
Did the $2000 estimate include the scraping, or was that just for the grinding. If it did include the scraping, did you also get an idea of what just the grinding would have cost.

uncle pete
05-03-2009, 10:39 PM
Robin, No the $2000 was not for grinding, That would have been cheaper. $2000 was an estimate to hand scrape it in. For what little I know about scrapeing and how much work is involved that's a good price. The mill is exactly the same as a Jet 8-36 and as far as I can tell built in the same factory. Mine has a 3 speed power down feed on the spindle and sold by "Bemato" Model no. 1250S
I paid $5000 for this brand new so I can't justify another 2 grand to fix a .001 twist in the table. I'll live with it but it helps to know where the defects are so you can compensate for it on longer parts. I still think the mill is accurate enough that I bought a Newall 4 axis DP900 DRO for it. Yeah I know it's overkill but if the parts have wrong dimensions on em then I'm gonna blame the DRO.

Pete

Robin R
05-03-2009, 11:45 PM
Thank's for that Pete, I recently got a smaller lathe, that might be in need of a bed grind. It's good to know of a reputable company, if it does end up coming to that. Once I get it up and running, I can get a better idea as to the accuracy it's currently capable of.

oldtiffie
05-04-2009, 08:08 AM
Robin, No the $2000 was not for grinding, That would have been cheaper. $2000 was an estimate to hand scrape it in. For what little I know about scrapeing and how much work is involved that's a good price. The mill is exactly the same as a Jet 8-36 and as far as I can tell built in the same factory. Mine has a 3 speed power down feed on the spindle and sold by "Bemato" Model no. 1250S
I paid $5000 for this brand new so I can't justify another 2 grand to fix a .001 twist in the table. I'll live with it but it helps to know where the defects are so you can compensate for it on longer parts. I still think the mill is accurate enough that I bought a Newall 4 axis DP900 DRO for it. Yeah I know it's overkill but if the parts have wrong dimensions on em then I'm gonna blame the DRO.

Pete

Peter.

I'd be very careful about assuming that DRO's will cover all contingencies. They won't and they don't. They do what they are intended to do and designed for very well - but that is all.

In your case, no DRO ("Z" DRO included) will detect the "Z" error as your table rises and falls - ie as it tilts - as the "X" traverses end to end between its limits of if a large "out of balance" load is placed on it - same applies for the same result is a large rotary table or vise is left on the end of the table.

Lateral movement of the table in the "Y" plane due to slack table gibs will not be detected by the "Y" DRO.

Lateral movement of the saddle in the "X" plane due to slack saddle gibs will not be detected by the "X" DRO.

There is a large potential for "Y" error in setting a vice jaw with its jaw face in the "X" plane and use the vice jaw face as a "zero" or as a reference, if the "X" dove-tail is bearing against the front (ie gib) side rather than if it bears on the back of the dove-tail if the dove-tail is slack and also if the clamps are not fastened. If it is bearing on the gib, the clamps will move the gib which will first take up its own slack and then the slack in the dove-tail by moving the table "back" in the "Y" plane. Your "Y" DRO will not detect it but a dial indicator on the front or back face of your table will detect it.

Further, a DRO will not detect any flexing or movement in your set-up, your cutter adaptor in the quill of the flexing of the cutter either.

I would never rely on a DRO in many cases as the real answer is to physically measure the cut/finished part.

Unless the machine has no lead-screw back-lash or end-play, I would always use the final setting in the traditional way toward the position to be cut - never away from it - as I prefer to rely on BOTH the clamps (where applicable) and the high resistance to back-driving in a common acme form lead-screw and nut - as well as taking up the end-play.

Cutting loads can soon find the weak points as regards resistance to thrust under cutting loads.

DRO's are an excellent aid and very accurate in doing what they are designed to do. But they may give you a false sense of security as regards machine part placement/location.

uncle pete
05-04-2009, 11:25 PM
Robin, Price Williams and White quoted over the phone was $400-$450 to resurface my mill table, 35 in. x 9 in. this was their best guess, After they looked at it they said it should be cheaper. They originaly figured 10 min. to do the grinding but my table spent close to 2 hrs. sitting on the grinding table. No my problem was not resolved at a price I was willing to pay verses what I paid for the mill brand new but that was not william and whites decision. I've got more problems than I thought.

If you need a grinding company then yes you could probably get a cheaper company but there is no doubt in my mind that if you want a top quality regrind done then if accuracy verses $$$ spent is what you want, Then they are the company to go to. Location is a little hard to find but if you need directions then PM me.

Oldtiffie, I agree with your input 100% No DRO will allow perfect work to be done on a imperfect machine but I also own a lot of very high quality precise measuring equipment. Not to brag but I've bought Mitutoyo digital mics. from 0-4 in.Grade 2 gage blocks, And Mitutoyo dial indicators from 1 thou to 20 millionth's repeatable accuracy. For the most part I know how to use these very well and fully understand the effects of temperture. I very much appreciate your input and have no doubt I'll be directing some questions your way once this DRO is mounted and operational. That said I firmly belieave that between the DRO and my high end measuring equipment, when a real precise part is required then I can spend the time reqired to "tweak" my set up to get what I want. Industry can't afford, Or to be truthfull the end user won't pay the cost's for this. I'm a hobbiest and work to my own standards. I've been saving for a DRO for the last 5 yrs. And bought what I considered the most durable/accurate system for the money avalible. I'll also be buying this same DRO system for the new lathe I ordered. Yes it's overkill for a home shop enviroment but I'd rather have far more than what's required than not quite enough.

Pete

oldtiffie
05-05-2009, 02:22 AM
.............................................

Oldtiffie, I agree with your input 100% No DRO will allow perfect work to be done on a imperfect machine but I also own a lot of very high quality precise measuring equipment. Not to brag but I've bought Mitutoyo digital mics. from 0-4 in.Grade 2 gage blocks, And Mitutoyo dial indicators from 1 thou to 20 millionth's repeatable accuracy. For the most part I know how to use these very well and fully understand the effects of temperture. I very much appreciate your input and have no doubt I'll be directing some questions your way once this DRO is mounted and operational. That said I firmly belieave that between the DRO and my high end measuring equipment, when a real precise part is required then I can spend the time reqired to "tweak" my set up to get what I want. Industry can't afford, Or to be truthfull the end user won't pay the cost's for this. I'm a hobbiest and work to my own standards. I've been saving for a DRO for the last 5 yrs. And bought what I considered the most durable/accurate system for the money avalible. I'll also be buying this same DRO system for the new lathe I ordered. Yes it's overkill for a home shop enviroment but I'd rather have far more than what's required than not quite enough.

Pete

Thanks Pete.

I was not down-playing your DRO, machine, tools or ability as I guess you had those bases covered - as well as how to use a machine with and without a DRO.

My comments were for a wider audience - particularly some that might think that a DRO is a god's gift to machinists as well as a panacea to cure all ills - it isn't. It will solve some problems but may well create others for the unwary (or lazy) machinist.

From what I've read, your machine is in pretty good shape and you are aware of the "pit-falls" and their "work-arounds" to allow for any "adjustments" to be made. I'd guess that your machine would be well up in the first quartile of machines here.

No machine is perfect, but providing it is adequate for a good machinist to get the job done as well as he needs - its good enough. Anything better than that is a bonus.

Thanks for the reply and comment - appreciated.

Evan
05-05-2009, 04:06 AM
Williams and White isn't just a machine shop. They also manufacture specialized milling and grinding machines which my wife brokers. They make very high quality products such as 20 foot bed grinders and this automated saw blade grinder as well as other industrial machines.

http://ixian.ca/pics6/ww1.jpg