planer

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

Moderators: Harold_V, GlennW

Harold_V
Posts: 17747
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: planer

Post by Harold_V » Tue Aug 27, 2019 1:57 am

One of the things that must be addressed when surface grinding is how the part being ground mates with the magnetic chuck. The chuck has enough power to pull relatively rigid items, especially when they are slender, as would be a table, or even a bed.

I saw no evidence of any attempt to shim in video, and at the end there was mention of the deflection of the bed (most likely the table as well), resulting in a less than straight surface.

In my years of precision grinding, it was always common practice for items to be shimmed, so they were not able to deflect. Once shimmed, the part, what ever it may be, would receive a cleanup pass, then flipped, with the process of shimming repeated. It may take more than one iteration to eliminate a less than flat condition, but it is possible, and pays huge dividends in the end.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

pete
Posts: 1718
Joined: Tue Feb 10, 2009 6:04 am

Re: planer

Post by pete » Tue Aug 27, 2019 10:53 am

Yeah I noticed that as well Harold. No practical hands on experience with surface grinding on my part, but everything I've studied about it usually mentions shims at some point. Parts deflecting due to the pull from the chuck seems to be a constant issue if your not ultra careful. Since he's going to scrape for final alignment anyway and the job had taken 3 days already then maybe it was considered as good enough? A couple of thou over 12' is still pretty accurate as it is though.

armscor 1
Posts: 90
Joined: Sun Jun 12, 2016 3:12 am

Re: planer

Post by armscor 1 » Tue Aug 27, 2019 3:28 pm

Another thought too Harold, maybe insignificant, is the mass of a piece of 12 foot cast iron which is bowed or twisted when lowered and settles on the Mag chuck will move.
Don't know how you would compensate for that?

Harold_V
Posts: 17747
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: planer

Post by Harold_V » Tue Aug 27, 2019 3:36 pm

A couple thou of unnecessary metal can be a long process to eliminate by scraping when such a large item is involved. Any time spent shimming would have been well spent, and it doesn't take much under normal conditions. With the piece sitting on the chuck, a feeler gauge is used to determine clearance, then a shim installed in its place. That prevents deflection.

In the case of such robust pieces as were ground, even a single shimming in the center of each of them would have eliminated virtually all deflection. Could have ended up with a thou error (or less) without much issue.

This makes me wonder how the (table) ways on the surface grinder I have managed to get off by a whopping .005" over 32". I expect for the same reason, but there's no way I can make that determination.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

Harold_V
Posts: 17747
Joined: Fri Dec 20, 2002 11:02 pm
Location: Onalaska, WA USA

Re: planer

Post by Harold_V » Tue Aug 27, 2019 3:57 pm

armscor 1 wrote:
Tue Aug 27, 2019 3:28 pm
Another thought too Harold, maybe insignificant, is the mass of a piece of 12 foot cast iron which is bowed or twisted when lowered and settles on the Mag chuck will move.
Don't know how you would compensate for that?
Very simple. The item is placed on the chuck on the intended mounting surfaces, which should have received hand dressing to ensure there were no high spots. The mag chuck is NOT energized. Feeler gauges are then employed, to ensure there is no clearance between the mounting surfaces and the chuck. If any are found, proper shimming is installed, and that can be anything that fits the opening, including a piece of thin paper (eyeglass wipers are only a thou thick, as is aluminum foil). Once all the pads are properly shimmed, at least one place between the mounting surfaces should be shimmed, to prevent the center from deflecting when the chuck is energized. The longer the item, the more places being shimmed. For such a robust piece as was shown, shimming at 2' intervals would most likely suffice, and it takes very little time.

Once the first side is kissed (to clean up), it becomes the mounting surface for the second side. At that point you can easily eliminate any distortion, although if the first shimming was done properly, there may not be any.

Keep in mind, gray iron tends to have a minimum of 30,000 psi tensile. It is quite rigid, and will deflect very little from its own weight. The process of elimination by flipping and shimming should eliminate such a condition. That was routine when I was working in grinding.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

hoppercar
Posts: 230
Joined: Sun Jul 22, 2018 4:09 pm

Re: planer

Post by hoppercar » Thu Sep 19, 2019 7:13 am

why he drilled those feet castings for leveling screws is beyond me.....should have used adjustable fixators.

armscor 1
Posts: 90
Joined: Sun Jun 12, 2016 3:12 am

Re: planer

Post by armscor 1 » Thu Sep 19, 2019 4:34 pm

Another problem I anticipate is the machine walking all over the workshop!

pete
Posts: 1718
Joined: Tue Feb 10, 2009 6:04 am

Re: planer

Post by pete » Thu Sep 19, 2019 5:04 pm

One problem with planers that I've read about that could be fairly serious is a failure within the mechanical auto table return. Most of the old planers seem to be a rack and pinion drive and if the auto return happens to fail and not start to reverse the drive direction the table runs off the end of the bed ways. Since most if not all planers seem to only use V ways it's only the weight of the table and part being machined that holds the table on the bed ways. I've read a few mentions on the PM Antiques forum of some instances where the table went right through the wall of the shop it was in. It's recommended that a fairly heavy steel cable anchored to the bed and the table be used as a safety strap to prevent the table coming off the bed ways if it goes too far. Those would of course be the larger planers that have the size and weight to do some real damage. But it's something to be aware of on the smaller bench top ones as well.

Lazz
Posts: 136
Joined: Sun Jul 29, 2012 11:06 pm
Location: The Warm Arizona Deserts... Phoenix to be precise...

Re: planer

Post by Lazz » Sat Sep 21, 2019 9:04 am

Here is another planner repair video series.
https://www.youtube.com/watch?v=zhWO6Zoz-EU

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