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  1. #1
    Join Date
    Jun 2008
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    Default Macson Bench Surface Grinder Rebuild

    Recently a Macson Bench Surface Grinder found its way into the workshop ).

    I was after a small grinder as I don't really have the space for a big one and it seemed a good project to use those scraping skills from the Phil's and Marko's scraping course.
    Searching for information on-line regarding the Macson didn't really come up with much in terms of technical information (btw if someone has any info e.g. manuals, more detailed pictures on these grinders please let me know).

    I thought that starting a thread on the rebuild might help someone in the future.

    Here's an original advert from a McPherson's catalogue circa 1955.
    Attachment 211231

    The one I have has 75 stamped on most components. I'm not sure what it means? number 75 built? builder 75?

    Here's the grinder in the workshop.
    Attachment 211232

    Its on the trolley because things didn't go as planned (. It was quite a bit heavier than I thought. The trolley is probably the same vintage as the grinder and built as strongly as well. With no immediate way to lift it, I decided that as I was going to strip it down to check it out anyway, the floor was a good place to start.

    Here's the magnetic chuck and the wheel removed. More on the chuck in another thread.
    Attachment 211233

    Here's the motor removed showing the original paint. At this stage I'm not sure what i'll do with the motor. I don't have 3 phrase or 415v. Inverter?, new motor?
    Attachment 211234

    Below is a photo of the x-axis ways.
    Attachment 211235

    Y-axis saddle:
    Attachment 211236

    Y saddle removed:
    Attachment 211237

    The bearing surfaces are all pretty clean. Hopefully is means it hasn't had a particularly hard life. Once its fully stripped down i'll get it on the surface plate and start checking things out.

    Its stripped down enough to get it on its side. I now know why it was heavier than I thought.
    Attachment 211238

    Interesting counter balance mechanism for the Z-axis:
    Attachment 211239

    Top of the counter balance mechanism:
    Attachment 211240


    More to follow

    Christian
    Last edited by CGroves; 6th Jun 2012 at 09:38 PM. Reason: Duplicate photo removed

  2. #2
    Join Date
    Nov 2008
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    Perth WA
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    Default

    A neat, handy bit of gear Christian. I saw one years ago over here but the seller was chasing an exorbitant sum for it. I liked the size of the machine, great for a too crowded shed.

    BT

  3. #3
    Join Date
    Dec 2011
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    South East Queensland, Australia
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    Default

    Good catch . It's a goodun, looks to be in pretty good condition overall too.

    Cheers.
    If I'm not right, then I'm wrong, I'll just go bend some more bananas.

  4. #4
    Ueee's Avatar
    Ueee is offline Blacksmith, Cabinetmaker, Machinist, Messmaker
    Join Date
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    Default

    Looks good

    Seems to be in overall ok condition to start with so thats a bonus! Look forward to seeing your updates.
    1915 17"x50" LeBlond heavy duty Lathe, 24" Queen city shaper, 1970's G Vernier FV.3.TO Universal Mill, 1958 Blohm HFS 6 surface grinder, 1942 Rivett 715 Lathe, 14"x40" Antrac Lathe, Startrite H225 Bandsaw, 1949 Hercus Camelback Drill press, 1947 Holbrook C10 Lathe.

  5. #5
    Join Date
    Jun 2008
    Location
    Newport, Victoria
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    Default

    Here's some more on the components. Below is the y-axis screw. I should have taken a picture of the inside of the bronze nut. There's only two little "teeth" that cause the screw to advance when turned.
    Attachment 211538

    Below is the z-axis screw:
    Attachment 211539
    I think it was Bob who mentioned about the fine feed of surface grinders.

    Another shot of the spindle.
    Attachment 211540

    I haven't taken it apart yet. There's an internal lock washer that is refusing to budge. I don't want to resort to a hammer and punch. So I'm planning on machining a socket to create a couple of teeth to fit the lock washer.

    I decided to remove the grease nipples/zerks. I wanted to get in and clean out all the oil and grease channels properly. The grease nipples were all push in types so they wouldn't simply screw out. After trying a couple of methods I found that a pair of pincers worked well. I plan on replacing the nipples with new ones and giving the castings a new paint job so I wasn't worried about paint chips.
    Attachment 211541

    To clean out the channel I used some small "pipe cleaner" type brushes that I found in a paint supply place. Apparently used for cleaning out spray guns. They work a treat.

    The picture shows the underside of the y-axis casting.
    Attachment 211542

    Christian

  6. #6
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    Nup Christian, It was PDW.

    There is a Hercus No.3 Tool and Cutter grinder on Ebay at present and the plonker trying to sell it has described it as a surface grinder. PDW said they are not much chop as even a pretend surface grinder because the vertical feed and its measurement
    are too coarse.

    BT

  7. #7
    Join Date
    Jun 2008
    Location
    Newport, Victoria
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    Default

    In rebuilding the surface grinder some scraping is going to be in order. So I figured that I better get the stand for the surface plate finished. After reading some of the other threads I figured a three point mounting system I steel balls was the way to go. A search on-line came up with a ball joint for surface plates:
    http://www.schlitt-werkzeuge.de/pdf/...htmittel-E.pdf

    So I decided to emulate something similar. Below is what was planned:
    Attachment 215255

    I want to epoxy the brass component to the bottom of the surface plate. The design allows for some movement in the metal frame.

    Here's the resulting parts:
    Attachment 215256

    Fully assembled:
    Attachment 215257

    The adjustment bolt is a M22 superfine pitch. I don't have a lathe so it was helically milled. Here's a picture helically milling a frame member to accept the bolt.
    Attachment 215258

    A test fit:
    Attachment 215259

    Here's the completed frame.
    Attachment 215260

    Its on height adjustable castors so hopefully I can perform course levelling via the castors and do any fine levelling via the surface plate mounting points. Now to get the surface plate on the stand.....

    Christian

  8. #8
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    Melbourne
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    Default

    Hi Christian,
    Certainly looks the part. Wheels do have a lot going for them.
    Any reason for using brass?
    How did you machine the radius to match the ball? I gave it up as to hard to get spot on. If its not spot on you end up with line contact somewhere. By giving up at least I can control where that line is.
    Did you mill all the other parts?

    Stuart

  9. #9
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    Aug 2010
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    Near Bendigo, Victoria, AUS
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    May I suggest that you get a VFD for your motor?
    The main reason is that you can set the acceleration to grinding speed to be nice and gentle and the deceleration as well. That way you can be certain that the wheel never moves on its spindle - which it can if you replaced it with a single phase motor. Secondly, a 3-phase motor runs with far less vibration (less acceleration and deceleration in each revolution) than a single phase motor. Lastly, you can adjust the surface speed of the wheel to exactly suit the wheel diameter and materials you are grinding.
    Given that you have the correct motor, the cost of a VFD would be similar to that of of a replacement single phase motor - which incidentally is likely to be heavier and upset the z-axis counter balance.
    Cheers,
    Joe

  10. #10
    Join Date
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    Germany, Outback of Munich
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    Default

    That doesn't look too bad. Except for the Y-ways. Too small, the table will rock.
    There's no surface grinder below 1000 kg.
    But for the size, she looks quite promising.

    The 75 stamped in some pieces is a fitting number. Parts are machined, matched an fitted. And those that actually match or belong together get the same number. You can expect that it starts all over again with a 1 after 99.


    Nick
    PS: Happy scraping!

  11. #11
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    Jun 2008
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    Newport, Victoria
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    Default

    Stuart: I used brass as I vaguely recalled seeing that's what Phil used (I could be wrong) on his plate on the scrapping course and at 45mm it was the largest round material I had on hand. I probably could ave beefed up the parts but I was trying to keep the distance between the plate and frame around 50mm it order to keep the high the same as another small bench I have.
    The radius was machined using my CNC mill using a 10mm ball nose endmill. There's some slight scalloping but I think the contact area is pretty good. It was easier to machine than an angle.
    I milled all the parts in the mechanism apart from the balls. I fabricated the frame its 50mm RHS 4mm thick. The casters are Carrymaster casters:
    AUTO CFT

    Joe: I think i'll follow your suggestion. I've been following the other thread on VFDs and what i'll try to do is see if the motor can be changed from 415v to 240v 3phase and then by a VFD. I'd like to keep the original motor if possible. I need to open it up and have a look and give it a clean and replace the bearings. Otherwise I think the electrics are a write off. Lots of grey and blacks marks in the switch box (held together by duct tape) so all that will be replaced. I'm not sure that for this grinder having a heavier motor will affect the Z-counter balance as it doesn't move up/down with the spindle. Its attached to the side via an axle and will pivot providing tension to the drive belt. At least that's my theory ).

    Nick: I've always been telling myself size doesn't matter ;-). I'd love a bigger machine but space is at a premium... I did find an oops in the numbering. The thrust bearings on the spindle have no.77 engraved on them. So if someone out there has machine no.77 I have your bearings....

    Christian

  12. #12
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    Default

    Its taken a little while to disassemble the spindle. I needed to make a tools to remove an internal lock washer on either end of the spindle. I also need to make up a pair of pin spanners to remove a couple of components from the ends.

    Here's a picture of the tools.
    Attachment 215273

    As I mentioned previously I don't have a lathe so I turned the pins using the mill as a vertical lathe. I borrowed the idea from Tormach about using quick change tooling.
    Attachment 215274

    You can find more details / videos here: ftp://sprutfiles:[email protected]%20(2).zip
    (btw: the file is around 68meg)

    With the tools it was fairly straight forward to remove the spindle. You can see the lock washer and the component with the pin holes.
    Attachment 215276

    Here's the whole spindle (assembled):
    Attachment 215275

    Components from the grinding wheel end:
    Attachment 215277

    Components from the pulley end:
    Attachment 215278

    On the grinding wheel end it has two matched Hoffman 125ACDEP N1785 Thrust bearings. There's a bit of play in them so they will be replaced. Apparently the new equivalent bearing is a RHP 7205CTRDULP4. On the pulley end it has a Hoffman 125 deep groove ball bearing. According to the local bearing place an equivalent bearing is a FAG 6205. Now it seems strange to me to have a P4 and P6 rated bearing on the same spindle? However its probably not going make a measurable difference.

    The other mystery is that there was no gasket on the grinding wheel end only on the pulley end. I would have thought there would be one on both ends? I'll need to make up a couple of new ones. Its 0.3mm thick however I'm not sure what the material is, however when teared it does have a fibrous structure. So I was thinking of using 0.4mm gasket paper as a replacement. Does anyone else have other recommendations?

    A further mystery is in these end components:
    Attachment 215279

    There appears to be a nicely formed circular groove. It looks ideal for an o-ring as it would seat with the inside of the outer bearing ring. However there were no o-rings in sight. Anyone seen this sort of set up before?

    It appears there's also some wear / scoring:
    Attachment 215280

    You can see the comparison between the two components. The wear appears to be caused by the outside of the inner bearing ring. Maybe its due to over tightening to try to keep the oil in the spindle with a gasket and o-rings missing? I'll probably stone the burr off the part and see if oil leaks.

    BTW does anyone have a recommendation on what oil should be used to fill the spindle head?

    Christian

  13. #13
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    Hi Christian,
    "Its what I had on hand" is always a valid reason. I think you'll find Phils table is on cad plated steel. Mine are 55mm dia from memory, but given the size of our plates and the size of Phils I cant see it being an issue for either of us. I did machine the the center way on the back to make sure it was contacting closer to the edges*, though the hole in yours and you using epoxy should sort that out.

    With the male thread did you hold that in the spindle and turn it or helical mill it like the female.

    I wonder if "no gasket" is about rigidity?

    Stuart

  14. #14
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    Quote Originally Posted by CGroves View Post

    On the grinding wheel end it has two matched Hoffman 125ACDEP N1785 Thrust bearings. There's a bit of play in them so they will be replaced. Apparently the new equivalent bearing is a RHP 7205CTRDULP4.
    A fafnir number would be 2mm205WIDUL. (you could probably even go DUM) You might get some cheap ones off US ebay.. I could not imagine a retail set of those would be cheap...

    fafnir 2mm205 | eBay

    Before you assemble them I suggest you get good advice, you do not just shove them on any old way.. The bearings will have the high spot marked on them and have to be orientated the correct way..
    Gold, the colour of choice for the discerning person.

  15. #15
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    Stuart: I think what I've done is probably overkill but it was a good exercise. I hadn't played with helical thread milling before. The male thread I machined like the female one with a 60deg equal angle cutter going around the outside.

    I hadn't thought about rigidity. I'm not sure that it would make a difference, the bearings are seated in the spindle housing. The gasket is placed between the endcap and the spindle housing. The endcaps seem just to keep everything together and hopefully the oil in.

    RC: thanks for the fafnir number. Luckily I did record which way they were mounted on the spindle, back-to-back. The advice from RPH on the bearings is: "Both rings of the bearings are marked with high points of eccentricity. The bearings should be mounted so that the high points on the inner rings are diametrically opposite those on the shaft, thus ensuring maximum concentricity of the rotating part."
    As the bearings are a matched pair I assume that you want to keep the high spots of the outer ring of both bearing in the same position also.

    Christian

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