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Harbots Surface Grinder Rebuilding Advice Request

Tray

Aluminum
Joined
Jul 22, 2009
Location
Southampton UK
I originally posted some details about this grinder on the Abrasive machining thread and got some good advice from the guys there including Michiganbuck.

https://www.practicalmachinist.com/vb/abrasive-machining/harbots-leicester-surface-grinder-351643/

I seems this machine is fairly rare (I know that does not mean good nor valuable) given that I have not found any information about it, but it seems to follow fairly standard design practise. The ways are arranged as follows; traverse (X?) one inverted V and a flat, back to front (Y?) two inverted V's, Spindle rise & fall (Z?) two front flats with two more at the rear, a flat gib to take up play in the X plane. No gib in the Y plane; this seems to rely on the torque applied to 4 caps screws that hold a large plate to the back ways.

The machine was very dirty and dry so I did not feel it was wise to move any of the axes too much to check for wear. As I said in the other thread the machine doesn't owe me much.

Now I have the Z axis apart I'm looking for guidance; I have cleaned up and rewired an M250 Lathe and a Taiwanese BP clone and replaced parts but have no rebuilding / scaping experience. I appreciate that I will need to acquire some tools and some skills If I am to rebuild it. Being able to scrape will come in useful for new build projects.

I have had an initial look at the Z ways, they are approx. 22" long and approx. 10"� apart. With a borrowed 18" �straight knife type edge (I know, too short) I can see there is wear on the front faces of the front ways but I could not get a 0.002"� feeler gauge in the gaps. The sides of the front ways don't look as bad. Back ways are hard to see.

If I were to want to try to recondition these ways it looks like I could take the column off the base as there are four machine screws accessed from the back of the machine and two dowels which look like they were installed from the front at an angle; I'm concerned that if they are at different angles to each other I may run into trouble, I don't know if the can be punched though. Clearly I'll need to borrow a hoist to lift it off and set it on the surface plate each time I need to take a rub.
It's not surprising those ways are worn given the amount of congealed oil / grinding residue that was filling the oil grooves and generally under the ways.
I'm thinking I will need a surface plate 24"� long and at least 18"� wide. What do folks think about this one?

Rotagrip - Black Granite Surface Plate 24 x 18 x 3in With Ledges

Are the ledges more trouble that they are worth ? and Is an AA grade Ok in a workshop where the temperature fluctuates. There are used plates on auction sites (mostly CI) but they seem to be pricey given that their surfaces look less than pristine and their accuracy is undetermined.

In other Z axis news the feed screw is ¾ x 10 V form and noticeably worn in comparison to a thread gauge. I seems I can get an ACME replacement from Roton the US far easier and cheaper than in the UK. At $13 a ft and $40 for the nut it's not worth me trying to machine them. Can anyone see a downside to going from V form to ACME ?


Thanks in advance
Column.JPGSpindleCarriageBackplateIMG_0990.jpgSpindleCarriage.JPGDowels.JPG
 

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Clean everything up and leave the column on for now. Those are probably tapered pins and are bigger on top so don't try to pound them down. Clean it up and take some more pictures. Measure the box ways on the column with a micrometer. It looks like s super cheap machine and from the lousy pictures it doesn't looked scraped.
There is a group of men I taught a scraping class near Hastings UK. Message me your email address and I will send all of them an email. That way someone can help you. Demon 73, Pete, Mark and Tyrone are regulars in this forum and they are can help you. That is not a special machine. It's a simple design. What do you want to grind on it when your done and what spec's do you expect?
 
Clean everything up and leave the column on for now. Those are probably tapered pins and are bigger on top so don't try to pound them down.

Thanks I hadn't considered that they might be tapered. I can feel them projecting on the underside but that's all.

Thanks for the compliments on the photography! I'll fire up a camera and try harder...

I'll get the mikes out and report back

Yes it is at the low end and I have see no evidence of scraping anywhere.

I'm making a taper turning attachment that has a dovetailed slideway so am thinking it would be useful for those mating surfaces and generally removing machining marks.

Thanks for the info re yoor Hastings contacts and offer to put me in touch I'll PM you.
 
Many thanks Richard,

I tried to mikle the ways but ran into a few issues

1. My 2" mike is 0.012" or so too small i.e. I'm getting 2.012" typically

2. I'm not great at measuring

3. The ways are 3/8" or so off set so its hard to be sure that I am miking perpendicularly and therefore accurately.


I was seeing less than 0.001" on one set of ways over the 19" length. I locked the anvil and used the mike like a gauge and moved it along the length of the way, it dragged slightly in places. I expected to see more of a difference given what I saw with my friends (unproven) straight edge. Is it possible that the ways are not flat but have worn equally so that the distance between them is consistent ?


If I had a long parallel I could use that as a reference with an indicator.. but I don't.

Anyway I will not attempt anything on the ways until I or someone is able to assess them correctly, determine if any variance is significant, identify what corrective action is necessary and I have access to the skills required to apply that correction if required.


In the meantime I'll keep cleaning
 
I emailed Pete and Andrew....Hopefully they will alert the others and someone can help. I would think you could square cut the unexposed surfaces of the ways and put it back together and use it. Making sure you make sure the lube ports are working. When installing the headstock be sure not to tighten the gib to tight as the head has to hang on the feed screw nut so when you feed down it moves on the nut. To tight and will pull down when grinding.
 
I'm not familiar with the square cut technique, is it simply cutting across the ways in order to improve oil retention in these vertical surfaces?
 
Thanks for taking the time to post the link, I understand the principle now. You advised me not to take the column off - once I have practised this on a horizontal surface do you think I will be able to do it on the vertical column ways ? I can of course orient my practise piece ( 9" x 5" CI) vertically and try it but no point in trying if you think I'd be on a hiding to nothing on the machine. Failing that I'll have to look at a way of tilting the whole machine base over I'd certainly be asking for some advice here before trying to do that.

Clean up is progressing, I should be able to post some images of the ways on all 3 axes this weekend.
 
Thanks for taking the time to post the link, I understand the principle now. You advised me not to take the column off - once I have practised this on a horizontal surface do you think I will be able to do it on the vertical column ways ? I can of course orient my practise piece ( 9" x 5" CI) vertically and try it but no point in trying if you think I'd be on a hiding to nothing on the machine. Failing that I'll have to look at a way of tilting the whole machine base over I'd certainly be asking for some advice here before trying to do that.

Clean up is progressing, I should be able to post some images of the ways on all 3 axes this weekend.

On a Ground long surface grinder like yours if the column ways don't show any ware I would only square cut hidden ways on the headstock. If you cut shallow holes or square cuts in the exposed ways that could catch small pieces of grit from the grinder and start scratches. Many times a well meaning owner assumes he has to scrape everything. But if the MFG of the machine did not scrape it, leave it alone if it measures OK. Your welcome :-)
 








 
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