-
Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.
-
Several Regions have held meetups already, but others are being planned or are evaluating the interest. The Ontario GTA West area meetup is planned for Saturday April 26th at Greasemonkeys shop in Aylmer Ontario. If you are interested and haven’t signed up yet, click here! Arbutus has also explored interest in a Fraser Valley meetup but it seems members either missed his thread or had other plans. Let him know if you are interested in a meetup later in the year by posting here! Slowpoke is trying to pull together an Ottawa area meetup later this summer. No date has been selected yet, so let him know if you are interested here! We are not aware of any other meetups being planned this year. If you are interested in doing something in your area, let everyone know and make it happen! Meetups are a great way to make new machining friends and get hands on help in your area. Don’t be shy, sign up and come, or plan your own meetup!
Tips/Techniques Need help surface grinding a tapered cross slide gib (Okanagan)
- Thread starter Nesh559
- Start date
Tips/Techniques
Nesh559
Active Member
the two ground faces are parallel to each other and the width is the same throughout but it tapers down the length of the gib. it would have to be ground or milled using a mag chuck with either gauge blocks stacking at one end to get it parallel to the grinding wheel/fly cutter or using a mag chuck attached to a sine plate. hope the pictures help
Attachments
Maybe able to help you out I got 6x18 SG but the chuck on its 12" and my biggest since plate is maybe 10" I got some machinist jacks so maybe could make it work if your not looking for thenths.
No cost for the risk lol I'm in lumby
What am I missing here? The parallel surfaces don't need any special finish, they don't do anything (and .400 is a huge amount to grind.) It's the opposing tapered surfaces that are in contact. Is this just hogging off material to make a bigger gib fit?
Cast iron? I've milled and scraped tapered gibs and think grinding would be quite challenging. The reason is you must perfectly replicate the angle and fit between the two mating parts. That where scraping is so perfect - you use the existing surface to spot the gib. You say tapered gib stock, there is such a thing? Still, its going to need to be custom fit, i.e. scraping.
Apologies if you know exactly what you want, but can we back up a sec and find out exactly what the problem is? Missing gib or worn gib?
Nesh559
Active Member
All good, the issue was I bought the lathe at auction with a stuck cross slide and apparently some mongoloid before me had decided that drilling it out was the first thing they would try rather then just taking the apron off and tapping out the gib lightly, so the existing gib had holes in it from both sides and was cracked. I ordered a new gib from the manufacturer but unfortunately they only supply gib “stock” that has the correct taper for all their lathes but needs to be fitted hence the massive .400” that needs to be taking off. I unfortunately don’t own a sine plate to get the correct angle and support while taking it down to approximate size on my mill but figured if someone had a surface grinder with such an attachment potentially I could pay them to hog it down for me.
Reminds me of buying my milling machine who knew bottle jacking the knee upwards would make it worse? Previous owner didn't.
I've been tossing few ideas around the skull I'm limited in my fixturing but not limited with my machine sizes. My mill is 10x50 and grinder is 6x18 and I got select of shell mills to work with. Aswell as few smaller fixtures. Got gauge blocks and plenty of measuring stuff.
My only real plan so far is milling a angle block on milling machine then glueing gib down to it then mill the bulk of material then grind the rest. If we use some thick enough to support it should work?
Maybe another Other option if old gib is not too messed up could do some repair work on it by brazing/silver soldering it up and re shaping make it usable till someone with better fixturing can tackle job.
I had to add couple inches to milling machine Gib as it was broken and so far has worked out I will one day replace when i get around to doing the final touches to mill to bring it back into tight.
Attachments
Makes sense now, thanks for explaining.
I've milled the angle before by setting up with mill vices and gauge blocks, but concede the length here makes it tough and super accurate milling (machine tool bearing fits) over that length is dicey to the say the least. Mill is to a thou (on a perfect machine) and I gib should be a much better fit than that. Fastening it to a piece of cold rolled, 3/4 x 3 or something, than clamp the cold rolled on a bunch of angle plates seems doable. If the angle is already correct, no need for a sine anything, just indicate across the top.
I still think you'll need to scrape it to get a good fit. I've done it by bluing the sliding part and inserting the gib. Get your rough dimensions on both ends using feeler gauges and mill almost to that leaving a maybe two thou for fitting. Wear comes into play on how good you can make the fit of course, but ideally you want a gib to have the same very small amount of clearance over the whole length of the mating surface such that with a thin film of oil it becomes pretty solid. That gives you rigidity and long wear.
All just imho..... there is more than one way to skin the cat.
I've milled the angle before by setting up with mill vices and gauge blocks, but concede the length here makes it tough and super accurate milling (machine tool bearing fits) over that length is dicey to the say the least. Mill is to a thou (on a perfect machine) and I gib should be a much better fit than that. Fastening it to a piece of cold rolled, 3/4 x 3 or something, than clamp the cold rolled on a bunch of angle plates seems doable. If the angle is already correct, no need for a sine anything, just indicate across the top.
I still think you'll need to scrape it to get a good fit. I've done it by bluing the sliding part and inserting the gib. Get your rough dimensions on both ends using feeler gauges and mill almost to that leaving a maybe two thou for fitting. Wear comes into play on how good you can make the fit of course, but ideally you want a gib to have the same very small amount of clearance over the whole length of the mating surface such that with a thin film of oil it becomes pretty solid. That gives you rigidity and long wear.
All just imho..... there is more than one way to skin the cat.
Last edited:
PS, if its for a dovertail (vs boxway) you'll need to tip the head over. Easily done but creates another problem if grinding - you need a angle dresser and even then that means you can't traverse the work so end up with not the best grind, i.e. no traversing to spark out..
You got me digging through old files and I found some photos... so you'll have to suffer through them. I'm using scrap cast iron. For very large sections of durabar, they saw away the outer 3/4 - 1" because it can be full of cracks. I've got such a slab and use it slice gibs off of .... but occasionally you encounter such a crack and a piece falls out!
Measure each end will feeler gauges, calculated stack heights and set up with gauge blocks.
Here's slicing some off the slab .... I haven't a vertical bandsaw so just bury a thin horizontal cutter into it
You got me digging through old files and I found some photos... so you'll have to suffer through them. I'm using scrap cast iron. For very large sections of durabar, they saw away the outer 3/4 - 1" because it can be full of cracks. I've got such a slab and use it slice gibs off of .... but occasionally you encounter such a crack and a piece falls out!
Measure each end will feeler gauges, calculated stack heights and set up with gauge blocks.
Here's slicing some off the slab .... I haven't a vertical bandsaw so just bury a thin horizontal cutter into it
Fwiw, I enjoyed the post.
Bridgeport gibs are notorious for breaking, and as you found the vertical way can get jammed if you try to push the knee instead of the gib. An option is to flip the mill upside down and drill access thru base for a brass drift to push the vertical gib up. (Thanks to Forrest Addy for that tip) Don’t know about you, but I don’t have the means to do that safely in my crowded shop. Another option is to pre drill the knee for a strap clamp gib pusher when doing a rescrape knowing that at some point the gib is going to misbehave. Now that I’ve done this to my latest mill, the gib won’t dare misbehave ;-)
Attachments
I did the forest Addy method of extracting that Gib the original owner of the mill did a very good job at jamming it then after failing to unjam they just ran it as is for few years as they mostly used the mill to modify aluminium extrusions height.
Did a post while back about the hole endeavor.
https://canadianhobbymetalworkers.com/threads/bought-a-diamond-in-the-rough-mill-probly.6614/page-2
Also would be curious about more info strap clamping pusher as I had a scare few months ago when it tried to stick agian when the lower adjustment came loose.
Maybe better to move the post as it could turn into good topic
Ah, sorry, didn’t realize you’ve already been done that path. Nice work!
Nothing sophisticated about what I did to the knee. Just a well placed hole so I can pull a strap clamp with spacers on each end for enough leverage into bottom of gib. Kinda hard to drill a hole into bottom of the knee with it stuck on the column though…
Nesh559
Active Member
Wow I didn’t expect this many replies to this post. Thanks for all the pictures and ideas. At the moment I only have a precision Matthew’s pm940 bench style mill but I’d like to eventually get a full Bridgeport/clone style knee mill so this is all super good information for the future.
KeeponDragon
no problems... just challenges
we are a helpful bunch of son of a guns here lol
It's ok. @Nesh559 was looking for help not selling something. You are doing just that.
In any event, we wouldn't delete it. At most we would move everything to someplace else in one go.
@Mcgyver is certainly right about the correct way to do all this, but that might be beyond what you want to take on.
Perhaps I might suggest an easier option for you to consider. You said the previous owner drilled out the ends of the gib. Do you still have the damaged gib? Could you repair it? Fitting the two repaired ends might be a lot easier than fitting a whole new one.....