Replacing The Gap In The Bed

[planeflyer21]

I've yet to own a gap bed lathe but have seen others say they would never remove the gap, due to the impossibility of getting it back correctly.

Found this video by accident...it really looks like a non-issue:

 

[Chipper5783]

I've yet to own a gap bed lathe but have seen others say they would never remove the gap, due to the impossibility of getting it back correctly.

Found this video by accident...it really looks like a non-issue:

I agree, not a big deal. Certainly, be very deliberate about taking care of the mating surfaces of the bed and gap section (when the gap is out, put the section away in a safe location). When re-installing be VERY fussy about all mating surfaces clean and burr free. Of course they will be burr free, because you took super good care of it (but check and double check).

I would not hesitate to tackle a job that required pulling the gap section (be sure to consider the time associated with that remove/install as part of the over all project). Also, I don't leave the gap section out on normal turning (if it does not need to be out, put it in, even if it does not need to be there).

 

[tertiaryjim]

The guy demonstrating replacement makes a good point that you don't know what the last person did when installing the gap.
Even factory people sometimes mess-up.
I had to pull the gap on a Nardini and had already noticed greater resistance running over the gap and slight visable wear.
There was some grit in the fits and they had hammered the location dowels in. This lathe had been through at least 5 other operators before me.
I got it true after a lot of effort but always disliked pulling afterwards as it was hard to return it with the damage done.

 

[george wilson]

The lathe illustrated has the English style carriage,where the large handwheel that engages the rack is on the right hand side. American carriages have the handwheel on the left side,and they run off the rack when the gap is removed.

So,it is definitely an issue on American style lathes.

 

[george wilson]

The lathe illustrated has the English style carriage,where the large handwheel that engages the rack is on the right hand side. American carriages have the handwheel on the left side,and they run off the rack when the gap is removed.

So,it is definitely an issue on American style lathes. I do not know how much the carriage is hanging off the end of the ways on the lathe in the video. But,I'm pretty sure that it is not the best situation as far as rigidity is concerned. His gap is pretty wide.

Myford lathes have no gap to replace,and still have the English style carriage. But,their gaps are quite narrow. Probably their carriages do not hang off the edge very far.

I have seen on Ebay a rare South Bend 9" lathe which has a gap with no gap block at all. But,its carriage is built in the English style so the hand wheel doesn't run off the rack. Its compound is moved over,too,to the left hand side of the carriage,instead of being in the center. Thus,the carriage does not have to be cranked too far out over the edge of the ways to do work close to the chuck or faceplate,or collets.

It is indeed a gamble whether the gap piece will go back perfectly. I bought 2 identical 16" Grizzly lathes in 1986. One for the shop,one for me. I had to remove the gap at work to turn a 20" bandsaw wheel true. It had been welded and needed to be turned true again.

The gap did not go back perfectly on the lathe at work. Fortunately,we got funds to get a larger lathe soon after that,so I did not have to try machining the bottom of the gap piece,which would have been a tricky job to get perfectly right.

The gap pieces are machined and ground and induction hardened in situ. This no doubt releases stress in the gap piece,causing it to be out of perfect alignment if unbolted and removed. There are any number of directions that the gap piece can move in once it is unbolted. That includes the ways moving inwards,which is a very difficult situation.

Last year,I had to remove the gap in my 1986 lathe to do a large job. I did so with trepidation. Fortunately,the gap piece went back in perfectly. I was just plain lucky! Its brother lathe at work had not gone back perfectly. It was about .015" out of alignment after being replaced.

 

[4GSR]

About all that gap is good for is a selling point when the lathe was sold.
Yeah, I know, it is usable when a larger swing lathe is not available. I guess I've always been lucky and had access to larger swing lathes in my past when needed.
Some good pointers at replacing the gap after it has been removed.
If not already done, add large edge chamfers to all holes, especially the tapped holes. This will eliminate the "mushroom" effect you get from holes when loads are applied to what's in them. Next, take a flat honing stone and some mineral spirits and hone all surfaces to remove any unseen burrs. Do this to both the bed and the insert. Once done, rinse off with mineral spirits. DO NOT DRY OFF using compressed air, just air dry. Should only take a few minutes. Spray all surfaces with Starrett M-1 or LPS-1. Please don't use WD-40! If you do, you will be kicking yourself in 5-10 years down the road for doing so! Last carefully slide the insert into place. Slide it back and forth to "ring it" in place. Install fasteners and torque evenly to all.

EDIT: Oops! forgot to add to the last before torquing fasteners, align way surfaces using a dial test indicator. If you have a test indicator that reads in tenths, use it! On the lubricant, if you like, use a good grade of oil, like a hydraulic oil ISO 46 instead of the Starrett or LPS. This will protect these surfaces from coolant damage and other elements over the years. Don't use way lube, its too thick and slippery!

 

[Bill C.]

I have seen gap lathes before. Not sure if I setup one up. We had weld wheels used on a seam welder that we would need to resurface the copper faces from time to time. That lathe had a big swing to it.

I would have thought the manufacture would have had some sort of keyway to speed up re-installing the block.

 

[kd4gij]

Where I work removing the gap in our 2 big lathes is a must. Just clean everything and no problems. You do have to be carefull not to run the cariage off the end.Don't Ask me how I know.

 

[kd4gij]

About all that gap is good for is a selling point when the lathe was sold.
Yeah, I know, it is usable when a larger swing lathe is not available. I guess I've always been lucky and had access to larger swing lathes in my past when needed.
Some good pointers at replacing the gap after it has been removed.
If not already done, add large edge chamfers to all holes, especially the tapped holes. This will eliminate the "mushroom" effect you get from holes when loads are applied to what's in them. Next, take a flat honing stone and some mineral spirits and hone all surfaces to remove any unseen burrs. Do this to both the bed and the insert. Once done, rinse off with mineral spirits. DO NOT DRY OFF using compressed air, just air dry. Should only take a few minutes. Spray all surfaces with Starrett M-1 or LPS-1. Please don't use WD-40! If you do, you will be kicking yourself in 5-10 years down the road for doing so! Last carefully slide the insert into place. Slide it back and forth to "ring it" in place. Install fasteners and torque evenly to all.

EDIT: Oops! forgot to add to the last before torquing fasteners, align way surfaces using a dial test indicator. If you have a test indicator that reads in tenths, use it! On the lubricant, if you like, use a good grade of oil, like a hydraulic oil ISO 46 instead of the Starrett or LPS. This will protect these surfaces from coolant damage and other elements over the years. Don't use way lube, its too thick and slippery!

Well I had to pull the gap out of a 40" swing lathe today. Hard to find a bigger lathe around here.

 

[Silverbullet]

I seem to remember seeing lathes that the ways were able to slide off the end where the tail stock is. I don't rmember the brand but I thought that set up was smarter then the removing the gap. They had a separate rack gear to move the ways back away from the headstock. Sure wish I had one of those but at my age it's a pipe dream , I'll have to settle for my old Logan 11" . It's done a lot of work for me and made more then it's ever cost. She's kinda my baby even tho she's been neglected over the last 6 yrs. I ll give her a good cleaning and reoiling , she still loves me . Machines are better then women they don't belch at your every move.