Stiffening Lathe Bed

[Dontheo55]

I have performed most of the more common upgrades for stiffening my 7x mini lathe but now want to stiffen the bed by bolting it down to a solid surface such as a steel plate or a piece of granite. Looking at pictures from others who have done this already I see where many of the attempts to stiffen the bed still include the original rubber mounting feet. Is there a purpose for including the rubber feet? I would think it hinders the concept of stiffening the bed rather than helping it.

Ted

 

[GrifterGuru]

Keeping the rubber feet is an attempt to absorb the vibration and stop reverb through the bench which to be honest, is not exactly a wise choice when trying to gain rigidity.

Personally, I never used the rubber feet given the already noodle-like quality of a 7x and bolt it down to the 50mm worktop it is on every time I use it. I unbolt it and slide it back to the wall when not in use due to a constraint on space, plus I can use the small amount of space in front in the meantime. Also makes clean-up easier after use too both of the lathe itself and the surface it sits on.

I have performed most of the more common upgrades for stiffening my 7x mini lathe

What "more common upgrades" are you referring to?

 

[silence dogood]

An interesting Question. I have three lathes (one of them is a 7") and none of them have rubber feet. I think it is more important that the plate is flat and rigid. On a small lathe like yours, I suppose the rubber feet when compressed may not make much difference. When you tighten down the bolts, try to make sure that the bed is not twisted. If nothing else, try it with the feet and then without. Pick the one that gives the best results. All my lathes are bolted down on a thick heavy plate. It does make a difference.

 

[Jake M]

I would agree.

If you're bolting it to a wobbly old workbench that lost it's "flat" a hundred years ago, then yes, rubber feet are good.

If you're bolting down to something flat, bolt it down hard and shim if it's needed. (The bed's very short, it's PROBABLY not needed....)

 

[SouthernChap]

I put my 7x on a 30 mm thick granite kitchen countertop cut off (no rubber feet).

Amongst the other stuff I've done that appear to have made a difference, I'd say that would be one of the easier wins.

Not to rigidity; you can't really make a lathe more rigid by bolting it to something. The difference it' made is the damping.

Have you seen the central shear plate Steve Jordan showed in one of his YouTube videos?

 

[Dontheo55]

Thanks. Upgrades have been the bearings, removed compound slide unless I need it, upgraded the QCTP from an aluminum one to a steel wedge style, upgraded the ways on the carriage and on the cross slide. I had to do a bunch of milling and scraping to get it into proper shape and reduce the play. It became a hole I wish I never started going down. I also upgraded the motor so I have more torque. Not sure if the motor really adds to the stability but that and the 5” chuck are awesome improvements.

It will be mounted to a flat hard surface so I plan to toss the rubber feet. I was just trying to figure out what they were for.

My shop is on pier and beams or I would have bought a heavier lathe. I liked learning how to hand scape, somewhat, but that is not something you want to be doing a lot of at my age.

 

[GrifterGuru]

I would agree.

If you're bolting it to a wobbly old workbench that lost it's "flat" a hundred years ago, then yes, rubber feet are good.

If you're bolting down to something flat, bolt it down hard and shim if it's needed. (The bed's very short, it's PROBABLY not needed....)

@Jake M

Because the bed of a 7x is short and of "noodle like" quality, it is easy to induce "twist" by the simple expedient of bolting it down to a bench, which is why checking it is "level to itself" is so important.

upgraded the ways on the carriage and on the cross slide.

@Dontheo55

Upgraded how? Other than machining to correct spec to suit the bed, I can honestly think of no "upgrades" to the ways on the carriage and cross slide.

Even then, machining to correct spec is just that, it is not necessarily an upgrade which implies replacement to improve factory componantry. E.G swapping headstock bearings from standard bearing races to Angular contact or Taper Roller Bearings is an upgrade.

I put my 7x on a 30 mm thick granite kitchen countertop cut off (no rubber feet).

The difference it' made is the damping.

@SouthernChap

I can attest to the fact that bolting down dampens things. I found 50mm worktop works for me.

 

[SouthernChap]

Upgraded how? Other than machining to correct spec to suit the bed, I can honestly think of no "upgrades" to the ways on the carriage and cross slide.

The underside of the ways where the saddle retaining plates run are machined, but on mine are of dubious parallelism to the top.

I spotted this lack of parallelism by the fact that initially, when working on adjusting out play on the saddle, I tightened up the SHCSs on the apron-side and saw that at a given tightness, the saddle would be progressively tighter on the bed, the closer to the headstock it was moved. I saw the same with the rear retaining plate but in the opposite direction (no guesses as to how that happened during manufacture ).

The underside surface was also hardly beautifully smooth. I could just feel the machining marks with my finger tips (no need even for the fingernail test).

The solution that I used for the front and rear way undersides, was to put valve grinding paste on those shear plates, mount just the saddle to the bed, tighten both retaining plates to an appropriate level and then move the saddle up and down the bed by hand. I'd then clean the bed, saddle and retaining plates completely, reassemble the saddle, tighten again and test the smoothness of movement by hand and tighten appropriately and then rinse and repeat... that was a process that took a fair few hours of tedious effort.

After getting a reasonably play free movement along the bed, I replaced the SHCSs with some M6 studs loctited into the saddle and nylock nuts, and dispensed with the two horrid locking grub screws and used shims to set the hold.

As you know, I also added a central retaining plate and that required dealing with the almost unmachined undersides of the ways in the middle of the bed. I eschewed the tedious and time wasting lapping with that and used a Proxxon rotary tool with a mini grinding wheel, held in a simple shop-made fixture, itself held in a vertical milling slide. Getting the undersides of the ways in the middle reasonably parallel took about 30 minutes and that was with the measuring with a mic!

All the above came from Steve Jordan videos (it was he who suggested the lapping with valve grinding paste, curse him).

In addition to my efforts, possibly hand scraping the sliding surfaces on the saddle, cross slide, top slide rest and top slide are other things that can be done.

The latter stuff though was further than I wanted to go. The sliding surfaces on all of those components on my Amadeal/Weiss lathe, were pretty good as were the ways/dovetails they ran on.

 

[GrifterGuru]

The underside of the ways where the saddle retaining plates run are machined, but on mine are of dubious parallelism to the top.

I spotted this lack of parallelism by the fact that initially, when working on adjusting out play on the saddle, I tightened up the SHCSs on the apron-side and saw that at a given tightness, the saddle would be progressively tighter on the bed, the closer to the headstock it was moved. I saw the same with the rear retaining plate but in the opposite direction (no guesses as to how that happened during manufacture ).

The underside surface was also hardly beautifully smooth. I could just feel the machining marks with my finger tips (no need even for the fingernail test).

The solution that I used for the front and rear way undersides, was to put valve grinding paste on those shear plates, mount just the saddle to the bed, tighten both retaining plates to an appropriate level and then move the saddle up and down the bed by hand. I'd then clean the bed, saddle and retaining plates completely, reassemble the saddle, tighten again and test the smoothness of movement by hand and tighten appropriately and then rinse and repeat... that was a process that took a fair few hours of tedious effort.

After getting a reasonably play free movement along the bed, I replaced the SHCSs with some M6 studs loctited into the saddle and nylock nuts, and dispensed with the two horrid locking grub screws and used shims to set the hold.

As you know, I also added a central retaining plate and that required dealing with the almost unmachined undersides of the ways in the middle of the bed. I eschewed the tedious and time wasting lapping with that and used a Proxxon rotary tool with a mini grinding wheel, held in a simple shop-made fixture, itself held in a vertical milling slide. Getting the undersides of the ways in the middle reasonably parallel took about 30 minutes and that was with the measuring with a mic!

All the above came from Steve Jordan videos (it was he who suggested the lapping with valve grinding paste, curse him).

In addition to my efforts, possibly hand scraping the sliding surfaces on the saddle, cross slide, top slide rest and top slide are other things that can be done.

The latter stuff though was further than I wanted to go. The sliding surfaces on all of those components on my Amadeal/Weiss lathe, were pretty good as were the ways/dovetails they ran on.

@SouthernChap

With the exception of the central ways plate, stud & nut conversion* and sheer plate shims, what you describe is what I call "fettling"

As for "lapping" the sliding surfaces of the bedway, I "sort of" cheated. I used some sandpaper from an old beltsander on top of the sheer plates. It worked much better than grinding paste for the heavy work. Simply fit to the sheer plates, tighten the sheer-plate bolts up a little, work it, tighten a little more, work it and keep going until full travel was acheived between tailstock end and headstock. Yes, I had the headstock fitted. I then used fine paste to finish it up

* = I converted to stud & nut mounting (12.9) for the headstock. So much easier to deal with than messing about with an allen key. and does not mean removing the dang motor to take the headstock off. Simply only have to remove the control panel, change-gear cover, the alloy plate on the back of the headstock, timing belt and nothing else. Motor stays in place. Plain nuts with HS (High Strength) thread lock.

I saw the same with the rear retaining plate but in the opposite direction (no guesses as to how that happened during manufacture ).

I would imagine that either the bedway was swapped end for end during machining or that the setup was way off. I suspect the latter over the former though. Either way, a LOT of 7x bedways have the same issue.

 

[SouthernChap]

I can attest to the fact that bolting down dampens things. I found 50mm worktop works for me

Yep, the chipboard core of the worktop should do a nice job of damping.

I picked the granite offcut, as I figured it would likely be flatter and stay flatter than a standard kitchen worktop.

I was nervous about bolting down the bed, lest I cause additional twist to the bed (due to its rectangular layout of bolt holes).

So the headstock end bed foot is bolted down, reasonably firmly, through clearance holes in a a pretty flat and smooth surfaced piece of 10 mm plate, the granite offcut and the 6mm steel plate top I used to bridge the two cabinets, to the underlying headstock-end cabinet.

However, the tailstock-end bed foot is bolted lightly to another piece of the same 10 mm plate and that plate is bolted to the tailstock-end cabinet (via the abovementioned granite offcut and 6 mm steel plate top), with two bolts located centrally between the tailstock-end bed feet (the two bolts are not side-by-side but run parallel to the ways). One bolt rather than two might have been better, but I reckon I was pretty precise with my layout and putting in my centre pops.

Anyway, the point was to have the fixture points form a triangle.

I'm not sure I've done a great job of explaining this so, I'll grab some photos to illustrate the above, in a bit.