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Thread: Mounting a benchtop lathe, advice sought

  1. #1
    Join Date
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    Mounting a benchtop lathe, advice sought

    I do ride the short bus.

    Two lathes in my shop. I have a Penmaster by PSI mounted to 5/8 plywood, the plywood screwed to a saw horse and that one is working good.

    The other is my problem child. 1980s vintage B&H, 57" ways, 1 hp motor. Total length is 72 inches counting the motor. I have no factory parts below the ways, it is a 'benchmount.'

    I have it on a 2x4 frame screwed to the wall studs of the house, 2x4 legs, with doubled 3/4 ply for the surface, and some extra weight (2 cinder blocks) on the mounting surface. It's jiggling, unloaded, like a hotel bed from the 1970s with a quarter slot mounted to the headboard. The tailstock isn't too bad, but watching the surface of a cup of water straddling the ways at the headstock end makes me seasick.

    I am trying to turn a 35" piece of white oak from 5/8 up to 9/8 and then back down to 5/8 over the 35" run. With my hollow ground skew honed to 4k on DMT and stropped, with three steady rests in use, it looks like a barber pole.

    The lathe, as most early 1980s hardware, has mixed SAE and metric fasteners on it. I am suspicious of the bearings in the headstock and motor, but also suspect the bearings might be no longer available.

    My tentative plan is to remove the wallmounted shelf; and build a 6 foot workbench to mount the lathe to, 6" thick birch at 24x72 is 6 cubic feet, the top alone should come in around 258#. I have a ton of basalt in fist to volleyball sized chunks and should be able to crate or bin another 800# on the lower shelf easily with an undercarriage of 4x6 Doug Fir. One ton of basalt from my local rock quarry was $16, but two trips with my truck to bring home.

    At what point is my bench stiff enough and heavy enough to be looking at the bearings in my motor and headstock rather than adding more weight?

    Thanks.

  2. #2
    Join Date
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    Quote Originally Posted by Scott Winners View Post
    I do ride the short bus.

    Two lathes in my shop. I have a Penmaster by PSI mounted to 5/8 plywood, the plywood screwed to a saw horse and that one is working good.

    The other is my problem child. 1980s vintage B&H, 57" ways, 1 hp motor. Total length is 72 inches counting the motor. I have no factory parts below the ways, it is a 'benchmount.'

    I have it on a 2x4 frame screwed to the wall studs of the house, 2x4 legs, with doubled 3/4 ply for the surface, and some extra weight (2 cinder blocks) on the mounting surface. It's jiggling, unloaded, like a hotel bed from the 1970s with a quarter slot mounted to the headboard. The tailstock isn't too bad, but watching the surface of a cup of water straddling the ways at the headstock end makes me seasick.

    I am trying to turn a 35" piece of white oak from 5/8 up to 9/8 and then back down to 5/8 over the 35" run. With my hollow ground skew honed to 4k on DMT and stropped, with three steady rests in use, it looks like a barber pole.

    The lathe, as most early 1980s hardware, has mixed SAE and metric fasteners on it. I am suspicious of the bearings in the headstock and motor, but also suspect the bearings might be no longer available.

    My tentative plan is to remove the wallmounted shelf; and build a 6 foot workbench to mount the lathe to, 6" thick birch at 24x72 is 6 cubic feet, the top alone should come in around 258#. I have a ton of basalt in fist to volleyball sized chunks and should be able to crate or bin another 800# on the lower shelf easily with an undercarriage of 4x6 Doug Fir. One ton of basalt from my local rock quarry was $16, but two trips with my truck to bring home.

    At what point is my bench stiff enough and heavy enough to be looking at the bearings in my motor and headstock rather than adding more weight?

    Thanks.
    Pictures of your lathe and how it is secured might help to secure some useful advice.

    Without those, I'm guessing you can stiffen a bench with 2x4 legs by adding some diagonal supports, or perhaps better, fastening pieces of plywood to the ends, adding extra supports to the wall if needed to secure. I'd want the front open for my feet but some diagonal braces near the top perhaps combined with a plywood web across the front near the top. This might be more than enough without building the massive bench you mentioned.

    I know nothing about that lathe. Other variables I don't see described: what is the swing of the lathe and do you plan on turning heave, out of balance blanks? If you do, is the headstock and spindle stout enough? For example, most larger modern lathes use a large diameter spindle with a 1-1/4" thread, supported by some pretty stout bearings. If that machine isn't built to be that sturdy perhaps it is intended to be a spindle-turning lathe for chair and stair parts.

    You can check the bearings before you build Fort Knox to support the lathe. Nearly all bearings are standardized. If you remove any belts you can usually turn the spindle by hand, applying pressure in various directions, and feel for a bearing problem. The spindle should spin freely by hand. If the bearings feel rough or have play disassemble the headstock and remove the spindle/bearings. Most bearings have stamped numbers allowing you to order replacements which will fit. If not, take the bearings to a place that sells bearings and they will match them up. There are bearing "stores" all over the country.

    The "barber pole" syndrome might be related to skew technique. A common problem is putting too much pressure on the bevel which causes it to follow and amplify small fluctuations until you are turning a spiral. If so, there are ways to avoid that. Again, a picture is worth a 1000 words. It can also be exacerbated by normal vibration from the wood flexing. There are ways to control that too, with and without a steady rest. How are you supporting the blank on both ends? One good way is mount between centers, turn a tenon on each end, and grip one end securely in a chuck. Or quicker, depending on what chuck jaws you have, grip the square stock directly in the chuck. I use both methods. Without a chuck with the proper jaws there is a third way: turn a tenon on one end then jam it into a hole in a scrap piece mounted on a faceplate. A forth way: turn a short #2 Morse Taper on one end and jam that into the tapered headstock socket. I do that a lot on thin spindles. All of these methods keep the left 1/3rd or so stiff to minimize flex. Flex in the middle needs to be controlled by another method.

    Again, I'm commenting based on speculation without pictures and/or more description from you.

    JKJ

  3. #3
    Is the lathe bouncing when there is no wood mounted on it?

    One problem with spindles is how they 'whip'. I heard once about a 10 to 1 ratio for spindles, which means that a 1 inch diameter spindle 10 inches long will not whip as you turn. Anything over that length will whip. By whip, I mean the spindle will flex as you try to turn it. This whipping action is made worst by lots of pressure from the tailstock, and too much pressure on the tool bevel as you cut. I am thinking this may be the problem. If you have nice spiral ridges in your spindle, that is because of whipping. You can remove a lot of it with the very lightest of cuts, but that is a master level skill. Sanding with 80 or 120 grit on a board can get rid of those nice swirls. I have wished I could to it on purpose for a texture thing, but it is always inconsistent, some long swirls and some short ones... You want enough pressure on the tailstock to hold it in place without it flexing the spindle, but not so loose that it wants to fly off, and only practice will solve that one. Depending on what you are toing to do with the tailstock end, you can drill a hole with a Jacobs chuck and use a 'dead' center pin and some wax so you don't get burning.

    There could be lathe mounting problems. I did have a 4 speed Atlas as my first lathe. I had it mounted on a home made glue lam beam that was about 3 inched thick, and another one for a shelf where the motor was mounted. It would walk around the shop with an unbalanced bowl blank on it till I got it rounded out, in part because minimum speed was 500 or so rpm. All 4 feet on your bench top lathe must be equally touching the wood bench top. If they are not all sitting flat, that will add to the vibration. If you just bolt it down without making sure all 4 mounts are touching the same, this will add to vibration.

    robo hippy

  4. #4
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    Another thing to check on your lathe. If you put a pointed center in both the headstock and the tailstock and bring the tailstock up close do the points align perfectly? If not, the lathe bed may be twisted. It is usually an easy fix.

  5. #5
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    Thanks for helping to clarify my thinking.

    It seems like the bench my lathe mounts to needs to be both strong enough to hold up the lathe (mine is) and stable enough to vibrate minimally while in use. Flatness of mounting surface and the possibility of introducing twist to the ways I will hve to examine carefully.

    I think vibration of the surface is part of my problem, and how much vibration is aceptable is going to vary with the length and diameter of the spindle once I am down to round. Probably a lot of other variables too. I can turn smooth cylinders two inches in diamter and 24 inches long, but not 35 inch spindles at one inch diameter.

    Aside towards John K Jordan the lathe has a six inch swing and I have no forseeable desire to turn bowls on it.

    Tailstock pressure I have been fooling with. Right now I have it as loose as I can get it and feel safe turning, might have overcorrected from when I used to have it too tight.

    When I bring the tailstock up to the headstock the point of my spur drive and dead center tail line up really well.

    I might be pushing the tool too hard and my tools may not be sharp enough.

    My 40 year old bearings may have nothing left to give. Given 1980s vintage I guess I will just take it apart and replace them.

    I have put an advert up on my local Craigslist looking for someone with some experience and a long bed lathe so I can take my spindle and tools over to someone in person.

    One other thing I though of that didn't get mentioned is spindle speed. I was turning at 3250 rpm, which might be too low for a spindle that small. I could go up one more pulley set to 4860 rpm nominal but I stopped working on it because the hair on the back of my neck was standing up.

    Thanks again for the short list of things I need to evaluate.

  6. #6
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    Quote Originally Posted by Scott Winners View Post
    ...how much vibration is aceptable is going to vary with the length and diameter of the spindle once I am down to round. Probably a lot of other variables too. I can turn smooth cylinders two inches in diamter and 24 inches long, but not 35 inch spindles at one inch diameter.
    ...
    I might be pushing the tool too hard and my tools may not be sharp enough.
    ...
    spindle speed. I was turning at 3250 rpm...
    Scott,

    Based on what you said, I don't think vibration of the bed is the problem. I've turned thin spindles on flimsy lathes that were rocking a bit while turning. The forces involved are TINY compared to those in turning a heavy bowl or vessel blank.

    I find that 3000 RPM or so is the perfect speed for a small diameter spindle. I turn a lot of thin spindles and I always turn the speed on my Powermatic up as high as it will go, nearly the speed you mentioned. Works well. I've personally never turned faster or heard of anyone turning faster.

    The skew must be super sharp. I sharpen on a 600 grit CBN wheel then remove the grinding burr then hone/strop the edge until it's almost polished. A good test is if it will easily shave hair from my arm. Between sharpenings I strop on a piece of MDF with polishing compound rubbed into the roughened surface (made by resawing a piece maybe 4"x6" or so.) I hold the skew flat on the MDF with the edge and bevel heel in tight contact, then lift the handle every so slightly and pull the skew back with a considerable amount of pressure. I can tell that it's removing steel by the black marks on the MDF.

    You absolutely have to get rid of the vibration in the spinning wood. NONE is acceptable. Pressure from the tailstock can be a problem and when I get excessive vibration I sometimes increase and sometimes decrease the pressure to see if that helps. As mentioned earlier, it absolutely helps to grip one end of the spindle tightly by some means.

    During the cut with the skew the heel of the bevel can only touch the wood very lightly or not at all. If you develop spirals going out of control, the best thing I've found is to remove them with the skew by a cut normally not used: with the short point of the skew. This plows the ripples away leaving a much straighter, although not entirely smooth, surface. The next pass with the skew can clean up the surface now the ripples are gone.

    To control vibration without a steady rest (I have never used one) I use my left hand. I hold the skew in my right hand near the tool rest and support the end of the handle by pressing it against my forearm. I hook my left fingers around the spindle and help guide the working end of the skew with my left thumb. A picture or three, left to right, right to left, and an overhand support to dampen vibration on a very thin section while cutting on another section.

    D02_thinner_IMG_5030.jpg E01_reverse_IMG_5036.jpg E02_crossover_IMG_5031.jpg

    I often turn thin spindle holding in a chuck but there are several advantages to holding with a morse taper instead. For example, a blank with a taper can be removed from the lathe then remounted later with perfect registration - not usually possible when holding with a chuck. Example of short morse tapers for holding:

    morse_taper_IMG_5054 - Copy.jpg

    BTW, turning thin spindles is one of my favorite things on the lathe. I've posted thin spindle pics many times but if you haven't seen them:

    Some "magic" wands.

    A01_wands_IMG_5046.jpg cedar_and_ebony2_IMG_7528.jpg

    I made these do demonstrate: over 24" long, tapering from 1/2" down to 1/16", left-hand steady, made with shelving pine from Home Depot and walnut. Also held with a short #2MT but I had to use a drawbar to pull tightly into the headstock since I couldn't apply any pressure with the tailstock.

    pointers_B_IMG_20140311_113.jpg

    One more thin spindle, a handle for my favorite shuffle hoe, hickory, no steady rest. I got a lot of vibration on this since it was so long, although the diameter was not real small. The lathe bed is 35" + an 18" bed extension and I had both the headstock and tailstock overhanging the end of the bed as far as I could. For this one I think I did turn the speed down a little.

    handle_shuffle_hoe_comp.jpg

    And, wow, Fairbanks is a long way from the nearest AAW chapter club, according to the list on the AAW site! But there have to be other woodturners around. If you can get in touch with others, about starting a club in your area?

    I see there is a Great Alaskan Bowl Company in Fairbanks - their website describes turning bowls. Is this done by hand on a lathe or on some industrial machine? Perhaps they know of local turners or some that might even work there.

    JKJ
    Last edited by John K Jordan; 02-21-2021 at 6:24 PM.

  7. #7
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    Thanks John. I spent some time looking today. My skew, gouge and scraper are all sharper than they have ever been before, about all I "did" today. Teh skew and gouge are shaving forearm hair tomy satisfaction. I did also remount my spindle and fiddle with tailstock pressure.

    Everywhere between "that's not enough tailstock pressure for me to feel safe turning, its barely touching" up to "I can't tighten the tailstock anymore without workgloves" my spindle was vibrating while spinning. About the best ghost I could get to was about 1/8 of an inch, at some tail stock pressures the spindle was vibrating more and every few seconds would take a bigger jump. I couldn't feel my mounting surface moving at all for this, so I guess bearing, belt and motor are the next places to look. And bed flatness/ straightness/ squareness.

    I am kinda hosed on Morse Taper accessories. I do have some bed length to work with, but both my head and tail stocks shafts are half inch solid round stock with flats for set screws. And the set screw on the drive spur on my headstock is stripped out from hex key to round.

    I do mark my spindles with a penciled star so I can mount them on the same drive spur orientation every time. I tend to turn four billets to round and then set up the duplicator to turn four rounds to leg shape. And then make a table.

    The (Great Alaskan) Bowl Company uses a pretty impressive robot lathe. They can chuck up essentially a round of firewood, a log section 10-16 inches long and 10-16 inches in diameter, and cut a set of four or five nesting bowls out of the blank in a few minutes. The tool looks sorta like what your would see on a 10 wheeled truck for transplanting mature trees, except they can cut all the bowls simultaneously. Not sure if they have a website but you can certainly find them on facebook. I can't seem to escape them on facebook.

    Hopefully my CL add with get me some face time with some one who knows what they are doing. I appreciate the internet advice, but I am right at the edge of my comfort/ safety zone and want to stay out of the Emergency Room and the morgue. A few stitches every now and again is OK, but I definitely want to stay out of the morgue.

    I go back on 1:3 night call tomorrow, but I will make a point to stop by the Bowl Company to ask if any of the staff have lathes at home ASAP.

  8. #8
    I got vibration on my Rikon 70-220 VSR lathe once. It seemed like a bearing was going out. I ended up discovering that after I changed the belt on pulleys I tightened the belt too tight. I loosened it a little and the vibration was gone.

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