Can someone explain to me what are parallelogram beds on a jointer and why are they desirable? Grizzly advertises this as a feature on some of their jointers. I’m about to buy one of their jointers and would like to understand what this is. Thanks.
Jeff
Replies
A parallelogram table has four independent adjusters which allow you to raise or lower each of the four corners of the table. There are four for the infeed table, and four for the outfeed table.
The advantage over dovetailed ways is, if you must replace a table or it's not perfectly flat, you can fix just that table on its own. Once it's dead flat, you can make it coplanar with the other table and the cutterhead by using its adjusters. If a table is damaged and must be reground, you can take just that table to be ground; the other table need not be machined.
On jointers with dovetailed ways, there is no way to "tip" one table in relation to the other; if a table must be reground, the entire jointer must be ground together.
I do not have enough experience to have any idea of how likely it is that the parallelogram design will actually impact you in any way. In a home shop, what's the incidence of issues with jointers with dovetailed ways?
Some dislike parallelogram jointers, due to the hassle of getting the tables correctly adjusted. I can say, on my parallelogram jointer (Grizzly G0490) at least, getting the tables coplanar wasn't difficult (and it did require some adjustment, took less than an hour). I had a jointer with dovetailed ways, and it arrived dead correct, so its lack of adjustability didn't impact me at all.
John,
You should read my thread about the DJ-20 saga... My experience in getting the unit co-planer after having a new in-feed table installed was clearly different than yours. It took me a number of hours to get both of them set correctly. First I had to set the out-feed table into proper position, then I tackled the in-feed table. It was challenging for me.
Marty
Well, I should confess that it wasn't so hard for me. Each table, at its surface, needed to be tipped less than 1/64". I had to make only the tiniest adjustment. I suspect the thing was aligned correctly at the factory, but the box was dropped and knocked out of alignment, or lifting the thing by its tables might have knocked it out. I have no experience with installing a new table, and I may well be wishing for this easy result one day!!!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I do not like how parallelogram beds on a jointer adjust. Those I have looked at need to be locked to keep from changing adjustment.
The large and expensive machines do not use a parallelogram design. I have a 12" Oliver and it adjusts at four points on each bed but is not a parallelogram design. A parallelogram design machine would seem to be easier and cheaper to make.
Edited 3/31/2006 9:35 am by gb93433
The system on the older Oliver jointers and Crescent jointers as well as a few other makers is called an "inclined adjustment". I find this a much simpler set up than a parallelgram system. If you've ever had to change a table on a parallelogram jointer you would know what I mean. On the other hand I find the parallelogram system easy to adjust. I've been rebuilding machinery for over 25 years so I've done a fair share of jointer restorations.
The parallelogram system is common on most European jointers and Invicta from South America and is being done with more Asian imports. Wilke is selling the York 12" for under $2,000 I hear.
Edited 3/31/2006 11:38 am ET by RickL
Thanks everyone for your comments. I've made my decision and purchased a machine with the parallelogram table design. In regards to changing tables making it difficult to readjust, I would say that if I need to pull the table off to change it, get it reground, whatever, I've made a poor choice in machines, and not because it's a parallelogram design....;-)
Jeff
Tables can just as easily warp on a new machine or an old machine. Most of the warped tables I've dealt with were on machines from the 50's, mostly Olivers. I've had to change a table on a new DJ-20. Considering how many machines Delta makes that's not a bad ratio.
If you get a warped one it will have nothing to do with your choice of brands. Stuff happens!
I appreciate what you're saying. A long time ago, in the shop I apprenticed in, we used to buy old milling machines and rebuild them, scrape ways etc.. This was back in the 70's, the things I've seen over the years.....Stuff does happen, all the time. Still, so long as these machines are not abused, used properly, are built with quality materials and are RIGHT TO BEGIN WITH, a guy shouldn't have problems with tables warping. I check mine regularly, I've got a thing about flat and square surfaces and accurate movement! I just haven't had problems with warping tables.
Jeff
Rick,
I have personal experience in adjusting both types of jointer systems and far prefer the parallelogram system.
Marty
I've done hundreds of jointers and can easily do the incline or paralleogram system just as fast but when it comes to removing a table and reinstalling the inclines are much faster and easier. The parallelogram system has a massive spring and requires a lot more finesse. I'll never forget the time I had to replace some broken brackets on a 16" Minimax with parallogram tables. Challenging to say the least. All the 16" Olivers were cakewalks for having tables reground and reinstalled.
This has been an interesting discussion. From my point of view I tend to prefer the //gram type, provided the bushes are kept clean and correctly lubricated. From the manufacturers point of view I suspect they prefer it as well becuase there has to be less mass of cast iron -it is only required for the tables and not for a complete base or semi-base that has to accommodate the dovetail ways-i.e it is easier and cheaper to manufacture. That's the price of satisfying the clamour for "a better price".
But I still like to have the old style -all cast iron tables and base.Philip Marcou
Philip, thanks for this comment, it got my attention. I went back and compared 2 of Grizzly's 8" jointers, one without and one with the parallogram tables. I see what you mean about the mass of the base on the dovetailed configuration, however the tables extend far out beyond the center support base. The tables on the parall. machine sit in a much wider base and appear to be better supported on the bottom along the length of the table, possibly being a more stable design? Can anyone who has experience rebuilding these machines comment on which design they've seen come in more often with warped tables?
Thanks.
Jeff
I do not like how parallelogram beds on a jointer adjust. Those I have looked at need to be locked to keep from changing adjustment.
I've seen you say this twice, and still don't understand it. There are two classes of adjustment on such a table. The first is a set of four large bushings you turn to change the plane in which the table's top sits. The second is the normal height adjustment one does to change cut depth (for infeed), or to align with the blades (for outfeed).
Are you saying that the adjustment changes if you don't lock the bushings (the first type of adjustment)? If so, that's not at all surprising. The bushings should always be locked (on my jointer there's a set screw per bushing that stops its motion), except when you're adjusting the table's plane. This is analogous to using the lock on your table saw once you've set your blade height where you want it. Without the lock, that height won't remain precisely set.
Or are you saying that once you have the tables perfectly parallel and aligned to the blade (and you've locked the bushings as described above), that raising and lowering the table (the second adjustment, typically changing cut depth) knocks out the alignment of the tables to each other and to the cutterhead? If this is your experience, there is indeed a problem, but I'm amazed that every such jointer you've seen has this issue.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I don't understand what he means either. Doesn't fit with my observations and experience.
One thing that holds true is if you adjust the unit it's best to run the tables up and down a few times to settle everything in. Often you need to go back and tweak it a tiny bit.
On the DJ series from Delta they use two setscrews to lock the cams in. So if you loosen the top one not knowing about the bottom locking one you damage the cam so you loose that tiny bit of adjustment that is critical. Basically the dimple will pull the cam to the old setting.
I think maybe you misunderstood me. What I meant is when I am using the machine. Most any other machine will hold the table height without locking it down because it pushes against the adjusting screw and nut. I have used a parallel machine which changed the depth of cut from where it was set simply because it does move so easy and has nothing to stop it. In fact years ago I was working on a machine design and the parallelogram design is what I came up with until I realized I had not come up with a very satisfactory way of keeping the bed from moving especially when a heavy piece of wood was on top.As far as a jointer bed moving hard it seems to depend on the machine. On my Oliver 12" jointer I can move the bed up and down using one finger on the screws. Whereas some smaller machines I own move harder. All are oiled well.
I don't see what the height adjustment has to do with the means of making the tables parallel.
The two ways of allowing table parallel adjustment with which I am familiar are parallelogram, and dovetailed ways. These are normally adjusted at machine installation, and barring settle-in issues (pointed out by another poster), shouldn't need tweaking for months or years at a time.
There are two means of adjusting table height (distinct from setting parallelism) with which I am familiar: handwheels and levers. With handwheels, you typically unlock the height lock, dial in your height, then lock the height lock. With levers, you unlock the height lock, raise or lower the table with the lever, then lock the height lock.
If you're doing this height adjustment and not using the lock knob, well, it's no surprise you're getting table movement, and you are exposing yourself to serious danger. This movement happens more easily with levers, but can happen with handwheels too... but you should ALWAYS lock the tables before feeding stock. If the table drops 1/4" during the feed you are nearly certain to experience kickback in a deeply impacting way. I hope you're standing out of the kickback zone!
If I had to bet, I think you're mixing up parallelogram table alignment with lever-style table height adjustment. If so, you really REALLY need to lock the table before using that jointer. If I've got this wrong, sorry, but I'm trying hard to understand what's going on there...My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
"If I had to bet, I think you're mixing up parallelogram table alignment with lever-style table height adjustment. If so, you really REALLY need to lock the table before using that jointer."You are right. That is my point exactly.
Ahh, I think I see. I'm going to stick to my position that you should never, on ANY jointer, fail to lock the table prior to jointing.
I will also assert that this has nothing to do with the parallelogram adjustment mechanism. Some jointers' tables simply move more easily than others, and that's independent of the table adjust mechanism, and much more related to the table elevate mechanism.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
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