Sedgwick MB rise and fall damage

[jetsetwilly]

Morning all, inspired partly by the excellent refurb thread from @deema and @Sideways, I have acquired a Sedgwick MB in green, but I think I've already broken it getting it home. It was slung under the thicknesser table as per the manual, with a block of wood jammed between thicknesser table and rollers/cutterblock, but after it was loaded I noticed that the wood was actually on the fingers, and now the thicknesser table falls nicely but when lifting it sticks, seemingly once per handle revolution. I can't see any damage from underneath, but clearly there is some.

My question is where is it likely to be? I can't see how a pull on the table could stress the worm gears (as the acme rise/fall thread should not transfer any force to them), but I also can't see how it could be anything else.

I hadn't planned it, but looks like I might be doing my own stripdown thread....

 

[jetsetwilly]

Whipped the rise/fall threaded block out. Thread looks mullered to me…. I guess the next step is to find a machine shop, but are there any other suggestions?

 

[johnnyb]

Helicoil

 

[jetsetwilly]

Yebbut I think it's a special thread...

 

[Amplidyne]

Let's have a look at the male thread. Give us some more idea of what sort of thread it is, and it the thread is indeed deaded.

 

[Housey210]

Morning all, inspired partly by the excellent refurb thread from @deema and @Sideways, I have acquired a Sedgwick MB in green, but I think I've already broken it getting it home. It was slung under the thicknesser table as per the manual, with a block of wood jammed between thicknesser table and rollers/cutterblock, but after it was loaded I noticed that the wood was actually on the fingers, and now the thicknesser table falls nicely but when lifting it sticks, seemingly once per handle revolution. I can't see any damage from underneath, but clearly there is some.

My question is where is it likely to be? I can't see how a pull on the table could stress the worm gears (as the acme rise/fall thread should not transfer any force to them), but I also can't see how it could be anything else.

I hadn't planned it, but looks like I might be doing my own stripdown thread

 

[Housey210]

Morning all, inspired partly by the excellent refurb thread from @deema and @Sideways, I have acquired a Sedgwick MB in green, but I think I've already broken it getting it home. It was slung under the thicknesser table as per the manual, with a block of wood jammed between thicknesser table and rollers/cutterblock, but after it was loaded I noticed that the wood was actually on the fingers, and now the thicknesser table falls nicely but when lifting it sticks, seemingly once per handle revolution. I can't see any damage from underneath, but clearly there is some.

My question is where is it likely to be? I can't see how a pull on the table could stress the worm gears (as the acme rise/fall thread should not transfer any force to them), but I also can't see how it could be anything else.

I hadn't planned it, but looks like I might be doing my own stripdown thread....

Get a screw pitch gauge, cheap enough. Measure hole, my guess M16, and get a tap

 

[jetsetwilly]

Get a screw pitch gauge, cheap enough. Measure hole, my guess M16, and get a tap

Are the old Sedgwicks metric? Can't find my thread gauges but with a dial gauge it's possibly M20x2.5 (seems too big for 3/4-10). I thought it was trapezoidal but actually looks like a plain thread, in which case a tap might be worth a try, though to me it looks like a fair bit of material has gone.

The male thread is fine, I'm guessing it's hardened steel.

 

[toolsntat]

Are the old Sedgwicks metric? Can't find my thread gauges but with a dial gauge it's possibly M20x2.5 (seems too big for 3/4-10). I thought it was trapezoidal but actually looks like a plain thread, in which case a tap might be worth a try, though to me it looks like a fair bit of material has gone.

The male thread is fine, I'm guessing it's hardened steel.

I wouldn't be so sure about that thread being ok, it looks "rolled" over to me?
Cheers Andy

 

[Fergie 307]

Another vote for Helicoil. You will probably need to buy separate inserts as the ones that typically come in the kit are fairly short. Looks like your thread is quite deep. I know some people who have "stacked" short inserts to get a deep thread, but probably not to be recommended.
I would certainly run a die on the male as well to clean it up.

 

[Against_The_Grain]

The male thread is fine, I'm guessing it's hardened steel.

Aside from the castings, Sedgwick only ever used bright mild steel for all their mechanical components, it makes the machines quite easy and inexpensive to produce.

If the binding happens at the same spot every time that to me would suggest something has very slightly bent somewhere, I would check the straightness of the threaded shaft.

 

[deema]

Helicoil wouldn’t be too successful as the reason it’s cast iron is for the lubricant properties of cast iron. The screw raises the thicknesser bed so the cast iron aides in the smooth operation. A helicoil is great for fixed fasteners and not for this application IMO.

A solution other than buying one from Sedgwick with limited engineering tools would be to buy a top hat brass / bronze threaded sleeve. You would then drill out to the right size and fit the sleeve. There are lots of ways to retain the sleeve from press fit, epoxy glue to silver solder or with a file flatten two opposed sides of the sleeve and drill and screw two metal blocks to locate against the flattened sides. You now have a replaceable item should it happen again.

 

[Amplidyne]

Helicoil wouldn’t be too successful as the reason it’s cast iron is for the lubricant properties of cast iron. The screw raises the thicknesser bed so the cast iron aides in the smooth operation. A helicoil is great for fixed fasteners and not for this application IMO.

A solution other than buying one from Sedgwick with limited engineering tools would be to buy a top hat brass / bronze threaded sleeve. You would then drill out to the right size and fit the sleeve. There are lots of ways to retain the sleeve from press fit, epoxy glue to silver solder or with a file flatten two opposed sides of the sleeve and drill and screw two metal blocks to locate against the flattened sides. You now have a replaceable item should it happen again.

An insert of some sort is certainly the way to go with this failing a completely new part. The thread looks too far gone for a tap.

 

[J-G]

Are the old Sedgwicks metric? Can't find my thread gauges but with a dial gauge it's possibly M20x2.5 (seems too big for 3/4-10). I thought it was trapezoidal but actually looks like a plain thread, in which case a tap might be worth a try, though to me it looks like a fair bit of material has gone.

The male thread is fine, I'm guessing it's hardened steel.

The chance that that thread is hardened is vanishingly small. The hardening process distorts the material such that further finishing has to be done. In the case of threads that would be by Grinding. This is a time-consuming - read 'expensive' - process.

Looking at the images posted I suspect that that is a Rolled thread probably Whit. form - certainly not Trapizoidal.

I've enlarged the image and measured it at 10x - based upon you assessment that it might be 20mm but also looking at the posibility that it is 3/4". Neither give me 100% confidence! If I assume 3/4"Ø (19.05mm) the the pitch seems to be 2.42mm which is 10.492 tpi whereas taking the O/D to be 20mm then the pitch is 2.548 or 9.968 tpi.

Although possible, it seems unlikely that Sedgwick would mix the standards to make a 20mm x 10 tpi special.but from the information provided that looks to be the most likely wierd!

Oh yes - - - there is no such thing as a 'Plain' thread.

 

[Fergie 307]

Helicoil wouldn’t be too successful as the reason it’s cast iron is for the lubricant properties of cast iron. The screw raises the thicknesser bed so the cast iron aides in the smooth operation. A helicoil is great for fixed fasteners and not for this application IMO.

A solution other than buying one from Sedgwick with limited engineering tools would be to buy a top hat brass / bronze threaded sleeve. You would then drill out to the right size and fit the sleeve. There are lots of ways to retain the sleeve from press fit, epoxy glue to silver solder or with a file flatten two opposed sides of the sleeve and drill and screw two metal blocks to locate against the flattened sides. You now have a replaceable item should it happen again.

Fair point, although I would think an insert would be ok if properly lubricated, moly or graphite based grease maybe? Or graphite powder if you don't want the thread to collect sawdust.

 

[Fergie 307]

One big issue with the Helicoil option is going to be cost. A kit is probably going to be £50+, based on for example M20x2.5, unless you can find someone to do it for you who already has a kit that size. Would be quick and easy, but not particularly cheap.
The bush option is going to be cheaper, even if you have to buy a suitable tap.
The other option that occurs to me is whether you could go up a size on the thread. So use a new larger threaded rod and drill out and tap the hole to suit. How much bigger will obviously depend on the core diameter of the "new" thread versus your existing hole. Also whether the pitch has any bearing on the calibration of the rise and fall.
Depends if the design would allow you to do that, and how the threaded rod attaches to whatever turns it.
I'm guessing it will be reduced to a smaller diameter round shaft running in bushes or bearings, and with a keyway and thread to attach the handle, or maybe the handle is secured with a roll pin or similar?
Would be a neat and tidy way to do it, and easy enough to make if you have the kit, but not otherwise. I would think a larger thread is probably going to last better as well.
My concern would be that the existing male thread looks distinctly "sub optimal" as one of my mates would put it, and might ideally also need to be replaced.

 

[deema]

I’m with @Fergie 307 I too think the thread on the shaft looks unusual. I don’t know if you have access to a lathe, but if you do buy a length of say trapezoid threaded bar and the matching top hat bronze bush. They are not very expensive from say Accu Engineering. Then get the rod turned at one end down to fit the gear. Anyone with a lathe could do it for you and it would be a very cheap option. You would end up with a much better solution than the original and its what I would do if I were refurbishing the lathe.

 

[Housey210]

more likely a standard metric thread with worm gear dowel / taper pinned on. Had same issue on sedwick tenoner, just bought new studding! OMG the replies.

 

[jetsetwilly]

Thanks all for your collected wisdom.

@J-G it's probably rolled as you said which does harden it - point was just that it's a lot harder than the cast iron lifting foot And 'plain thread' just meant it's not not square, acme or trapezoidal. Still haven't found my thread gauge but crudely measuring and counting is consistent with M20x2.5.

@deema and @Fergie 307 thanks I had the same worries about cost and viability of a thread repair, and I've been trying to ignore the slightly shonky male thread but you're right, it's not perfect. I hadn't thought of buying a leadscrew and nut - my word they are cheap! Certainly cheaper than £329 for a new foot from Sedgwick anyway!

Got some thinking to do now

 

[Against_The_Grain]

it's probably rolled as you said which does harden it

This would be easy to identify as the threaded portion will be larger than the smooth portion of the shaft as the metal deforms during the rolling process it becomes larger.

You must remember that Sedgwick is a very small artisanal manufacturer of woodworking machinery, there are no special processes or expensive machinery involved in the production of these machines, in fact it's very archaic and they almost always go for the cheapest possible way of manufacture whilst keeping the quality somewhat acceptable. I can say without a doubt that they cut all their in-house threads with dies or single-point cut in the lathe, because when you examine their threads you will often see the burr left behind by the dies or the steps in the thread at the end where they've pulled the cross-slide back and the tolerances vary massively from machine to machine, particularly spindle moulder shafts where one nut will thread on very loosely and another will be so tight to thread on that you need a spanner just to wind it on.