Wide belt sander questions..

[Rick Fisher]

I have some questions which can hopefully be answered by folks who own widebelt sanders..

Most of these machines dont offer variable speed, rather they have 4.5m/sec or 9 m/sec feed speeds.. is it a big deal?

With a drum sander, I get the height close and turn the height adjustment handle on a slow speed to until I hear the paper hit the wood.. With electronic table height.. how does this work? I guess what I am asking is how do you establish the correct height?

How big a deal is HP. The motors are huge to begin with.. How often do you wish you had more power? Is the platten what causes the need for all the power? When running, how often do you max out the amp meter?

Do you have a rubber roller or a steel contact roller?

How is the dust collection .. when they call for 1200 cfm.. everyone calls for 900 - 1200 cfm, on every tool.. I would have thought it would need to be much .. much more.

Most need 3-4 cfm of air at 70 - 80 psi.. you can get that from a small compressor.. how big a compressor do you REALLY need ..

Any features you highly recommend?

Electronic belt tracking?

Thickness reading device?

[J.R. Rutter]

Most of these machines dont offer variable speed, rather they have 4.5m/sec or 9 m/sec feed speeds.. is it a big deal?

I don't think so. I run mine at the slow speed for just about everything. Slower is better for quality and thickness consistency. For less critical things like long strips, I run the faster speed. You could always retrofit a VFD for the feed motor if you wanted to.

With a drum sander, I get the height close and turn the height adjustment handle on a slow speed to until I hear the paper hit the wood.. With electronic table height.. how does this work? I guess what I am asking is how do you establish the correct height?

Some machines have a built-in position sensor that you can set to remove a certain amount when you insert your part. The table raises automatically until the sensor trips and it is ready to go. As a practical matter, I know the thickness of just about everything that goes into the sander, having established it at the planer or moulder beforehand. For unknowns, I check with a digital caliper and remove my standard .4 mm, or whatever.

How big a deal is HP. The motors are huge to begin with.. How often do you wish you had more power? Is the platten what causes the need for all the power? When running, how often do you max out the amp meter?

Not a big deal if you use it for sanding, not thicknessing. The power required for stock removal is huge compared to a planer head. On my 43" 2-head SCMI, there is a 30 HP motor driving both heads. If you are maxing out the meter, you are pushing the machine too hard and will be going through abrasives quickly, and stressing the various components and frame. I have mine set up with 3 contact points: both drums and the platen. You can watch the amp meter tick up slightly as a part hits the various points. For a single head combination setup, I would have the drum calibrate and the platen finish. But again, don't expect to hog off and finish sand in one pass. I have never maxed out my machine.

Do you have a rubber roller or a steel contact roller?

I have a steel first drum and rubber second drum. Steel does a good job at calibrating. Rubber is better for smoothing. But lots of machines run a hard rubber first head. A combi head will be a happy medium...

How is the dust collection .. when they call for 1200 cfm.. everyone calls for 900 - 1200 cfm, on every tool.. I would have thought it would need to be much .. much more.

DC is excellent. Some dust left in raised panel doors, but for flat parts, none. I went the overkill route on dust collection and dedicated a 3500 cfm collector to my sander. If you are considering a well engineered unit, then you can go by the port size.

Most need 3-4 cfm of air at 70 - 80 psi.. you can get that from a small compressor.. how big a compressor do you REALLY need ..

For just belt oscillation with electronic sensor, you don't need a huge amount of air since you are just pushing a small piston back and forth. Air jet belt cleaning uses a fair amount though.

Any features you highly recommend?

2 heads! For me this allows us to run the same grits all the time: 120/180. But changes are not too big a deal - just get the platen to drum relationship dialed in to work with a variety of grits. I also like the pneumatic head positioning. There are times when I just want to take a second pass with just the finish head and can switch the first head off. You can also do this with the platen on a combi head if it is equipped with this feature. Run drum only with coarse grits and run both or just platen with fine. Digital height readout is a must for consistency and productivity. A digital positioning setup is also very handy, but I make do without.

QUOTE=Rick Fisher;1141333]
Electronic belt tracking?[/QUOTE]

Recommended.

QUOTE=Rick Fisher;1141333]
Thickness reading device?[/QUOTE]

Nice for some situations, but for consistency of finished parts, you don't want to rely on it.

[Rick Fisher]

The two heads is a puzzle..
Does the sander do the job in one pass? My experience is with a Drum Sander, where one pass isnt the norm.. Is it possible to take a panel off a planer and sand to 180 in a single pass?

The main purpose is for finishing.... Is the idea of stock removal in your case when working a 36" wide panel? because the planer isnt wide enough?

Your machine has a 30hp motor.. Would it be fair to say that it would do the same job, just as well, with a 20hp motor?

Have you ever run laquered panels through your sander, or can you?

[J.R. Rutter]

Does the sander do the job in one pass? My experience is with a Drum Sander, where one pass isnt the norm.. Is it possible to take a panel off a planer and sand to 180 in a single pass?

Yes, we do it every day on the 2-head. For softer woods, you can even do this right out of the clamps if the alignment is good. For a single head, this would be pushing it.

QUOTE=Rick Fisher;1141362]
The main purpose is for finishing.... Is the idea of stock removal in your case when working a 36" wide panel? because the planer isnt wide enough? [/QUOTE]

Some people try to run sanders as if they were planers. I don't remove more than .5 mm per pass for any part. For wide panels in hard woods, it is more like .3 mm. So for panels wider than the planer, we glue up close to final thickness and allow an extra pass per side.

QUOTE=Rick Fisher;1141362]
Your machine has a 30hp motor.. Would it be fair to say that it would do the same job, just as well, with a 20hp motor?[/QUOTE]

I don't honestly know... For finish sanding, I think that would work.

QUOTE=Rick Fisher;1141362]
Have you ever run laquered panels through your sander, or can you?[/QUOTE]

Supposedly you can, but in my shop this never comes up. I do have a soft platen for this but have never tried it. I think that you would want a vacuum feed belt/bed to hold the panel as flat as possible.

[Larry Edgerton]

JR

Sounds like you are happy with that machine? Would you buy it again, and how has it been for breakdowns?

That is the machine that is on my short list, and I have always had great luck with SCMI and figured why change.

Larry

[J.R. Rutter]

Sounds like you are happy with that machine? Would you buy it again, and how has it been for breakdowns?

Hi Larry - Yes, I have been happy with it. I spent AWFS 2 years ago looking at sanders. Came away feeling that SCMI had best balance between features and build, but was priced a bit high. Ended up finding one on the used market a month or two later. It was not run enough to break it in completely and was 30% less than new.

Mine has only one roller at infeed and outfeed - 2 or 3 would be nice (although it does make for a smaller footprint). We got some belt slipping under moderate/heavy loads until the motor got tensioned higher. I think this is typical machine break-in. No breakdowns yet, but we only run it an hour or two per day. I would buy it again. After evaluating a few different abrasives, I settled on SIA paper belts for both heads: 120 g alum oxide first and 180 g carbide second. At one point, SCM was running a clearance on the belt blower unit, so I got one extra to try as a panel cleaning jet to blow the dust out of raised panel doors. Have not had a chance to work out how to install it yet.

[Rick Fisher]

You had slippage until the motor tension was increased?

Do you mean the motor that ran the conveyor or the main motor ?

Edit..

I read it again..

By slippage, I thought you meant material slipping on the conveyor.

My bad.

[J.R. Rutter]

You are right, there are two places that can slip, both involving belts. The main motor belts that drive the sanding heads needed to be tensioned a couple of times as they broke in.

But there was also an issue of parts, especially wide, short pieces slipping on the conveyor. The SCM (and other euro machines) have a waffle grid type belt. It is firm for good control over thickness, but does eventually glaze over a little. The fix was to get a 60 grit belt on the first head, override the minimum thickness limit switch, and kiss the surface of the feed belt with the first drum while everything was running for several minutes. This gets done once or twice a year.

[Chris Peterson]

I see most of your questions have been answered. I hope I can offer a little more insight. I’ve been repairing widebelt sanders a little more than 18 years and have seen it all…almost.

When it comes to conveyor speed, slower speed will result in better tolerance, more consistent scratch, and less wear on the abrasive belts. I recommend 15-20 feet/min (5-6 m/min) for small shops and won’t guarantee tolerances for any speed over 30 ft/min (10 m/min) in larger factories. You can send the wood through at a faster speed, but the sanding won’t happen. The piece will simply deflect into the rubber of the conveyor belt and/or the rubber contact drum.

As for the correct height to set the bed, it’s all related to what grit abrasive you’re using. A 36 grit belt is capable of removing at least .060” (1.5 mm) per pass on oak while 220 grit is only capable of removing .004” (.1mm).
You have to know what the thickness of the wood is going in, what grit you’re using and how much that grit abrasive is capable of removing.

Horsepower. Generally, it takes between 1 to 2 horsepower per inch of abrasive width on most hardwoods (oak, cherry, birch, etc.)
Remember that just because your machine is outfitted with a 50 horsepower motor doesn’t mean that you’ll be using 50 horsepower worth of energy - you just won't be using the full potential of the motor. I’ve seen a couple machines where the abrasive belt actually slowed down because there wasn’t adequate horsepower to drive it – very frustrating, indeed.

Steel drum vs rubber drum. Steel drums are great for holding excellent tolerance and are great protection for “accidents” (feeding in wood that is far too thick), however they tend to leave deeper chatter marks (from the splice in the abrasive belt) and push the abrasive grit scratch deeper into the wood.
Rubber drums leave a “softer” scratch but are expensive to repair when an “accident” happens.
Especially in schools, I usually recommend a steel drum. Proper use of the platen will eliminate the chatter marks a steel drum is known to leave.

On most newer sanders with electronic abrasive belt tracking, the amount of compressed air is minimal – just enough to cycle the tracking cylinder once a second or so.

I’d say skip the automatic thickness device because it’s too unreliable in too many cases, but most manufacturers offer it as standard – marketing games.

A digital thickness gauge is a must, but most manufacturers have that as a standard accessory now anyway.

Make sure the manufacturer has contact drums, conveyor belts, and tracking eyes in stock. Any other part is usually available somewhere.

I hope this helps.
- Chris Peterson
- ComprehensiveRepair.com

[Rick Fisher]

Chris, thanks for reviving this old post..

I had a set back in my plans.. but am actually heading over to Vancouver this week to look at a lightly used SCM wide belt.. I am taking the money with me.. which means if it checks out good, I will buy it ..

Its a sandya win.. 24" machine.. I have been running a 24" dual drum for some time now, and rarely wish for greater width.. I am only a hobby woodworker and space is a huge issue for me.. so a good deal on a clean 24" machine makes sense for me..

This machine has a 10hp motor.. so its a little light, but my 24" Dual drum has 3hp.. I know that with the platten there is much more load on the Wide Belt motor, but as I said, I am just a hobby woodworker.. The machine wont run an hour a week..

This machine has a steel contact roller.. Apparently the conveyor is immaculate.. the machine has very low hours.. It is in a shop with 2 x 36" Wide Belts and was always the last machine to get run.. Now, its on the chopping block..

So what should I look for ? I am handy enough with wrenches, but hate waiting for parts. lol.

If you where looking at this machine, what would you look at ?

Its an early 2000 model. White in color..

[Chris Peterson]

Rick,

I had some trouble logging on, but I think I got that figured out.

I'm sure you've found your sander by now, but I'll answer your question for anyone else stumbling across this post.

When I look at used sanders, I examine the condition of the conveyor belt and contact drum (if it's rubber coated). Each will cost around $1,000 to repair/replace.
Even though SCMI is a good name like Timesavers and AEM, there were times and models that didn't live up to the name. I look to see how hard it is to replace the conveyor belt and contact drum. I also see how hard it is to adjust the head if it's not parallel to the conveyor belt.
I look to see how hard it is to replace the platen - some manufactures still haven't figured out that the platen should be easy to put in and take out as well as replace the graphite.

Although it's not an indication of the quality of the machine manufactured, I look to see how clean it is. Machines with graffiti and other writing on it indicate that the machine was likely neglected and possibly abused. Another tell-tale sign is the amount of missing items like screws and washers - if the person responsible for maintaining it cut corners by not putting all the fasteners back in, what other corners were cut?

-Chris Peterson
ComprehensiveRepair.com

[Kelly Foster]

As I study up on wide belt sanders, having purchased a 43" Halsty a few days ago, I am amazed that a 13yo thread is very educational. Thanks J.R. Rutter and Chris Peterson!

[Dave Cav]

I have a 36" single phase (10 HP) Safety Speed I got at AWFS ten or so years ago. For a one man, low volume shop it works very well and is simple and easy to work on. I recently put a Proscale DRO on it (replaced a nearly useless Wixy) which really helps.