Slowing down the BT motor. On purpose.

[sparkeyjames]

I just put my sanding blade to use on my 21829 today and boy it can sand off the wood in a hurry. What I want to know is is there a way to slow down the BT motor so that I'm not sanding on a 4500 rpm sanding surface? (yes it's out of warranty) Kind of like the external speed circuit for an older router. Or is the BT motor not one of those types of motors you can do that too?

[crokett]

You are talking about a variable speed controller - like what you would use on a router. I am not sure if you can use one with the BT though.

[LCHIEN]

You are talking about a variable speed controller - like what you would use on a router. I am not sure if you can use one with the BT though.

You should be able to use a router speed controller on the BT3000, it has a universal motor which is fine with those type of controllers. Make sure you get one rated for 15 Amps, though.

[sparkeyjames]

You are talking about a variable speed controller - like what you would use on a router. I am not sure if you can use one with the BT though.

Yes that is exactly what I'm referring too. I'm also not beyond making my own if that becomes necessary.

Ok now I have 2 conflicting views here. Anyone Else?

[LCHIEN]

life is all about knowing who to believe.

[Uncle Cracker]

I saw one "yes you can" and one "I don't know". There does not appear to be a conflict...

[jgrobler]

I haven't tried it yet, but I have a BT3 motor that I'm keeping for a shop-built drum sander, with the intention of using a variable speed controller to slow it down. AFAIK any universal motor will work with those. I'm still in the "thinking about it" phase.

[leehljp]

Loring, or anyone -
Can a variable transformer work on universal motors without causing any problems? I have used one to take my BT3000 to 120 volts and you can definitely hear the speed change when it goes from 100V to 120V.

Does this hurt the motor if it were cut to 80V to slow it down as in the case of wanting to use it as a sander?

(GLOAT: Because of the question of this topic, I looked up online - Variable Transformers. I have four 20 amp 2KVA 0-130V VTs. While old (at least 30 years) they work fine. I just looked up current models and the 20 amp models, new with LED readouts, run $400 to $600 or so. I didn't realize that I had a gold mine on hand.)

[crokett]

YOk now I have 2 conflicting views here. Anyone Else?

No conflicting views. I know a speed controller will slow the motor down, I did not know you could use with the BT. Thanks to Loring now I know you can. I was giving you a place to start looking.

[LCHIEN]

Loring, or anyone -
Can a variable transformer work on universal motors without causing any problems? I have used one to take my BT3000 to 120 volts and you can definitely hear the speed change when it goes from 100V to 120V.

Does this hurt the motor if it were cut to 80V to slow it down as in the case of wanting to use it as a sander?

(GLOAT: Because of the question of this topic, I looked up online - Variable Transformers. I have four 20 amp 2KVA 0-130V VTs. While old (at least 30 years) they work fine. I just looked up current models and the 20 amp models, new with LED readouts, run $400 to $600 or so. I didn't realize that I had a gold mine on hand.)

Yes, variable transformers or autotransformers (Variacs are a trade name) will work quite well, but they will cost quite a bit more than the router speed controllers due to the copper and iron involved. Also much heavier and larger, too.

A router speed controller can be had for around $20 and a variac will cost you probably over $100 for the cheapest ones.

[wardprobst]

Router speed control will work on a BT3000, I've done it. Variac will also work.
DP

[poolhound]

It had never even occurred to me to use the BT as a sander, where do you get the disks, do they come with abrasive already on or use stick on?

I wonder what other great things the BT can do, rocket ship, make tea - BEER?

[Tom Slick]

sears sells a flat sanding disc and the abrasives. you can put a different grit on each side and have two grits available.
http://www.sears.com/shc/s/p_10153_1...+%26+Abrasives

woodworker's supply sells a disc with a convex beveled side that lets you run the board across it like a poor man's micro jointer.
http://www.woodworker.com/cgi-bin/FU...PARTNUM=95-430

I read discussion about these discs loading the arbor bearings in a way they aren't designed to handle but I haven't read anyone who actually noticed wear from their use.

[docrowan]

I have a woodworking author hero - Rosario Capotosto - who wrote about the beveled sanding disk in one of his books. I was afraid it did not exist anymore. Thanks for posting the link to Woodworker's Supply. That will go on my Christmas list.

[Uncle Cracker]

I read discussion about these discs loading the arbor bearings in a way they aren't designed to handle but I haven't read anyone who actually noticed wear from their use.

That is a valid point. Perhaps the reason nobody has reported a problem is that it takes prolonged usage to damage the bearings, or maybe it's because it is too embarrassing to admit that you kayoed your table saw trying to sand with it.

For what a cheap disc sander costs, why would you wish to try anything else??