Will a spindle/bobbin sander help me? vs pillar drill

[Tetsuaiga]

I am trying to speed up as well as make easier the shaping of some concave curves, these also happen to be in end grain.

I know a spindle sander will remove material faster, and using the drill press as a sander can be bad for the machine.

What i'd like to ask is do you think i'll find it's any easier to produce smooth curves using a bobbin sander? Using my drill press I tended to struggle with this as the shape of the barrel would leave undulations that would need removing by hand sanding, which is pretty slow even with low grit.

Presumably the larger the drum the less tendency there is to create undulations in the curve.




Thanks =).

 

[Hitch]

Depending on what you may already have machine wise, and the shape of the curves in question, I use the end roller of my belt/disc sander.
I use a quick lashed up side table effort to keep the edge square, basically a bit of 18mm MDF fixed on the side, with another bit fixed to that to space it twards the belt.

Only major disadvantage is it uses the same strip of belt all the time. Can remove lot of material quite quickly.

 

[custard]

Presumably the larger the drum the less tendency there is to create undulations in the curve.

In theory yes. In reality unless the radius of the bobbin is the same or just a bit less than the radius you're shaping then you need a lot of practise and a very delicate touch to produce a genuinely fair curve. You might be better off making exactly shaped sanding blocks or thinking about copy routing.

 

[Tetsuaiga]

I think I will have to try template routing before anything else. I've done it before but get a bit concerned about the possibilities of tear out or kickbacks, particularly as its end grain.

 

[Adam9453]

I would probably rough out the curve using the bandsaw and then just hand sand the last few thou

 

[custard]

I think I will have to try template routing before anything else. I've done it before but get a bit concerned about the possibilities of tear out or kickbacks, particularly as its end grain.

You're right to be concerned about tear out and kickback, but there are reliable solutions, they might need a bit of forethought and planning but they pretty much remove the risk.

The first thing is to roughly bandsaw the blank so that you're only trimming one or two mill away with the router cutter. After that you must design the template so that there's a lead in and a lead out for the cutter, you've got to avoid a sudden engagement between the cutter and the workpiece.

If tear out is a serious risk then you can attach the template with double sided tape and have it either above or below the workpiece, by switching between "bearing at the top" and "bearing at the bottom" router bits you can always be cutting with the grain. In fact I use copy router bits at the router table that have a bearing at both ends and a cutter in the middle, that way it only takes a moment to flip the workpiece/template sandwich over, wind the router cutter up or down to place the bearing at the height of the template, and then carry on working with the grain all the time, even going around a complete circle.

Good luck!

 

[yetloh]

Make yourself one of these and save the money you would spend on a bobbin sander

with inserts for various size drums, it works brilliantly with no detectable dust escaping when connected to my shop vac. I have used it extensively and have found no disadvtantage in the lack of the limited rise and fall offered by most bobbin sanders.

Jim

 

[worn thumbs]

Without knowing more about the job in question,its not easy to give a useful answer.What type of wood are we dealing with and how thick?For a one off job it might be hard to justify buying a bobbin sander but for a regular production item it might be.At some point a router following a template might be a better answer.For a one off thats not too thick then maybe a sanding bobbin in a pillar drill would be workable.

 

[Tetsuaiga]

Thanks for all the help and suggestions. I think I also used scrapers and rasps in the past, the actual shape doesn't have to match a template but it does have to have the same looking curve on two sides.

If any further information helps its hard maple about an inch thick. I'm doing a production run plus i'm quite a lazy person so really like to have things as efficient as possible.

 

[Hemsby]

Until a couple of weeks ago like you I was using my pillar drill with a drum sander which was fairly successful but I found that the expanding foam drum tended to distort when tightening the screw that secured the abrasive disc, causing run out and consequently a “bumpy” finish

I decided to buy the Rutland’s Bobbin sander and wished I had done so before.

I am currently making some largish mirror frames that have an arch at the top with a 250mm internal & external radius.

I have made a template so I can use a bearing guided cutter to produce the frames. After roughly cutting the frame shape I used the largish bobbin to dress both of the radius profiles to the pencil lines and found it very easy to produce a smooth finish on the template.

The other advantage a Bobbin sander has over an adapted pillar drill is that it can be used on the floor or bench or whatever height is comfortable for you or the project.

Last point is that the dust extraction on mine is very good with virtually no airborne dust =D>

Regards,

Keith

 

[AES]

@Yetloh:

I think (only think mind) that I understand the picture of your "big drum sander on the pillar drill" in your post above, but could I ask a couple of extra Qs please?

Does the abrasive drum rise and fall at all? If so, how, & by how much? How is the drive from the pillar drill transferred to the big drum (it looks like a drive shaft is simply gripped in the pillar drill chuck)? What steps (if any) have you taken to reduce/eliminate side thrust on the pillar drill quill/bearings?

TIA

Krgds
AES

 

[yetloh]

AES,

No, the drum doesn't rise ands fall, except to the extent that the normal rise and fall of the pillar drill's chuck can be used. Mine has a slack area of travel at the top of its range where the spring return is ineffective so I do use thatto give a bit of variation in the area of abrasive used but perhaps surprisingly I haven't found this to be a significant proble in practice. When an area of abrasive becomes worn it is easy enough to raise or lower the table and even easier to simple put a block under the workpiece to raise it.

The drum sander has a mandrel which is clamped in the drill chuck. Incidentally, I often use much smaller drums with wider insert rings to maintain extraction.

I used to worry about the effect of side forces on the drill bearings but it hasn't been a problem so far. This may to some extent be influenced by the quality of the pillar drill; mine is a Record bought about 20 years ago, whether current Record drills are as well engineered, I don't know. As with all machine sanding it is about letting the abrasive rather than excessive pressure do the work and resisting the temptation to persist with a sanding belt once it has become worn. That may be the reason why my drill doesn't seem to have suffered. The only problem I have suffered in those 20 years is a broken rise and fall spring.

Jim

 

[Monkey Mark]

AES,

No, the drum doesn't rise ands fall, except to the extent that the normal rise and fall of the pillar drill's chuck can be used. Mine has a slack area of travel at the top of its range where the spring return is ineffective so I do use thatto give a bit of variation in the area of abrasive used but perhaps surprisingly I haven't found this to be a significant proble in practice. When an area of abrasive becomes worn it is easy enough to raise or lower the tablunie and even easier to simple put a block under the workpiece to raise it.

The drum sander has a mandrel which is clamped in the drill chuck. Incidentally, I often use much smaller drums with wider insert rings to maintain extraction.

I used to worry about the effect of side forces on the drill bearings but it hasn't been a problem so far. This may to some extent be influenced by the quality of the pillar drill; mine is a Record bought about 20 years ago, whether current Record drills are as well engineered, I don't know. As with all machine sanding it is about letting the abrasive rather than excessive pressure do the work and resisting the temptation to persist with a sanding belt once it has become worn. That may be the reason why my drill doesn't seem to have suffered. The only problem I have suffered in those 20 years is a broken rise and fall spring.

Jim

I like your set up, nice andtidy. How did you make your drums? It looks like foam or silar for the compression part.

 

[AES]

Thanks Jim (yetloh), very clear answers. And I agree with Monkey Mark, that looks a very neat and efficient set up -good extraction too. And Monkey Mark's Q is exactly what I was going to ask next too! :lol:

Krgds
AES

 

[davo453]

I am fortunate enough to have a large industrial bobbin sander that has bobbins ranging from 1" up to 6" in diameter it is the just the best thing for smoothing curves.

The workshop belonged to a pattern maker they don't really do straight lines and the craftsman (retired) though this machine was his most important tool.

I have used a sanding drum on a drill press it is cheap and it has it's place but like most things there is a correct tool for the job and for curves that is the rise and fall bobbin sander.

 

[yetloh]

The drums are I use are commercial. The biggest is a foam version I have had for many years and is like this onehttp://www.axminster.co.uk/black-decker-cushion-drum-sander. I also use a set of Carroll drums which are solid with a very thin squidgy overlay; these are better if it is vital that there should be no trace of rounding in the vertical dimension of he workpiece. Lastly I have a couple of pneumatic drums. I use these only partially inflated when I do want the worpiece to be curved in the vertical dimension as well as the horizonta,l as in this chair

- this one is nearly complete lacking only shellac and upholstery; I'm making three more as a batch, but it's a long haul.

Jim