Connection coils for Makita RT0701C field and switch

Hi All,

brian.lambert.3511 said:

Looks like they come with the stator, and I would guess that they are to "ground" the rotor. View attachment 403866

Click to expand...

Thank you Brian for posting this. I think the stator is the same as the field in the diagram I found on the Makita website although they aren't shown in that overview. I spoke to Makita today as well as to a local repair shop for Makita (found on their website) but neither recognized the parts or could tell me which part they should come with. I do have to replace the field so I'll order that and see if it comes with the coils. If not, I'll probably hobby-Bob something together since I don't see any use for those coils other than being removable as opposed to being soldered on. I think I can achieve the same think with a small connector and the other end soldered to the brush holder. I have nothing to lose so I'm simply going to try that once the other parts come in.

To Reuelt, thank you for your input but it's definitely not part of the speed pot since that part is still funtional and undamaged.

To JW2170 and Old55, thank you for your warm welcome messages.

I would tend to agree with Reuelt about the coils (when intact) being the contacts connecting the brushholders to the rest of the unit. No experience with the unit in question, but it has been a fairly common practice with lower powered brushed motors for a long time as it distributes the current around the brush holder fairly evenly to eliminate hot spots. Look at the brushholders inside the housing, if they are circular in section outside with a rectangular or square hole broached through for the carbon brushes, and have a machined semicircular recess around the outside, the coil slides over the brushholder body and into the recess.

Beware that if the field winding/stator can be installed in two orientations, and the coils land close to and ready to connect to the brushholders, the orientation will be important, and getting it wrong may reverse the direction of rotation of the spindle, remove collets, collet nuts etc before attempting to power up the first time after reassembly to avoid the spindle throwing these parts off. If the field winding/stator is asymmetrical or has something to index it into the housing so it can only go in in one position, reverse rotation shouldn't be an issue.

If the coils are the contacts for the brushholders, given the damage shown in the picture, there is a good hance that at least one armature winding is fried and a short circuit. If that is the case, a replacement machine maybe a cheaper option than buying parts to rebuild your unit. Investigate your armature before committing to buying parts.

If my thoughts about the use of the coils is correct, ( just looked through a parts breakdown and they as I described) the two coils (actually springs) are most likely an integral part of the field winding. Basic current flow for the unit is:

through the control and switch module
through one winding of the stator
to one brush holder
through brush to armature and out the other brush
through second brush holder
to second stator winding
to mains neutral

Based on above and the style of brusholder used, the stator would have two connection terminals and two pigtails with the coil (spring) attached at the free end ready to slip over the brushholder.This is the brushholder image I found in a parts supply listing.